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authorNeilBrown <neilb@suse.com>2017-08-30 13:47:12 +0200
committerJens Axboe <axboe@kernel.dk>2017-08-30 08:10:02 -0600
commit974c58566e0b047d785701b6cf788a810072a4c1 (patch)
tree449f46a687f10defc40ac4bcc14e077d940ae7ae /drivers/block
parent5fc1efd5de1a1685e68d80981c7676c4d323d93c (diff)
downloadlinux-974c58566e0b047d785701b6cf788a810072a4c1.tar.bz2
drbd: remove BIOSET_NEED_RESCUER flag from drbd_{md_,}io_bio_set
Careful analysis shows that this flag is not needed. The RESCUER flag is only needed when a make_request_fn might: - allocate a bio from the bioset - submit it with generic_make_request() or similar - allocate another bio from the bioset The second allocation can block until the first bio is processed, so a rescuer is needed to ensure the first bio does get processed. With a rescuer it will only get processed when the make_request_fn completes. In drbd, allocations from drbd_io_bio_set happen from drbd_new_req() or w_restart_disk_io() which is only called to handle RESTART_FROZEN_DISK_IO. In former is called precisely once from the make_request_fn. The later is never called by within the make_request_fn. So there cannot be two allocations in the same call to the make_request_fn, so a rescuer is not needed. Allocations from drbd_md_io_bio_set are used for IO to the bitmap and the activity log. There are only accessed from worker threads and workqueues, never directly from make_request_fn. Again, the rescuer isn't needed. Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/drbd/drbd_main.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 92ba4c08835c..8cb3791898ae 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2178,13 +2178,12 @@ static int drbd_create_mempools(void)
goto Enomem;
/* mempools */
- drbd_io_bio_set = bioset_create(BIO_POOL_SIZE, 0, BIOSET_NEED_RESCUER);
+ drbd_io_bio_set = bioset_create(BIO_POOL_SIZE, 0, 0);
if (drbd_io_bio_set == NULL)
goto Enomem;
drbd_md_io_bio_set = bioset_create(DRBD_MIN_POOL_PAGES, 0,
- BIOSET_NEED_BVECS |
- BIOSET_NEED_RESCUER);
+ BIOSET_NEED_BVECS);
if (drbd_md_io_bio_set == NULL)
goto Enomem;