diff options
| author | Dennis Zhou (Facebook) <dennisszhou@gmail.com> | 2018-09-11 21:41:28 +0300 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2018-09-22 05:29:05 +0300 |
| commit | 07b05bcc3213ac9f8c28c9d835b4bf3d5798cc60 (patch) | |
| tree | efab6cd44e334f64c1a98ae1b57a6894d9130c23 /block/bio.c | |
| parent | 49f4c2dc2b5066e9211101c59cc0828e81d41614 (diff) | |
| download | linux-07b05bcc3213ac9f8c28c9d835b4bf3d5798cc60.tar.xz | |
blkcg: convert blkg_lookup_create to find closest blkg
There are several scenarios where blkg_lookup_create can fail. Examples
include the blkcg dying, request_queue is dying, or simply being OOM. At
the end of the day, most handle this by simply falling back to the
q->root_blkg and calling it a day.
This patch implements the notion of closest blkg. During
blkg_lookup_create, if it fails to create, return the closest blkg
found or the q->root_blkg. blkg_try_get_closest is introduced and used
during association so a bio is always attached to a blkg.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Dennis Zhou <dennisszhou@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/bio.c')
| -rw-r--r-- | block/bio.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/block/bio.c b/block/bio.c index 083f1c9cde0a..bfd41e8b53a8 100644 --- a/block/bio.c +++ b/block/bio.c @@ -2007,21 +2007,24 @@ int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css) EXPORT_SYMBOL_GPL(bio_associate_blkcg); /** - * bio_associate_blkg - associate a bio with the specified blkg + * bio_associate_blkg - associate a bio with the a blkg * @bio: target bio * @blkg: the blkg to associate * - * Associate @bio with the blkg specified by @blkg. This is the queue specific - * blkcg information associated with the @bio, a reference will be taken on the - * @blkg and will be freed when the bio is freed. + * This tries to associate @bio with the specified blkg. Association failure + * is handled by walking up the blkg tree. Therefore, the blkg associated can + * be anything between @blkg and the root_blkg. This situation only happens + * when a cgroup is dying and then the remaining bios will spill to the closest + * alive blkg. + * + * A reference will be taken on the @blkg and will be released when @bio is + * freed. */ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg) { if (unlikely(bio->bi_blkg)) return -EBUSY; - if (!blkg_try_get(blkg)) - return -ENODEV; - bio->bi_blkg = blkg; + bio->bi_blkg = blkg_try_get_closest(blkg); return 0; } |