On Tue, Apr 23, 2013 at 10:54:53AM -0400, Josef Bacik
wrote:> A user sent me a btrfs-image that was panicing because of some corruption.
This
> is because we pass in a bogus value to btrfs_num_copies, and it panics.
Instead
> just return 1. We only call btrfs_num_copies to see if there are other
copies
> to try and read for things, so if we just return 1 it will make the callers
exit
> out with an appropriate error value. Thanks,
>
> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
> ---
> fs/btrfs/volumes.c | 20 ++++++++++++++++++--
> 1 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index c8a315d..c1a2217 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -4232,9 +4232,25 @@ int btrfs_num_copies(struct btrfs_fs_info *fs_info,
u64 logical, u64 len)
> read_lock(&em_tree->lock);
> em = lookup_extent_mapping(em_tree, logical, len);
> read_unlock(&em_tree->lock);
> - BUG_ON(!em);
>
> - BUG_ON(em->start > logical || em->start + em->len <
logical);
> + /*
> + * We could return errors for these cases, but that could get ugly and
> + * we''d probably do the same thing which is just not do anything
else
> + * and exit, so return 1 so the callers don''t try to use other
copies.
> + */
This is safe on all the repair paths, they bail out if there''s only one
copy. In the integrity checker btrfs_num_copies value is used to process
all copies, btrfs(ic)_map_block is called afterwards and bails out
eventually. Both functions fail on the same call to
lookup_extent_mapping(), so it adds only some minor extra work but
we''re
interested if it''s safe to return 1, I think it is.
> + if (!em) {
> + btrfs_emerg(fs_info, "No mapping for %Lu-%Lu\n", logical,
> + logical+len);
(unsigned long long)logical,
(unsigned long long)(logical + len)
> + return 1;
> + }
> +
> + if (em->start > logical || em->start + em->len < logical)
{
> + btrfs_emerg(fs_info, "Invalid mapping for %Lu-%Lu, got "
> + "%Lu-%Lu\n", logical, logical+len, em->start,
> + em->start + em->len);
dtto
> + return 1;
> + }
> +
> map = (struct map_lookup *)em->bdev;
> if (map->type & (BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID1))
> ret = map->num_stripes;
Reviewed-by: David Sterba <dsterba@suse.cz>
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