linux-stable.git/drivers/md/dm-thin.c, branch linux-6.4.y

dm thin: fix issue_discard to pass GFP_NOIO to __blkdev_issue_discard

2023-06-15T16:46:59+00:00

issue_discard() passes GFP_NOWAIT to __blkdev_issue_discard() despite
its code assuming bio_alloc() always succeeds.

Commit 3dba53a958a75 ("dm thin: use __blkdev_issue_discard for async
discard support") clearly shows where things went bad:

Before commit 3dba53a958a75, dm-thin.c's open-coded
__blkdev_issue_discard_async() properly handled using GFP_NOWAIT.
Unfortunately __blkdev_issue_discard() doesn't and it was missed
during review.

Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer

dm bio prison v1: add dm_cell_key_has_valid_range

2023-03-30T19:57:51+00:00

Don't have bio_detain() BUG_ON if a dm_cell_key is beyond
BIO_PRISON_MAX_RANGE or spans a boundary.

Update dm-thin.c:build_key() to use dm_cell_key_has_valid_range() which
will do this checking without using BUG_ON. Also update
process_discard_bio() to check the discard bio that DM core passes in
(having first imposed max_discard_granularity based splitting).

dm_cell_key_has_valid_range() will merely WARN_ON_ONCE if it returns
false because if it does: it is programmer error that should be caught
with proper testing. So relax the BUG_ONs to be WARN_ON_ONCE.

Signed-off-by: Mike Snitzer

dm bio prison v1: improve concurrent IO performance

2023-03-30T19:57:51+00:00

Split the bio prison into multiple regions, with a separate rbtree and
associated lock for each region.

To get fast bio prison locking and not damage the performance of
discards too much the bio-prison now stipulates that discards should
not cross a BIO_PRISON_MAX_RANGE boundary.

Because the range of a key (block_end - block_begin) must not exceed
BIO_PRISON_MAX_RANGE: break_up_discard_bio() now ensures the data
range reflected in PHYSICAL key doesn't exceed BIO_PRISON_MAX_RANGE.
And splitting the thin target's discards (handled with VIRTUAL key) is
achieved by updating dm-thin.c to set limits->max_discard_sectors in
terms of BIO_PRISON_MAX_RANGE _and_ setting the thin and thin-pool
targets' max_discard_granularity to true.

Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer

dm thin: speed up cell_defer_no_holder()

2023-03-30T19:57:50+00:00

Reduce the time that a spinlock is held in cell_defer_no_holder().

Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer

dm thin: fix deadlock when swapping to thin device

2023-03-06T21:37:06+00:00

This is an already known issue that dm-thin volume cannot be used as
swap, otherwise a deadlock may happen when dm-thin internal memory
demand triggers swap I/O on the dm-thin volume itself.

But thanks to commit a666e5c05e7c ("dm: fix deadlock when swapping to
encrypted device"), the limit_swap_bios target flag can also be used
for dm-thin to avoid the recursive I/O when it is used as swap.

Fix is to simply set ti->limit_swap_bios to true in both pool_ctr()
and thin_ctr().

In my test, I create a dm-thin volume /dev/vg/swap and use it as swap
device. Then I run fio on another dm-thin volume /dev/vg/main and use
large --blocksize to trigger swap I/O onto /dev/vg/swap.

The following fio command line is used in my test,
  fio --name recursive-swap-io --lockmem 1 --iodepth 128 \
     --ioengine libaio --filename /dev/vg/main --rw randrw \
    --blocksize 1M --numjobs 32 --time_based --runtime=12h

Without this fix, the whole system can be locked up within 15 seconds.

With this fix, there is no any deadlock or hung task observed after
2 hours of running fio.

Furthermore, if blocksize is changed from 1M to 128M, after around 30
seconds fio has no visible I/O, and the out-of-memory killer message
shows up in kernel message. After around 20 minutes all fio processes
are killed and the whole system is back to being alive.

This is exactly what is expected when recursive I/O happens on dm-thin
volume when it is used as swap.

Depends-on: a666e5c05e7c ("dm: fix deadlock when swapping to encrypted device")
Cc: stable@vger.kernel.org
Signed-off-by: Coly Li 
Acked-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm thin: add cond_resched() to various workqueue loops

2023-02-17T19:46:27+00:00

Otherwise on resource constrained systems these workqueues may be too
greedy.

Signed-off-by: Mike Snitzer

dm: declare variables static when sensible

2023-02-14T19:23:07+00:00

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Mike Snitzer

dm: avoid using symbolic permissions

2023-02-14T19:23:07+00:00

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Mike Snitzer

dm: add missing empty lines

2023-02-14T19:23:06+00:00

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Mike Snitzer

dm: correct block comments format.

2023-02-14T19:23:06+00:00

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Mike Snitzer