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author | NeilBrown <neilb@suse.com> | 2017-08-30 14:47:12 +0300 |
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committer | Jens Axboe <axboe@kernel.dk> | 2017-08-30 17:10:02 +0300 |
commit | 974c58566e0b047d785701b6cf788a810072a4c1 (patch) | |
tree | 449f46a687f10defc40ac4bcc14e077d940ae7ae /fs/kernfs/mount.c | |
parent | 5fc1efd5de1a1685e68d80981c7676c4d323d93c (diff) | |
download | linux-974c58566e0b047d785701b6cf788a810072a4c1.tar.xz |
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 'fs/kernfs/mount.c')
0 files changed, 0 insertions, 0 deletions