dm bufio: drop the lock when doing GFP_NOIO allocation

If the first allocation attempt using GFP_NOWAIT fails, drop the lock
and retry using GFP_NOIO allocation (lock is dropped because the
allocation can take some time).

Note that we won't do GFP_NOIO allocation when we loop for the second
time, because the lock shouldn't be dropped between __wait_for_free_buffer
and __get_unclaimed_buffer.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index 9ef88f0e238252ddf2f0b6d95615b70bb4f16426..1c2e1dd7ca16e6b843573b5a660310aa5438d73a 100644 (file)
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -822,6 +822,7 @@ enum new_flag {
 static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
 {
        struct dm_buffer *b;
+       bool tried_noio_alloc = false;
 
        /*
         * dm-bufio is resistant to allocation failures (it just keeps
@@ -846,6 +847,15 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client
                if (nf == NF_PREFETCH)
                        return NULL;
 
+               if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
+                       dm_bufio_unlock(c);
+                       b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
+                       dm_bufio_lock(c);
+                       if (b)
+                               return b;
+                       tried_noio_alloc = true;
+               }
+
                if (!list_empty(&c->reserved_buffers)) {
                        b = list_entry(c->reserved_buffers.next,
                                       struct dm_buffer, lru_list);