[PATCH 5.17 0113/1126] dm: interlock pending dm_io and dm_wait_for_bios_completion

Greg Kroah-Hartman
2022-04-05T08:00:33Z

From: Mike Snitzer <snitzer@redhat.com>

commit 9f6dc633761006f974701d4c88da71ab68670749 upstream.

Commit d208b89401e0 ("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: d208b89401e0 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/md/dm-core.h | 2 ++
drivers/md/dm.c | 35 +++++++++++++++++++++++------------
2 files changed, 25 insertions(+), 12 deletions(-)

--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -65,6 +65,8 @@ 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.
*/
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -507,10 +507,6 @@ static void end_io_acct(struct mapped_de
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)
@@ -531,6 +527,7 @@ static struct dm_io *alloc_io(struct map
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);
@@ -828,6 +825,12 @@ void dm_io_dec_pending(struct dm_io *io,
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;
@@ -1622,6 +1625,11 @@ static void cleanup_mapped_device(struct
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);
@@ -1723,6 +1731,10 @@ static struct mapped_device *alloc_dev(i
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 */
@@ -2130,16 +2142,13 @@ 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;
}
@@ -2152,7 +2161,7 @@ static int dm_wait_for_bios_completion(s
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)) {
@@ -2164,6 +2173,8 @@ static int dm_wait_for_bios_completion(s
}
finish_wait(&md->wait, &wait);

+ smp_rmb();
+
return r;
}