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3008 lines
86 KiB
3008 lines
86 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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#include <linux/kernel.h> |
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#include <linux/errno.h> |
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#include <linux/err.h> |
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#include <linux/spinlock.h> |
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|
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#include <linux/mm.h> |
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#include <linux/memremap.h> |
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#include <linux/pagemap.h> |
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#include <linux/rmap.h> |
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#include <linux/swap.h> |
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#include <linux/swapops.h> |
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#include <linux/secretmem.h> |
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|
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#include <linux/sched/signal.h> |
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#include <linux/rwsem.h> |
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#include <linux/hugetlb.h> |
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#include <linux/migrate.h> |
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#include <linux/mm_inline.h> |
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#include <linux/sched/mm.h> |
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|
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#include <asm/mmu_context.h> |
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#include <asm/tlbflush.h> |
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|
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#include "internal.h" |
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|
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struct follow_page_context { |
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struct dev_pagemap *pgmap; |
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unsigned int page_mask; |
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}; |
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|
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static void hpage_pincount_add(struct page *page, int refs) |
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{ |
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VM_BUG_ON_PAGE(!hpage_pincount_available(page), page); |
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VM_BUG_ON_PAGE(page != compound_head(page), page); |
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|
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atomic_add(refs, compound_pincount_ptr(page)); |
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} |
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|
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static void hpage_pincount_sub(struct page *page, int refs) |
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{ |
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VM_BUG_ON_PAGE(!hpage_pincount_available(page), page); |
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VM_BUG_ON_PAGE(page != compound_head(page), page); |
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|
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atomic_sub(refs, compound_pincount_ptr(page)); |
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} |
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|
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/* Equivalent to calling put_page() @refs times. */ |
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static void put_page_refs(struct page *page, int refs) |
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{ |
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#ifdef CONFIG_DEBUG_VM |
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if (VM_WARN_ON_ONCE_PAGE(page_ref_count(page) < refs, page)) |
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return; |
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#endif |
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|
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/* |
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* Calling put_page() for each ref is unnecessarily slow. Only the last |
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* ref needs a put_page(). |
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*/ |
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if (refs > 1) |
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page_ref_sub(page, refs - 1); |
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put_page(page); |
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} |
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|
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/* |
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* Return the compound head page with ref appropriately incremented, |
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* or NULL if that failed. |
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*/ |
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static inline struct page *try_get_compound_head(struct page *page, int refs) |
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{ |
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struct page *head = compound_head(page); |
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|
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if (WARN_ON_ONCE(page_ref_count(head) < 0)) |
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return NULL; |
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if (unlikely(!page_cache_add_speculative(head, refs))) |
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return NULL; |
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|
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/* |
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* At this point we have a stable reference to the head page; but it |
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* could be that between the compound_head() lookup and the refcount |
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* increment, the compound page was split, in which case we'd end up |
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* holding a reference on a page that has nothing to do with the page |
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* we were given anymore. |
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* So now that the head page is stable, recheck that the pages still |
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* belong together. |
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*/ |
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if (unlikely(compound_head(page) != head)) { |
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put_page_refs(head, refs); |
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return NULL; |
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} |
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|
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return head; |
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} |
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|
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/** |
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* try_grab_compound_head() - attempt to elevate a page's refcount, by a |
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* flags-dependent amount. |
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* |
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* Even though the name includes "compound_head", this function is still |
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* appropriate for callers that have a non-compound @page to get. |
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* |
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* @page: pointer to page to be grabbed |
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* @refs: the value to (effectively) add to the page's refcount |
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* @flags: gup flags: these are the FOLL_* flag values. |
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* |
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* "grab" names in this file mean, "look at flags to decide whether to use |
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* FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount. |
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* |
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* Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the |
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* same time. (That's true throughout the get_user_pages*() and |
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* pin_user_pages*() APIs.) Cases: |
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* |
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* FOLL_GET: page's refcount will be incremented by @refs. |
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* |
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* FOLL_PIN on compound pages that are > two pages long: page's refcount will |
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* be incremented by @refs, and page[2].hpage_pinned_refcount will be |
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* incremented by @refs * GUP_PIN_COUNTING_BIAS. |
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* |
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* FOLL_PIN on normal pages, or compound pages that are two pages long: |
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* page's refcount will be incremented by @refs * GUP_PIN_COUNTING_BIAS. |
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* |
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* Return: head page (with refcount appropriately incremented) for success, or |
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* NULL upon failure. If neither FOLL_GET nor FOLL_PIN was set, that's |
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* considered failure, and furthermore, a likely bug in the caller, so a warning |
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* is also emitted. |
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*/ |
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struct page *try_grab_compound_head(struct page *page, |
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int refs, unsigned int flags) |
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{ |
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if (flags & FOLL_GET) |
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return try_get_compound_head(page, refs); |
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else if (flags & FOLL_PIN) { |
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/* |
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* Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a |
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* right zone, so fail and let the caller fall back to the slow |
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* path. |
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*/ |
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if (unlikely((flags & FOLL_LONGTERM) && |
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!is_pinnable_page(page))) |
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return NULL; |
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|
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/* |
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* CAUTION: Don't use compound_head() on the page before this |
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* point, the result won't be stable. |
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*/ |
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page = try_get_compound_head(page, refs); |
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if (!page) |
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return NULL; |
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|
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/* |
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* When pinning a compound page of order > 1 (which is what |
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* hpage_pincount_available() checks for), use an exact count to |
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* track it, via hpage_pincount_add/_sub(). |
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* |
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* However, be sure to *also* increment the normal page refcount |
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* field at least once, so that the page really is pinned. |
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* That's why the refcount from the earlier |
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* try_get_compound_head() is left intact. |
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*/ |
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if (hpage_pincount_available(page)) |
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hpage_pincount_add(page, refs); |
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else |
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page_ref_add(page, refs * (GUP_PIN_COUNTING_BIAS - 1)); |
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|
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mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, |
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refs); |
|
|
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return page; |
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} |
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|
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WARN_ON_ONCE(1); |
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return NULL; |
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} |
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|
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static void put_compound_head(struct page *page, int refs, unsigned int flags) |
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{ |
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if (flags & FOLL_PIN) { |
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mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, |
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refs); |
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|
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if (hpage_pincount_available(page)) |
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hpage_pincount_sub(page, refs); |
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else |
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refs *= GUP_PIN_COUNTING_BIAS; |
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} |
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|
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put_page_refs(page, refs); |
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} |
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|
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/** |
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* try_grab_page() - elevate a page's refcount by a flag-dependent amount |
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* |
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* This might not do anything at all, depending on the flags argument. |
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* |
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* "grab" names in this file mean, "look at flags to decide whether to use |
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* FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount. |
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* |
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* @page: pointer to page to be grabbed |
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* @flags: gup flags: these are the FOLL_* flag values. |
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* |
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* Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same |
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* time. Cases: please see the try_grab_compound_head() documentation, with |
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* "refs=1". |
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* |
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* Return: true for success, or if no action was required (if neither FOLL_PIN |
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* nor FOLL_GET was set, nothing is done). False for failure: FOLL_GET or |
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* FOLL_PIN was set, but the page could not be grabbed. |
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*/ |
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bool __must_check try_grab_page(struct page *page, unsigned int flags) |
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{ |
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if (!(flags & (FOLL_GET | FOLL_PIN))) |
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return true; |
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|
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return try_grab_compound_head(page, 1, flags); |
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} |
|
|
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/** |
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* unpin_user_page() - release a dma-pinned page |
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* @page: pointer to page to be released |
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* |
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* Pages that were pinned via pin_user_pages*() must be released via either |
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* unpin_user_page(), or one of the unpin_user_pages*() routines. This is so |
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* that such pages can be separately tracked and uniquely handled. In |
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* particular, interactions with RDMA and filesystems need special handling. |
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*/ |
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void unpin_user_page(struct page *page) |
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{ |
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put_compound_head(compound_head(page), 1, FOLL_PIN); |
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} |
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EXPORT_SYMBOL(unpin_user_page); |
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|
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static inline void compound_range_next(unsigned long i, unsigned long npages, |
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struct page **list, struct page **head, |
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unsigned int *ntails) |
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{ |
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struct page *next, *page; |
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unsigned int nr = 1; |
|
|
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if (i >= npages) |
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return; |
|
|
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next = *list + i; |
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page = compound_head(next); |
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if (PageCompound(page) && compound_order(page) >= 1) |
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nr = min_t(unsigned int, |
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page + compound_nr(page) - next, npages - i); |
|
|
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*head = page; |
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*ntails = nr; |
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} |
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|
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#define for_each_compound_range(__i, __list, __npages, __head, __ntails) \ |
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for (__i = 0, \ |
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compound_range_next(__i, __npages, __list, &(__head), &(__ntails)); \ |
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__i < __npages; __i += __ntails, \ |
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compound_range_next(__i, __npages, __list, &(__head), &(__ntails))) |
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|
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static inline void compound_next(unsigned long i, unsigned long npages, |
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struct page **list, struct page **head, |
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unsigned int *ntails) |
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{ |
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struct page *page; |
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unsigned int nr; |
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|
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if (i >= npages) |
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return; |
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|
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page = compound_head(list[i]); |
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for (nr = i + 1; nr < npages; nr++) { |
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if (compound_head(list[nr]) != page) |
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break; |
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} |
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|
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*head = page; |
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*ntails = nr - i; |
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} |
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|
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#define for_each_compound_head(__i, __list, __npages, __head, __ntails) \ |
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for (__i = 0, \ |
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compound_next(__i, __npages, __list, &(__head), &(__ntails)); \ |
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__i < __npages; __i += __ntails, \ |
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compound_next(__i, __npages, __list, &(__head), &(__ntails))) |
|
|
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/** |
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* unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages |
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* @pages: array of pages to be maybe marked dirty, and definitely released. |
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* @npages: number of pages in the @pages array. |
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* @make_dirty: whether to mark the pages dirty |
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* |
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* "gup-pinned page" refers to a page that has had one of the get_user_pages() |
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* variants called on that page. |
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* |
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* For each page in the @pages array, make that page (or its head page, if a |
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* compound page) dirty, if @make_dirty is true, and if the page was previously |
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* listed as clean. In any case, releases all pages using unpin_user_page(), |
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* possibly via unpin_user_pages(), for the non-dirty case. |
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* |
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* Please see the unpin_user_page() documentation for details. |
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* |
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* set_page_dirty_lock() is used internally. If instead, set_page_dirty() is |
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* required, then the caller should a) verify that this is really correct, |
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* because _lock() is usually required, and b) hand code it: |
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* set_page_dirty_lock(), unpin_user_page(). |
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* |
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*/ |
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void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, |
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bool make_dirty) |
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{ |
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unsigned long index; |
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struct page *head; |
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unsigned int ntails; |
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|
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if (!make_dirty) { |
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unpin_user_pages(pages, npages); |
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return; |
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} |
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|
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for_each_compound_head(index, pages, npages, head, ntails) { |
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/* |
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* Checking PageDirty at this point may race with |
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* clear_page_dirty_for_io(), but that's OK. Two key |
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* cases: |
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* |
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* 1) This code sees the page as already dirty, so it |
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* skips the call to set_page_dirty(). That could happen |
|
* because clear_page_dirty_for_io() called |
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* page_mkclean(), followed by set_page_dirty(). |
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* However, now the page is going to get written back, |
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* which meets the original intention of setting it |
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* dirty, so all is well: clear_page_dirty_for_io() goes |
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* on to call TestClearPageDirty(), and write the page |
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* back. |
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* |
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* 2) This code sees the page as clean, so it calls |
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* set_page_dirty(). The page stays dirty, despite being |
|
* written back, so it gets written back again in the |
|
* next writeback cycle. This is harmless. |
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*/ |
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if (!PageDirty(head)) |
|
set_page_dirty_lock(head); |
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put_compound_head(head, ntails, FOLL_PIN); |
|
} |
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} |
|
EXPORT_SYMBOL(unpin_user_pages_dirty_lock); |
|
|
|
/** |
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* unpin_user_page_range_dirty_lock() - release and optionally dirty |
|
* gup-pinned page range |
|
* |
|
* @page: the starting page of a range maybe marked dirty, and definitely released. |
|
* @npages: number of consecutive pages to release. |
|
* @make_dirty: whether to mark the pages dirty |
|
* |
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* "gup-pinned page range" refers to a range of pages that has had one of the |
|
* pin_user_pages() variants called on that page. |
|
* |
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* For the page ranges defined by [page .. page+npages], make that range (or |
|
* its head pages, if a compound page) dirty, if @make_dirty is true, and if the |
|
* page range was previously listed as clean. |
|
* |
|
* set_page_dirty_lock() is used internally. If instead, set_page_dirty() is |
|
* required, then the caller should a) verify that this is really correct, |
|
* because _lock() is usually required, and b) hand code it: |
|
* set_page_dirty_lock(), unpin_user_page(). |
|
* |
|
*/ |
|
void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages, |
|
bool make_dirty) |
|
{ |
|
unsigned long index; |
|
struct page *head; |
|
unsigned int ntails; |
|
|
|
for_each_compound_range(index, &page, npages, head, ntails) { |
|
if (make_dirty && !PageDirty(head)) |
|
set_page_dirty_lock(head); |
|
put_compound_head(head, ntails, FOLL_PIN); |
|
} |
|
} |
|
EXPORT_SYMBOL(unpin_user_page_range_dirty_lock); |
|
|
|
/** |
|
* unpin_user_pages() - release an array of gup-pinned pages. |
|
* @pages: array of pages to be marked dirty and released. |
|
* @npages: number of pages in the @pages array. |
|
* |
|
* For each page in the @pages array, release the page using unpin_user_page(). |
|
* |
|
* Please see the unpin_user_page() documentation for details. |
|
*/ |
|
void unpin_user_pages(struct page **pages, unsigned long npages) |
|
{ |
|
unsigned long index; |
|
struct page *head; |
|
unsigned int ntails; |
|
|
|
/* |
|
* If this WARN_ON() fires, then the system *might* be leaking pages (by |
|
* leaving them pinned), but probably not. More likely, gup/pup returned |
|
* a hard -ERRNO error to the caller, who erroneously passed it here. |
|
*/ |
|
if (WARN_ON(IS_ERR_VALUE(npages))) |
|
return; |
|
|
|
for_each_compound_head(index, pages, npages, head, ntails) |
|
put_compound_head(head, ntails, FOLL_PIN); |
|
} |
|
EXPORT_SYMBOL(unpin_user_pages); |
|
|
|
/* |
|
* Set the MMF_HAS_PINNED if not set yet; after set it'll be there for the mm's |
|
* lifecycle. Avoid setting the bit unless necessary, or it might cause write |
|
* cache bouncing on large SMP machines for concurrent pinned gups. |
|
*/ |
|
static inline void mm_set_has_pinned_flag(unsigned long *mm_flags) |
|
{ |
|
if (!test_bit(MMF_HAS_PINNED, mm_flags)) |
|
set_bit(MMF_HAS_PINNED, mm_flags); |
|
} |
|
|
|
#ifdef CONFIG_MMU |
|
static struct page *no_page_table(struct vm_area_struct *vma, |
|
unsigned int flags) |
|
{ |
|
/* |
|
* When core dumping an enormous anonymous area that nobody |
|
* has touched so far, we don't want to allocate unnecessary pages or |
|
* page tables. Return error instead of NULL to skip handle_mm_fault, |
|
* then get_dump_page() will return NULL to leave a hole in the dump. |
|
* But we can only make this optimization where a hole would surely |
|
* be zero-filled if handle_mm_fault() actually did handle it. |
|
*/ |
|
if ((flags & FOLL_DUMP) && |
|
(vma_is_anonymous(vma) || !vma->vm_ops->fault)) |
|
return ERR_PTR(-EFAULT); |
|
return NULL; |
|
} |
|
|
|
static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, |
|
pte_t *pte, unsigned int flags) |
|
{ |
|
/* No page to get reference */ |
|
if (flags & FOLL_GET) |
|
return -EFAULT; |
|
|
|
if (flags & FOLL_TOUCH) { |
|
pte_t entry = *pte; |
|
|
|
if (flags & FOLL_WRITE) |
|
entry = pte_mkdirty(entry); |
|
entry = pte_mkyoung(entry); |
|
|
|
if (!pte_same(*pte, entry)) { |
|
set_pte_at(vma->vm_mm, address, pte, entry); |
|
update_mmu_cache(vma, address, pte); |
|
} |
|
} |
|
|
|
/* Proper page table entry exists, but no corresponding struct page */ |
|
return -EEXIST; |
|
} |
|
|
|
/* |
|
* FOLL_FORCE can write to even unwritable pte's, but only |
|
* after we've gone through a COW cycle and they are dirty. |
|
*/ |
|
static inline bool can_follow_write_pte(pte_t pte, unsigned int flags) |
|
{ |
|
return pte_write(pte) || |
|
((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte)); |
|
} |
|
|
|
static struct page *follow_page_pte(struct vm_area_struct *vma, |
|
unsigned long address, pmd_t *pmd, unsigned int flags, |
|
struct dev_pagemap **pgmap) |
|
{ |
|
struct mm_struct *mm = vma->vm_mm; |
|
struct page *page; |
|
spinlock_t *ptl; |
|
pte_t *ptep, pte; |
|
int ret; |
|
|
|
/* FOLL_GET and FOLL_PIN are mutually exclusive. */ |
|
if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == |
|
(FOLL_PIN | FOLL_GET))) |
|
return ERR_PTR(-EINVAL); |
|
retry: |
|
if (unlikely(pmd_bad(*pmd))) |
|
return no_page_table(vma, flags); |
|
|
|
ptep = pte_offset_map_lock(mm, pmd, address, &ptl); |
|
pte = *ptep; |
|
if (!pte_present(pte)) { |
|
swp_entry_t entry; |
|
/* |
|
* KSM's break_ksm() relies upon recognizing a ksm page |
|
* even while it is being migrated, so for that case we |
|
* need migration_entry_wait(). |
|
*/ |
|
if (likely(!(flags & FOLL_MIGRATION))) |
|
goto no_page; |
|
if (pte_none(pte)) |
|
goto no_page; |
|
entry = pte_to_swp_entry(pte); |
|
if (!is_migration_entry(entry)) |
|
goto no_page; |
|
pte_unmap_unlock(ptep, ptl); |
|
migration_entry_wait(mm, pmd, address); |
|
goto retry; |
|
} |
|
if ((flags & FOLL_NUMA) && pte_protnone(pte)) |
|
goto no_page; |
|
if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) { |
|
pte_unmap_unlock(ptep, ptl); |
|
return NULL; |
|
} |
|
|
|
page = vm_normal_page(vma, address, pte); |
|
if (!page && pte_devmap(pte) && (flags & (FOLL_GET | FOLL_PIN))) { |
|
/* |
|
* Only return device mapping pages in the FOLL_GET or FOLL_PIN |
|
* case since they are only valid while holding the pgmap |
|
* reference. |
|
*/ |
|
*pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap); |
|
if (*pgmap) |
|
page = pte_page(pte); |
|
else |
|
goto no_page; |
|
} else if (unlikely(!page)) { |
|
if (flags & FOLL_DUMP) { |
|
/* Avoid special (like zero) pages in core dumps */ |
|
page = ERR_PTR(-EFAULT); |
|
goto out; |
|
} |
|
|
|
if (is_zero_pfn(pte_pfn(pte))) { |
|
page = pte_page(pte); |
|
} else { |
|
ret = follow_pfn_pte(vma, address, ptep, flags); |
|
page = ERR_PTR(ret); |
|
goto out; |
|
} |
|
} |
|
|
|
/* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */ |
|
if (unlikely(!try_grab_page(page, flags))) { |
|
page = ERR_PTR(-ENOMEM); |
|
goto out; |
|
} |
|
/* |
|
* We need to make the page accessible if and only if we are going |
|
* to access its content (the FOLL_PIN case). Please see |
|
* Documentation/core-api/pin_user_pages.rst for details. |
|
*/ |
|
if (flags & FOLL_PIN) { |
|
ret = arch_make_page_accessible(page); |
|
if (ret) { |
|
unpin_user_page(page); |
|
page = ERR_PTR(ret); |
|
goto out; |
|
} |
|
} |
|
if (flags & FOLL_TOUCH) { |
|
if ((flags & FOLL_WRITE) && |
|
!pte_dirty(pte) && !PageDirty(page)) |
|
set_page_dirty(page); |
|
/* |
|
* pte_mkyoung() would be more correct here, but atomic care |
|
* is needed to avoid losing the dirty bit: it is easier to use |
|
* mark_page_accessed(). |
|
*/ |
|
mark_page_accessed(page); |
|
} |
|
if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { |
|
/* Do not mlock pte-mapped THP */ |
|
if (PageTransCompound(page)) |
|
goto out; |
|
|
|
/* |
|
* The preliminary mapping check is mainly to avoid the |
|
* pointless overhead of lock_page on the ZERO_PAGE |
|
* which might bounce very badly if there is contention. |
|
* |
|
* If the page is already locked, we don't need to |
|
* handle it now - vmscan will handle it later if and |
|
* when it attempts to reclaim the page. |
|
*/ |
|
if (page->mapping && trylock_page(page)) { |
|
lru_add_drain(); /* push cached pages to LRU */ |
|
/* |
|
* Because we lock page here, and migration is |
|
* blocked by the pte's page reference, and we |
|
* know the page is still mapped, we don't even |
|
* need to check for file-cache page truncation. |
|
*/ |
|
mlock_vma_page(page); |
|
unlock_page(page); |
|
} |
|
} |
|
out: |
|
pte_unmap_unlock(ptep, ptl); |
|
return page; |
|
no_page: |
|
pte_unmap_unlock(ptep, ptl); |
|
if (!pte_none(pte)) |
|
return NULL; |
|
return no_page_table(vma, flags); |
|
} |
|
|
|
static struct page *follow_pmd_mask(struct vm_area_struct *vma, |
|
unsigned long address, pud_t *pudp, |
|
unsigned int flags, |
|
struct follow_page_context *ctx) |
|
{ |
|
pmd_t *pmd, pmdval; |
|
spinlock_t *ptl; |
|
struct page *page; |
|
struct mm_struct *mm = vma->vm_mm; |
|
|
|
pmd = pmd_offset(pudp, address); |
|
/* |
|
* The READ_ONCE() will stabilize the pmdval in a register or |
|
* on the stack so that it will stop changing under the code. |
|
*/ |
|
pmdval = READ_ONCE(*pmd); |
|
if (pmd_none(pmdval)) |
|
return no_page_table(vma, flags); |
|
if (pmd_huge(pmdval) && is_vm_hugetlb_page(vma)) { |
|
page = follow_huge_pmd(mm, address, pmd, flags); |
|
if (page) |
|
return page; |
|
return no_page_table(vma, flags); |
|
} |
|
if (is_hugepd(__hugepd(pmd_val(pmdval)))) { |
|
page = follow_huge_pd(vma, address, |
|
__hugepd(pmd_val(pmdval)), flags, |
|
PMD_SHIFT); |
|
if (page) |
|
return page; |
|
return no_page_table(vma, flags); |
|
} |
|
retry: |
|
if (!pmd_present(pmdval)) { |
|
if (likely(!(flags & FOLL_MIGRATION))) |
|
return no_page_table(vma, flags); |
|
VM_BUG_ON(thp_migration_supported() && |
|
!is_pmd_migration_entry(pmdval)); |
|
if (is_pmd_migration_entry(pmdval)) |
|
pmd_migration_entry_wait(mm, pmd); |
|
pmdval = READ_ONCE(*pmd); |
|
/* |
|
* MADV_DONTNEED may convert the pmd to null because |
|
* mmap_lock is held in read mode |
|
*/ |
|
if (pmd_none(pmdval)) |
|
return no_page_table(vma, flags); |
|
goto retry; |
|
} |
|
if (pmd_devmap(pmdval)) { |
|
ptl = pmd_lock(mm, pmd); |
|
page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap); |
|
spin_unlock(ptl); |
|
if (page) |
|
return page; |
|
} |
|
if (likely(!pmd_trans_huge(pmdval))) |
|
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); |
|
|
|
if ((flags & FOLL_NUMA) && pmd_protnone(pmdval)) |
|
return no_page_table(vma, flags); |
|
|
|
retry_locked: |
|
ptl = pmd_lock(mm, pmd); |
|
if (unlikely(pmd_none(*pmd))) { |
|
spin_unlock(ptl); |
|
return no_page_table(vma, flags); |
|
} |
|
if (unlikely(!pmd_present(*pmd))) { |
|
spin_unlock(ptl); |
|
if (likely(!(flags & FOLL_MIGRATION))) |
|
return no_page_table(vma, flags); |
|
pmd_migration_entry_wait(mm, pmd); |
|
goto retry_locked; |
|
} |
|
if (unlikely(!pmd_trans_huge(*pmd))) { |
|
spin_unlock(ptl); |
|
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); |
|
} |
|
if (flags & FOLL_SPLIT_PMD) { |
|
int ret; |
|
page = pmd_page(*pmd); |
|
if (is_huge_zero_page(page)) { |
|
spin_unlock(ptl); |
|
ret = 0; |
|
split_huge_pmd(vma, pmd, address); |
|
if (pmd_trans_unstable(pmd)) |
|
ret = -EBUSY; |
|
} else { |
|
spin_unlock(ptl); |
|
split_huge_pmd(vma, pmd, address); |
|
ret = pte_alloc(mm, pmd) ? -ENOMEM : 0; |
|
} |
|
|
|
return ret ? ERR_PTR(ret) : |
|
follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); |
|
} |
|
page = follow_trans_huge_pmd(vma, address, pmd, flags); |
|
spin_unlock(ptl); |
|
ctx->page_mask = HPAGE_PMD_NR - 1; |
|
return page; |
|
} |
|
|
|
static struct page *follow_pud_mask(struct vm_area_struct *vma, |
|
unsigned long address, p4d_t *p4dp, |
|
unsigned int flags, |
|
struct follow_page_context *ctx) |
|
{ |
|
pud_t *pud; |
|
spinlock_t *ptl; |
|
struct page *page; |
|
struct mm_struct *mm = vma->vm_mm; |
|
|
|
pud = pud_offset(p4dp, address); |
|
if (pud_none(*pud)) |
|
return no_page_table(vma, flags); |
|
if (pud_huge(*pud) && is_vm_hugetlb_page(vma)) { |
|
page = follow_huge_pud(mm, address, pud, flags); |
|
if (page) |
|
return page; |
|
return no_page_table(vma, flags); |
|
} |
|
if (is_hugepd(__hugepd(pud_val(*pud)))) { |
|
page = follow_huge_pd(vma, address, |
|
__hugepd(pud_val(*pud)), flags, |
|
PUD_SHIFT); |
|
if (page) |
|
return page; |
|
return no_page_table(vma, flags); |
|
} |
|
if (pud_devmap(*pud)) { |
|
ptl = pud_lock(mm, pud); |
|
page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap); |
|
spin_unlock(ptl); |
|
if (page) |
|
return page; |
|
} |
|
if (unlikely(pud_bad(*pud))) |
|
return no_page_table(vma, flags); |
|
|
|
return follow_pmd_mask(vma, address, pud, flags, ctx); |
|
} |
|
|
|
static struct page *follow_p4d_mask(struct vm_area_struct *vma, |
|
unsigned long address, pgd_t *pgdp, |
|
unsigned int flags, |
|
struct follow_page_context *ctx) |
|
{ |
|
p4d_t *p4d; |
|
struct page *page; |
|
|
|
p4d = p4d_offset(pgdp, address); |
|
if (p4d_none(*p4d)) |
|
return no_page_table(vma, flags); |
|
BUILD_BUG_ON(p4d_huge(*p4d)); |
|
if (unlikely(p4d_bad(*p4d))) |
|
return no_page_table(vma, flags); |
|
|
|
if (is_hugepd(__hugepd(p4d_val(*p4d)))) { |
|
page = follow_huge_pd(vma, address, |
|
__hugepd(p4d_val(*p4d)), flags, |
|
P4D_SHIFT); |
|
if (page) |
|
return page; |
|
return no_page_table(vma, flags); |
|
} |
|
return follow_pud_mask(vma, address, p4d, flags, ctx); |
|
} |
|
|
|
/** |
|
* follow_page_mask - look up a page descriptor from a user-virtual address |
|
* @vma: vm_area_struct mapping @address |
|
* @address: virtual address to look up |
|
* @flags: flags modifying lookup behaviour |
|
* @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a |
|
* pointer to output page_mask |
|
* |
|
* @flags can have FOLL_ flags set, defined in <linux/mm.h> |
|
* |
|
* When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches |
|
* the device's dev_pagemap metadata to avoid repeating expensive lookups. |
|
* |
|
* On output, the @ctx->page_mask is set according to the size of the page. |
|
* |
|
* Return: the mapped (struct page *), %NULL if no mapping exists, or |
|
* an error pointer if there is a mapping to something not represented |
|
* by a page descriptor (see also vm_normal_page()). |
|
*/ |
|
static struct page *follow_page_mask(struct vm_area_struct *vma, |
|
unsigned long address, unsigned int flags, |
|
struct follow_page_context *ctx) |
|
{ |
|
pgd_t *pgd; |
|
struct page *page; |
|
struct mm_struct *mm = vma->vm_mm; |
|
|
|
ctx->page_mask = 0; |
|
|
|
/* make this handle hugepd */ |
|
page = follow_huge_addr(mm, address, flags & FOLL_WRITE); |
|
if (!IS_ERR(page)) { |
|
WARN_ON_ONCE(flags & (FOLL_GET | FOLL_PIN)); |
|
return page; |
|
} |
|
|
|
pgd = pgd_offset(mm, address); |
|
|
|
if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd))) |
|
return no_page_table(vma, flags); |
|
|
|
if (pgd_huge(*pgd)) { |
|
page = follow_huge_pgd(mm, address, pgd, flags); |
|
if (page) |
|
return page; |
|
return no_page_table(vma, flags); |
|
} |
|
if (is_hugepd(__hugepd(pgd_val(*pgd)))) { |
|
page = follow_huge_pd(vma, address, |
|
__hugepd(pgd_val(*pgd)), flags, |
|
PGDIR_SHIFT); |
|
if (page) |
|
return page; |
|
return no_page_table(vma, flags); |
|
} |
|
|
|
return follow_p4d_mask(vma, address, pgd, flags, ctx); |
|
} |
|
|
|
struct page *follow_page(struct vm_area_struct *vma, unsigned long address, |
|
unsigned int foll_flags) |
|
{ |
|
struct follow_page_context ctx = { NULL }; |
|
struct page *page; |
|
|
|
if (vma_is_secretmem(vma)) |
|
return NULL; |
|
|
|
page = follow_page_mask(vma, address, foll_flags, &ctx); |
|
if (ctx.pgmap) |
|
put_dev_pagemap(ctx.pgmap); |
|
return page; |
|
} |
|
|
|
static int get_gate_page(struct mm_struct *mm, unsigned long address, |
|
unsigned int gup_flags, struct vm_area_struct **vma, |
|
struct page **page) |
|
{ |
|
pgd_t *pgd; |
|
p4d_t *p4d; |
|
pud_t *pud; |
|
pmd_t *pmd; |
|
pte_t *pte; |
|
int ret = -EFAULT; |
|
|
|
/* user gate pages are read-only */ |
|
if (gup_flags & FOLL_WRITE) |
|
return -EFAULT; |
|
if (address > TASK_SIZE) |
|
pgd = pgd_offset_k(address); |
|
else |
|
pgd = pgd_offset_gate(mm, address); |
|
if (pgd_none(*pgd)) |
|
return -EFAULT; |
|
p4d = p4d_offset(pgd, address); |
|
if (p4d_none(*p4d)) |
|
return -EFAULT; |
|
pud = pud_offset(p4d, address); |
|
if (pud_none(*pud)) |
|
return -EFAULT; |
|
pmd = pmd_offset(pud, address); |
|
if (!pmd_present(*pmd)) |
|
return -EFAULT; |
|
VM_BUG_ON(pmd_trans_huge(*pmd)); |
|
pte = pte_offset_map(pmd, address); |
|
if (pte_none(*pte)) |
|
goto unmap; |
|
*vma = get_gate_vma(mm); |
|
if (!page) |
|
goto out; |
|
*page = vm_normal_page(*vma, address, *pte); |
|
if (!*page) { |
|
if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte))) |
|
goto unmap; |
|
*page = pte_page(*pte); |
|
} |
|
if (unlikely(!try_grab_page(*page, gup_flags))) { |
|
ret = -ENOMEM; |
|
goto unmap; |
|
} |
|
out: |
|
ret = 0; |
|
unmap: |
|
pte_unmap(pte); |
|
return ret; |
|
} |
|
|
|
/* |
|
* mmap_lock must be held on entry. If @locked != NULL and *@flags |
|
* does not include FOLL_NOWAIT, the mmap_lock may be released. If it |
|
* is, *@locked will be set to 0 and -EBUSY returned. |
|
*/ |
|
static int faultin_page(struct vm_area_struct *vma, |
|
unsigned long address, unsigned int *flags, int *locked) |
|
{ |
|
unsigned int fault_flags = 0; |
|
vm_fault_t ret; |
|
|
|
/* mlock all present pages, but do not fault in new pages */ |
|
if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK) |
|
return -ENOENT; |
|
if (*flags & FOLL_WRITE) |
|
fault_flags |= FAULT_FLAG_WRITE; |
|
if (*flags & FOLL_REMOTE) |
|
fault_flags |= FAULT_FLAG_REMOTE; |
|
if (locked) |
|
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; |
|
if (*flags & FOLL_NOWAIT) |
|
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT; |
|
if (*flags & FOLL_TRIED) { |
|
/* |
|
* Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED |
|
* can co-exist |
|
*/ |
|
fault_flags |= FAULT_FLAG_TRIED; |
|
} |
|
|
|
ret = handle_mm_fault(vma, address, fault_flags, NULL); |
|
if (ret & VM_FAULT_ERROR) { |
|
int err = vm_fault_to_errno(ret, *flags); |
|
|
|
if (err) |
|
return err; |
|
BUG(); |
|
} |
|
|
|
if (ret & VM_FAULT_RETRY) { |
|
if (locked && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) |
|
*locked = 0; |
|
return -EBUSY; |
|
} |
|
|
|
/* |
|
* The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when |
|
* necessary, even if maybe_mkwrite decided not to set pte_write. We |
|
* can thus safely do subsequent page lookups as if they were reads. |
|
* But only do so when looping for pte_write is futile: in some cases |
|
* userspace may also be wanting to write to the gotten user page, |
|
* which a read fault here might prevent (a readonly page might get |
|
* reCOWed by userspace write). |
|
*/ |
|
if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE)) |
|
*flags |= FOLL_COW; |
|
return 0; |
|
} |
|
|
|
static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) |
|
{ |
|
vm_flags_t vm_flags = vma->vm_flags; |
|
int write = (gup_flags & FOLL_WRITE); |
|
int foreign = (gup_flags & FOLL_REMOTE); |
|
|
|
if (vm_flags & (VM_IO | VM_PFNMAP)) |
|
return -EFAULT; |
|
|
|
if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma)) |
|
return -EFAULT; |
|
|
|
if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma)) |
|
return -EOPNOTSUPP; |
|
|
|
if (vma_is_secretmem(vma)) |
|
return -EFAULT; |
|
|
|
if (write) { |
|
if (!(vm_flags & VM_WRITE)) { |
|
if (!(gup_flags & FOLL_FORCE)) |
|
return -EFAULT; |
|
/* |
|
* We used to let the write,force case do COW in a |
|
* VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could |
|
* set a breakpoint in a read-only mapping of an |
|
* executable, without corrupting the file (yet only |
|
* when that file had been opened for writing!). |
|
* Anon pages in shared mappings are surprising: now |
|
* just reject it. |
|
*/ |
|
if (!is_cow_mapping(vm_flags)) |
|
return -EFAULT; |
|
} |
|
} else if (!(vm_flags & VM_READ)) { |
|
if (!(gup_flags & FOLL_FORCE)) |
|
return -EFAULT; |
|
/* |
|
* Is there actually any vma we can reach here which does not |
|
* have VM_MAYREAD set? |
|
*/ |
|
if (!(vm_flags & VM_MAYREAD)) |
|
return -EFAULT; |
|
} |
|
/* |
|
* gups are always data accesses, not instruction |
|
* fetches, so execute=false here |
|
*/ |
|
if (!arch_vma_access_permitted(vma, write, false, foreign)) |
|
return -EFAULT; |
|
return 0; |
|
} |
|
|
|
/** |
|
* __get_user_pages() - pin user pages in memory |
|
* @mm: mm_struct of target mm |
|
* @start: starting user address |
|
* @nr_pages: number of pages from start to pin |
|
* @gup_flags: flags modifying pin behaviour |
|
* @pages: array that receives pointers to the pages pinned. |
|
* Should be at least nr_pages long. Or NULL, if caller |
|
* only intends to ensure the pages are faulted in. |
|
* @vmas: array of pointers to vmas corresponding to each page. |
|
* Or NULL if the caller does not require them. |
|
* @locked: whether we're still with the mmap_lock held |
|
* |
|
* Returns either number of pages pinned (which may be less than the |
|
* number requested), or an error. Details about the return value: |
|
* |
|
* -- If nr_pages is 0, returns 0. |
|
* -- If nr_pages is >0, but no pages were pinned, returns -errno. |
|
* -- If nr_pages is >0, and some pages were pinned, returns the number of |
|
* pages pinned. Again, this may be less than nr_pages. |
|
* -- 0 return value is possible when the fault would need to be retried. |
|
* |
|
* The caller is responsible for releasing returned @pages, via put_page(). |
|
* |
|
* @vmas are valid only as long as mmap_lock is held. |
|
* |
|
* Must be called with mmap_lock held. It may be released. See below. |
|
* |
|
* __get_user_pages walks a process's page tables and takes a reference to |
|
* each struct page that each user address corresponds to at a given |
|
* instant. That is, it takes the page that would be accessed if a user |
|
* thread accesses the given user virtual address at that instant. |
|
* |
|
* This does not guarantee that the page exists in the user mappings when |
|
* __get_user_pages returns, and there may even be a completely different |
|
* page there in some cases (eg. if mmapped pagecache has been invalidated |
|
* and subsequently re faulted). However it does guarantee that the page |
|
* won't be freed completely. And mostly callers simply care that the page |
|
* contains data that was valid *at some point in time*. Typically, an IO |
|
* or similar operation cannot guarantee anything stronger anyway because |
|
* locks can't be held over the syscall boundary. |
|
* |
|
* If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If |
|
* the page is written to, set_page_dirty (or set_page_dirty_lock, as |
|
* appropriate) must be called after the page is finished with, and |
|
* before put_page is called. |
|
* |
|
* If @locked != NULL, *@locked will be set to 0 when mmap_lock is |
|
* released by an up_read(). That can happen if @gup_flags does not |
|
* have FOLL_NOWAIT. |
|
* |
|
* A caller using such a combination of @locked and @gup_flags |
|
* must therefore hold the mmap_lock for reading only, and recognize |
|
* when it's been released. Otherwise, it must be held for either |
|
* reading or writing and will not be released. |
|
* |
|
* In most cases, get_user_pages or get_user_pages_fast should be used |
|
* instead of __get_user_pages. __get_user_pages should be used only if |
|
* you need some special @gup_flags. |
|
*/ |
|
static long __get_user_pages(struct mm_struct *mm, |
|
unsigned long start, unsigned long nr_pages, |
|
unsigned int gup_flags, struct page **pages, |
|
struct vm_area_struct **vmas, int *locked) |
|
{ |
|
long ret = 0, i = 0; |
|
struct vm_area_struct *vma = NULL; |
|
struct follow_page_context ctx = { NULL }; |
|
|
|
if (!nr_pages) |
|
return 0; |
|
|
|
start = untagged_addr(start); |
|
|
|
VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN))); |
|
|
|
/* |
|
* If FOLL_FORCE is set then do not force a full fault as the hinting |
|
* fault information is unrelated to the reference behaviour of a task |
|
* using the address space |
|
*/ |
|
if (!(gup_flags & FOLL_FORCE)) |
|
gup_flags |= FOLL_NUMA; |
|
|
|
do { |
|
struct page *page; |
|
unsigned int foll_flags = gup_flags; |
|
unsigned int page_increm; |
|
|
|
/* first iteration or cross vma bound */ |
|
if (!vma || start >= vma->vm_end) { |
|
vma = find_extend_vma(mm, start); |
|
if (!vma && in_gate_area(mm, start)) { |
|
ret = get_gate_page(mm, start & PAGE_MASK, |
|
gup_flags, &vma, |
|
pages ? &pages[i] : NULL); |
|
if (ret) |
|
goto out; |
|
ctx.page_mask = 0; |
|
goto next_page; |
|
} |
|
|
|
if (!vma) { |
|
ret = -EFAULT; |
|
goto out; |
|
} |
|
ret = check_vma_flags(vma, gup_flags); |
|
if (ret) |
|
goto out; |
|
|
|
if (is_vm_hugetlb_page(vma)) { |
|
i = follow_hugetlb_page(mm, vma, pages, vmas, |
|
&start, &nr_pages, i, |
|
gup_flags, locked); |
|
if (locked && *locked == 0) { |
|
/* |
|
* We've got a VM_FAULT_RETRY |
|
* and we've lost mmap_lock. |
|
* We must stop here. |
|
*/ |
|
BUG_ON(gup_flags & FOLL_NOWAIT); |
|
goto out; |
|
} |
|
continue; |
|
} |
|
} |
|
retry: |
|
/* |
|
* If we have a pending SIGKILL, don't keep faulting pages and |
|
* potentially allocating memory. |
|
*/ |
|
if (fatal_signal_pending(current)) { |
|
ret = -EINTR; |
|
goto out; |
|
} |
|
cond_resched(); |
|
|
|
page = follow_page_mask(vma, start, foll_flags, &ctx); |
|
if (!page) { |
|
ret = faultin_page(vma, start, &foll_flags, locked); |
|
switch (ret) { |
|
case 0: |
|
goto retry; |
|
case -EBUSY: |
|
ret = 0; |
|
fallthrough; |
|
case -EFAULT: |
|
case -ENOMEM: |
|
case -EHWPOISON: |
|
goto out; |
|
case -ENOENT: |
|
goto next_page; |
|
} |
|
BUG(); |
|
} else if (PTR_ERR(page) == -EEXIST) { |
|
/* |
|
* Proper page table entry exists, but no corresponding |
|
* struct page. |
|
*/ |
|
goto next_page; |
|
} else if (IS_ERR(page)) { |
|
ret = PTR_ERR(page); |
|
goto out; |
|
} |
|
if (pages) { |
|
pages[i] = page; |
|
flush_anon_page(vma, page, start); |
|
flush_dcache_page(page); |
|
ctx.page_mask = 0; |
|
} |
|
next_page: |
|
if (vmas) { |
|
vmas[i] = vma; |
|
ctx.page_mask = 0; |
|
} |
|
page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask); |
|
if (page_increm > nr_pages) |
|
page_increm = nr_pages; |
|
i += page_increm; |
|
start += page_increm * PAGE_SIZE; |
|
nr_pages -= page_increm; |
|
} while (nr_pages); |
|
out: |
|
if (ctx.pgmap) |
|
put_dev_pagemap(ctx.pgmap); |
|
return i ? i : ret; |
|
} |
|
|
|
static bool vma_permits_fault(struct vm_area_struct *vma, |
|
unsigned int fault_flags) |
|
{ |
|
bool write = !!(fault_flags & FAULT_FLAG_WRITE); |
|
bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE); |
|
vm_flags_t vm_flags = write ? VM_WRITE : VM_READ; |
|
|
|
if (!(vm_flags & vma->vm_flags)) |
|
return false; |
|
|
|
/* |
|
* The architecture might have a hardware protection |
|
* mechanism other than read/write that can deny access. |
|
* |
|
* gup always represents data access, not instruction |
|
* fetches, so execute=false here: |
|
*/ |
|
if (!arch_vma_access_permitted(vma, write, false, foreign)) |
|
return false; |
|
|
|
return true; |
|
} |
|
|
|
/** |
|
* fixup_user_fault() - manually resolve a user page fault |
|
* @mm: mm_struct of target mm |
|
* @address: user address |
|
* @fault_flags:flags to pass down to handle_mm_fault() |
|
* @unlocked: did we unlock the mmap_lock while retrying, maybe NULL if caller |
|
* does not allow retry. If NULL, the caller must guarantee |
|
* that fault_flags does not contain FAULT_FLAG_ALLOW_RETRY. |
|
* |
|
* This is meant to be called in the specific scenario where for locking reasons |
|
* we try to access user memory in atomic context (within a pagefault_disable() |
|
* section), this returns -EFAULT, and we want to resolve the user fault before |
|
* trying again. |
|
* |
|
* Typically this is meant to be used by the futex code. |
|
* |
|
* The main difference with get_user_pages() is that this function will |
|
* unconditionally call handle_mm_fault() which will in turn perform all the |
|
* necessary SW fixup of the dirty and young bits in the PTE, while |
|
* get_user_pages() only guarantees to update these in the struct page. |
|
* |
|
* This is important for some architectures where those bits also gate the |
|
* access permission to the page because they are maintained in software. On |
|
* such architectures, gup() will not be enough to make a subsequent access |
|
* succeed. |
|
* |
|
* This function will not return with an unlocked mmap_lock. So it has not the |
|
* same semantics wrt the @mm->mmap_lock as does filemap_fault(). |
|
*/ |
|
int fixup_user_fault(struct mm_struct *mm, |
|
unsigned long address, unsigned int fault_flags, |
|
bool *unlocked) |
|
{ |
|
struct vm_area_struct *vma; |
|
vm_fault_t ret; |
|
|
|
address = untagged_addr(address); |
|
|
|
if (unlocked) |
|
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; |
|
|
|
retry: |
|
vma = find_extend_vma(mm, address); |
|
if (!vma || address < vma->vm_start) |
|
return -EFAULT; |
|
|
|
if (!vma_permits_fault(vma, fault_flags)) |
|
return -EFAULT; |
|
|
|
if ((fault_flags & FAULT_FLAG_KILLABLE) && |
|
fatal_signal_pending(current)) |
|
return -EINTR; |
|
|
|
ret = handle_mm_fault(vma, address, fault_flags, NULL); |
|
if (ret & VM_FAULT_ERROR) { |
|
int err = vm_fault_to_errno(ret, 0); |
|
|
|
if (err) |
|
return err; |
|
BUG(); |
|
} |
|
|
|
if (ret & VM_FAULT_RETRY) { |
|
mmap_read_lock(mm); |
|
*unlocked = true; |
|
fault_flags |= FAULT_FLAG_TRIED; |
|
goto retry; |
|
} |
|
|
|
return 0; |
|
} |
|
EXPORT_SYMBOL_GPL(fixup_user_fault); |
|
|
|
/* |
|
* Please note that this function, unlike __get_user_pages will not |
|
* return 0 for nr_pages > 0 without FOLL_NOWAIT |
|
*/ |
|
static __always_inline long __get_user_pages_locked(struct mm_struct *mm, |
|
unsigned long start, |
|
unsigned long nr_pages, |
|
struct page **pages, |
|
struct vm_area_struct **vmas, |
|
int *locked, |
|
unsigned int flags) |
|
{ |
|
long ret, pages_done; |
|
bool lock_dropped; |
|
|
|
if (locked) { |
|
/* if VM_FAULT_RETRY can be returned, vmas become invalid */ |
|
BUG_ON(vmas); |
|
/* check caller initialized locked */ |
|
BUG_ON(*locked != 1); |
|
} |
|
|
|
if (flags & FOLL_PIN) |
|
mm_set_has_pinned_flag(&mm->flags); |
|
|
|
/* |
|
* FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior |
|
* is to set FOLL_GET if the caller wants pages[] filled in (but has |
|
* carelessly failed to specify FOLL_GET), so keep doing that, but only |
|
* for FOLL_GET, not for the newer FOLL_PIN. |
|
* |
|
* FOLL_PIN always expects pages to be non-null, but no need to assert |
|
* that here, as any failures will be obvious enough. |
|
*/ |
|
if (pages && !(flags & FOLL_PIN)) |
|
flags |= FOLL_GET; |
|
|
|
pages_done = 0; |
|
lock_dropped = false; |
|
for (;;) { |
|
ret = __get_user_pages(mm, start, nr_pages, flags, pages, |
|
vmas, locked); |
|
if (!locked) |
|
/* VM_FAULT_RETRY couldn't trigger, bypass */ |
|
return ret; |
|
|
|
/* VM_FAULT_RETRY cannot return errors */ |
|
if (!*locked) { |
|
BUG_ON(ret < 0); |
|
BUG_ON(ret >= nr_pages); |
|
} |
|
|
|
if (ret > 0) { |
|
nr_pages -= ret; |
|
pages_done += ret; |
|
if (!nr_pages) |
|
break; |
|
} |
|
if (*locked) { |
|
/* |
|
* VM_FAULT_RETRY didn't trigger or it was a |
|
* FOLL_NOWAIT. |
|
*/ |
|
if (!pages_done) |
|
pages_done = ret; |
|
break; |
|
} |
|
/* |
|
* VM_FAULT_RETRY triggered, so seek to the faulting offset. |
|
* For the prefault case (!pages) we only update counts. |
|
*/ |
|
if (likely(pages)) |
|
pages += ret; |
|
start += ret << PAGE_SHIFT; |
|
lock_dropped = true; |
|
|
|
retry: |
|
/* |
|
* Repeat on the address that fired VM_FAULT_RETRY |
|
* with both FAULT_FLAG_ALLOW_RETRY and |
|
* FAULT_FLAG_TRIED. Note that GUP can be interrupted |
|
* by fatal signals, so we need to check it before we |
|
* start trying again otherwise it can loop forever. |
|
*/ |
|
|
|
if (fatal_signal_pending(current)) { |
|
if (!pages_done) |
|
pages_done = -EINTR; |
|
break; |
|
} |
|
|
|
ret = mmap_read_lock_killable(mm); |
|
if (ret) { |
|
BUG_ON(ret > 0); |
|
if (!pages_done) |
|
pages_done = ret; |
|
break; |
|
} |
|
|
|
*locked = 1; |
|
ret = __get_user_pages(mm, start, 1, flags | FOLL_TRIED, |
|
pages, NULL, locked); |
|
if (!*locked) { |
|
/* Continue to retry until we succeeded */ |
|
BUG_ON(ret != 0); |
|
goto retry; |
|
} |
|
if (ret != 1) { |
|
BUG_ON(ret > 1); |
|
if (!pages_done) |
|
pages_done = ret; |
|
break; |
|
} |
|
nr_pages--; |
|
pages_done++; |
|
if (!nr_pages) |
|
break; |
|
if (likely(pages)) |
|
pages++; |
|
start += PAGE_SIZE; |
|
} |
|
if (lock_dropped && *locked) { |
|
/* |
|
* We must let the caller know we temporarily dropped the lock |
|
* and so the critical section protected by it was lost. |
|
*/ |
|
mmap_read_unlock(mm); |
|
*locked = 0; |
|
} |
|
return pages_done; |
|
} |
|
|
|
/** |
|
* populate_vma_page_range() - populate a range of pages in the vma. |
|
* @vma: target vma |
|
* @start: start address |
|
* @end: end address |
|
* @locked: whether the mmap_lock is still held |
|
* |
|
* This takes care of mlocking the pages too if VM_LOCKED is set. |
|
* |
|
* Return either number of pages pinned in the vma, or a negative error |
|
* code on error. |
|
* |
|
* vma->vm_mm->mmap_lock must be held. |
|
* |
|
* If @locked is NULL, it may be held for read or write and will |
|
* be unperturbed. |
|
* |
|
* If @locked is non-NULL, it must held for read only and may be |
|
* released. If it's released, *@locked will be set to 0. |
|
*/ |
|
long populate_vma_page_range(struct vm_area_struct *vma, |
|
unsigned long start, unsigned long end, int *locked) |
|
{ |
|
struct mm_struct *mm = vma->vm_mm; |
|
unsigned long nr_pages = (end - start) / PAGE_SIZE; |
|
int gup_flags; |
|
|
|
VM_BUG_ON(!PAGE_ALIGNED(start)); |
|
VM_BUG_ON(!PAGE_ALIGNED(end)); |
|
VM_BUG_ON_VMA(start < vma->vm_start, vma); |
|
VM_BUG_ON_VMA(end > vma->vm_end, vma); |
|
mmap_assert_locked(mm); |
|
|
|
gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK; |
|
if (vma->vm_flags & VM_LOCKONFAULT) |
|
gup_flags &= ~FOLL_POPULATE; |
|
/* |
|
* We want to touch writable mappings with a write fault in order |
|
* to break COW, except for shared mappings because these don't COW |
|
* and we would not want to dirty them for nothing. |
|
*/ |
|
if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE) |
|
gup_flags |= FOLL_WRITE; |
|
|
|
/* |
|
* We want mlock to succeed for regions that have any permissions |
|
* other than PROT_NONE. |
|
*/ |
|
if (vma_is_accessible(vma)) |
|
gup_flags |= FOLL_FORCE; |
|
|
|
/* |
|
* We made sure addr is within a VMA, so the following will |
|
* not result in a stack expansion that recurses back here. |
|
*/ |
|
return __get_user_pages(mm, start, nr_pages, gup_flags, |
|
NULL, NULL, locked); |
|
} |
|
|
|
/* |
|
* faultin_vma_page_range() - populate (prefault) page tables inside the |
|
* given VMA range readable/writable |
|
* |
|
* This takes care of mlocking the pages, too, if VM_LOCKED is set. |
|
* |
|
* @vma: target vma |
|
* @start: start address |
|
* @end: end address |
|
* @write: whether to prefault readable or writable |
|
* @locked: whether the mmap_lock is still held |
|
* |
|
* Returns either number of processed pages in the vma, or a negative error |
|
* code on error (see __get_user_pages()). |
|
* |
|
* vma->vm_mm->mmap_lock must be held. The range must be page-aligned and |
|
* covered by the VMA. |
|
* |
|
* If @locked is NULL, it may be held for read or write and will be unperturbed. |
|
* |
|
* If @locked is non-NULL, it must held for read only and may be released. If |
|
* it's released, *@locked will be set to 0. |
|
*/ |
|
long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start, |
|
unsigned long end, bool write, int *locked) |
|
{ |
|
struct mm_struct *mm = vma->vm_mm; |
|
unsigned long nr_pages = (end - start) / PAGE_SIZE; |
|
int gup_flags; |
|
|
|
VM_BUG_ON(!PAGE_ALIGNED(start)); |
|
VM_BUG_ON(!PAGE_ALIGNED(end)); |
|
VM_BUG_ON_VMA(start < vma->vm_start, vma); |
|
VM_BUG_ON_VMA(end > vma->vm_end, vma); |
|
mmap_assert_locked(mm); |
|
|
|
/* |
|
* FOLL_TOUCH: Mark page accessed and thereby young; will also mark |
|
* the page dirty with FOLL_WRITE -- which doesn't make a |
|
* difference with !FOLL_FORCE, because the page is writable |
|
* in the page table. |
|
* FOLL_HWPOISON: Return -EHWPOISON instead of -EFAULT when we hit |
|
* a poisoned page. |
|
* FOLL_POPULATE: Always populate memory with VM_LOCKONFAULT. |
|
* !FOLL_FORCE: Require proper access permissions. |
|
*/ |
|
gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK | FOLL_HWPOISON; |
|
if (write) |
|
gup_flags |= FOLL_WRITE; |
|
|
|
/* |
|
* We want to report -EINVAL instead of -EFAULT for any permission |
|
* problems or incompatible mappings. |
|
*/ |
|
if (check_vma_flags(vma, gup_flags)) |
|
return -EINVAL; |
|
|
|
return __get_user_pages(mm, start, nr_pages, gup_flags, |
|
NULL, NULL, locked); |
|
} |
|
|
|
/* |
|
* __mm_populate - populate and/or mlock pages within a range of address space. |
|
* |
|
* This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap |
|
* flags. VMAs must be already marked with the desired vm_flags, and |
|
* mmap_lock must not be held. |
|
*/ |
|
int __mm_populate(unsigned long start, unsigned long len, int ignore_errors) |
|
{ |
|
struct mm_struct *mm = current->mm; |
|
unsigned long end, nstart, nend; |
|
struct vm_area_struct *vma = NULL; |
|
int locked = 0; |
|
long ret = 0; |
|
|
|
end = start + len; |
|
|
|
for (nstart = start; nstart < end; nstart = nend) { |
|
/* |
|
* We want to fault in pages for [nstart; end) address range. |
|
* Find first corresponding VMA. |
|
*/ |
|
if (!locked) { |
|
locked = 1; |
|
mmap_read_lock(mm); |
|
vma = find_vma(mm, nstart); |
|
} else if (nstart >= vma->vm_end) |
|
vma = vma->vm_next; |
|
if (!vma || vma->vm_start >= end) |
|
break; |
|
/* |
|
* Set [nstart; nend) to intersection of desired address |
|
* range with the first VMA. Also, skip undesirable VMA types. |
|
*/ |
|
nend = min(end, vma->vm_end); |
|
if (vma->vm_flags & (VM_IO | VM_PFNMAP)) |
|
continue; |
|
if (nstart < vma->vm_start) |
|
nstart = vma->vm_start; |
|
/* |
|
* Now fault in a range of pages. populate_vma_page_range() |
|
* double checks the vma flags, so that it won't mlock pages |
|
* if the vma was already munlocked. |
|
*/ |
|
ret = populate_vma_page_range(vma, nstart, nend, &locked); |
|
if (ret < 0) { |
|
if (ignore_errors) { |
|
ret = 0; |
|
continue; /* continue at next VMA */ |
|
} |
|
break; |
|
} |
|
nend = nstart + ret * PAGE_SIZE; |
|
ret = 0; |
|
} |
|
if (locked) |
|
mmap_read_unlock(mm); |
|
return ret; /* 0 or negative error code */ |
|
} |
|
#else /* CONFIG_MMU */ |
|
static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start, |
|
unsigned long nr_pages, struct page **pages, |
|
struct vm_area_struct **vmas, int *locked, |
|
unsigned int foll_flags) |
|
{ |
|
struct vm_area_struct *vma; |
|
unsigned long vm_flags; |
|
long i; |
|
|
|
/* calculate required read or write permissions. |
|
* If FOLL_FORCE is set, we only require the "MAY" flags. |
|
*/ |
|
vm_flags = (foll_flags & FOLL_WRITE) ? |
|
(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD); |
|
vm_flags &= (foll_flags & FOLL_FORCE) ? |
|
(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE); |
|
|
|
for (i = 0; i < nr_pages; i++) { |
|
vma = find_vma(mm, start); |
|
if (!vma) |
|
goto finish_or_fault; |
|
|
|
/* protect what we can, including chardevs */ |
|
if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) || |
|
!(vm_flags & vma->vm_flags)) |
|
goto finish_or_fault; |
|
|
|
if (pages) { |
|
pages[i] = virt_to_page(start); |
|
if (pages[i]) |
|
get_page(pages[i]); |
|
} |
|
if (vmas) |
|
vmas[i] = vma; |
|
start = (start + PAGE_SIZE) & PAGE_MASK; |
|
} |
|
|
|
return i; |
|
|
|
finish_or_fault: |
|
return i ? : -EFAULT; |
|
} |
|
#endif /* !CONFIG_MMU */ |
|
|
|
/** |
|
* get_dump_page() - pin user page in memory while writing it to core dump |
|
* @addr: user address |
|
* |
|
* Returns struct page pointer of user page pinned for dump, |
|
* to be freed afterwards by put_page(). |
|
* |
|
* Returns NULL on any kind of failure - a hole must then be inserted into |
|
* the corefile, to preserve alignment with its headers; and also returns |
|
* NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found - |
|
* allowing a hole to be left in the corefile to save disk space. |
|
* |
|
* Called without mmap_lock (takes and releases the mmap_lock by itself). |
|
*/ |
|
#ifdef CONFIG_ELF_CORE |
|
struct page *get_dump_page(unsigned long addr) |
|
{ |
|
struct mm_struct *mm = current->mm; |
|
struct page *page; |
|
int locked = 1; |
|
int ret; |
|
|
|
if (mmap_read_lock_killable(mm)) |
|
return NULL; |
|
ret = __get_user_pages_locked(mm, addr, 1, &page, NULL, &locked, |
|
FOLL_FORCE | FOLL_DUMP | FOLL_GET); |
|
if (locked) |
|
mmap_read_unlock(mm); |
|
return (ret == 1) ? page : NULL; |
|
} |
|
#endif /* CONFIG_ELF_CORE */ |
|
|
|
#ifdef CONFIG_MIGRATION |
|
/* |
|
* Check whether all pages are pinnable, if so return number of pages. If some |
|
* pages are not pinnable, migrate them, and unpin all pages. Return zero if |
|
* pages were migrated, or if some pages were not successfully isolated. |
|
* Return negative error if migration fails. |
|
*/ |
|
static long check_and_migrate_movable_pages(unsigned long nr_pages, |
|
struct page **pages, |
|
unsigned int gup_flags) |
|
{ |
|
unsigned long i; |
|
unsigned long isolation_error_count = 0; |
|
bool drain_allow = true; |
|
LIST_HEAD(movable_page_list); |
|
long ret = 0; |
|
struct page *prev_head = NULL; |
|
struct page *head; |
|
struct migration_target_control mtc = { |
|
.nid = NUMA_NO_NODE, |
|
.gfp_mask = GFP_USER | __GFP_NOWARN, |
|
}; |
|
|
|
for (i = 0; i < nr_pages; i++) { |
|
head = compound_head(pages[i]); |
|
if (head == prev_head) |
|
continue; |
|
prev_head = head; |
|
/* |
|
* If we get a movable page, since we are going to be pinning |
|
* these entries, try to move them out if possible. |
|
*/ |
|
if (!is_pinnable_page(head)) { |
|
if (PageHuge(head)) { |
|
if (!isolate_huge_page(head, &movable_page_list)) |
|
isolation_error_count++; |
|
} else { |
|
if (!PageLRU(head) && drain_allow) { |
|
lru_add_drain_all(); |
|
drain_allow = false; |
|
} |
|
|
|
if (isolate_lru_page(head)) { |
|
isolation_error_count++; |
|
continue; |
|
} |
|
list_add_tail(&head->lru, &movable_page_list); |
|
mod_node_page_state(page_pgdat(head), |
|
NR_ISOLATED_ANON + |
|
page_is_file_lru(head), |
|
thp_nr_pages(head)); |
|
} |
|
} |
|
} |
|
|
|
/* |
|
* If list is empty, and no isolation errors, means that all pages are |
|
* in the correct zone. |
|
*/ |
|
if (list_empty(&movable_page_list) && !isolation_error_count) |
|
return nr_pages; |
|
|
|
if (gup_flags & FOLL_PIN) { |
|
unpin_user_pages(pages, nr_pages); |
|
} else { |
|
for (i = 0; i < nr_pages; i++) |
|
put_page(pages[i]); |
|
} |
|
if (!list_empty(&movable_page_list)) { |
|
ret = migrate_pages(&movable_page_list, alloc_migration_target, |
|
NULL, (unsigned long)&mtc, MIGRATE_SYNC, |
|
MR_LONGTERM_PIN, NULL); |
|
if (ret && !list_empty(&movable_page_list)) |
|
putback_movable_pages(&movable_page_list); |
|
} |
|
|
|
return ret > 0 ? -ENOMEM : ret; |
|
} |
|
#else |
|
static long check_and_migrate_movable_pages(unsigned long nr_pages, |
|
struct page **pages, |
|
unsigned int gup_flags) |
|
{ |
|
return nr_pages; |
|
} |
|
#endif /* CONFIG_MIGRATION */ |
|
|
|
/* |
|
* __gup_longterm_locked() is a wrapper for __get_user_pages_locked which |
|
* allows us to process the FOLL_LONGTERM flag. |
|
*/ |
|
static long __gup_longterm_locked(struct mm_struct *mm, |
|
unsigned long start, |
|
unsigned long nr_pages, |
|
struct page **pages, |
|
struct vm_area_struct **vmas, |
|
unsigned int gup_flags) |
|
{ |
|
unsigned int flags; |
|
long rc; |
|
|
|
if (!(gup_flags & FOLL_LONGTERM)) |
|
return __get_user_pages_locked(mm, start, nr_pages, pages, vmas, |
|
NULL, gup_flags); |
|
flags = memalloc_pin_save(); |
|
do { |
|
rc = __get_user_pages_locked(mm, start, nr_pages, pages, vmas, |
|
NULL, gup_flags); |
|
if (rc <= 0) |
|
break; |
|
rc = check_and_migrate_movable_pages(rc, pages, gup_flags); |
|
} while (!rc); |
|
memalloc_pin_restore(flags); |
|
|
|
return rc; |
|
} |
|
|
|
static bool is_valid_gup_flags(unsigned int gup_flags) |
|
{ |
|
/* |
|
* FOLL_PIN must only be set internally by the pin_user_pages*() APIs, |
|
* never directly by the caller, so enforce that with an assertion: |
|
*/ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) |
|
return false; |
|
/* |
|
* FOLL_PIN is a prerequisite to FOLL_LONGTERM. Another way of saying |
|
* that is, FOLL_LONGTERM is a specific case, more restrictive case of |
|
* FOLL_PIN. |
|
*/ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) |
|
return false; |
|
|
|
return true; |
|
} |
|
|
|
#ifdef CONFIG_MMU |
|
static long __get_user_pages_remote(struct mm_struct *mm, |
|
unsigned long start, unsigned long nr_pages, |
|
unsigned int gup_flags, struct page **pages, |
|
struct vm_area_struct **vmas, int *locked) |
|
{ |
|
/* |
|
* Parts of FOLL_LONGTERM behavior are incompatible with |
|
* FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on |
|
* vmas. However, this only comes up if locked is set, and there are |
|
* callers that do request FOLL_LONGTERM, but do not set locked. So, |
|
* allow what we can. |
|
*/ |
|
if (gup_flags & FOLL_LONGTERM) { |
|
if (WARN_ON_ONCE(locked)) |
|
return -EINVAL; |
|
/* |
|
* This will check the vmas (even if our vmas arg is NULL) |
|
* and return -ENOTSUPP if DAX isn't allowed in this case: |
|
*/ |
|
return __gup_longterm_locked(mm, start, nr_pages, pages, |
|
vmas, gup_flags | FOLL_TOUCH | |
|
FOLL_REMOTE); |
|
} |
|
|
|
return __get_user_pages_locked(mm, start, nr_pages, pages, vmas, |
|
locked, |
|
gup_flags | FOLL_TOUCH | FOLL_REMOTE); |
|
} |
|
|
|
/** |
|
* get_user_pages_remote() - pin user pages in memory |
|
* @mm: mm_struct of target mm |
|
* @start: starting user address |
|
* @nr_pages: number of pages from start to pin |
|
* @gup_flags: flags modifying lookup behaviour |
|
* @pages: array that receives pointers to the pages pinned. |
|
* Should be at least nr_pages long. Or NULL, if caller |
|
* only intends to ensure the pages are faulted in. |
|
* @vmas: array of pointers to vmas corresponding to each page. |
|
* Or NULL if the caller does not require them. |
|
* @locked: pointer to lock flag indicating whether lock is held and |
|
* subsequently whether VM_FAULT_RETRY functionality can be |
|
* utilised. Lock must initially be held. |
|
* |
|
* Returns either number of pages pinned (which may be less than the |
|
* number requested), or an error. Details about the return value: |
|
* |
|
* -- If nr_pages is 0, returns 0. |
|
* -- If nr_pages is >0, but no pages were pinned, returns -errno. |
|
* -- If nr_pages is >0, and some pages were pinned, returns the number of |
|
* pages pinned. Again, this may be less than nr_pages. |
|
* |
|
* The caller is responsible for releasing returned @pages, via put_page(). |
|
* |
|
* @vmas are valid only as long as mmap_lock is held. |
|
* |
|
* Must be called with mmap_lock held for read or write. |
|
* |
|
* get_user_pages_remote walks a process's page tables and takes a reference |
|
* to each struct page that each user address corresponds to at a given |
|
* instant. That is, it takes the page that would be accessed if a user |
|
* thread accesses the given user virtual address at that instant. |
|
* |
|
* This does not guarantee that the page exists in the user mappings when |
|
* get_user_pages_remote returns, and there may even be a completely different |
|
* page there in some cases (eg. if mmapped pagecache has been invalidated |
|
* and subsequently re faulted). However it does guarantee that the page |
|
* won't be freed completely. And mostly callers simply care that the page |
|
* contains data that was valid *at some point in time*. Typically, an IO |
|
* or similar operation cannot guarantee anything stronger anyway because |
|
* locks can't be held over the syscall boundary. |
|
* |
|
* If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page |
|
* is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must |
|
* be called after the page is finished with, and before put_page is called. |
|
* |
|
* get_user_pages_remote is typically used for fewer-copy IO operations, |
|
* to get a handle on the memory by some means other than accesses |
|
* via the user virtual addresses. The pages may be submitted for |
|
* DMA to devices or accessed via their kernel linear mapping (via the |
|
* kmap APIs). Care should be taken to use the correct cache flushing APIs. |
|
* |
|
* See also get_user_pages_fast, for performance critical applications. |
|
* |
|
* get_user_pages_remote should be phased out in favor of |
|
* get_user_pages_locked|unlocked or get_user_pages_fast. Nothing |
|
* should use get_user_pages_remote because it cannot pass |
|
* FAULT_FLAG_ALLOW_RETRY to handle_mm_fault. |
|
*/ |
|
long get_user_pages_remote(struct mm_struct *mm, |
|
unsigned long start, unsigned long nr_pages, |
|
unsigned int gup_flags, struct page **pages, |
|
struct vm_area_struct **vmas, int *locked) |
|
{ |
|
if (!is_valid_gup_flags(gup_flags)) |
|
return -EINVAL; |
|
|
|
return __get_user_pages_remote(mm, start, nr_pages, gup_flags, |
|
pages, vmas, locked); |
|
} |
|
EXPORT_SYMBOL(get_user_pages_remote); |
|
|
|
#else /* CONFIG_MMU */ |
|
long get_user_pages_remote(struct mm_struct *mm, |
|
unsigned long start, unsigned long nr_pages, |
|
unsigned int gup_flags, struct page **pages, |
|
struct vm_area_struct **vmas, int *locked) |
|
{ |
|
return 0; |
|
} |
|
|
|
static long __get_user_pages_remote(struct mm_struct *mm, |
|
unsigned long start, unsigned long nr_pages, |
|
unsigned int gup_flags, struct page **pages, |
|
struct vm_area_struct **vmas, int *locked) |
|
{ |
|
return 0; |
|
} |
|
#endif /* !CONFIG_MMU */ |
|
|
|
/** |
|
* get_user_pages() - pin user pages in memory |
|
* @start: starting user address |
|
* @nr_pages: number of pages from start to pin |
|
* @gup_flags: flags modifying lookup behaviour |
|
* @pages: array that receives pointers to the pages pinned. |
|
* Should be at least nr_pages long. Or NULL, if caller |
|
* only intends to ensure the pages are faulted in. |
|
* @vmas: array of pointers to vmas corresponding to each page. |
|
* Or NULL if the caller does not require them. |
|
* |
|
* This is the same as get_user_pages_remote(), just with a less-flexible |
|
* calling convention where we assume that the mm being operated on belongs to |
|
* the current task, and doesn't allow passing of a locked parameter. We also |
|
* obviously don't pass FOLL_REMOTE in here. |
|
*/ |
|
long get_user_pages(unsigned long start, unsigned long nr_pages, |
|
unsigned int gup_flags, struct page **pages, |
|
struct vm_area_struct **vmas) |
|
{ |
|
if (!is_valid_gup_flags(gup_flags)) |
|
return -EINVAL; |
|
|
|
return __gup_longterm_locked(current->mm, start, nr_pages, |
|
pages, vmas, gup_flags | FOLL_TOUCH); |
|
} |
|
EXPORT_SYMBOL(get_user_pages); |
|
|
|
/** |
|
* get_user_pages_locked() - variant of get_user_pages() |
|
* |
|
* @start: starting user address |
|
* @nr_pages: number of pages from start to pin |
|
* @gup_flags: flags modifying lookup behaviour |
|
* @pages: array that receives pointers to the pages pinned. |
|
* Should be at least nr_pages long. Or NULL, if caller |
|
* only intends to ensure the pages are faulted in. |
|
* @locked: pointer to lock flag indicating whether lock is held and |
|
* subsequently whether VM_FAULT_RETRY functionality can be |
|
* utilised. Lock must initially be held. |
|
* |
|
* It is suitable to replace the form: |
|
* |
|
* mmap_read_lock(mm); |
|
* do_something() |
|
* get_user_pages(mm, ..., pages, NULL); |
|
* mmap_read_unlock(mm); |
|
* |
|
* to: |
|
* |
|
* int locked = 1; |
|
* mmap_read_lock(mm); |
|
* do_something() |
|
* get_user_pages_locked(mm, ..., pages, &locked); |
|
* if (locked) |
|
* mmap_read_unlock(mm); |
|
* |
|
* We can leverage the VM_FAULT_RETRY functionality in the page fault |
|
* paths better by using either get_user_pages_locked() or |
|
* get_user_pages_unlocked(). |
|
* |
|
*/ |
|
long get_user_pages_locked(unsigned long start, unsigned long nr_pages, |
|
unsigned int gup_flags, struct page **pages, |
|
int *locked) |
|
{ |
|
/* |
|
* FIXME: Current FOLL_LONGTERM behavior is incompatible with |
|
* FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on |
|
* vmas. As there are no users of this flag in this call we simply |
|
* disallow this option for now. |
|
*/ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) |
|
return -EINVAL; |
|
/* |
|
* FOLL_PIN must only be set internally by the pin_user_pages*() APIs, |
|
* never directly by the caller, so enforce that: |
|
*/ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) |
|
return -EINVAL; |
|
|
|
return __get_user_pages_locked(current->mm, start, nr_pages, |
|
pages, NULL, locked, |
|
gup_flags | FOLL_TOUCH); |
|
} |
|
EXPORT_SYMBOL(get_user_pages_locked); |
|
|
|
/* |
|
* get_user_pages_unlocked() is suitable to replace the form: |
|
* |
|
* mmap_read_lock(mm); |
|
* get_user_pages(mm, ..., pages, NULL); |
|
* mmap_read_unlock(mm); |
|
* |
|
* with: |
|
* |
|
* get_user_pages_unlocked(mm, ..., pages); |
|
* |
|
* It is functionally equivalent to get_user_pages_fast so |
|
* get_user_pages_fast should be used instead if specific gup_flags |
|
* (e.g. FOLL_FORCE) are not required. |
|
*/ |
|
long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, |
|
struct page **pages, unsigned int gup_flags) |
|
{ |
|
struct mm_struct *mm = current->mm; |
|
int locked = 1; |
|
long ret; |
|
|
|
/* |
|
* FIXME: Current FOLL_LONGTERM behavior is incompatible with |
|
* FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on |
|
* vmas. As there are no users of this flag in this call we simply |
|
* disallow this option for now. |
|
*/ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) |
|
return -EINVAL; |
|
|
|
mmap_read_lock(mm); |
|
ret = __get_user_pages_locked(mm, start, nr_pages, pages, NULL, |
|
&locked, gup_flags | FOLL_TOUCH); |
|
if (locked) |
|
mmap_read_unlock(mm); |
|
return ret; |
|
} |
|
EXPORT_SYMBOL(get_user_pages_unlocked); |
|
|
|
/* |
|
* Fast GUP |
|
* |
|
* get_user_pages_fast attempts to pin user pages by walking the page |
|
* tables directly and avoids taking locks. Thus the walker needs to be |
|
* protected from page table pages being freed from under it, and should |
|
* block any THP splits. |
|
* |
|
* One way to achieve this is to have the walker disable interrupts, and |
|
* rely on IPIs from the TLB flushing code blocking before the page table |
|
* pages are freed. This is unsuitable for architectures that do not need |
|
* to broadcast an IPI when invalidating TLBs. |
|
* |
|
* Another way to achieve this is to batch up page table containing pages |
|
* belonging to more than one mm_user, then rcu_sched a callback to free those |
|
* pages. Disabling interrupts will allow the fast_gup walker to both block |
|
* the rcu_sched callback, and an IPI that we broadcast for splitting THPs |
|
* (which is a relatively rare event). The code below adopts this strategy. |
|
* |
|
* Before activating this code, please be aware that the following assumptions |
|
* are currently made: |
|
* |
|
* *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to |
|
* free pages containing page tables or TLB flushing requires IPI broadcast. |
|
* |
|
* *) ptes can be read atomically by the architecture. |
|
* |
|
* *) access_ok is sufficient to validate userspace address ranges. |
|
* |
|
* The last two assumptions can be relaxed by the addition of helper functions. |
|
* |
|
* This code is based heavily on the PowerPC implementation by Nick Piggin. |
|
*/ |
|
#ifdef CONFIG_HAVE_FAST_GUP |
|
|
|
static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start, |
|
unsigned int flags, |
|
struct page **pages) |
|
{ |
|
while ((*nr) - nr_start) { |
|
struct page *page = pages[--(*nr)]; |
|
|
|
ClearPageReferenced(page); |
|
if (flags & FOLL_PIN) |
|
unpin_user_page(page); |
|
else |
|
put_page(page); |
|
} |
|
} |
|
|
|
#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL |
|
static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, |
|
unsigned int flags, struct page **pages, int *nr) |
|
{ |
|
struct dev_pagemap *pgmap = NULL; |
|
int nr_start = *nr, ret = 0; |
|
pte_t *ptep, *ptem; |
|
|
|
ptem = ptep = pte_offset_map(&pmd, addr); |
|
do { |
|
pte_t pte = ptep_get_lockless(ptep); |
|
struct page *head, *page; |
|
|
|
/* |
|
* Similar to the PMD case below, NUMA hinting must take slow |
|
* path using the pte_protnone check. |
|
*/ |
|
if (pte_protnone(pte)) |
|
goto pte_unmap; |
|
|
|
if (!pte_access_permitted(pte, flags & FOLL_WRITE)) |
|
goto pte_unmap; |
|
|
|
if (pte_devmap(pte)) { |
|
if (unlikely(flags & FOLL_LONGTERM)) |
|
goto pte_unmap; |
|
|
|
pgmap = get_dev_pagemap(pte_pfn(pte), pgmap); |
|
if (unlikely(!pgmap)) { |
|
undo_dev_pagemap(nr, nr_start, flags, pages); |
|
goto pte_unmap; |
|
} |
|
} else if (pte_special(pte)) |
|
goto pte_unmap; |
|
|
|
VM_BUG_ON(!pfn_valid(pte_pfn(pte))); |
|
page = pte_page(pte); |
|
|
|
head = try_grab_compound_head(page, 1, flags); |
|
if (!head) |
|
goto pte_unmap; |
|
|
|
if (unlikely(page_is_secretmem(page))) { |
|
put_compound_head(head, 1, flags); |
|
goto pte_unmap; |
|
} |
|
|
|
if (unlikely(pte_val(pte) != pte_val(*ptep))) { |
|
put_compound_head(head, 1, flags); |
|
goto pte_unmap; |
|
} |
|
|
|
VM_BUG_ON_PAGE(compound_head(page) != head, page); |
|
|
|
/* |
|
* We need to make the page accessible if and only if we are |
|
* going to access its content (the FOLL_PIN case). Please |
|
* see Documentation/core-api/pin_user_pages.rst for |
|
* details. |
|
*/ |
|
if (flags & FOLL_PIN) { |
|
ret = arch_make_page_accessible(page); |
|
if (ret) { |
|
unpin_user_page(page); |
|
goto pte_unmap; |
|
} |
|
} |
|
SetPageReferenced(page); |
|
pages[*nr] = page; |
|
(*nr)++; |
|
|
|
} while (ptep++, addr += PAGE_SIZE, addr != end); |
|
|
|
ret = 1; |
|
|
|
pte_unmap: |
|
if (pgmap) |
|
put_dev_pagemap(pgmap); |
|
pte_unmap(ptem); |
|
return ret; |
|
} |
|
#else |
|
|
|
/* |
|
* If we can't determine whether or not a pte is special, then fail immediately |
|
* for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not |
|
* to be special. |
|
* |
|
* For a futex to be placed on a THP tail page, get_futex_key requires a |
|
* get_user_pages_fast_only implementation that can pin pages. Thus it's still |
|
* useful to have gup_huge_pmd even if we can't operate on ptes. |
|
*/ |
|
static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, |
|
unsigned int flags, struct page **pages, int *nr) |
|
{ |
|
return 0; |
|
} |
|
#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */ |
|
|
|
#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE) |
|
static int __gup_device_huge(unsigned long pfn, unsigned long addr, |
|
unsigned long end, unsigned int flags, |
|
struct page **pages, int *nr) |
|
{ |
|
int nr_start = *nr; |
|
struct dev_pagemap *pgmap = NULL; |
|
int ret = 1; |
|
|
|
do { |
|
struct page *page = pfn_to_page(pfn); |
|
|
|
pgmap = get_dev_pagemap(pfn, pgmap); |
|
if (unlikely(!pgmap)) { |
|
undo_dev_pagemap(nr, nr_start, flags, pages); |
|
ret = 0; |
|
break; |
|
} |
|
SetPageReferenced(page); |
|
pages[*nr] = page; |
|
if (unlikely(!try_grab_page(page, flags))) { |
|
undo_dev_pagemap(nr, nr_start, flags, pages); |
|
ret = 0; |
|
break; |
|
} |
|
(*nr)++; |
|
pfn++; |
|
} while (addr += PAGE_SIZE, addr != end); |
|
|
|
put_dev_pagemap(pgmap); |
|
return ret; |
|
} |
|
|
|
static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, |
|
unsigned long end, unsigned int flags, |
|
struct page **pages, int *nr) |
|
{ |
|
unsigned long fault_pfn; |
|
int nr_start = *nr; |
|
|
|
fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); |
|
if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr)) |
|
return 0; |
|
|
|
if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { |
|
undo_dev_pagemap(nr, nr_start, flags, pages); |
|
return 0; |
|
} |
|
return 1; |
|
} |
|
|
|
static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, |
|
unsigned long end, unsigned int flags, |
|
struct page **pages, int *nr) |
|
{ |
|
unsigned long fault_pfn; |
|
int nr_start = *nr; |
|
|
|
fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); |
|
if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr)) |
|
return 0; |
|
|
|
if (unlikely(pud_val(orig) != pud_val(*pudp))) { |
|
undo_dev_pagemap(nr, nr_start, flags, pages); |
|
return 0; |
|
} |
|
return 1; |
|
} |
|
#else |
|
static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, |
|
unsigned long end, unsigned int flags, |
|
struct page **pages, int *nr) |
|
{ |
|
BUILD_BUG(); |
|
return 0; |
|
} |
|
|
|
static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr, |
|
unsigned long end, unsigned int flags, |
|
struct page **pages, int *nr) |
|
{ |
|
BUILD_BUG(); |
|
return 0; |
|
} |
|
#endif |
|
|
|
static int record_subpages(struct page *page, unsigned long addr, |
|
unsigned long end, struct page **pages) |
|
{ |
|
int nr; |
|
|
|
for (nr = 0; addr != end; addr += PAGE_SIZE) |
|
pages[nr++] = page++; |
|
|
|
return nr; |
|
} |
|
|
|
#ifdef CONFIG_ARCH_HAS_HUGEPD |
|
static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end, |
|
unsigned long sz) |
|
{ |
|
unsigned long __boundary = (addr + sz) & ~(sz-1); |
|
return (__boundary - 1 < end - 1) ? __boundary : end; |
|
} |
|
|
|
static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, |
|
unsigned long end, unsigned int flags, |
|
struct page **pages, int *nr) |
|
{ |
|
unsigned long pte_end; |
|
struct page *head, *page; |
|
pte_t pte; |
|
int refs; |
|
|
|
pte_end = (addr + sz) & ~(sz-1); |
|
if (pte_end < end) |
|
end = pte_end; |
|
|
|
pte = huge_ptep_get(ptep); |
|
|
|
if (!pte_access_permitted(pte, flags & FOLL_WRITE)) |
|
return 0; |
|
|
|
/* hugepages are never "special" */ |
|
VM_BUG_ON(!pfn_valid(pte_pfn(pte))); |
|
|
|
head = pte_page(pte); |
|
page = head + ((addr & (sz-1)) >> PAGE_SHIFT); |
|
refs = record_subpages(page, addr, end, pages + *nr); |
|
|
|
head = try_grab_compound_head(head, refs, flags); |
|
if (!head) |
|
return 0; |
|
|
|
if (unlikely(pte_val(pte) != pte_val(*ptep))) { |
|
put_compound_head(head, refs, flags); |
|
return 0; |
|
} |
|
|
|
*nr += refs; |
|
SetPageReferenced(head); |
|
return 1; |
|
} |
|
|
|
static int gup_huge_pd(hugepd_t hugepd, unsigned long addr, |
|
unsigned int pdshift, unsigned long end, unsigned int flags, |
|
struct page **pages, int *nr) |
|
{ |
|
pte_t *ptep; |
|
unsigned long sz = 1UL << hugepd_shift(hugepd); |
|
unsigned long next; |
|
|
|
ptep = hugepte_offset(hugepd, addr, pdshift); |
|
do { |
|
next = hugepte_addr_end(addr, end, sz); |
|
if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr)) |
|
return 0; |
|
} while (ptep++, addr = next, addr != end); |
|
|
|
return 1; |
|
} |
|
#else |
|
static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr, |
|
unsigned int pdshift, unsigned long end, unsigned int flags, |
|
struct page **pages, int *nr) |
|
{ |
|
return 0; |
|
} |
|
#endif /* CONFIG_ARCH_HAS_HUGEPD */ |
|
|
|
static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, |
|
unsigned long end, unsigned int flags, |
|
struct page **pages, int *nr) |
|
{ |
|
struct page *head, *page; |
|
int refs; |
|
|
|
if (!pmd_access_permitted(orig, flags & FOLL_WRITE)) |
|
return 0; |
|
|
|
if (pmd_devmap(orig)) { |
|
if (unlikely(flags & FOLL_LONGTERM)) |
|
return 0; |
|
return __gup_device_huge_pmd(orig, pmdp, addr, end, flags, |
|
pages, nr); |
|
} |
|
|
|
page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); |
|
refs = record_subpages(page, addr, end, pages + *nr); |
|
|
|
head = try_grab_compound_head(pmd_page(orig), refs, flags); |
|
if (!head) |
|
return 0; |
|
|
|
if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { |
|
put_compound_head(head, refs, flags); |
|
return 0; |
|
} |
|
|
|
*nr += refs; |
|
SetPageReferenced(head); |
|
return 1; |
|
} |
|
|
|
static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, |
|
unsigned long end, unsigned int flags, |
|
struct page **pages, int *nr) |
|
{ |
|
struct page *head, *page; |
|
int refs; |
|
|
|
if (!pud_access_permitted(orig, flags & FOLL_WRITE)) |
|
return 0; |
|
|
|
if (pud_devmap(orig)) { |
|
if (unlikely(flags & FOLL_LONGTERM)) |
|
return 0; |
|
return __gup_device_huge_pud(orig, pudp, addr, end, flags, |
|
pages, nr); |
|
} |
|
|
|
page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); |
|
refs = record_subpages(page, addr, end, pages + *nr); |
|
|
|
head = try_grab_compound_head(pud_page(orig), refs, flags); |
|
if (!head) |
|
return 0; |
|
|
|
if (unlikely(pud_val(orig) != pud_val(*pudp))) { |
|
put_compound_head(head, refs, flags); |
|
return 0; |
|
} |
|
|
|
*nr += refs; |
|
SetPageReferenced(head); |
|
return 1; |
|
} |
|
|
|
static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, |
|
unsigned long end, unsigned int flags, |
|
struct page **pages, int *nr) |
|
{ |
|
int refs; |
|
struct page *head, *page; |
|
|
|
if (!pgd_access_permitted(orig, flags & FOLL_WRITE)) |
|
return 0; |
|
|
|
BUILD_BUG_ON(pgd_devmap(orig)); |
|
|
|
page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); |
|
refs = record_subpages(page, addr, end, pages + *nr); |
|
|
|
head = try_grab_compound_head(pgd_page(orig), refs, flags); |
|
if (!head) |
|
return 0; |
|
|
|
if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) { |
|
put_compound_head(head, refs, flags); |
|
return 0; |
|
} |
|
|
|
*nr += refs; |
|
SetPageReferenced(head); |
|
return 1; |
|
} |
|
|
|
static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned long end, |
|
unsigned int flags, struct page **pages, int *nr) |
|
{ |
|
unsigned long next; |
|
pmd_t *pmdp; |
|
|
|
pmdp = pmd_offset_lockless(pudp, pud, addr); |
|
do { |
|
pmd_t pmd = READ_ONCE(*pmdp); |
|
|
|
next = pmd_addr_end(addr, end); |
|
if (!pmd_present(pmd)) |
|
return 0; |
|
|
|
if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) || |
|
pmd_devmap(pmd))) { |
|
/* |
|
* NUMA hinting faults need to be handled in the GUP |
|
* slowpath for accounting purposes and so that they |
|
* can be serialised against THP migration. |
|
*/ |
|
if (pmd_protnone(pmd)) |
|
return 0; |
|
|
|
if (!gup_huge_pmd(pmd, pmdp, addr, next, flags, |
|
pages, nr)) |
|
return 0; |
|
|
|
} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) { |
|
/* |
|
* architecture have different format for hugetlbfs |
|
* pmd format and THP pmd format |
|
*/ |
|
if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr, |
|
PMD_SHIFT, next, flags, pages, nr)) |
|
return 0; |
|
} else if (!gup_pte_range(pmd, addr, next, flags, pages, nr)) |
|
return 0; |
|
} while (pmdp++, addr = next, addr != end); |
|
|
|
return 1; |
|
} |
|
|
|
static int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, unsigned long end, |
|
unsigned int flags, struct page **pages, int *nr) |
|
{ |
|
unsigned long next; |
|
pud_t *pudp; |
|
|
|
pudp = pud_offset_lockless(p4dp, p4d, addr); |
|
do { |
|
pud_t pud = READ_ONCE(*pudp); |
|
|
|
next = pud_addr_end(addr, end); |
|
if (unlikely(!pud_present(pud))) |
|
return 0; |
|
if (unlikely(pud_huge(pud))) { |
|
if (!gup_huge_pud(pud, pudp, addr, next, flags, |
|
pages, nr)) |
|
return 0; |
|
} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) { |
|
if (!gup_huge_pd(__hugepd(pud_val(pud)), addr, |
|
PUD_SHIFT, next, flags, pages, nr)) |
|
return 0; |
|
} else if (!gup_pmd_range(pudp, pud, addr, next, flags, pages, nr)) |
|
return 0; |
|
} while (pudp++, addr = next, addr != end); |
|
|
|
return 1; |
|
} |
|
|
|
static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned long end, |
|
unsigned int flags, struct page **pages, int *nr) |
|
{ |
|
unsigned long next; |
|
p4d_t *p4dp; |
|
|
|
p4dp = p4d_offset_lockless(pgdp, pgd, addr); |
|
do { |
|
p4d_t p4d = READ_ONCE(*p4dp); |
|
|
|
next = p4d_addr_end(addr, end); |
|
if (p4d_none(p4d)) |
|
return 0; |
|
BUILD_BUG_ON(p4d_huge(p4d)); |
|
if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) { |
|
if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr, |
|
P4D_SHIFT, next, flags, pages, nr)) |
|
return 0; |
|
} else if (!gup_pud_range(p4dp, p4d, addr, next, flags, pages, nr)) |
|
return 0; |
|
} while (p4dp++, addr = next, addr != end); |
|
|
|
return 1; |
|
} |
|
|
|
static void gup_pgd_range(unsigned long addr, unsigned long end, |
|
unsigned int flags, struct page **pages, int *nr) |
|
{ |
|
unsigned long next; |
|
pgd_t *pgdp; |
|
|
|
pgdp = pgd_offset(current->mm, addr); |
|
do { |
|
pgd_t pgd = READ_ONCE(*pgdp); |
|
|
|
next = pgd_addr_end(addr, end); |
|
if (pgd_none(pgd)) |
|
return; |
|
if (unlikely(pgd_huge(pgd))) { |
|
if (!gup_huge_pgd(pgd, pgdp, addr, next, flags, |
|
pages, nr)) |
|
return; |
|
} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) { |
|
if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr, |
|
PGDIR_SHIFT, next, flags, pages, nr)) |
|
return; |
|
} else if (!gup_p4d_range(pgdp, pgd, addr, next, flags, pages, nr)) |
|
return; |
|
} while (pgdp++, addr = next, addr != end); |
|
} |
|
#else |
|
static inline void gup_pgd_range(unsigned long addr, unsigned long end, |
|
unsigned int flags, struct page **pages, int *nr) |
|
{ |
|
} |
|
#endif /* CONFIG_HAVE_FAST_GUP */ |
|
|
|
#ifndef gup_fast_permitted |
|
/* |
|
* Check if it's allowed to use get_user_pages_fast_only() for the range, or |
|
* we need to fall back to the slow version: |
|
*/ |
|
static bool gup_fast_permitted(unsigned long start, unsigned long end) |
|
{ |
|
return true; |
|
} |
|
#endif |
|
|
|
static int __gup_longterm_unlocked(unsigned long start, int nr_pages, |
|
unsigned int gup_flags, struct page **pages) |
|
{ |
|
int ret; |
|
|
|
/* |
|
* FIXME: FOLL_LONGTERM does not work with |
|
* get_user_pages_unlocked() (see comments in that function) |
|
*/ |
|
if (gup_flags & FOLL_LONGTERM) { |
|
mmap_read_lock(current->mm); |
|
ret = __gup_longterm_locked(current->mm, |
|
start, nr_pages, |
|
pages, NULL, gup_flags); |
|
mmap_read_unlock(current->mm); |
|
} else { |
|
ret = get_user_pages_unlocked(start, nr_pages, |
|
pages, gup_flags); |
|
} |
|
|
|
return ret; |
|
} |
|
|
|
static unsigned long lockless_pages_from_mm(unsigned long start, |
|
unsigned long end, |
|
unsigned int gup_flags, |
|
struct page **pages) |
|
{ |
|
unsigned long flags; |
|
int nr_pinned = 0; |
|
unsigned seq; |
|
|
|
if (!IS_ENABLED(CONFIG_HAVE_FAST_GUP) || |
|
!gup_fast_permitted(start, end)) |
|
return 0; |
|
|
|
if (gup_flags & FOLL_PIN) { |
|
seq = raw_read_seqcount(¤t->mm->write_protect_seq); |
|
if (seq & 1) |
|
return 0; |
|
} |
|
|
|
/* |
|
* Disable interrupts. The nested form is used, in order to allow full, |
|
* general purpose use of this routine. |
|
* |
|
* With interrupts disabled, we block page table pages from being freed |
|
* from under us. See struct mmu_table_batch comments in |
|
* include/asm-generic/tlb.h for more details. |
|
* |
|
* We do not adopt an rcu_read_lock() here as we also want to block IPIs |
|
* that come from THPs splitting. |
|
*/ |
|
local_irq_save(flags); |
|
gup_pgd_range(start, end, gup_flags, pages, &nr_pinned); |
|
local_irq_restore(flags); |
|
|
|
/* |
|
* When pinning pages for DMA there could be a concurrent write protect |
|
* from fork() via copy_page_range(), in this case always fail fast GUP. |
|
*/ |
|
if (gup_flags & FOLL_PIN) { |
|
if (read_seqcount_retry(¤t->mm->write_protect_seq, seq)) { |
|
unpin_user_pages(pages, nr_pinned); |
|
return 0; |
|
} |
|
} |
|
return nr_pinned; |
|
} |
|
|
|
static int internal_get_user_pages_fast(unsigned long start, |
|
unsigned long nr_pages, |
|
unsigned int gup_flags, |
|
struct page **pages) |
|
{ |
|
unsigned long len, end; |
|
unsigned long nr_pinned; |
|
int ret; |
|
|
|
if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | |
|
FOLL_FORCE | FOLL_PIN | FOLL_GET | |
|
FOLL_FAST_ONLY))) |
|
return -EINVAL; |
|
|
|
if (gup_flags & FOLL_PIN) |
|
mm_set_has_pinned_flag(¤t->mm->flags); |
|
|
|
if (!(gup_flags & FOLL_FAST_ONLY)) |
|
might_lock_read(¤t->mm->mmap_lock); |
|
|
|
start = untagged_addr(start) & PAGE_MASK; |
|
len = nr_pages << PAGE_SHIFT; |
|
if (check_add_overflow(start, len, &end)) |
|
return 0; |
|
if (unlikely(!access_ok((void __user *)start, len))) |
|
return -EFAULT; |
|
|
|
nr_pinned = lockless_pages_from_mm(start, end, gup_flags, pages); |
|
if (nr_pinned == nr_pages || gup_flags & FOLL_FAST_ONLY) |
|
return nr_pinned; |
|
|
|
/* Slow path: try to get the remaining pages with get_user_pages */ |
|
start += nr_pinned << PAGE_SHIFT; |
|
pages += nr_pinned; |
|
ret = __gup_longterm_unlocked(start, nr_pages - nr_pinned, gup_flags, |
|
pages); |
|
if (ret < 0) { |
|
/* |
|
* The caller has to unpin the pages we already pinned so |
|
* returning -errno is not an option |
|
*/ |
|
if (nr_pinned) |
|
return nr_pinned; |
|
return ret; |
|
} |
|
return ret + nr_pinned; |
|
} |
|
|
|
/** |
|
* get_user_pages_fast_only() - pin user pages in memory |
|
* @start: starting user address |
|
* @nr_pages: number of pages from start to pin |
|
* @gup_flags: flags modifying pin behaviour |
|
* @pages: array that receives pointers to the pages pinned. |
|
* Should be at least nr_pages long. |
|
* |
|
* Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to |
|
* the regular GUP. |
|
* Note a difference with get_user_pages_fast: this always returns the |
|
* number of pages pinned, 0 if no pages were pinned. |
|
* |
|
* If the architecture does not support this function, simply return with no |
|
* pages pinned. |
|
* |
|
* Careful, careful! COW breaking can go either way, so a non-write |
|
* access can get ambiguous page results. If you call this function without |
|
* 'write' set, you'd better be sure that you're ok with that ambiguity. |
|
*/ |
|
int get_user_pages_fast_only(unsigned long start, int nr_pages, |
|
unsigned int gup_flags, struct page **pages) |
|
{ |
|
int nr_pinned; |
|
/* |
|
* Internally (within mm/gup.c), gup fast variants must set FOLL_GET, |
|
* because gup fast is always a "pin with a +1 page refcount" request. |
|
* |
|
* FOLL_FAST_ONLY is required in order to match the API description of |
|
* this routine: no fall back to regular ("slow") GUP. |
|
*/ |
|
gup_flags |= FOLL_GET | FOLL_FAST_ONLY; |
|
|
|
nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags, |
|
pages); |
|
|
|
/* |
|
* As specified in the API description above, this routine is not |
|
* allowed to return negative values. However, the common core |
|
* routine internal_get_user_pages_fast() *can* return -errno. |
|
* Therefore, correct for that here: |
|
*/ |
|
if (nr_pinned < 0) |
|
nr_pinned = 0; |
|
|
|
return nr_pinned; |
|
} |
|
EXPORT_SYMBOL_GPL(get_user_pages_fast_only); |
|
|
|
/** |
|
* get_user_pages_fast() - pin user pages in memory |
|
* @start: starting user address |
|
* @nr_pages: number of pages from start to pin |
|
* @gup_flags: flags modifying pin behaviour |
|
* @pages: array that receives pointers to the pages pinned. |
|
* Should be at least nr_pages long. |
|
* |
|
* Attempt to pin user pages in memory without taking mm->mmap_lock. |
|
* If not successful, it will fall back to taking the lock and |
|
* calling get_user_pages(). |
|
* |
|
* Returns number of pages pinned. This may be fewer than the number requested. |
|
* If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns |
|
* -errno. |
|
*/ |
|
int get_user_pages_fast(unsigned long start, int nr_pages, |
|
unsigned int gup_flags, struct page **pages) |
|
{ |
|
if (!is_valid_gup_flags(gup_flags)) |
|
return -EINVAL; |
|
|
|
/* |
|
* The caller may or may not have explicitly set FOLL_GET; either way is |
|
* OK. However, internally (within mm/gup.c), gup fast variants must set |
|
* FOLL_GET, because gup fast is always a "pin with a +1 page refcount" |
|
* request. |
|
*/ |
|
gup_flags |= FOLL_GET; |
|
return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages); |
|
} |
|
EXPORT_SYMBOL_GPL(get_user_pages_fast); |
|
|
|
/** |
|
* pin_user_pages_fast() - pin user pages in memory without taking locks |
|
* |
|
* @start: starting user address |
|
* @nr_pages: number of pages from start to pin |
|
* @gup_flags: flags modifying pin behaviour |
|
* @pages: array that receives pointers to the pages pinned. |
|
* Should be at least nr_pages long. |
|
* |
|
* Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See |
|
* get_user_pages_fast() for documentation on the function arguments, because |
|
* the arguments here are identical. |
|
* |
|
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please |
|
* see Documentation/core-api/pin_user_pages.rst for further details. |
|
*/ |
|
int pin_user_pages_fast(unsigned long start, int nr_pages, |
|
unsigned int gup_flags, struct page **pages) |
|
{ |
|
/* FOLL_GET and FOLL_PIN are mutually exclusive. */ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_GET)) |
|
return -EINVAL; |
|
|
|
gup_flags |= FOLL_PIN; |
|
return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages); |
|
} |
|
EXPORT_SYMBOL_GPL(pin_user_pages_fast); |
|
|
|
/* |
|
* This is the FOLL_PIN equivalent of get_user_pages_fast_only(). Behavior |
|
* is the same, except that this one sets FOLL_PIN instead of FOLL_GET. |
|
* |
|
* The API rules are the same, too: no negative values may be returned. |
|
*/ |
|
int pin_user_pages_fast_only(unsigned long start, int nr_pages, |
|
unsigned int gup_flags, struct page **pages) |
|
{ |
|
int nr_pinned; |
|
|
|
/* |
|
* FOLL_GET and FOLL_PIN are mutually exclusive. Note that the API |
|
* rules require returning 0, rather than -errno: |
|
*/ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_GET)) |
|
return 0; |
|
/* |
|
* FOLL_FAST_ONLY is required in order to match the API description of |
|
* this routine: no fall back to regular ("slow") GUP. |
|
*/ |
|
gup_flags |= (FOLL_PIN | FOLL_FAST_ONLY); |
|
nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags, |
|
pages); |
|
/* |
|
* This routine is not allowed to return negative values. However, |
|
* internal_get_user_pages_fast() *can* return -errno. Therefore, |
|
* correct for that here: |
|
*/ |
|
if (nr_pinned < 0) |
|
nr_pinned = 0; |
|
|
|
return nr_pinned; |
|
} |
|
EXPORT_SYMBOL_GPL(pin_user_pages_fast_only); |
|
|
|
/** |
|
* pin_user_pages_remote() - pin pages of a remote process |
|
* |
|
* @mm: mm_struct of target mm |
|
* @start: starting user address |
|
* @nr_pages: number of pages from start to pin |
|
* @gup_flags: flags modifying lookup behaviour |
|
* @pages: array that receives pointers to the pages pinned. |
|
* Should be at least nr_pages long. Or NULL, if caller |
|
* only intends to ensure the pages are faulted in. |
|
* @vmas: array of pointers to vmas corresponding to each page. |
|
* Or NULL if the caller does not require them. |
|
* @locked: pointer to lock flag indicating whether lock is held and |
|
* subsequently whether VM_FAULT_RETRY functionality can be |
|
* utilised. Lock must initially be held. |
|
* |
|
* Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See |
|
* get_user_pages_remote() for documentation on the function arguments, because |
|
* the arguments here are identical. |
|
* |
|
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please |
|
* see Documentation/core-api/pin_user_pages.rst for details. |
|
*/ |
|
long pin_user_pages_remote(struct mm_struct *mm, |
|
unsigned long start, unsigned long nr_pages, |
|
unsigned int gup_flags, struct page **pages, |
|
struct vm_area_struct **vmas, int *locked) |
|
{ |
|
/* FOLL_GET and FOLL_PIN are mutually exclusive. */ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_GET)) |
|
return -EINVAL; |
|
|
|
gup_flags |= FOLL_PIN; |
|
return __get_user_pages_remote(mm, start, nr_pages, gup_flags, |
|
pages, vmas, locked); |
|
} |
|
EXPORT_SYMBOL(pin_user_pages_remote); |
|
|
|
/** |
|
* pin_user_pages() - pin user pages in memory for use by other devices |
|
* |
|
* @start: starting user address |
|
* @nr_pages: number of pages from start to pin |
|
* @gup_flags: flags modifying lookup behaviour |
|
* @pages: array that receives pointers to the pages pinned. |
|
* Should be at least nr_pages long. Or NULL, if caller |
|
* only intends to ensure the pages are faulted in. |
|
* @vmas: array of pointers to vmas corresponding to each page. |
|
* Or NULL if the caller does not require them. |
|
* |
|
* Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and |
|
* FOLL_PIN is set. |
|
* |
|
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please |
|
* see Documentation/core-api/pin_user_pages.rst for details. |
|
*/ |
|
long pin_user_pages(unsigned long start, unsigned long nr_pages, |
|
unsigned int gup_flags, struct page **pages, |
|
struct vm_area_struct **vmas) |
|
{ |
|
/* FOLL_GET and FOLL_PIN are mutually exclusive. */ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_GET)) |
|
return -EINVAL; |
|
|
|
gup_flags |= FOLL_PIN; |
|
return __gup_longterm_locked(current->mm, start, nr_pages, |
|
pages, vmas, gup_flags); |
|
} |
|
EXPORT_SYMBOL(pin_user_pages); |
|
|
|
/* |
|
* pin_user_pages_unlocked() is the FOLL_PIN variant of |
|
* get_user_pages_unlocked(). Behavior is the same, except that this one sets |
|
* FOLL_PIN and rejects FOLL_GET. |
|
*/ |
|
long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages, |
|
struct page **pages, unsigned int gup_flags) |
|
{ |
|
/* FOLL_GET and FOLL_PIN are mutually exclusive. */ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_GET)) |
|
return -EINVAL; |
|
|
|
gup_flags |= FOLL_PIN; |
|
return get_user_pages_unlocked(start, nr_pages, pages, gup_flags); |
|
} |
|
EXPORT_SYMBOL(pin_user_pages_unlocked); |
|
|
|
/* |
|
* pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked(). |
|
* Behavior is the same, except that this one sets FOLL_PIN and rejects |
|
* FOLL_GET. |
|
*/ |
|
long pin_user_pages_locked(unsigned long start, unsigned long nr_pages, |
|
unsigned int gup_flags, struct page **pages, |
|
int *locked) |
|
{ |
|
/* |
|
* FIXME: Current FOLL_LONGTERM behavior is incompatible with |
|
* FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on |
|
* vmas. As there are no users of this flag in this call we simply |
|
* disallow this option for now. |
|
*/ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) |
|
return -EINVAL; |
|
|
|
/* FOLL_GET and FOLL_PIN are mutually exclusive. */ |
|
if (WARN_ON_ONCE(gup_flags & FOLL_GET)) |
|
return -EINVAL; |
|
|
|
gup_flags |= FOLL_PIN; |
|
return __get_user_pages_locked(current->mm, start, nr_pages, |
|
pages, NULL, locked, |
|
gup_flags | FOLL_TOUCH); |
|
} |
|
EXPORT_SYMBOL(pin_user_pages_locked);
|
|
|