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author | Qu Wenruo <wqu@suse.com> | 2021-09-27 15:22:05 +0800 |
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committer | David Sterba <dsterba@suse.com> | 2021-10-26 19:08:05 +0200 |
commit | e55a0de185726ca43e8a31d363ad73c4f0a6770b (patch) | |
tree | ec509be60248c679a7228fd7c8f7c85be918fe3c /fs/btrfs/subpage.c | |
parent | d4088803f51140e9324f66453bdd24e48f982a1e (diff) | |
download | linux-e55a0de185726ca43e8a31d363ad73c4f0a6770b.tar.bz2 |
btrfs: rework page locking in __extent_writepage()
Pages passed to __extent_writepage() are always locked, but they may be
locked by different functions.
There are two types of locked page for __extent_writepage():
- Page locked by plain lock_page()
It should not have any subpage::writers count.
Can be unlocked by unlock_page().
This is the most common locked page for __extent_writepage() called
inside extent_write_cache_pages() or extent_write_full_page().
Rarer cases include the @locked_page from extent_write_locked_range().
- Page locked by lock_delalloc_pages()
There is only one caller, all pages except @locked_page for
extent_write_locked_range().
In this case, we have to call subpage helper to handle the case.
So here we introduce a helper, btrfs_page_unlock_writer(), to allow
__extent_writepage() to unlock different locked pages.
And since for all other callers of __extent_writepage() their pages are
ensured to be locked by lock_page(), also add an extra check for
epd::extent_locked to unlock such pages directly.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/subpage.c')
-rw-r--r-- | fs/btrfs/subpage.c | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c index ed9936cdd267..265b6aa1c662 100644 --- a/fs/btrfs/subpage.c +++ b/fs/btrfs/subpage.c @@ -690,3 +690,46 @@ void btrfs_page_assert_not_dirty(const struct btrfs_fs_info *fs_info, ASSERT(PagePrivate(page) && page->private); ASSERT(subpage_test_bitmap_all_zero(fs_info, subpage, dirty)); } + +/* + * Handle different locked pages with different page sizes: + * + * - Page locked by plain lock_page() + * It should not have any subpage::writers count. + * Can be unlocked by unlock_page(). + * This is the most common locked page for __extent_writepage() called + * inside extent_write_cache_pages() or extent_write_full_page(). + * Rarer cases include the @locked_page from extent_write_locked_range(). + * + * - Page locked by lock_delalloc_pages() + * There is only one caller, all pages except @locked_page for + * extent_write_locked_range(). + * In this case, we have to call subpage helper to handle the case. + */ +void btrfs_page_unlock_writer(struct btrfs_fs_info *fs_info, struct page *page, + u64 start, u32 len) +{ + struct btrfs_subpage *subpage; + + ASSERT(PageLocked(page)); + /* For regular page size case, we just unlock the page */ + if (fs_info->sectorsize == PAGE_SIZE) + return unlock_page(page); + + ASSERT(PagePrivate(page) && page->private); + subpage = (struct btrfs_subpage *)page->private; + + /* + * For subpage case, there are two types of locked page. With or + * without writers number. + * + * Since we own the page lock, no one else could touch subpage::writers + * and we are safe to do several atomic operations without spinlock. + */ + if (atomic_read(&subpage->writers)) + /* No writers, locked by plain lock_page() */ + return unlock_page(page); + + /* Have writers, use proper subpage helper to end it */ + btrfs_page_end_writer_lock(fs_info, page, start, len); +} |