diff options
| author | Tejun Heo <tj@kernel.org> | 2019-06-27 13:39:52 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-07-10 09:00:57 -0600 |
| commit | d3f77dfdc71835f8db71ca57d272b1fbec9dfc18 (patch) | |
| tree | ced59cee416b39c3c2f80c647c736a2d378772e3 /include/linux/blk_types.h | |
| parent | 653c45c6b90c9659facbef10546d1f3a8e37d0cf (diff) | |
blkcg: implement REQ_CGROUP_PUNT
When a shared kthread needs to issue a bio for a cgroup, doing so
synchronously can lead to priority inversions as the kthread can be
trapped waiting for that cgroup. This patch implements
REQ_CGROUP_PUNT flag which makes submit_bio() punt the actual issuing
to a dedicated per-blkcg work item to avoid such priority inversions.
This will be used to fix priority inversions in btrfs compression and
should be generally useful as we grow filesystem support for
comprehensive IO control.
Cc: Chris Mason <clm@fb.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/linux/blk_types.h')
| -rw-r--r-- | include/linux/blk_types.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index 6a53799c3fe2..feff3fe4467e 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -311,6 +311,14 @@ enum req_flag_bits { __REQ_RAHEAD, /* read ahead, can fail anytime */ __REQ_BACKGROUND, /* background IO */ __REQ_NOWAIT, /* Don't wait if request will block */ + /* + * When a shared kthread needs to issue a bio for a cgroup, doing + * so synchronously can lead to priority inversions as the kthread + * can be trapped waiting for that cgroup. CGROUP_PUNT flag makes + * submit_bio() punt the actual issuing to a dedicated per-blkcg + * work item to avoid such priority inversions. + */ + __REQ_CGROUP_PUNT, /* command specific flags for REQ_OP_WRITE_ZEROES: */ __REQ_NOUNMAP, /* do not free blocks when zeroing */ @@ -337,6 +345,8 @@ enum req_flag_bits { #define REQ_RAHEAD (1ULL << __REQ_RAHEAD) #define REQ_BACKGROUND (1ULL << __REQ_BACKGROUND) #define REQ_NOWAIT (1ULL << __REQ_NOWAIT) +#define REQ_CGROUP_PUNT (1ULL << __REQ_CGROUP_PUNT) + #define REQ_NOUNMAP (1ULL << __REQ_NOUNMAP) #define REQ_HIPRI (1ULL << __REQ_HIPRI) |