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547 lines
13 KiB
547 lines
13 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* Ram backed block device driver. |
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* |
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* Copyright (C) 2007 Nick Piggin |
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* Copyright (C) 2007 Novell Inc. |
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* |
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* Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright |
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* of their respective owners. |
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*/ |
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|
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#include <linux/init.h> |
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#include <linux/initrd.h> |
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#include <linux/module.h> |
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#include <linux/moduleparam.h> |
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#include <linux/major.h> |
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#include <linux/blkdev.h> |
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#include <linux/bio.h> |
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#include <linux/highmem.h> |
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#include <linux/mutex.h> |
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#include <linux/radix-tree.h> |
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#include <linux/fs.h> |
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#include <linux/slab.h> |
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#include <linux/backing-dev.h> |
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#include <linux/uaccess.h> |
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#define PAGE_SECTORS_SHIFT (PAGE_SHIFT - SECTOR_SHIFT) |
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#define PAGE_SECTORS (1 << PAGE_SECTORS_SHIFT) |
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|
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/* |
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* Each block ramdisk device has a radix_tree brd_pages of pages that stores |
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* the pages containing the block device's contents. A brd page's ->index is |
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* its offset in PAGE_SIZE units. This is similar to, but in no way connected |
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* with, the kernel's pagecache or buffer cache (which sit above our block |
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* device). |
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*/ |
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struct brd_device { |
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int brd_number; |
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struct request_queue *brd_queue; |
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struct gendisk *brd_disk; |
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struct list_head brd_list; |
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|
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/* |
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* Backing store of pages and lock to protect it. This is the contents |
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* of the block device. |
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*/ |
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spinlock_t brd_lock; |
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struct radix_tree_root brd_pages; |
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}; |
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/* |
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* Look up and return a brd's page for a given sector. |
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*/ |
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static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector) |
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{ |
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pgoff_t idx; |
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struct page *page; |
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|
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/* |
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* The page lifetime is protected by the fact that we have opened the |
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* device node -- brd pages will never be deleted under us, so we |
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* don't need any further locking or refcounting. |
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* |
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* This is strictly true for the radix-tree nodes as well (ie. we |
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* don't actually need the rcu_read_lock()), however that is not a |
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* documented feature of the radix-tree API so it is better to be |
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* safe here (we don't have total exclusion from radix tree updates |
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* here, only deletes). |
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*/ |
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rcu_read_lock(); |
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idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */ |
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page = radix_tree_lookup(&brd->brd_pages, idx); |
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rcu_read_unlock(); |
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BUG_ON(page && page->index != idx); |
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return page; |
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} |
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/* |
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* Look up and return a brd's page for a given sector. |
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* If one does not exist, allocate an empty page, and insert that. Then |
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* return it. |
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*/ |
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static struct page *brd_insert_page(struct brd_device *brd, sector_t sector) |
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{ |
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pgoff_t idx; |
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struct page *page; |
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gfp_t gfp_flags; |
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page = brd_lookup_page(brd, sector); |
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if (page) |
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return page; |
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/* |
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* Must use NOIO because we don't want to recurse back into the |
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* block or filesystem layers from page reclaim. |
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*/ |
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gfp_flags = GFP_NOIO | __GFP_ZERO | __GFP_HIGHMEM; |
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page = alloc_page(gfp_flags); |
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if (!page) |
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return NULL; |
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if (radix_tree_preload(GFP_NOIO)) { |
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__free_page(page); |
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return NULL; |
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} |
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spin_lock(&brd->brd_lock); |
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idx = sector >> PAGE_SECTORS_SHIFT; |
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page->index = idx; |
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if (radix_tree_insert(&brd->brd_pages, idx, page)) { |
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__free_page(page); |
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page = radix_tree_lookup(&brd->brd_pages, idx); |
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BUG_ON(!page); |
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BUG_ON(page->index != idx); |
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} |
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spin_unlock(&brd->brd_lock); |
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radix_tree_preload_end(); |
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return page; |
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} |
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/* |
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* Free all backing store pages and radix tree. This must only be called when |
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* there are no other users of the device. |
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*/ |
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#define FREE_BATCH 16 |
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static void brd_free_pages(struct brd_device *brd) |
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{ |
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unsigned long pos = 0; |
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struct page *pages[FREE_BATCH]; |
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int nr_pages; |
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do { |
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int i; |
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nr_pages = radix_tree_gang_lookup(&brd->brd_pages, |
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(void **)pages, pos, FREE_BATCH); |
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for (i = 0; i < nr_pages; i++) { |
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void *ret; |
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BUG_ON(pages[i]->index < pos); |
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pos = pages[i]->index; |
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ret = radix_tree_delete(&brd->brd_pages, pos); |
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BUG_ON(!ret || ret != pages[i]); |
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__free_page(pages[i]); |
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} |
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pos++; |
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/* |
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* It takes 3.4 seconds to remove 80GiB ramdisk. |
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* So, we need cond_resched to avoid stalling the CPU. |
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*/ |
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cond_resched(); |
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/* |
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* This assumes radix_tree_gang_lookup always returns as |
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* many pages as possible. If the radix-tree code changes, |
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* so will this have to. |
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*/ |
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} while (nr_pages == FREE_BATCH); |
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} |
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/* |
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* copy_to_brd_setup must be called before copy_to_brd. It may sleep. |
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*/ |
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static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n) |
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{ |
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unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; |
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size_t copy; |
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copy = min_t(size_t, n, PAGE_SIZE - offset); |
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if (!brd_insert_page(brd, sector)) |
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return -ENOSPC; |
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if (copy < n) { |
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sector += copy >> SECTOR_SHIFT; |
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if (!brd_insert_page(brd, sector)) |
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return -ENOSPC; |
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} |
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return 0; |
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} |
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/* |
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* Copy n bytes from src to the brd starting at sector. Does not sleep. |
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*/ |
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static void copy_to_brd(struct brd_device *brd, const void *src, |
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sector_t sector, size_t n) |
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{ |
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struct page *page; |
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void *dst; |
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unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; |
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size_t copy; |
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copy = min_t(size_t, n, PAGE_SIZE - offset); |
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page = brd_lookup_page(brd, sector); |
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BUG_ON(!page); |
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dst = kmap_atomic(page); |
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memcpy(dst + offset, src, copy); |
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kunmap_atomic(dst); |
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if (copy < n) { |
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src += copy; |
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sector += copy >> SECTOR_SHIFT; |
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copy = n - copy; |
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page = brd_lookup_page(brd, sector); |
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BUG_ON(!page); |
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dst = kmap_atomic(page); |
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memcpy(dst, src, copy); |
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kunmap_atomic(dst); |
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} |
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} |
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/* |
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* Copy n bytes to dst from the brd starting at sector. Does not sleep. |
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*/ |
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static void copy_from_brd(void *dst, struct brd_device *brd, |
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sector_t sector, size_t n) |
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{ |
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struct page *page; |
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void *src; |
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unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; |
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size_t copy; |
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copy = min_t(size_t, n, PAGE_SIZE - offset); |
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page = brd_lookup_page(brd, sector); |
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if (page) { |
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src = kmap_atomic(page); |
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memcpy(dst, src + offset, copy); |
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kunmap_atomic(src); |
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} else |
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memset(dst, 0, copy); |
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if (copy < n) { |
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dst += copy; |
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sector += copy >> SECTOR_SHIFT; |
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copy = n - copy; |
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page = brd_lookup_page(brd, sector); |
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if (page) { |
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src = kmap_atomic(page); |
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memcpy(dst, src, copy); |
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kunmap_atomic(src); |
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} else |
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memset(dst, 0, copy); |
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} |
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} |
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/* |
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* Process a single bvec of a bio. |
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*/ |
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static int brd_do_bvec(struct brd_device *brd, struct page *page, |
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unsigned int len, unsigned int off, unsigned int op, |
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sector_t sector) |
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{ |
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void *mem; |
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int err = 0; |
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if (op_is_write(op)) { |
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err = copy_to_brd_setup(brd, sector, len); |
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if (err) |
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goto out; |
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} |
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mem = kmap_atomic(page); |
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if (!op_is_write(op)) { |
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copy_from_brd(mem + off, brd, sector, len); |
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flush_dcache_page(page); |
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} else { |
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flush_dcache_page(page); |
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copy_to_brd(brd, mem + off, sector, len); |
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} |
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kunmap_atomic(mem); |
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out: |
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return err; |
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} |
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static blk_qc_t brd_submit_bio(struct bio *bio) |
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{ |
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struct brd_device *brd = bio->bi_bdev->bd_disk->private_data; |
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sector_t sector = bio->bi_iter.bi_sector; |
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struct bio_vec bvec; |
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struct bvec_iter iter; |
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bio_for_each_segment(bvec, bio, iter) { |
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unsigned int len = bvec.bv_len; |
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int err; |
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/* Don't support un-aligned buffer */ |
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WARN_ON_ONCE((bvec.bv_offset & (SECTOR_SIZE - 1)) || |
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(len & (SECTOR_SIZE - 1))); |
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err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset, |
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bio_op(bio), sector); |
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if (err) |
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goto io_error; |
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sector += len >> SECTOR_SHIFT; |
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} |
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bio_endio(bio); |
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return BLK_QC_T_NONE; |
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io_error: |
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bio_io_error(bio); |
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return BLK_QC_T_NONE; |
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} |
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static int brd_rw_page(struct block_device *bdev, sector_t sector, |
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struct page *page, unsigned int op) |
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{ |
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struct brd_device *brd = bdev->bd_disk->private_data; |
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int err; |
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if (PageTransHuge(page)) |
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return -ENOTSUPP; |
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err = brd_do_bvec(brd, page, PAGE_SIZE, 0, op, sector); |
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page_endio(page, op_is_write(op), err); |
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return err; |
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} |
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static const struct block_device_operations brd_fops = { |
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.owner = THIS_MODULE, |
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.submit_bio = brd_submit_bio, |
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.rw_page = brd_rw_page, |
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}; |
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/* |
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* And now the modules code and kernel interface. |
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*/ |
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static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT; |
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module_param(rd_nr, int, 0444); |
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MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices"); |
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unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE; |
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module_param(rd_size, ulong, 0444); |
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MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes."); |
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static int max_part = 1; |
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module_param(max_part, int, 0444); |
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MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices"); |
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MODULE_LICENSE("GPL"); |
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MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR); |
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MODULE_ALIAS("rd"); |
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#ifndef MODULE |
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/* Legacy boot options - nonmodular */ |
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static int __init ramdisk_size(char *str) |
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{ |
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rd_size = simple_strtol(str, NULL, 0); |
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return 1; |
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} |
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__setup("ramdisk_size=", ramdisk_size); |
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#endif |
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/* |
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* The device scheme is derived from loop.c. Keep them in synch where possible |
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* (should share code eventually). |
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*/ |
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static LIST_HEAD(brd_devices); |
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static DEFINE_MUTEX(brd_devices_mutex); |
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static struct brd_device *brd_alloc(int i) |
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{ |
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struct brd_device *brd; |
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struct gendisk *disk; |
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brd = kzalloc(sizeof(*brd), GFP_KERNEL); |
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if (!brd) |
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goto out; |
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brd->brd_number = i; |
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spin_lock_init(&brd->brd_lock); |
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INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC); |
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brd->brd_queue = blk_alloc_queue(NUMA_NO_NODE); |
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if (!brd->brd_queue) |
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goto out_free_dev; |
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/* This is so fdisk will align partitions on 4k, because of |
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* direct_access API needing 4k alignment, returning a PFN |
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* (This is only a problem on very small devices <= 4M, |
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* otherwise fdisk will align on 1M. Regardless this call |
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* is harmless) |
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*/ |
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blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE); |
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disk = brd->brd_disk = alloc_disk(max_part); |
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if (!disk) |
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goto out_free_queue; |
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disk->major = RAMDISK_MAJOR; |
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disk->first_minor = i * max_part; |
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disk->fops = &brd_fops; |
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disk->private_data = brd; |
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disk->flags = GENHD_FL_EXT_DEVT; |
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sprintf(disk->disk_name, "ram%d", i); |
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set_capacity(disk, rd_size * 2); |
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/* Tell the block layer that this is not a rotational device */ |
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blk_queue_flag_set(QUEUE_FLAG_NONROT, brd->brd_queue); |
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blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, brd->brd_queue); |
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return brd; |
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out_free_queue: |
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blk_cleanup_queue(brd->brd_queue); |
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out_free_dev: |
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kfree(brd); |
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out: |
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return NULL; |
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} |
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static void brd_free(struct brd_device *brd) |
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{ |
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put_disk(brd->brd_disk); |
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blk_cleanup_queue(brd->brd_queue); |
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brd_free_pages(brd); |
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kfree(brd); |
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} |
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static void brd_probe(dev_t dev) |
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{ |
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struct brd_device *brd; |
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int i = MINOR(dev) / max_part; |
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mutex_lock(&brd_devices_mutex); |
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list_for_each_entry(brd, &brd_devices, brd_list) { |
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if (brd->brd_number == i) |
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goto out_unlock; |
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} |
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brd = brd_alloc(i); |
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if (brd) { |
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brd->brd_disk->queue = brd->brd_queue; |
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add_disk(brd->brd_disk); |
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list_add_tail(&brd->brd_list, &brd_devices); |
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} |
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out_unlock: |
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mutex_unlock(&brd_devices_mutex); |
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} |
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static void brd_del_one(struct brd_device *brd) |
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{ |
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list_del(&brd->brd_list); |
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del_gendisk(brd->brd_disk); |
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brd_free(brd); |
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} |
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static inline void brd_check_and_reset_par(void) |
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{ |
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if (unlikely(!max_part)) |
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max_part = 1; |
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/* |
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* make sure 'max_part' can be divided exactly by (1U << MINORBITS), |
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* otherwise, it is possiable to get same dev_t when adding partitions. |
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*/ |
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if ((1U << MINORBITS) % max_part != 0) |
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max_part = 1UL << fls(max_part); |
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if (max_part > DISK_MAX_PARTS) { |
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pr_info("brd: max_part can't be larger than %d, reset max_part = %d.\n", |
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DISK_MAX_PARTS, DISK_MAX_PARTS); |
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max_part = DISK_MAX_PARTS; |
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} |
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} |
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static int __init brd_init(void) |
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{ |
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struct brd_device *brd, *next; |
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int i; |
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/* |
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* brd module now has a feature to instantiate underlying device |
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* structure on-demand, provided that there is an access dev node. |
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* |
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* (1) if rd_nr is specified, create that many upfront. else |
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* it defaults to CONFIG_BLK_DEV_RAM_COUNT |
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* (2) User can further extend brd devices by create dev node themselves |
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* and have kernel automatically instantiate actual device |
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* on-demand. Example: |
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* mknod /path/devnod_name b 1 X # 1 is the rd major |
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* fdisk -l /path/devnod_name |
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* If (X / max_part) was not already created it will be created |
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* dynamically. |
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*/ |
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if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe)) |
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return -EIO; |
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brd_check_and_reset_par(); |
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mutex_lock(&brd_devices_mutex); |
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for (i = 0; i < rd_nr; i++) { |
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brd = brd_alloc(i); |
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if (!brd) |
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goto out_free; |
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list_add_tail(&brd->brd_list, &brd_devices); |
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} |
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/* point of no return */ |
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list_for_each_entry(brd, &brd_devices, brd_list) { |
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/* |
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* associate with queue just before adding disk for |
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* avoiding to mess up failure path |
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*/ |
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brd->brd_disk->queue = brd->brd_queue; |
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add_disk(brd->brd_disk); |
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} |
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mutex_unlock(&brd_devices_mutex); |
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pr_info("brd: module loaded\n"); |
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return 0; |
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out_free: |
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list_for_each_entry_safe(brd, next, &brd_devices, brd_list) { |
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list_del(&brd->brd_list); |
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brd_free(brd); |
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} |
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mutex_unlock(&brd_devices_mutex); |
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unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); |
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pr_info("brd: module NOT loaded !!!\n"); |
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return -ENOMEM; |
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} |
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static void __exit brd_exit(void) |
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{ |
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struct brd_device *brd, *next; |
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list_for_each_entry_safe(brd, next, &brd_devices, brd_list) |
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brd_del_one(brd); |
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unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); |
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pr_info("brd: module unloaded\n"); |
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} |
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module_init(brd_init); |
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module_exit(brd_exit); |
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