linux-stable.git/drivers/block/drbd/drbd_req.c, branch linux-5.4.y

drbd: fix potential silent data corruption

2022-04-15T12:18:01+00:00

commit f4329d1f848ac35757d9cc5487669d19dfc5979c upstream.

Scenario:
---------

bio chain generated by blk_queue_split().
Some split bio fails and propagates its error status to the "parent" bio.
But then the (last part of the) parent bio itself completes without error.

We would clobber the already recorded error status with BLK_STS_OK,
causing silent data corruption.

Reproducer:
-----------

How to trigger this in the real world within seconds:

DRBD on top of degraded parity raid,
small stripe_cache_size, large read_ahead setting.
Drop page cache (sysctl vm.drop_caches=1, fadvise "DONTNEED",
umount and mount again, "reboot").

Cause significant read ahead.

Large read ahead request is split by blk_queue_split().
Parts of the read ahead that are already in the stripe cache,
or find an available stripe cache to use, can be serviced.
Parts of the read ahead that would need "too much work",
would need to wait for a "stripe_head" to become available,
are rejected immediately.

For larger read ahead requests that are split in many pieces, it is very
likely that some "splits" will be serviced, but then the stripe cache is
exhausted/busy, and the remaining ones will be rejected.

Signed-off-by: Lars Ellenberg 
Signed-off-by: Christoph Böhmwalder 
Cc:  # 4.13.x
Link: https://lore.kernel.org/r/20220330185551.3553196-1-christoph.boehmwalder@linbit.com
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 91

2019-05-24T15:37:53+00:00

Based on 1 normalized pattern(s):

  is free software you can redistribute it and or modify it under the
  terms of the gnu general public license as published by the free
  software foundation either version 2 or at your option any later
  version [drbd] is distributed in the hope that it will be useful but
  without any warranty without even the implied warranty of
  merchantability or fitness for a particular purpose see the gnu
  general public license for more details you should have received a
  copy of the gnu general public license along with [drbd] see the
  file copying if not write to the free software foundation 675 mass
  ave cambridge ma 02139 usa

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 16 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Allison Randal 
Reviewed-by: Richard Fontana 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520075212.050796421@linutronix.de
Signed-off-by: Greg Kroah-Hartman

block: Mark expected switch fall-throughs

2019-04-09T16:48:15+00:00

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

This patch fixes the following warnings:

drivers/block/drbd/drbd_int.h:1774:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_int.h:1774:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_int.h:1774:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_int.h:1774:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_int.h:1774:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_receiver.c:3093:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_receiver.c:3120:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_req.c:856:6: warning: this statement may fall through [-Wimplicit-fallthrough=]

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough

Reviewed-by: Chaitanya Kulkarni 
Acked-by: Roland Kammerer 
Signed-off-by: Gustavo A. R. Silva

drbd: introduce P_ZEROES (REQ_OP_WRITE_ZEROES on the "wire")

2018-12-20T16:51:31+00:00

And also re-enable partial-zero-out + discard aligned.

With the introduction of REQ_OP_WRITE_ZEROES,
we started to use that for both WRITE_ZEROES and DISCARDS,
hoping that WRITE_ZEROES would "do what we want",
UNMAP if possible, zero-out the rest.

The example scenario is some LVM "thin" backend.

While an un-allocated block on dm-thin reads as zeroes, on a dm-thin
with "skip_block_zeroing=true", after a partial block write allocated
that block, that same block may well map "undefined old garbage" from
the backends on LBAs that have not yet been written to.

If we cannot distinguish between zero-out and discard on the receiving
side, to avoid "undefined old garbage" to pop up randomly at later times
on supposedly zero-initialized blocks, we'd need to map all discards to
zero-out on the receiving side.  But that would potentially do a full
alloc on thinly provisioned backends, even when the expectation was to
unmap/trim/discard/de-allocate.

We need to distinguish on the protocol level, whether we need to guarantee
zeroes (and thus use zero-out, potentially doing the mentioned full-alloc),
or if we want to put the emphasis on discard, and only do a "best effort
zeroing" (by "discarding" blocks aligned to discard-granularity, and zeroing
only potential unaligned head and tail clippings to at least *try* to
avoid "false positives" in an online-verify later), hoping that someone
set skip_block_zeroing=false.

For some discussion regarding this on dm-devel, see also
https://www.mail-archive.com/dm-devel%40redhat.com/msg07965.html
https://www.redhat.com/archives/dm-devel/2018-January/msg00271.html

For backward compatibility, P_TRIM means zero-out, unless the
DRBD_FF_WZEROES feature flag is agreed upon during handshake.

To have upper layers even try to submit WRITE ZEROES requests,
we need to announce "efficient zeroout" independently.

We need to fixup max_write_zeroes_sectors after blk_queue_stack_limits():
if we can handle "zeroes" efficiently on the protocol,
we want to do that, even if our backend does not announce
max_write_zeroes_sectors itself.

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

block: Finish renaming REQ_DISCARD into REQ_OP_DISCARD

2018-10-03T22:12:28+00:00

Some time ago REQ_DISCARD was renamed into REQ_OP_DISCARD. Some comments
and documentation files were not updated however. Update these comments
and documentation files. See also commit 4e1b2d52a80d ("block, fs,
drivers: remove REQ_OP compat defs and related code").

Signed-off-by: Bart Van Assche 
Cc: Mike Christie 
Cc: Martin K. Petersen 
Cc: Philipp Reisner 
Cc: Lars Ellenberg 
Signed-off-by: Jens Axboe

block: Add and use op_stat_group() for indexing disk_stat fields.

2018-07-18T14:44:20+00:00

Add and use a new op_stat_group() function for indexing partition stat
fields rather than indexing them by rq_data_dir() or bio_data_dir().
This function works similarly to op_is_sync() in that it takes the
request::cmd_flags or bio::bi_opf flags and determines which stats
should et updated.

In addition, the second parameter to generic_start_io_acct() and
generic_end_io_acct() is now a REQ_OP rather than simply a read or
write bit and it uses op_stat_group() on the parameter to determine
the stat group.

Note that the partition in_flight counts are not part of the per-cpu
statistics and as such are not indexed via this function.  It's now
indexed by op_is_write().

tj: Refreshed on top of v4.17.  Updated to pass around REQ_OP.

Signed-off-by: Michael Callahan 
Signed-off-by: Tejun Heo 
Cc: Minchan Kim 
Cc: Dan Williams 
Cc: Joshua Morris 
Cc: Philipp Reisner 
Cc: Matias Bjorling 
Cc: Kent Overstreet 
Cc: Alasdair Kergon 
Signed-off-by: Jens Axboe

drbd: Fix drbd_request_prepare() discard handling

2018-06-29T13:53:21+00:00

Fix the test that verifies whether bio_op(bio) represents a discard
or write zeroes operation. Compile-tested only.

Cc: Philipp Reisner 
Cc: Lars Ellenberg 
Fixes: 7435e9018f91 ("drbd: zero-out partial unaligned discards on local backend")
Signed-off-by: Bart Van Assche 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

drbd: convert to bioset_init()/mempool_init()

2018-05-30T21:33:32+00:00

Convert drbd to embedded bio sets and mempools.

Signed-off-by: Kent Overstreet 
Signed-off-by: Jens Axboe

drbd: Convert timers to use timer_setup()

2017-11-06T20:49:57+00:00

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Philipp Reisner 
Cc: Lars Ellenberg 
Cc: drbd-dev@lists.linbit.com
Signed-off-by: Kees Cook

drbd: add explicit plugging when submitting batches

2017-08-29T21:34:44+00:00

When submitting batches of requests which had been queued on the
submitter thread, typically because they needed to wait for an
activity log transactions, use explicit plugging to help potential
merging of requests in the backend io-scheduler.

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