From: ethanwu ethanwu@synology.com
commit 7ac8b88ee668a5b4743ebf3e9888fabac85c334a upstream.
When resolving one backref of type EXTENT_DATA_REF, we collect all references that simply reference 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 for.
This patch adds additional check so that we only collect references whose (file_pos - file_extent_item::offset) == btrfs_extent_data_ref::offset.
Reviewed-by: Josef Bacik josef@toxicpanda.com Reviewed-by: Johannes Thumshirn johannes.thumshirn@wdc.com Signed-off-by: ethanwu ethanwu@synology.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/backref.c | 63 +++++++++++++++++++++++++++-------------------------- 1 file changed, 33 insertions(+), 30 deletions(-)
--- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -347,33 +347,10 @@ static int add_prelim_ref(const struct b 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_ 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_
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 b 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 b 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);