On 08/25/2015 12:11 PM, Tejun Heo wrote:
e79729123f63 ("writeback: don't issue wb_writeback_work if clean") updated writeback path to avoid kicking writeback work items if there are no inodes to be written out; unfortunately, the avoidance logic was too aggressive and broke sync_inodes_sb().* sync_inodes_sb() must write out I_DIRTY_TIME inodes but I_DIRTY_TIME inodes dont't contribute to bdi/wb_has_dirty_io() tests and were being skipped over. * inodes are taken off wb->b_dirty/io/more_io lists after writeback starts on them. sync_inodes_sb() skipping wait_sb_inodes() when bdi_has_dirty_io() breaks it by making it return while writebacks are in-flight. This patch fixes the breakages by * Removing bdi_has_dirty_io() shortcut from bdi_split_work_to_wbs(). The callers are already testing the condition. * Removing bdi_has_dirty_io() shortcut from sync_inodes_sb() so that it always calls into bdi_split_work_to_wbs() and wait_sb_inodes(). * Making bdi_split_work_to_wbs() consider the b_dirty_time list for WB_SYNC_ALL writebacks. Kudos to Eryu, Dave and Jan for tracking down the issue. Signed-off-by: Tejun Heo <[email protected]> Fixes: e79729123f63 ("writeback: don't issue wb_writeback_work if clean") Link: http://lkml.kernel.org/g/[email protected] Reported-and-bisected-by: Eryu Guan <[email protected]> Cc: Dave Chinner <[email protected]> Cc: Jan Kara <[email protected]> Cc: Ted Ts'o <[email protected]>
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