[4/4] btrfs: make find_workspace warn if there are no workspaces

Commit Message

David Sterba May 5, 2016, 4:36 p.m. UTC

Be verbose if there are no workspaces at all, ie. the module init time
preallocation failed.

Signed-off-by: David Sterba <[e-mail]>
---
 fs/btrfs/compression.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

Patch

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index c70625560265..658c39b70fba 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -834,7 +834,21 @@  static struct list_head *find_workspace(int type)
 		 * workspace preallocated for each type and the compression
 		 * time is bounded so we get to a workspace eventually. This
 		 * makes our caller's life easier.
+		 *
+		 * To prevent silent and low-probability deadlocks (when the
+		 * initial preallocation fails), check if there are any
+		 * workspaces at all.
 		 */
+		if (atomic_read(total_ws) == 0) {
+			static DEFINE_RATELIMIT_STATE(_rs,
+					/* once per minute */ 60 * HZ,
+					/* no burst */ 1);
+
+			if (__ratelimit(&_rs)) {
+				printk(KERN_WARNING
+			    "no compression workspaces, low memory, retrying");
+			}
+		}
 		goto again;
 	}
 	return workspace;