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>

1 files changed, 14 insertions, 0 deletions

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 @@ 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;