linux/drivers/block/drbd
NeilBrown 974c58566e 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>
2017-08-30 08:10:02 -06:00
..
drbd_actlog.c block: replace bi_bdev with a gendisk pointer and partitions index 2017-08-23 12:49:55 -06:00
drbd_bitmap.c block: replace bi_bdev with a gendisk pointer and partitions index 2017-08-23 12:49:55 -06:00
drbd_debugfs.c drbd: make intelligent use of blkdev_issue_zeroout 2017-04-08 11:25:38 -06:00
drbd_debugfs.h drbd: debugfs: add basic hierarchy 2014-07-10 18:35:16 +02:00
drbd_int.h drbd: move global variables to drbd namespace and make some static 2017-08-29 15:34:46 -06:00
drbd_interval.c drbd: use RB_DECLARE_CALLBACKS() to define augment callbacks 2014-09-18 09:00:17 -06:00
drbd_interval.h drbd: code cleanups without semantic changes 2016-06-13 21:43:07 -06:00
drbd_main.c drbd: remove BIOSET_NEED_RESCUER flag from drbd_{md_,}io_bio_set 2017-08-30 08:10:02 -06:00
drbd_nl.c drbd: rename "usermode_helper" to "drbd_usermode_helper" 2017-08-29 15:34:46 -06:00
drbd_nla.c netlink: pass extended ACK struct to parsing functions 2017-04-13 13:58:22 -04:00
drbd_nla.h
drbd_proc.c drbd: move global variables to drbd namespace and make some static 2017-08-29 15:34:46 -06:00
drbd_protocol.h drbd: introduce WRITE_SAME support 2016-06-13 21:43:07 -06:00
drbd_receiver.c drbd: switch from kmalloc() to kmalloc_array() 2017-08-29 15:34:46 -06:00
drbd_req.c drbd: add explicit plugging when submitting batches 2017-08-29 15:34:44 -06:00
drbd_req.h drbd: introduce drbd_recv_header_maybe_unplug 2017-08-29 15:34:43 -06:00
drbd_state_change.h drbd: Backport the "events2" command 2015-11-25 09:22:00 -07:00
drbd_state.c drbd: fix potential deadlock when trying to detach during handshake 2017-08-29 15:34:45 -06:00
drbd_state.h drbd: fix potential deadlock when trying to detach during handshake 2017-08-29 15:34:45 -06:00
drbd_strings.c drbd: code cleanups without semantic changes 2016-06-13 21:43:07 -06:00
drbd_strings.h drbd: Move string function prototypes from linux/drbd.h to drbd_string.h 2014-02-17 16:50:37 +01:00
drbd_vli.h
drbd_worker.c drbd: abort drbd_start_resync if there is no connection 2017-08-29 15:34:46 -06:00
Kconfig
Makefile drbd: debugfs: add basic hierarchy 2014-07-10 18:35:16 +02:00