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authorYu Kuai <yukuai3@huawei.com>2023-01-03 11:47:55 +0300
committerJens Axboe <axboe@kernel.dk>2023-01-16 06:53:27 +0300
commit216f764716f34fe68cedc7296ae2043a7727e640 (patch)
tree2e5261483bfdff8833f016b56ea997a1b48294d7 /block
parentee16c404f9bd03c6e083f76d45be0b6a774c0d14 (diff)
downloadlinux-216f764716f34fe68cedc7296ae2043a7727e640.tar.xz
block, bfq: switch 'bfqg->ref' to use atomic refcount apis
The updating of 'bfqg->ref' should be protected by 'bfqd->lock', however, during code review, we found that bfq_pd_free() update 'bfqg->ref' without holding the lock, which is problematic: 1) bfq_pd_free() triggered by removing cgroup is called asynchronously; 2) bfqq will grab bfqg reference, and exit bfqq will drop the reference, which can concurrent with 1). Unfortunately, 'bfqd->lock' can't be held here because 'bfqd' might already be freed in bfq_pd_free(). Fix the problem by using atomic refcount apis. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20230103084755.1256479-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/bfq-cgroup.c8
-rw-r--r--block/bfq-iosched.h2
2 files changed, 4 insertions, 6 deletions
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 1b2829e99dad..7d9b15f0dbd5 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -316,14 +316,12 @@ struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
static void bfqg_get(struct bfq_group *bfqg)
{
- bfqg->ref++;
+ refcount_inc(&bfqg->ref);
}
static void bfqg_put(struct bfq_group *bfqg)
{
- bfqg->ref--;
-
- if (bfqg->ref == 0)
+ if (refcount_dec_and_test(&bfqg->ref))
kfree(bfqg);
}
@@ -530,7 +528,7 @@ static struct blkg_policy_data *bfq_pd_alloc(gfp_t gfp, struct request_queue *q,
}
/* see comments in bfq_bic_update_cgroup for why refcounting */
- bfqg_get(bfqg);
+ refcount_set(&bfqg->ref, 1);
return &bfqg->pd;
}
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 41aa151ccc22..466e4865ace6 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -928,7 +928,7 @@ struct bfq_group {
char blkg_path[128];
/* reference counter (see comments in bfq_bic_update_cgroup) */
- int ref;
+ refcount_t ref;
/* Is bfq_group still online? */
bool online;