From 8d91c1e411f55d7ea91b1183a2e9f8088fb4d5be Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Andr=C3=A9=20Fabian=20Silva=20Delgado?= Date: Tue, 15 Dec 2015 14:52:16 -0300 Subject: Linux-libre 4.3.2-gnu --- fs/btrfs/backref.c | 35 +++++++++++++++++++++++++++-------- 1 file changed, 27 insertions(+), 8 deletions(-) (limited to 'fs/btrfs/backref.c') diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c index 34cbe3505..9a2ec79e8 100644 --- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -206,10 +206,33 @@ static int __add_prelim_ref(struct list_head *head, u64 root_id, return -ENOMEM; ref->root_id = root_id; - if (key) + if (key) { ref->key_for_search = *key; - else + /* + * 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 { memset(&ref->key_for_search, 0, sizeof(ref->key_for_search)); + } ref->inode_list = NULL; ref->level = level; @@ -632,7 +655,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq, struct btrfs_delayed_tree_ref *ref; ref = btrfs_delayed_node_to_tree_ref(node); - ret = __add_prelim_ref(prefs, ref->root, NULL, + ret = __add_prelim_ref(prefs, 0, NULL, ref->level + 1, ref->parent, node->bytenr, node->ref_mod * sgn, GFP_ATOMIC); @@ -664,11 +687,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq, struct btrfs_delayed_data_ref *ref; ref = btrfs_delayed_node_to_data_ref(node); - - key.objectid = ref->objectid; - key.type = BTRFS_EXTENT_DATA_KEY; - key.offset = ref->offset; - ret = __add_prelim_ref(prefs, ref->root, &key, 0, + ret = __add_prelim_ref(prefs, 0, NULL, 0, ref->parent, node->bytenr, node->ref_mod * sgn, GFP_ATOMIC); break; -- cgit v1.2.3