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561 lines
18 KiB
561 lines
18 KiB
// SPDX-License-Identifier: GPL-2.0 |
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#include <linux/slab.h> |
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#include "ctree.h" |
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#include "subpage.h" |
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#include "btrfs_inode.h" |
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|
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/* |
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* Subpage (sectorsize < PAGE_SIZE) support overview: |
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* |
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* Limitations: |
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* |
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* - Only support 64K page size for now |
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* This is to make metadata handling easier, as 64K page would ensure |
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* all nodesize would fit inside one page, thus we don't need to handle |
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* cases where a tree block crosses several pages. |
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* |
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* - Only metadata read-write for now |
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* The data read-write part is in development. |
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* |
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* - Metadata can't cross 64K page boundary |
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* btrfs-progs and kernel have done that for a while, thus only ancient |
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* filesystems could have such problem. For such case, do a graceful |
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* rejection. |
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* |
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* Special behavior: |
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* |
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* - Metadata |
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* Metadata read is fully supported. |
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* Meaning when reading one tree block will only trigger the read for the |
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* needed range, other unrelated range in the same page will not be touched. |
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* |
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* Metadata write support is partial. |
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* The writeback is still for the full page, but we will only submit |
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* the dirty extent buffers in the page. |
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* |
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* This means, if we have a metadata page like this: |
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* |
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* Page offset |
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* 0 16K 32K 48K 64K |
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* |/////////| |///////////| |
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* \- Tree block A \- Tree block B |
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* |
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* Even if we just want to writeback tree block A, we will also writeback |
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* tree block B if it's also dirty. |
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* |
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* This may cause extra metadata writeback which results more COW. |
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* |
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* Implementation: |
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* |
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* - Common |
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* Both metadata and data will use a new structure, btrfs_subpage, to |
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* record the status of each sector inside a page. This provides the extra |
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* granularity needed. |
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* |
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* - Metadata |
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* Since we have multiple tree blocks inside one page, we can't rely on page |
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* locking anymore, or we will have greatly reduced concurrency or even |
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* deadlocks (hold one tree lock while trying to lock another tree lock in |
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* the same page). |
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* |
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* Thus for metadata locking, subpage support relies on io_tree locking only. |
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* This means a slightly higher tree locking latency. |
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*/ |
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int btrfs_attach_subpage(const struct btrfs_fs_info *fs_info, |
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struct page *page, enum btrfs_subpage_type type) |
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{ |
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struct btrfs_subpage *subpage = NULL; |
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int ret; |
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/* |
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* We have cases like a dummy extent buffer page, which is not mappped |
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* and doesn't need to be locked. |
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*/ |
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if (page->mapping) |
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ASSERT(PageLocked(page)); |
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/* Either not subpage, or the page already has private attached */ |
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if (fs_info->sectorsize == PAGE_SIZE || PagePrivate(page)) |
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return 0; |
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ret = btrfs_alloc_subpage(fs_info, &subpage, type); |
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if (ret < 0) |
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return ret; |
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attach_page_private(page, subpage); |
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return 0; |
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} |
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void btrfs_detach_subpage(const struct btrfs_fs_info *fs_info, |
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struct page *page) |
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{ |
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struct btrfs_subpage *subpage; |
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/* Either not subpage, or already detached */ |
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if (fs_info->sectorsize == PAGE_SIZE || !PagePrivate(page)) |
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return; |
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subpage = (struct btrfs_subpage *)detach_page_private(page); |
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ASSERT(subpage); |
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btrfs_free_subpage(subpage); |
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} |
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int btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info, |
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struct btrfs_subpage **ret, |
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enum btrfs_subpage_type type) |
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{ |
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if (fs_info->sectorsize == PAGE_SIZE) |
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return 0; |
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*ret = kzalloc(sizeof(struct btrfs_subpage), GFP_NOFS); |
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if (!*ret) |
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return -ENOMEM; |
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spin_lock_init(&(*ret)->lock); |
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if (type == BTRFS_SUBPAGE_METADATA) { |
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atomic_set(&(*ret)->eb_refs, 0); |
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} else { |
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atomic_set(&(*ret)->readers, 0); |
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atomic_set(&(*ret)->writers, 0); |
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} |
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return 0; |
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} |
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void btrfs_free_subpage(struct btrfs_subpage *subpage) |
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{ |
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kfree(subpage); |
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} |
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/* |
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* Increase the eb_refs of current subpage. |
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* |
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* This is important for eb allocation, to prevent race with last eb freeing |
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* of the same page. |
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* With the eb_refs increased before the eb inserted into radix tree, |
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* detach_extent_buffer_page() won't detach the page private while we're still |
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* allocating the extent buffer. |
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*/ |
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void btrfs_page_inc_eb_refs(const struct btrfs_fs_info *fs_info, |
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struct page *page) |
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{ |
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struct btrfs_subpage *subpage; |
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if (fs_info->sectorsize == PAGE_SIZE) |
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return; |
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ASSERT(PagePrivate(page) && page->mapping); |
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lockdep_assert_held(&page->mapping->private_lock); |
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subpage = (struct btrfs_subpage *)page->private; |
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atomic_inc(&subpage->eb_refs); |
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} |
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void btrfs_page_dec_eb_refs(const struct btrfs_fs_info *fs_info, |
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struct page *page) |
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{ |
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struct btrfs_subpage *subpage; |
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if (fs_info->sectorsize == PAGE_SIZE) |
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return; |
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ASSERT(PagePrivate(page) && page->mapping); |
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lockdep_assert_held(&page->mapping->private_lock); |
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subpage = (struct btrfs_subpage *)page->private; |
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ASSERT(atomic_read(&subpage->eb_refs)); |
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atomic_dec(&subpage->eb_refs); |
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} |
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static void btrfs_subpage_assert(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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/* Basic checks */ |
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ASSERT(PagePrivate(page) && page->private); |
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ASSERT(IS_ALIGNED(start, fs_info->sectorsize) && |
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IS_ALIGNED(len, fs_info->sectorsize)); |
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/* |
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* The range check only works for mapped page, we can still have |
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* unmapped page like dummy extent buffer pages. |
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*/ |
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if (page->mapping) |
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ASSERT(page_offset(page) <= start && |
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start + len <= page_offset(page) + PAGE_SIZE); |
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} |
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void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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const int nbits = len >> fs_info->sectorsize_bits; |
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btrfs_subpage_assert(fs_info, page, start, len); |
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atomic_add(nbits, &subpage->readers); |
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} |
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void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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const int nbits = len >> fs_info->sectorsize_bits; |
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bool is_data; |
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bool last; |
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btrfs_subpage_assert(fs_info, page, start, len); |
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is_data = is_data_inode(page->mapping->host); |
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ASSERT(atomic_read(&subpage->readers) >= nbits); |
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last = atomic_sub_and_test(nbits, &subpage->readers); |
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/* |
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* For data we need to unlock the page if the last read has finished. |
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* |
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* And please don't replace @last with atomic_sub_and_test() call |
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* inside if () condition. |
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* As we want the atomic_sub_and_test() to be always executed. |
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*/ |
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if (is_data && last) |
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unlock_page(page); |
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} |
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static void btrfs_subpage_clamp_range(struct page *page, u64 *start, u32 *len) |
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{ |
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u64 orig_start = *start; |
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u32 orig_len = *len; |
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*start = max_t(u64, page_offset(page), orig_start); |
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*len = min_t(u64, page_offset(page) + PAGE_SIZE, |
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orig_start + orig_len) - *start; |
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} |
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void btrfs_subpage_start_writer(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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const int nbits = (len >> fs_info->sectorsize_bits); |
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int ret; |
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btrfs_subpage_assert(fs_info, page, start, len); |
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ASSERT(atomic_read(&subpage->readers) == 0); |
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ret = atomic_add_return(nbits, &subpage->writers); |
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ASSERT(ret == nbits); |
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} |
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bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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const int nbits = (len >> fs_info->sectorsize_bits); |
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btrfs_subpage_assert(fs_info, page, start, len); |
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ASSERT(atomic_read(&subpage->writers) >= nbits); |
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return atomic_sub_and_test(nbits, &subpage->writers); |
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} |
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/* |
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* Lock a page for delalloc page writeback. |
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* |
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* Return -EAGAIN if the page is not properly initialized. |
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* Return 0 with the page locked, and writer counter updated. |
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* |
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* Even with 0 returned, the page still need extra check to make sure |
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* it's really the correct page, as the caller is using |
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* find_get_pages_contig(), which can race with page invalidating. |
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*/ |
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int btrfs_page_start_writer_lock(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) { |
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lock_page(page); |
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return 0; |
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} |
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lock_page(page); |
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if (!PagePrivate(page) || !page->private) { |
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unlock_page(page); |
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return -EAGAIN; |
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} |
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btrfs_subpage_clamp_range(page, &start, &len); |
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btrfs_subpage_start_writer(fs_info, page, start, len); |
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return 0; |
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} |
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void btrfs_page_end_writer_lock(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) |
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return unlock_page(page); |
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btrfs_subpage_clamp_range(page, &start, &len); |
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if (btrfs_subpage_end_and_test_writer(fs_info, page, start, len)) |
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unlock_page(page); |
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} |
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/* |
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* Convert the [start, start + len) range into a u16 bitmap |
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* |
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* For example: if start == page_offset() + 16K, len = 16K, we get 0x00f0. |
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*/ |
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static u16 btrfs_subpage_calc_bitmap(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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const int bit_start = offset_in_page(start) >> fs_info->sectorsize_bits; |
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const int nbits = len >> fs_info->sectorsize_bits; |
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btrfs_subpage_assert(fs_info, page, start, len); |
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/* |
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* Here nbits can be 16, thus can go beyond u16 range. We make the |
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* first left shift to be calculate in unsigned long (at least u32), |
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* then truncate the result to u16. |
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*/ |
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return (u16)(((1UL << nbits) - 1) << bit_start); |
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} |
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void btrfs_subpage_set_uptodate(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); |
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unsigned long flags; |
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spin_lock_irqsave(&subpage->lock, flags); |
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subpage->uptodate_bitmap |= tmp; |
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if (subpage->uptodate_bitmap == U16_MAX) |
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SetPageUptodate(page); |
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spin_unlock_irqrestore(&subpage->lock, flags); |
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} |
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void btrfs_subpage_clear_uptodate(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); |
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unsigned long flags; |
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spin_lock_irqsave(&subpage->lock, flags); |
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subpage->uptodate_bitmap &= ~tmp; |
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ClearPageUptodate(page); |
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spin_unlock_irqrestore(&subpage->lock, flags); |
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} |
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void btrfs_subpage_set_error(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); |
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unsigned long flags; |
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spin_lock_irqsave(&subpage->lock, flags); |
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subpage->error_bitmap |= tmp; |
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SetPageError(page); |
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spin_unlock_irqrestore(&subpage->lock, flags); |
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} |
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void btrfs_subpage_clear_error(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); |
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unsigned long flags; |
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spin_lock_irqsave(&subpage->lock, flags); |
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subpage->error_bitmap &= ~tmp; |
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if (subpage->error_bitmap == 0) |
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ClearPageError(page); |
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spin_unlock_irqrestore(&subpage->lock, flags); |
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} |
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void btrfs_subpage_set_dirty(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); |
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unsigned long flags; |
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spin_lock_irqsave(&subpage->lock, flags); |
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subpage->dirty_bitmap |= tmp; |
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spin_unlock_irqrestore(&subpage->lock, flags); |
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set_page_dirty(page); |
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} |
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/* |
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* Extra clear_and_test function for subpage dirty bitmap. |
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* |
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* Return true if we're the last bits in the dirty_bitmap and clear the |
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* dirty_bitmap. |
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* Return false otherwise. |
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* |
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* NOTE: Callers should manually clear page dirty for true case, as we have |
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* extra handling for tree blocks. |
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*/ |
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bool btrfs_subpage_clear_and_test_dirty(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); |
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unsigned long flags; |
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bool last = false; |
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spin_lock_irqsave(&subpage->lock, flags); |
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subpage->dirty_bitmap &= ~tmp; |
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if (subpage->dirty_bitmap == 0) |
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last = true; |
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spin_unlock_irqrestore(&subpage->lock, flags); |
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return last; |
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} |
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void btrfs_subpage_clear_dirty(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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bool last; |
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last = btrfs_subpage_clear_and_test_dirty(fs_info, page, start, len); |
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if (last) |
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clear_page_dirty_for_io(page); |
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} |
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void btrfs_subpage_set_writeback(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); |
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unsigned long flags; |
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spin_lock_irqsave(&subpage->lock, flags); |
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subpage->writeback_bitmap |= tmp; |
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set_page_writeback(page); |
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spin_unlock_irqrestore(&subpage->lock, flags); |
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} |
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void btrfs_subpage_clear_writeback(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); |
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unsigned long flags; |
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spin_lock_irqsave(&subpage->lock, flags); |
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subpage->writeback_bitmap &= ~tmp; |
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if (subpage->writeback_bitmap == 0) |
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end_page_writeback(page); |
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spin_unlock_irqrestore(&subpage->lock, flags); |
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} |
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void btrfs_subpage_set_ordered(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); |
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unsigned long flags; |
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spin_lock_irqsave(&subpage->lock, flags); |
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subpage->ordered_bitmap |= tmp; |
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SetPageOrdered(page); |
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spin_unlock_irqrestore(&subpage->lock, flags); |
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} |
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void btrfs_subpage_clear_ordered(const struct btrfs_fs_info *fs_info, |
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struct page *page, u64 start, u32 len) |
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{ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; |
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const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); |
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unsigned long flags; |
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spin_lock_irqsave(&subpage->lock, flags); |
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subpage->ordered_bitmap &= ~tmp; |
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if (subpage->ordered_bitmap == 0) |
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ClearPageOrdered(page); |
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spin_unlock_irqrestore(&subpage->lock, flags); |
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} |
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/* |
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* Unlike set/clear which is dependent on each page status, for test all bits |
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* are tested in the same way. |
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*/ |
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#define IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(name) \ |
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bool btrfs_subpage_test_##name(const struct btrfs_fs_info *fs_info, \ |
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struct page *page, u64 start, u32 len) \ |
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{ \ |
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struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private; \ |
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const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len); \ |
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unsigned long flags; \ |
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bool ret; \ |
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\ |
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spin_lock_irqsave(&subpage->lock, flags); \ |
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ret = ((subpage->name##_bitmap & tmp) == tmp); \ |
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spin_unlock_irqrestore(&subpage->lock, flags); \ |
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return ret; \ |
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} |
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IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(uptodate); |
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IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(error); |
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IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(dirty); |
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IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(writeback); |
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IMPLEMENT_BTRFS_SUBPAGE_TEST_OP(ordered); |
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|
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/* |
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* Note that, in selftests (extent-io-tests), we can have empty fs_info passed |
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* in. We only test sectorsize == PAGE_SIZE cases so far, thus we can fall |
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* back to regular sectorsize branch. |
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*/ |
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#define IMPLEMENT_BTRFS_PAGE_OPS(name, set_page_func, clear_page_func, \ |
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test_page_func) \ |
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void btrfs_page_set_##name(const struct btrfs_fs_info *fs_info, \ |
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struct page *page, u64 start, u32 len) \ |
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{ \ |
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if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) { \ |
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set_page_func(page); \ |
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return; \ |
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} \ |
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btrfs_subpage_set_##name(fs_info, page, start, len); \ |
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} \ |
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void btrfs_page_clear_##name(const struct btrfs_fs_info *fs_info, \ |
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struct page *page, u64 start, u32 len) \ |
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{ \ |
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if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) { \ |
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clear_page_func(page); \ |
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return; \ |
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} \ |
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btrfs_subpage_clear_##name(fs_info, page, start, len); \ |
|
} \ |
|
bool btrfs_page_test_##name(const struct btrfs_fs_info *fs_info, \ |
|
struct page *page, u64 start, u32 len) \ |
|
{ \ |
|
if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) \ |
|
return test_page_func(page); \ |
|
return btrfs_subpage_test_##name(fs_info, page, start, len); \ |
|
} \ |
|
void btrfs_page_clamp_set_##name(const struct btrfs_fs_info *fs_info, \ |
|
struct page *page, u64 start, u32 len) \ |
|
{ \ |
|
if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) { \ |
|
set_page_func(page); \ |
|
return; \ |
|
} \ |
|
btrfs_subpage_clamp_range(page, &start, &len); \ |
|
btrfs_subpage_set_##name(fs_info, page, start, len); \ |
|
} \ |
|
void btrfs_page_clamp_clear_##name(const struct btrfs_fs_info *fs_info, \ |
|
struct page *page, u64 start, u32 len) \ |
|
{ \ |
|
if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) { \ |
|
clear_page_func(page); \ |
|
return; \ |
|
} \ |
|
btrfs_subpage_clamp_range(page, &start, &len); \ |
|
btrfs_subpage_clear_##name(fs_info, page, start, len); \ |
|
} \ |
|
bool btrfs_page_clamp_test_##name(const struct btrfs_fs_info *fs_info, \ |
|
struct page *page, u64 start, u32 len) \ |
|
{ \ |
|
if (unlikely(!fs_info) || fs_info->sectorsize == PAGE_SIZE) \ |
|
return test_page_func(page); \ |
|
btrfs_subpage_clamp_range(page, &start, &len); \ |
|
return btrfs_subpage_test_##name(fs_info, page, start, len); \ |
|
} |
|
IMPLEMENT_BTRFS_PAGE_OPS(uptodate, SetPageUptodate, ClearPageUptodate, |
|
PageUptodate); |
|
IMPLEMENT_BTRFS_PAGE_OPS(error, SetPageError, ClearPageError, PageError); |
|
IMPLEMENT_BTRFS_PAGE_OPS(dirty, set_page_dirty, clear_page_dirty_for_io, |
|
PageDirty); |
|
IMPLEMENT_BTRFS_PAGE_OPS(writeback, set_page_writeback, end_page_writeback, |
|
PageWriteback); |
|
IMPLEMENT_BTRFS_PAGE_OPS(ordered, SetPageOrdered, ClearPageOrdered, |
|
PageOrdered);
|
|
|