diff options
| author | Yu Kuai <yukuai3@huawei.com> | 2023-01-03 16:47:55 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2023-01-15 20:53:27 -0700 |
| commit | 216f764716f34fe68cedc7296ae2043a7727e640 (patch) | |
| tree | 2e5261483bfdff8833f016b56ea997a1b48294d7 /block | |
| parent | ee16c404f9bd03c6e083f76d45be0b6a774c0d14 (diff) | |
| download | linux-216f764716f34fe68cedc7296ae2043a7727e640.tar.bz2 | |
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.c | 8 | ||||
| -rw-r--r-- | block/bfq-iosched.h | 2 |
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; |