btrfs: log messages at unpin_extent_range() during unexpected cases

At unpin_extent_range() we trigger a WARN_ON() when we don't find an
extent map or we find one with a start offset not matching the start
offset of the target range. This however isn't very useful for debugging
because:

1) We don't know which condition was triggered, as they are both in the
   same WARN_ON() call;

2) We don't know which inode was affected, from which root, for which
   range, what's the start offset of the extent map, and so on.

So trigger a separate warning for each case and log a message for each
case providing information about the inode, its root, the target range,
the generation and the start offset of the extent map we found.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index a3d69c943eec16c9b1c1b05148edb4b9e4998c62..48230a1179b088a56edb4947f78c4c03b28bebfa 100644 (file)
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -280,7 +280,7 @@ static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
 /*
  * Unpin an extent from the cache.
  *
- * @tree:      tree to unpin the extent in
+ * @inode:     the inode from which we are unpinning an extent range
  * @start:     logical offset in the file
  * @len:       length of the extent
  * @gen:       generation that this extent has been modified in
@@ -289,9 +289,10 @@ static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
  * to the generation that actually added the file item to the inode so we know
  * we need to sync this extent when we call fsync().
  */
-int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
-                      u64 gen)
+int unpin_extent_cache(struct btrfs_inode *inode, u64 start, u64 len, u64 gen)
 {
+       struct btrfs_fs_info *fs_info = inode->root->fs_info;
+       struct extent_map_tree *tree = &inode->extent_tree;
        int ret = 0;
        struct extent_map *em;
        bool prealloc = false;
@@ -299,10 +300,19 @@ int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
        write_lock(&tree->lock);
        em = lookup_extent_mapping(tree, start, len);
 
-       WARN_ON(!em || em->start != start);
-
-       if (!em)
+       if (WARN_ON(!em)) {
+               btrfs_warn(fs_info,
+"no extent map found for inode %llu (root %lld) when unpinning extent range [%llu, %llu), generation %llu",
+                          btrfs_ino(inode), btrfs_root_id(inode->root),
+                          start, len, gen);
                goto out;
+       }
+
+       if (WARN_ON(em->start != start))
+               btrfs_warn(fs_info,
+"found extent map for inode %llu (root %lld) with unexpected start offset %llu when unpinning extent range [%llu, %llu), generation %llu",
+                          btrfs_ino(inode), btrfs_root_id(inode->root),
+                          em->start, start, len, gen);
 
        em->generation = gen;
        clear_bit(EXTENT_FLAG_PINNED, &em->flags);

diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
index 5663137471fe5924f1585824109730b8f3bd2100..cd1a9115908d597f90e28096bba09ea9c30f5976 100644 (file)
--- a/fs/btrfs/extent_map.h
+++ b/fs/btrfs/extent_map.h
@@ -82,7 +82,7 @@ struct extent_map *alloc_extent_map(void);
 void free_extent_map(struct extent_map *em);
 int __init extent_map_init(void);
 void __cold extent_map_exit(void);
-int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len, u64 gen);
+int unpin_extent_cache(struct btrfs_inode *inode, u64 start, u64 len, u64 gen);
 void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em);
 struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
                                         u64 start, u64 len);

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 38adab92a0154bf1f60324917ac56e22b3d8c626..88614bb87b958b02d7d8b7b1f762fbc38871a3d6 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3127,7 +3127,7 @@ int btrfs_finish_one_ordered(struct btrfs_ordered_extent *ordered_extent)
                                                ordered_extent->disk_num_bytes);
                }
        }
-       unpin_extent_cache(&inode->extent_tree, ordered_extent->file_offset,
+       unpin_extent_cache(inode, ordered_extent->file_offset,
                           ordered_extent->num_bytes, trans->transid);
        if (ret < 0) {
                btrfs_abort_transaction(trans, ret);