linux.git/drivers/block/drbd, branch v4.14-rc4

drbd: remove BIOSET_NEED_RESCUER flag from drbd_{md_,}io_bio_set

2017-08-30T14:10:02+00:00

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 
Signed-off-by: Philipp Reisner 
Signed-off-by: Jens Axboe

drbd: Fix allyesconfig build, fix recent commit

2017-08-30T14:09:29+00:00

Globals where prefixed with drbd_, that was missed in the
in #ifdef'nd code when it is built-in.

Signed-off-by: Philipp Reisner 
Fixes: 183ece30053f ("drbd: move global variables to drbd namespace and make some static")
Signed-off-by: Jens Axboe

drbd: switch from kmalloc() to kmalloc_array()

2017-08-29T21:34:46+00:00

We had one call to kmalloc that actually allocates an array. Switch that
one to the kmalloc_array() function.

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: abort drbd_start_resync if there is no connection

2017-08-29T21:34:46+00:00

This was found by a static analysis tool. While highly unlikely, be sure
to return without dereferencing the NULL pointer.

Reported-by: Shaobo 
Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: move global variables to drbd namespace and make some static

2017-08-29T21:34:46+00:00

This is a follow-up to Gregs complaints that drbd clutteres the global
namespace.
Some of DRBD's module parameters are only used within one compilation
unit. Make these static.

Signed-off-by: Roland Kammerer 
Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: rename "usermode_helper" to "drbd_usermode_helper"

2017-08-29T21:34:46+00:00

Nothing like having a very generic global variable in a tiny driver
subsystem to make a mess of the global namespace...

Note, there are many other "generic" named global variables in the drbd
subsystem, someone should fix those up one day before they hit a linking
error.

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: fix race between handshake and admin disconnect/down

2017-08-29T21:34:46+00:00

conn_try_disconnect() could potentialy hit the BUG_ON()
in _conn_set_state() where it iterates over _drbd_set_state()
and "asserts" via BUG_ON() that the latter was successful.

If the STATE_SENT bit was not yet visible to conn_is_valid_transition()
early in _conn_request_state(), but became visible before conn_set_state()
later in that call path, we could hit the BUG_ON() after _drbd_set_state(),
because it returned SS_IN_TRANSIENT_STATE.

To avoid that race, we better protect set_bit(SENT_STATE) with the spinlock.

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: fix potential deadlock when trying to detach during handshake

2017-08-29T21:34:45+00:00

When requesting a detach, we first suspend IO, and also inhibit meta-data IO
by means of drbd_md_get_buffer(), because we don't want to "fail" the disk
while there is IO in-flight: the transition into D_FAILED for detach purposes
may get misinterpreted as actual IO error in a confused endio function.

We wrap it all into wait_event(), to retry in case the drbd_req_state()
returns SS_IN_TRANSIENT_STATE, as it does for example during an ongoing
connection handshake.

In that example, the receiver thread may need to grab drbd_md_get_buffer()
during the handshake to make progress.  To avoid potential deadlock with
detach, detach needs to grab and release the meta data buffer inside of
that wait_event retry loop. To avoid lock inversion between
mutex_lock(&device->state_mutex) and drbd_md_get_buffer(device),
introduce a new enum chg_state_flag CS_INHIBIT_MD_IO, and move the
call to drbd_md_get_buffer() inside the state_mutex grabbed in
drbd_req_state().

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: A single dot should be put into a sequence.

2017-08-29T21:34:45+00:00

Thus use the corresponding function "seq_putc".

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring 
Signed-off-by: Roland Kammerer 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: fix rmmod cleanup, remove _all_ debugfs entries

2017-08-29T21:34:45+00:00

If there are still resources defined, but "empty", no more volumes
or connections configured, they don't hold module reference counts,
so rmmod is possible.

To avoid DRBD leftovers in debugfs, we need to call our global
drbd_debugfs_cleanup() only after all resources have been cleaned up.

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe