diff options
| author |   NeilBrown <neilb@suse.com> | 2017-06-18 14:38:57 +1000 |
|---|---|---|
| committer |   Jens Axboe <axboe@kernel.dk> | 2017-06-18 12:40:59 -0600 |
| commit | 93b27e72904a9869e648c870bf0d04b124fda1c7 (patch) | |
| tree | 93c444acadcdd8e0b7f62b1fa6f545c776fb1a3a /block | |
| parent | blk: make the bioset rescue_workqueue optional. (diff) | |
| download | wireguard-linux-93b27e72904a9869e648c870bf0d04b124fda1c7.tar.xz wireguard-linux-93b27e72904a9869e648c870bf0d04b124fda1c7.zip | |
blk: use non-rescuing bioset for q->bio_split.
A rescuing bioset is only useful if there might be bios from
that same bioset on the bio_list_on_stack queue at a time
when bio_alloc_bioset() is called. This never applies to
q->bio_split.
Allocations from q->bio_split are only ever made from
blk_queue_split() which is only ever called early in each of
various make_request_fn()s. The original bio (call this A)
is then passed to generic_make_request() and is placed on
the bio_list_on_stack queue, and the bio that was allocated
from q->bio_split (B) is processed.
The processing of this may cause other bios to be passed to
generic_make_request() or may even cause the bio B itself to
be passed, possible after some prefix has been split off
(using some other bioset).
generic_make_request() now guarantees that all of these bios
(B and dependants) will be fully processed before the tail
of the original bio A gets handled. None of these early bios
can possible trigger an allocation from the original
q->bio_split as they are either too small to require
splitting or (more likely) are destined for a different queue.
The next time that the original q->bio_split might be used
by this thread is when A is processed again, as it might
still be too big to handle directly. By this time there
cannot be any other bios allocated from q->bio_split in the
generic_make_request() queue. So no rescuing will ever be
needed.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-core.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/block/blk-core.c b/block/blk-core.c index 9bd10c46a538..62cf92550512 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -790,8 +790,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) if (q->id < 0) goto fail_q; - q->bio_split = bioset_create(BIO_POOL_SIZE, 0, (BIOSET_NEED_BVECS | - BIOSET_NEED_RESCUER)); + q->bio_split = bioset_create(BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS); if (!q->bio_split) goto fail_id; |