[PATCH 3.17 086/141] dm bufio: change __GFP_IO to __GFP_FS in shrinker callbacks

Greg Kroah-Hartman
2014-11-19T22:13:08Z

From: Mikulas Patocka <mpatocka@redhat.com>

commit 9d28eb12447ee08bb5d1e8bb3195cf20e1ecd1c0 upstream.

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: 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-bufio.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -1435,9 +1435,9 @@ static void drop_buffers(struct dm_bufio

/*
* 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 d
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 *sh
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 *s
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;