1 files changed, 30 insertions, 13 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 05e1386b8bec..4eb4d2748bec 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4203,12 +4203,17 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
         struct btrfs_root *root = BTRFS_I(inode)->root;
         struct btrfs_block_rsv *block_rsv = &root->fs_info->delalloc_block_rsv;
         u64 to_reserve = 0;
+        u64 csum_bytes;
         unsigned nr_extents = 0;
+        int extra_reserve = 0;
         int flush = 1;
         int ret;
 
+        /* Need to be holding the i_mutex here if we aren't free space cache */
         if (btrfs_is_free_space_inode(root, inode))
                 flush = 0;
+        else
+                WARN_ON(!mutex_is_locked(&inode->i_mutex));
 
         if (flush && btrfs_transaction_in_commit(root->fs_info))
                 schedule_timeout(1);
@@ -4219,11 +4224,9 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
         BTRFS_I(inode)->outstanding_extents++;
 
         if (BTRFS_I(inode)->outstanding_extents >
-            BTRFS_I(inode)->reserved_extents) {
+            BTRFS_I(inode)->reserved_extents)
                 nr_extents = BTRFS_I(inode)->outstanding_extents -
                         BTRFS_I(inode)->reserved_extents;
-                BTRFS_I(inode)->reserved_extents += nr_extents;
-        }
 
         /*
          * Add an item to reserve for updating the inode when we complete the
@@ -4231,11 +4234,12 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
          */
         if (!BTRFS_I(inode)->delalloc_meta_reserved) {
                 nr_extents++;
-                BTRFS_I(inode)->delalloc_meta_reserved = 1;
+                extra_reserve = 1;
         }
 
         to_reserve = btrfs_calc_trans_metadata_size(root, nr_extents);
         to_reserve += calc_csum_metadata_size(inode, num_bytes, 1);
+        csum_bytes = BTRFS_I(inode)->csum_bytes;
         spin_unlock(&BTRFS_I(inode)->lock);
 
         ret = reserve_metadata_bytes(root, block_rsv, to_reserve, flush);
@@ -4245,22 +4249,35 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
 
                 spin_lock(&BTRFS_I(inode)->lock);
                 dropped = drop_outstanding_extent(inode);
-                to_free = calc_csum_metadata_size(inode, num_bytes, 0);
-                spin_unlock(&BTRFS_I(inode)->lock);
-                to_free += btrfs_calc_trans_metadata_size(root, dropped);
-
                 /*
-                 * Somebody could have come in and twiddled with the
-                 * reservation, so if we have to free more than we would have
-                 * reserved from this reservation go ahead and release those
-                 * bytes.
+                 * If the inodes csum_bytes is the same as the original
+                 * csum_bytes then we know we haven't raced with any free()ers
+                 * so we can just reduce our inodes csum bytes and carry on.
+                 * Otherwise we have to do the normal free thing to account for
+                 * the case that the free side didn't free up its reserve
+                 * because of this outstanding reservation.
                  */
-                to_free -= to_reserve;
+                if (BTRFS_I(inode)->csum_bytes == csum_bytes)
+                        calc_csum_metadata_size(inode, num_bytes, 0);
+                else
+                        to_free = calc_csum_metadata_size(inode, num_bytes, 0);
+                spin_unlock(&BTRFS_I(inode)->lock);
+                if (dropped)
+                        to_free += btrfs_calc_trans_metadata_size(root, dropped);
+
                 if (to_free)
                         btrfs_block_rsv_release(root, block_rsv, to_free);
                 return ret;
         }
 
+        spin_lock(&BTRFS_I(inode)->lock);
+        if (extra_reserve) {
+                BTRFS_I(inode)->delalloc_meta_reserved = 1;
+                nr_extents--;
+        }
+        BTRFS_I(inode)->reserved_extents += nr_extents;
+        spin_unlock(&BTRFS_I(inode)->lock);
+
         block_rsv_add_bytes(block_rsv, to_reserve, 1);
 
         return 0;