btrfs: fix check_shared for fiemap ioctl
Only in the case of different root_id or different object_id, check_shared
identified extent as the shared. However, If a extent was referred by
different offset of same file, it should also be identified as shared.
In addition, check_shared's loop scale is at least n^3, so if a extent
has too many references, even causes soft hang up.
First, add all delayed_ref to the ref_tree and calculate the unqiue_refs,
if the unique_refs is greater than one, return BACKREF_FOUND_SHARED.
Then individually add the on-disk reference(inline/keyed) to the ref_tree
and calculate the unique_refs of the ref_tree to check if the unique_refs
is greater than one.Because once there are two references to return
SHARED, so the time complexity is close to the constant.
Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 44fe66b..8644df8 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -20,6 +20,7 @@
#include "locking.h"
#include "rcu-string.h"
#include "backref.h"
+#include "transaction.h"
static struct kmem_cache *extent_state_cache;
static struct kmem_cache *extent_buffer_cache;
@@ -4487,21 +4488,36 @@
flags |= (FIEMAP_EXTENT_DELALLOC |
FIEMAP_EXTENT_UNKNOWN);
} else if (fieinfo->fi_extents_max) {
+ struct btrfs_trans_handle *trans;
+
u64 bytenr = em->block_start -
(em->start - em->orig_start);
disko = em->block_start + offset_in_extent;
/*
+ * We need a trans handle to get delayed refs
+ */
+ trans = btrfs_join_transaction(root);
+ /*
+ * It's OK if we can't start a trans we can still check
+ * from commit_root
+ */
+ if (IS_ERR(trans))
+ trans = NULL;
+
+ /*
* As btrfs supports shared space, this information
* can be exported to userspace tools via
* flag FIEMAP_EXTENT_SHARED. If fi_extents_max == 0
* then we're just getting a count and we can skip the
* lookup stuff.
*/
- ret = btrfs_check_shared(NULL, root->fs_info,
+ ret = btrfs_check_shared(trans, root->fs_info,
root->objectid,
btrfs_ino(inode), bytenr);
+ if (trans)
+ btrfs_end_transaction(trans, root);
if (ret < 0)
goto out_free;
if (ret)