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>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 53e12977bfd012672daf3fc1d2b9a2b2f4362021..85074845c5626f0fa4709d6ab6ee705ea326b12b 100644 (file)
--- 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: