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dm: interlock pending dm_io and dm_wait_for_bios_completion

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Commit d208b89401 ("dm: fix mempool NULL pointer race when
completing IO") didn't go far enough.

When bio_end_io_acct ends the count of in-flight I/Os may reach zero
and the DM device may be suspended. There is a possibility that the
suspend races with dm_stats_account_io.

Fix this by adding percpu "pending_io" counters to track outstanding
dm_io. Move kicking of suspend queue to dm_io_dec_pending(). Also,
rename md_in_flight_bios() to dm_in_flight_bios() and update it to
iterate all pending_io counters.

Fixes: d208b89401 ("dm: fix mempool NULL pointer race when completing IO")
Cc: stable@vger.kernel.org
Co-developed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mike Snitzer 2022-02-17 23:40:02 -05:00
parent bcd2be7632
commit 9f6dc63376
2 changed files with 25 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/md/dm-core.h
View File

@ -64,6 +64,8 @@ struct mapped_device {
struct gendisk *disk;
struct dax_device *dax_dev;
unsigned long __percpu *pending_io;
/*
* A list of ios that arrived while we were suspended.
*/

35
drivers/md/dm.c
View File

@ -508,10 +508,6 @@ static void end_io_acct(struct mapped_device *md, struct bio *bio,
dm_stats_account_io(&md->stats, bio_data_dir(bio),
bio->bi_iter.bi_sector, bio_sectors(bio),
true, duration, stats_aux);
/* nudge anyone waiting on suspend queue */
if (unlikely(wq_has_sleeper(&md->wait)))
wake_up(&md->wait);
}
static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
@ -530,6 +526,7 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
io->magic = DM_IO_MAGIC;
io->status = 0;
atomic_set(&io->io_count, 1);
this_cpu_inc(*md->pending_io);
io->orig_bio = bio;
io->md = md;
spin_lock_init(&io->endio_lock);
@ -827,6 +824,12 @@ void dm_io_dec_pending(struct dm_io *io, blk_status_t error)
stats_aux = io->stats_aux;
free_io(md, io);
end_io_acct(md, bio, start_time, &stats_aux);
smp_wmb();
this_cpu_dec(*md->pending_io);
/* nudge anyone waiting on suspend queue */
if (unlikely(wq_has_sleeper(&md->wait)))
wake_up(&md->wait);
if (io_error == BLK_STS_DM_REQUEUE)
return;
@ -1569,6 +1572,11 @@ static void cleanup_mapped_device(struct mapped_device *md)
blk_cleanup_disk(md->disk);
}
if (md->pending_io) {
free_percpu(md->pending_io);
md->pending_io = NULL;
}
cleanup_srcu_struct(&md->io_barrier);
mutex_destroy(&md->suspend_lock);
@ -1671,6 +1679,10 @@ static struct mapped_device *alloc_dev(int minor)
if (!md->wq)
goto bad;
md->pending_io = alloc_percpu(unsigned long);
if (!md->pending_io)
goto bad;
dm_stats_init(&md->stats);
/* Populate the mapping, nobody knows we exist yet */
@ -2078,16 +2090,13 @@ void dm_put(struct mapped_device *md)
}
EXPORT_SYMBOL_GPL(dm_put);
static bool md_in_flight_bios(struct mapped_device *md)
static bool dm_in_flight_bios(struct mapped_device *md)
{
int cpu;
struct block_device *part = dm_disk(md)->part0;
long sum = 0;
unsigned long sum = 0;
for_each_possible_cpu(cpu) {
sum += part_stat_local_read_cpu(part, in_flight[0], cpu);
sum += part_stat_local_read_cpu(part, in_flight[1], cpu);
}
for_each_possible_cpu(cpu)
sum += *per_cpu_ptr(md->pending_io, cpu);
return sum != 0;
}
@ -2100,7 +2109,7 @@ static int dm_wait_for_bios_completion(struct mapped_device *md, unsigned int ta
while (true) {
prepare_to_wait(&md->wait, &wait, task_state);
if (!md_in_flight_bios(md))
if (!dm_in_flight_bios(md))
break;
if (signal_pending_state(task_state, current)) {
@ -2112,6 +2121,8 @@ static int dm_wait_for_bios_completion(struct mapped_device *md, unsigned int ta
}
finish_wait(&md->wait, &wait);
smp_rmb();
return r;
}