From 79702f960693a85b2925dde7f73c623a034c8be4 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Thu, 16 Oct 2014 14:45:20 -0400 Subject: [PATCH] dm bufio: change __GFP_IO to __GFP_FS in shrinker callbacks 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 Signed-off-by: Mike Snitzer [bwh: Backported to 3.2: - There's only one shrinker callback - Adjust context] Signed-off-by: Ben Hutchings --- drivers/md/dm-bufio.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c index 8abd681eadf2..3bf726796906 100644 --- a/drivers/md/dm-bufio.c +++ b/drivers/md/dm-bufio.c @@ -1324,9 +1324,9 @@ 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) @@ -1334,7 +1334,7 @@ static int __cleanup_old_buffer(struct dm_buffer *b, gfp_t gfp, if (jiffies - b->last_accessed < max_jiffies) return 1; - 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)) @@ -1373,7 +1373,7 @@ static int shrink(struct shrinker *shrinker, struct shrink_control *sc) unsigned long r; unsigned long nr_to_scan = sc->nr_to_scan; - if (sc->gfp_mask & __GFP_IO) + if (sc->gfp_mask & __GFP_FS) dm_bufio_lock(c); else if (!dm_bufio_trylock(c)) return !nr_to_scan ? 0 : -1; -- 2.39.2