btrfs: Output more info for enospc_debug mount option

As one user in mail list report reproducible balance ENOSPC error, it's
better to add more debug info for enospc_debug mount option.

Reported-by: Marc Haber <mh+linux-btrfs@zugschlus.de>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 19 insertions, 2 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 53e12977bfd0..85074845c562 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -9386,15 +9386,23 @@ int btrfs_can_relocate(struct btrfs_root *root, u64 bytenr)
         u64 dev_min = 1;
         u64 dev_nr = 0;
         u64 target;
+        int debug;
         int index;
         int full = 0;
         int ret = 0;
 
+        debug = btrfs_test_opt(root, ENOSPC_DEBUG);
+
         block_group = btrfs_lookup_block_group(root->fs_info, bytenr);
 
         /* odd, couldn't find the block group, leave it alone */
-        if (!block_group)
+        if (!block_group) {
+                if (debug)
+                        btrfs_warn(root->fs_info,
+                                   "can't find block group for bytenr %llu",
+                                   bytenr);
                 return -1;
+        }
 
         min_free = btrfs_block_group_used(&block_group->item);
 
@@ -9448,8 +9456,13 @@ int btrfs_can_relocate(struct btrfs_root *root, u64 bytenr)
                  * this is just a balance, so if we were marked as full
                  * we know there is no space for a new chunk
                  */
-                if (full)
+                if (full) {
+                        if (debug)
+                                btrfs_warn(root->fs_info,
+                                        "no space to alloc new chunk for block group %llu",
+                                        block_group->key.objectid);
                         goto out;
+                }
 
                 index = get_block_group_index(block_group);
         }
@@ -9496,6 +9509,10 @@ int btrfs_can_relocate(struct btrfs_root *root, u64 bytenr)
                         ret = -1;
                 }
         }
+        if (debug && ret == -1)
+                btrfs_warn(root->fs_info,
+                        "no space to allocate a new chunk for block group %llu",
+                        block_group->key.objectid);
         mutex_unlock(&root->fs_info->chunk_mutex);
         btrfs_end_transaction(trans, root);
 out: