btrfs: fix bytes_may_use underflow in prealloc error condtition

[platform/kernel/linux-rpi.git] / fs / btrfs / inode.c

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b83eef4..58594d8 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -10464,6 +10464,7 @@ static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_key ins;
        u64 cur_offset = start;
+       u64 clear_offset = start;
        u64 i_size;
        u64 cur_bytes;
        u64 last_alloc = (u64)-1;
@@ -10498,6 +10499,15 @@ static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
                                btrfs_end_transaction(trans);
                        break;
                }
+
+               /*
+                * We've reserved this space, and thus converted it from
+                * ->bytes_may_use to ->bytes_reserved.  Any error that happens
+                * from here on out we will only need to clear our reservation
+                * for the remaining unreserved area, so advance our
+                * clear_offset by our extent size.
+                */
+               clear_offset += ins.offset;
                btrfs_dec_block_group_reservations(fs_info, ins.objectid);
 
                last_alloc = ins.offset;
@@ -10578,9 +10588,9 @@ next:
                if (own_trans)
                        btrfs_end_transaction(trans);
        }
-       if (cur_offset < end)
-               btrfs_free_reserved_data_space(inode, NULL, cur_offset,
-                       end - cur_offset + 1);
+       if (clear_offset < end)
+               btrfs_free_reserved_data_space(inode, NULL, clear_offset,
+                       end - clear_offset + 1);
        return ret;
 }