When resolving one backref of type EXTENT_DATA_REF, we collect all
references that simply references the EXTENT_ITEM even though
their (file_pos- file_extent_item::offset) are not the same as the
btrfs_extent_data_ref::offset we are searching.
This patch add additional check so that we only collect references whose
(file_pos- file_extent_item::offset) == btrfs_extent_data_ref::offset.
Signed-off-by: ethanwu <ethanwu@xxxxxxxxxxxx>
---
fs/btrfs/backref.c | 63 ++++++++++++++++++++++++----------------------
1 file changed, 33 insertions(+), 30 deletions(-)
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index e5d85311d5d5..1572eab3cc06 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -347,33 +347,10 @@ static int add_prelim_ref(const struct btrfs_fs_info *fs_info,
return -ENOMEM;
ref->root_id = root_id;
- if (key) {
+ if (key)
ref->key_for_search = *key;
- /*
- * We can often find data backrefs with an offset that is too
- * large (>= LLONG_MAX, maximum allowed file offset) due to
- * underflows when subtracting a file's offset with the data
- * offset of its corresponding extent data item. This can
- * happen for example in the clone ioctl.
- * So if we detect such case we set the search key's offset to
- * zero to make sure we will find the matching file extent item
- * at add_all_parents(), otherwise we will miss it because the
- * offset taken form the backref is much larger then the offset
- * of the file extent item. This can make us scan a very large
- * number of file extent items, but at least it will not make
- * us miss any.
- * This is an ugly workaround for a behaviour that should have
- * never existed, but it does and a fix for the clone ioctl
- * would touch a lot of places, cause backwards incompatibility
- * and would not fix the problem for extents cloned with older
- * kernels.
- */
- if (ref->key_for_search.type == BTRFS_EXTENT_DATA_KEY &&
- ref->key_for_search.offset >= LLONG_MAX)
- ref->key_for_search.offset = 0;
- } else {
+ else
memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
- }
ref->inode_list = NULL;
ref->level = level;
@@ -424,6 +401,7 @@ static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
u64 disk_byte;
u64 wanted_disk_byte = ref->wanted_disk_byte;
u64 count = 0;
+ u64 data_offset;
if (level != 0) {
eb = path->nodes[level];
@@ -457,11 +435,15 @@ static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
+ data_offset = btrfs_file_extent_offset(eb, fi);
if (disk_byte == wanted_disk_byte) {
eie = NULL;
old = NULL;
- count++;
+ if (ref->key_for_search.offset == key.offset - data_offset)
+ count++;
+ else
+ goto next;
if (extent_item_pos) {
ret = check_extent_in_eb(&key, eb, fi,
*extent_item_pos,
@@ -513,6 +495,7 @@ static int resolve_indirect_ref(struct btrfs_fs_info *fs_info,
int root_level;
int level = ref->level;
int index;
+ struct btrfs_key search_key = ref->key_for_search;
root_key.objectid = ref->root_id;
root_key.type = BTRFS_ROOT_ITEM_KEY;
@@ -545,13 +528,33 @@ static int resolve_indirect_ref(struct btrfs_fs_info *fs_info,
goto out;
}
+ /*
+ * We can often find data backrefs with an offset that is too
+ * large (>= LLONG_MAX, maximum allowed file offset) due to
+ * underflows when subtracting a file's offset with the data
+ * offset of its corresponding extent data item. This can
+ * happen for example in the clone ioctl.
+ * So if we detect such case we set the search key's offset to
+ * zero to make sure we will find the matching file extent item
+ * at add_all_parents(), otherwise we will miss it because the
+ * offset taken form the backref is much larger then the offset
+ * of the file extent item. This can make us scan a very large
+ * number of file extent items, but at least it will not make
+ * us miss any.
+ * This is an ugly workaround for a behaviour that should have
+ * never existed, but it does and a fix for the clone ioctl
+ * would touch a lot of places, cause backwards incompatibility
+ * and would not fix the problem for extents cloned with older
+ * kernels.
+ */
+ if (search_key.type == BTRFS_EXTENT_DATA_KEY &&
+ search_key.offset >= LLONG_MAX)
+ search_key.offset = 0;
path->lowest_level = level;
if (time_seq == SEQ_LAST)
- ret = btrfs_search_slot(NULL, root, &ref->key_for_search, path,
- 0, 0);
+ ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
else
- ret = btrfs_search_old_slot(root, &ref->key_for_search, path,
- time_seq);
+ ret = btrfs_search_old_slot(root, &search_key, path, time_seq);
/* root node has been locked, we can release @subvol_srcu safely here */
srcu_read_unlock(&fs_info->subvol_srcu, index);
--
2.17.1
