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authorJan Kara <jack@suse.cz>2024-01-23 18:58:26 +0100
committerJens Axboe <axboe@kernel.dk>2024-02-06 09:44:03 -0700
commitf814bdda774c183b0cc15ec8f3b6e7c6f4527ba5 (patch)
treef423245937edd1e7cf7be59f948d04c8c66ee956 /mm/backing-dev.c
parentf3c89983cb4fc00be64eb0d5cbcfcdf2cacb965e (diff)
blk-wbt: Fix detection of dirty-throttled tasks
The detection of dirty-throttled tasks in blk-wbt has been subtly broken since its beginning in 2016. Namely if we are doing cgroup writeback and the throttled task is not in the root cgroup, balance_dirty_pages() will set dirty_sleep for the non-root bdi_writeback structure. However blk-wbt checks dirty_sleep only in the root cgroup bdi_writeback structure. Thus detection of recently throttled tasks is not working in this case (we noticed this when we switched to cgroup v2 and suddently writeback was slow). Since blk-wbt has no easy way to get to proper bdi_writeback and furthermore its intention has always been to work on the whole device rather than on individual cgroups, just move the dirty_sleep timestamp from bdi_writeback to backing_dev_info. That fixes the checking for recently throttled task and saves memory for everybody as a bonus. CC: stable@vger.kernel.org Fixes: b57d74aff9ab ("writeback: track if we're sleeping on progress in balance_dirty_pages()") Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20240123175826.21452-1-jack@suse.cz [axboe: fixup indentation errors] Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'mm/backing-dev.c')
-rw-r--r--mm/backing-dev.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 1e3447bccdb1..e039d05304dd 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -436,7 +436,6 @@ static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
INIT_LIST_HEAD(&wb->work_list);
INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
INIT_DELAYED_WORK(&wb->bw_dwork, wb_update_bandwidth_workfn);
- wb->dirty_sleep = jiffies;
err = fprop_local_init_percpu(&wb->completions, gfp);
if (err)
@@ -921,6 +920,7 @@ int bdi_init(struct backing_dev_info *bdi)
INIT_LIST_HEAD(&bdi->bdi_list);
INIT_LIST_HEAD(&bdi->wb_list);
init_waitqueue_head(&bdi->wb_waitq);
+ bdi->last_bdp_sleep = jiffies;
return cgwb_bdi_init(bdi);
}