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dm-crypt: Convert from tasklet to BH workqueue

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The only generic interface to execute asynchronously in the BH context is
tasklet; however, it's marked deprecated and has some design flaws. To
replace tasklets, BH workqueue support was recently added. A BH workqueue
behaves similarly to regular workqueues except that the queued work items
are executed in the BH context.

This commit converts dm-crypt from tasklet to BH workqueue.  It
backfills tasklet code that was removed with commit 0a9bab391e
("dm-crypt, dm-verity: disable tasklets") and tweaks to use BH
workqueue.

Like a regular workqueue, a BH workqueue allows freeing the currently
executing work item. Converting from tasklet to BH workqueue removes the
need for deferring bio_endio() again to a work item, which was buggy anyway.

I tested this lightly with "--perf-no_read_workqueue
--perf-no_write_workqueue" + some code modifications, but would really
-appreciate if someone who knows the code base better could take a look.

Signed-off-by: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/82b964f0-c2c8-a2c6-5b1f-f3145dc2c8e5@redhat.com
[snitzer: rebase ontop of commit 0a9bab391e reduced this commit's changes]
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Tejun Heo 2024-01-29 23:11:54 -10:00 committed by Mike Snitzer
parent c6df327501
commit fb6ad4aec1
1 changed files with 5 additions and 1 deletions
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6
drivers/md/dm-crypt.c
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@ -2296,7 +2296,11 @@ static void kcryptd_queue_crypt(struct dm_crypt_io *io)
* irqs_disabled(): the kernel may run some IO completion from the idle thread, but
* it is being executed with irqs disabled.
*/
if (!(in_hardirq() || irqs_disabled())) {
if (in_hardirq() || irqs_disabled()) {
INIT_WORK(&io->work, kcryptd_crypt);
queue_work(system_bh_wq, &io->work);
return;
} else {
kcryptd_crypt(&io->work);
return;
}