Messages in this thread Patch in this message | | | Subject | [PATCH 5/5] page_writeback: put account_page_redirty() after set_page_dirty() | From | Konstantin Khlebnikov <> | Date | Mon, 08 Jul 2013 13:52:17 +0400 |
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Function account_page_redirty() fixes dirty pages counter for redieried pages. This patch prevents temporary underflows of dirty pages counters on zone/bdi and current->nr_dirtied. This puts decrement after increment.
__set_page_dirty_nobuffers() in redirty_page_for_writeback() always returns true because this page is locked and all ptes are write-protected by previously called clear_page_dirty_for_io(). Thus nobody can mark it dirty except current task. This prevents multy-threaded scenarios of taks->nr_dirtied underflows.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org> --- fs/btrfs/extent_io.c | 2 +- mm/page-writeback.c | 7 ++++++- 2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 6bca947..d17fb9b 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -1311,8 +1311,8 @@ int extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end) while (index <= end_index) { page = find_get_page(inode->i_mapping, index); BUG_ON(!page); /* Pages should be in the extent_io_tree */ - account_page_redirty(page); __set_page_dirty_nobuffers(page); + account_page_redirty(page); page_cache_release(page); index++; } diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 4514ad7..a599f38 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2061,6 +2061,8 @@ EXPORT_SYMBOL(__set_page_dirty_nobuffers); * counters (NR_WRITTEN, BDI_WRITTEN) in long term. The mismatches will lead to * systematic errors in balanced_dirty_ratelimit and the dirty pages position * control. + * + * Must be called after marking page dirty. */ void account_page_redirty(struct page *page) { @@ -2080,9 +2082,12 @@ EXPORT_SYMBOL(account_page_redirty); */ int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) { + int ret; + wbc->pages_skipped++; + ret = __set_page_dirty_nobuffers(page); account_page_redirty(page); - return __set_page_dirty_nobuffers(page); + return ret; } EXPORT_SYMBOL(redirty_page_for_writepage);
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