linux.git/drivers/block/drbd/drbd_worker.c, branch v3.16

drbd: always implicitly close last epoch when idle

2014-04-30T19:46:55+00:00

Once our sender thread needs to wait_for_work(),
and actually needs to schedule(), just before we do that,
we already check if it is useful to implicitly close the last epoch.

The condition was too strict: only implicitly close the epoch,
if there have been no new (write) requests at all.

The assumption was that if there were new requests, they would
always be communicated one way or another, and would send necessary
epoch separating barriers explicitly.

This is not always true, e.g. when becoming diskless,
or while explicitly starting a full resync.

The last communicated epoch could stay open for a long time,
locking down corresponding activity log extents.

It is safe to always implicitly send that last barrier, as soon as we
determin that there cannot be more requests in the last communicated
epoch, even if there have been (uncommunicated) new requests in new
epochs meanwhile.

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

drbd: fix a race between start_resync and send_and_submit

2014-04-30T19:46:55+00:00

In the drbd make request function, specifically in
drbd_send_and_submit(), we decide whether we want to send the actual
write request, or only a "set this block out of sync" information.

We do so based on the current connection state, while holding the req_lock.
The connection state is not supposed to change while holding the req_lock.

But in drbd_start_resync, we did change that state anyways,
while only holding the global_state_lock, which is enough to change
sync-after dependencies (paused vs active resync), but
not good enough to change the connection state.

Fix: in drbd_start_resync, first grab the req_lock to serialize with
drbd_send_and_submit(), before grabbing the global_state_lock
to be able to evaluate the sync-after dependencies.

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

drbd: prepare sending side for REQ_DISCARD

2014-04-30T19:46:55+00:00

Note that I do NOT call __drbd_chk_io_error for failed REQ_DISCARD.
That may be wrong, though, or needs to differ between EOPNOTSUPP and
other errors...

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

drbd: prepare receiving side for REQ_DISCARD

2014-04-30T19:46:55+00:00

If the receiver needs to serve a discard request on a queue that does
not announce to be discard cabable, it falls back to do synchronous
blkdev_issue_zeroout().

We expect only "reasonably" large (up to one activity log extent?)
discard requests.

We do this to not to not block the receiver for too long in this
fallback code path, and to not set/clear too many bits inside one
spinlock_irq_save() in drbd_set_in_sync/drbd_set_out_of_sync,

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

drbd: fix potential distributed deadlock during verify or resync

2014-04-30T19:46:54+00:00

If max-buffers and socket buffer sizes are "too small" for the chosen
resync rate, this could lead potentially lead to a distributed deadlock,
which may or may not resolve itself via the "ko-count" and request
timeout mechanism, or could be resolved by forced disconnect.

One option to deal with this is proper configuration:
use larger max-buffer and socket buffers settings,
or reduce the resync rate.

But even with bad configuration we should not deadlock,
but "gracefully" recover.

The issue is avoided by using only up to max-buffers/2 for resync
requests, and by using max-buffers not as a hard limit for data buffer
allocations, but as a throttle threshold only.

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

drbd: resync: fix too large bursts for very slow rates

2014-04-30T19:46:54+00:00

While merging adjacent dirty blocks into resync requests,
the resync rate throttle was disregarded.
For very low resync rates, the effective rate may have exceeded
the intended rate by a larger margin.

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

drbd: Use the right peer device

2014-02-17T15:50:47+00:00

in w_e_ (peer request) callbacks and in peer request I/O completion handlers

Signed-off-by: Andreas Gruenbacher 
Signed-off-by: Philipp Reisner

drbd: In the worker thread, process drbd_work instead of drbd_device_work items

2014-02-17T15:50:44+00:00

Signed-off-by: Andreas Gruenbacher 
Signed-off-by: Philipp Reisner

drbd: Turn w_make_ov_request and make_resync_request into "normal" functions

2014-02-17T15:50:43+00:00

These functions are not used as drbd_work callbacks.

Signed-off-by: Andreas Gruenbacher 
Signed-off-by: Philipp Reisner

drbd: Make w_make_resync_request() static

2014-02-17T15:50:42+00:00

Signed-off-by: Andreas Gruenbacher 
Signed-off-by: Philipp Reisner