1 files changed, 12 insertions, 8 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 38c058bcf359..c70625560265 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -785,8 +785,10 @@ void __init btrfs_init_compress(void)
 }
 
 /*
- * this finds an available workspace or allocates a new one
- * ERR_PTR is returned if things go bad.
+ * This finds an available workspace or allocates a new one.
+ * If it's not possible to allocate a new one, waits until there's one.
+ * Preallocation makes a forward progress guarantees and we do not return
+ * errors.
  */
 static struct list_head *find_workspace(int type)
 {
@@ -826,6 +828,14 @@ again:
         if (IS_ERR(workspace)) {
                 atomic_dec(total_ws);
                 wake_up(ws_wait);
+
+                /*
+                 * Do not return the error but go back to waiting. There's a
+                 * 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.
+                 */
+                goto again;
         }
         return workspace;
 }
@@ -913,8 +923,6 @@ int btrfs_compress_pages(int type, struct address_space *mapping,
         int ret;
 
         workspace = find_workspace(type);
-        if (IS_ERR(workspace))
-                return PTR_ERR(workspace);
 
         ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping,
                                                       start, len, pages,
@@ -949,8 +957,6 @@ static int btrfs_decompress_biovec(int type, struct page **pages_in,
         int ret;
 
         workspace = find_workspace(type);
-        if (IS_ERR(workspace))
-                return PTR_ERR(workspace);
 
         ret = btrfs_compress_op[type-1]->decompress_biovec(workspace, pages_in,
                                                          disk_start,
@@ -971,8 +977,6 @@ int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
         int ret;
 
         workspace = find_workspace(type);
-        if (IS_ERR(workspace))
-                return PTR_ERR(workspace);
 
         ret = btrfs_compress_op[type-1]->decompress(workspace, data_in,
                                                   dest_page, start_byte,