Commit 9d28eb12 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm bufio: change __GFP_IO to __GFP_FS in shrinker callbacks 



The shrinker uses gfp flags to indicate what kind of operation can the
driver wait for. If __GFP_IO flag is present, the driver can wait for
block I/O operations, if __GFP_FS flag is present, the driver can wait on
operations involving the filesystem.

dm-bufio tested for __GFP_IO. However, dm-bufio can run on a loop block
device that makes calls into the filesystem. If __GFP_IO is present and
__GFP_FS isn't, dm-bufio could still block on filesystem operations if it
runs on a loop block device.

The change from __GFP_IO to __GFP_FS supposedly fixes one observed (though
unreproducible) deadlock involving dm-bufio and loop device.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
parent a3f2af25

drivers/md/dm-bufio.c

+6 −6
Original line number Diff line number Diff line
@@ -1435,9 +1435,9 @@ static void drop_buffers(struct dm_bufio_client *c) 


/*

 * Test if the buffer is unused and too old, and commit it.

 * At if noio is set, we must not do any I/O because we hold

 * dm_bufio_clients_lock and we would risk deadlock if the I/O gets rerouted to

 * different bufio client.

 * And if GFP_NOFS is used, we must not do any I/O because we hold

 * dm_bufio_clients_lock and we would risk deadlock if the I/O gets

 * rerouted to different bufio client.

 */

static int __cleanup_old_buffer(struct dm_buffer *b, gfp_t gfp,

				unsigned long max_jiffies)
@@ -1445,7 +1445,7 @@ static int __cleanup_old_buffer(struct dm_buffer *b, gfp_t gfp, 
	if (jiffies - b->last_accessed < max_jiffies)

		return 0;



	if (!(gfp & __GFP_IO)) {

	if (!(gfp & __GFP_FS)) {

		if (test_bit(B_READING, &b->state) ||

		    test_bit(B_WRITING, &b->state) ||

		    test_bit(B_DIRTY, &b->state))
@@ -1487,7 +1487,7 @@ dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) 
	unsigned long freed;



	c = container_of(shrink, struct dm_bufio_client, shrinker);

	if (sc->gfp_mask & __GFP_IO)

	if (sc->gfp_mask & __GFP_FS)

		dm_bufio_lock(c);

	else if (!dm_bufio_trylock(c))

		return SHRINK_STOP;
@@ -1504,7 +1504,7 @@ dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc) 
	unsigned long count;



	c = container_of(shrink, struct dm_bufio_client, shrinker);

	if (sc->gfp_mask & __GFP_IO)

	if (sc->gfp_mask & __GFP_FS)

		dm_bufio_lock(c);

	else if (!dm_bufio_trylock(c))

		return 0;

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