Btrfs: fix regression in raid level conversion

Commit 2f0810880f082fa8ba66ab2c33b02e4ff9770a5e changed
btrfs_set_block_group_ro to avoid trying to allocate new chunks with the
new raid profile during conversion.  This fixed failures when there was
no space on the drive to allocate a new chunk, but the metadata
reserves were sufficient to continue the conversion.

But this ended up causing a regression when the drive had plenty of
space to allocate new chunks, mostly because reduce_alloc_profile isn't
using the new raid profile.

Fixing btrfs_reduce_alloc_profile is a bigger patch.  For now, do a
partial revert of 2f0810880, and don't error out if we hit ENOSPC.

Signed-off-by: Chris Mason <clm@fb.com>
Tested-by: Dave Sterba <dsterba@suse.cz>
Reported-by: Holger Hoffstaette <holger.hoffstaette@googlemail.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 45e3f086790b..0ec3acd14cbf 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8829,6 +8829,24 @@ again:
                 goto again;
         }
 
+        /*
+         * if we are changing raid levels, try to allocate a corresponding
+         * block group with the new raid level.
+         */
+        alloc_flags = update_block_group_flags(root, cache->flags);
+        if (alloc_flags != cache->flags) {
+                ret = do_chunk_alloc(trans, root, alloc_flags,
+                                     CHUNK_ALLOC_FORCE);
+                /*
+                 * ENOSPC is allowed here, we may have enough space
+                 * already allocated at the new raid level to
+                 * carry on
+                 */
+                if (ret == -ENOSPC)
+                        ret = 0;
+                if (ret < 0)
+                        goto out;
+        }
 
         ret = set_block_group_ro(cache, 0);
         if (!ret)