xfs: handle negative wbc->nr_to_write during sync writeback
authorDave Chinner <dchinner@redhat.com>
Tue, 24 Aug 2010 01:44:56 +0000 (11:44 +1000)
committerDave Chinner <david@fromorbit.com>
Tue, 24 Aug 2010 01:44:56 +0000 (11:44 +1000)
commitefceab1d563153a2b1a6e7d35376241a48126989
tree1c3f9cf4d947a60f4fa4055ef4847af084e9db0e
parent546a1924224078c6f582e68f890b05b387b42653
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: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
fs/xfs/linux-2.6/xfs_aops.c