The *_state functions can only return 0 or -EEXIST. This patch addresses
 the cases where those functions return -EEXIST, representing a locking
 failure. It handles them by panicking with an appropriate error message.

Signed-off-by: Jeff Mahoney <je...@suse.com>
---
 fs/btrfs/extent_io.c |   41 ++++++++++++++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 11 deletions(-)

--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -51,6 +51,12 @@ struct extent_page_data {
        unsigned int sync_io:1;
 };
 
+static inline struct btrfs_fs_info *
+tree_fs_info(struct extent_io_tree *tree)
+{
+       return btrfs_sb(tree->mapping->host->i_sb)->fs_info;
+}
+
 int __init extent_io_init(void)
 {
        extent_state_cache = kmem_cache_create("extent_state",
@@ -437,6 +443,13 @@ alloc_extent_state_atomic(struct extent_
        return prealloc;
 }
 
+NORET_TYPE void extent_io_tree_panic(struct extent_io_tree *tree, int err)
+{
+       btrfs_panic(tree_fs_info(tree), err, "Locking error: "
+                   "Extent tree was modified by another "
+                   "thread while locked.");
+}
+
 /*
  * clear some bits on a range in the tree.  This may require splitting
  * or inserting elements in the tree, so the gfp mask is used to
@@ -531,7 +544,9 @@ hit_next:
                prealloc = alloc_extent_state_atomic(prealloc);
                BUG_ON(!prealloc);
                err = split_state(tree, state, prealloc, start);
-               BUG_ON(err == -EEXIST);
+               if (err)
+                       extent_io_tree_panic(tree, err);
+
                prealloc = NULL;
                if (err)
                        goto out;
@@ -553,7 +568,9 @@ hit_next:
                prealloc = alloc_extent_state_atomic(prealloc);
                BUG_ON(!prealloc);
                err = split_state(tree, state, prealloc, end + 1);
-               BUG_ON(err == -EEXIST);
+               if (err)
+                       extent_io_tree_panic(tree, err);
+
                if (wake)
                        wake_up(&state->wq);
 
@@ -736,8 +753,10 @@ again:
                prealloc = alloc_extent_state_atomic(prealloc);
                BUG_ON(!prealloc);
                err = insert_state(tree, prealloc, start, end, &bits);
+               if (err)
+                       extent_io_tree_panic(tree, err);
+
                prealloc = NULL;
-               BUG_ON(err == -EEXIST);
                goto out;
        }
        state = rb_entry(node, struct extent_state, rb_node);
@@ -803,7 +822,9 @@ hit_next:
                prealloc = alloc_extent_state_atomic(prealloc);
                BUG_ON(!prealloc);
                err = split_state(tree, state, prealloc, start);
-               BUG_ON(err == -EEXIST);
+               if (err)
+                       extent_io_tree_panic(tree, err);
+
                prealloc = NULL;
                if (err)
                        goto out;
@@ -840,12 +861,9 @@ hit_next:
                 */
                err = insert_state(tree, prealloc, start, this_end,
                                   &bits);
-               BUG_ON(err == -EEXIST);
-               if (err) {
-                       free_extent_state(prealloc);
-                       prealloc = NULL;
-                       goto out;
-               }
+               if (err)
+                       extent_io_tree_panic(tree, err);
+
                cache_state(prealloc, cached_state);
                prealloc = NULL;
                start = this_end + 1;
@@ -867,7 +885,8 @@ hit_next:
                prealloc = alloc_extent_state_atomic(prealloc);
                BUG_ON(!prealloc);
                err = split_state(tree, state, prealloc, end + 1);
-               BUG_ON(err == -EEXIST);
+               if (err)
+                       extent_io_tree_panic(tree, err);
 
                set_state_bits(tree, prealloc, &bits);
                cache_state(prealloc, cached_state);



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