mm: avoid resetting wb_start after each writeback round
authorJan Kara <jack@suse.cz>
Tue, 10 Aug 2010 00:20:03 +0000 (17:20 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 10 Aug 2010 03:45:03 +0000 (20:45 -0700)
commit7624ee72aa09334af072853457a5d46d9901c3f8
tree046321fdf7f46c38a6e6d686c1cd962e70149c94
parentd9f8984c2c23b91e202a764fe4b15041a29a201a
mm: avoid resetting wb_start after each writeback round

WB_SYNC_NONE writeback is done in rounds of 1024 pages so that we don't
write out some huge inode for too long while starving writeout of other
inodes.  To avoid livelocks, we record time we started writeback in
wbc->wb_start and do not write out inodes which were dirtied after this
time.  But currently, writeback_inodes_wb() resets wb_start each time it
is called thus effectively invalidating this logic and making any
WB_SYNC_NONE writeback prone to livelocks.

This patch makes sure wb_start is set only once when we start writeback.

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Acked-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/fs-writeback.c