btrfs: make find_workspace warn if there are no workspaces

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

Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index c706255..658c39b 100644 (file)
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -834,7 +834,21 @@ again:
                 * 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;