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Commit efceab1d authored by Dave Chinner's avatar Dave Chinner Committed by Dave Chinner
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xfs: handle negative wbc->nr_to_write during sync writeback 



During data integrity (WB_SYNC_ALL) writeback, wbc->nr_to_write will
go negative on inodes with more than 1024 dirty pages due to
implementation details of write_cache_pages(). Currently XFS will
abort page clustering in writeback once nr_to_write drops below
zero, and so for data integrity writeback we will do very
inefficient page at a time allocation and IO submission for inodes
with large numbers of dirty pages.

Fix this by only aborting the page clustering code when
wbc->nr_to_write is negative and the sync mode is WB_SYNC_NONE.

Cc: <stable@kernel.org>
Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
parent 546a1924

fs/xfs/linux-2.6/xfs_aops.c

+2 −2
Original line number Diff line number Diff line
@@ -852,8 +852,8 @@ xfs_convert_page( 
		SetPageUptodate(page);



	if (count) {

		wbc->nr_to_write--;

		if (wbc->nr_to_write <= 0)

		if (--wbc->nr_to_write <= 0 &&

		    wbc->sync_mode == WB_SYNC_NONE)

			done = 1;

	}

	xfs_start_page_writeback(page, !page_dirty, count);