From: David Sterba <dsterba@suse.com>
Date: Wed, 27 Apr 2016 01:07:39 +0000 (+0200)
Subject: btrfs: make find_workspace warn if there are no workspaces
X-Git-Tag: Ubuntu-5.2.0-15.16~9132^2~1^2~3^2~4
X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=523567168da04bae0f88802ddef49d00072c5d58;p=mirror_ubuntu-eoan-kernel.git

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 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;