Hi all This is the version 4 patch set that attempts to get discard out of the jbd2 commit kthread. When the user delete a lot data and cause discard flooding, the jbd2 commit kthread can be blocked for very long time and then all of the metadata operations are blocked due to no journal space. The xfstest with following parameters, MODULAR=0 TEST_DIR=/mnt/test TEST_DEV=/dev/nbd37p1 SCRATCH_MNT=/mnt/scratch SCRATCH_DEV=/dev/nbd37p2 MOUNT_OPTIONS="-o discard" has passed. The result is consistent w/ or w/o this patch set. There are 5 patches, Patch 1 ~ 3, there are no functional changes in them, but just some preparation for following patches Patch 4 introduces a async kworker to do discard in fstrim fation which implements the core idea of this patch set. Patch 5 flush discard background work in ext4_should_retry_alloc, This fix the generic/371 Any comments are welcome ;) V3 -> V4: - In patch 1, avoid modify two lines in patch 1 when remove 'grou'p parameter - In patch 4, remove redunbant queue_work() in ext4_mb_release(). And queue background discard work to system_unbound_wq as it is not a urgent task. - In patch 5, flush discard kwork in ext4_should_retry_alloc(), instead of invoke ext4_should_retry_alloc in fallocate again. V2 -> V3 - Get rid of the per block group rb tree which carries freed entry. It is not neccesary because we have done aggregation when wait for journal commit. Just use a list to carry the free entries. V1 -> V2 - free the blocks back to mb buddy after commit and then do ftrim fashion discard fs/ext4/balloc.c | 8 ++- fs/ext4/ext4.h | 3 ++ fs/ext4/mballoc.c | 216 +++++++++++++++++++++++++++++++++++++++++++++++++++----------------------------- 3 files changed, 148 insertions(+), 79 deletions(-)
