On Mon, Jul 27, 2015 at 9:15 AM, Liu Bo <bo.li.liu@xxxxxxxxxx> wrote: > When we do backref walking, we search firstly in queued delayed refs > and then the on-disk backrefs, but we parse differently for shared > references, for delayed refs we also add 'ref->root' while for on-disk > backrefs we don't, this can prevent us from merging refs indexed > by the same bytenr and cause find_parent_nodes() to throw a warning at > 'WARN_ON(ref->count < 0)', for example, when we have a shared data extent > with 'ref_cnt=1' and a delayed shared data with a BTRFS_DROP_DELAYED_REF, > that happens. > > For shared references, no matter if it's delayed or on-disk, ref->root is > not at all used, instead it's ref->parent that really matters, so this has > delayed refs handled as the same way as on-disk refs. > > Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx> > --- > fs/btrfs/backref.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c > index 802fabb..2485b868 100644 > --- a/fs/btrfs/backref.c > +++ b/fs/btrfs/backref.c > @@ -632,7 +632,7 @@ 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); > @@ -665,10 +665,9 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq, > > ref = btrfs_delayed_node_to_data_ref(node); > > - key.objectid = ref->objectid; Why remove only this line and not the following 2 as well if key isn't used anymore? > 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; Do you have any reproducer to turn into an fstest? Would be nice, since this is a rather critical part of the code. thanks > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Filipe David Manana, "Reasonable men adapt themselves to the world. Unreasonable men adapt the world to themselves. That's why all progress depends on unreasonable men." -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
