btrfs: only free reserved extent if we didn't insert it

When we insert the file extent once the ordered extent completes we free
the reserved extent reservation as it'll have been migrated to the
bytes_used counter.  However if we error out after this step we'll still
clear the reserved extent reservation, resulting in a negative
accounting of the reserved bytes for the block group and space info.
Fix this by only doing the free if we didn't successfully insert a file
extent for this extent.

CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f98ddd886036ec18887d53d9a3d9a6df33b56f4f..28625f34495232a9eb9ef6719429efd09399db87 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2941,6 +2941,7 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
        bool truncated = false;
        bool range_locked = false;
        bool clear_new_delalloc_bytes = false;
+       bool clear_reserved_extent = true;
 
        if (!test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags) &&
            !test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags) &&
@@ -3044,10 +3045,12 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
                                                logical_len, logical_len,
                                                compress_type, 0, 0,
                                                BTRFS_FILE_EXTENT_REG);
-               if (!ret)
+               if (!ret) {
+                       clear_reserved_extent = false;
                        btrfs_release_delalloc_bytes(fs_info,
                                                     ordered_extent->start,
                                                     ordered_extent->disk_len);
+               }
        }
        unpin_extent_cache(&BTRFS_I(inode)->extent_tree,
                           ordered_extent->file_offset, ordered_extent->len,
@@ -3108,8 +3111,13 @@ out:
                 * wrong we need to return the space for this ordered extent
                 * back to the allocator.  We only free the extent in the
                 * truncated case if we didn't write out the extent at all.
+                *
+                * If we made it past insert_reserved_file_extent before we
+                * errored out then we don't need to do this as the accounting
+                * has already been done.
                 */
                if ((ret || !logical_len) &&
+                   clear_reserved_extent &&
                    !test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags) &&
                    !test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags))
                        btrfs_free_reserved_extent(fs_info,