On Fri, 23 Jan 2026, Zhihao Cheng wrote:
> 在 2026/1/16 20:07, Zhihao Cheng 写道:
>
> friendly ping
Hi
I find it quite hacky to set bi_bdev and overwrite it later. I came up
with this patch that clones the control group association explictely, it
fixes your testcase. Please test it and report if it works for you.
Mikulas
dm: use bio_clone_blkg_association
The origin bio carries blk-cgroup information which could be set from
foreground(task_css(css) - wbc->wb->blkcg_css), so the blkcg won't
control buffer io since commit ca522482e3eaf ("dm: pass NULL bdev to
bio_alloc_clone"). The synchronous io is still under control by blkcg,
because 'bio->bi_blkg' is set by io submitting task which has been added
into 'cgroup.procs'.
Fix it by using bio_clone_blkg_association when submitting a cloned bio.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=220985
Fixes: ca522482e3eaf ("dm: pass NULL bdev to bio_alloc_clone")
Reported-by: Zhihao Cheng <[email protected]>
Signed-off-by: Mikulas Patocka <[email protected]>
---
drivers/md/dm.c | 2 ++
1 file changed, 2 insertions(+)
Index: linux-2.6/drivers/md/dm.c
===================================================================
--- linux-2.6.orig/drivers/md/dm.c 2026-01-06 15:55:41.000000000 +0100
+++ linux-2.6/drivers/md/dm.c 2026-01-23 17:07:50.000000000 +0100
@@ -1364,6 +1364,8 @@ void dm_submit_bio_remap(struct bio *clo
if (!tgt_clone)
tgt_clone = clone;
+ bio_clone_blkg_association(tgt_clone, io->orig_bio);
+
/*
* Account io->origin_bio to DM dev on behalf of target
* that took ownership of IO with DM_MAPIO_SUBMITTED.
