On Fri, May 26, 2017 at 08:33:16PM +0200, David Sterba wrote:
> On Thu, May 25, 2017 at 06:26:31PM -0600, Liu Bo wrote:
> > Currently scrub only verify checksum of both metadata and data and
> > couldn't detect an invalid extent_item.
>
> This is a different kind of check that scrub was never designed to do.
> Scrub just verifies the checksums, not the sructural integrity. This has
> been referred to as an "on-line fsck". AFAIK xfs does not use 'scrub' in
> the same sense as btrfs, so things are going to be confusing for the
> users.
>
> The on-line fsck is still desired, but I'd like to see a discussion how
> exactly it should work, whether to extend scrub or add a new ioctl etc.
>
I was hesitating about scrub vs online fsck when posting, just thought
it'd be good when users got this error while doing a regular scrub
ahead of really getting into trouble. If we have a plan for online
fsck, I'm happy to let fsck do the job.
Or we can do this kind of sanity check at the time when reading the
eb.
Thanks,
-liubo
> > This adds sanity check for extent item, now it can check if
> > extent_inline_ref_type is valid.
> >
> > Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
> > ---
> > fs/btrfs/scrub.c | 43 +++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 43 insertions(+)
> >
> > diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> > index b0251eb..e87b752 100644
> > --- a/fs/btrfs/scrub.c
> > +++ b/fs/btrfs/scrub.c
> > @@ -3058,6 +3058,39 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
> > return ret < 0 ? ret : 0;
> > }
> >
> > +static int check_extent_item(struct extent_buffer *l, int slot,
>
> Please use 'eb' for the extent_buffer.
>
> > + struct btrfs_extent_item *ei, int key_type)
>
> key_type should be u8
>
> > +{
> > + unsigned long ptr;
> > + unsigned long end;
> > + struct btrfs_extent_inline_ref *iref;
> > + u64 flags = btrfs_extent_flags(l, ei);
> > + int is_data = !!(flags & BTRFS_EXTENT_FLAG_DATA);
> > + int type;
> > +
> > + ptr = (unsigned long)(ei + 1);
> > + if (!is_data &&
> > + key_type != BTRFS_METADATA_ITEM_KEY)
> > + ptr += sizeof(struct btrfs_tree_block_info);
> > + end = (unsigned long)ei +
> > + btrfs_item_size_nr(l, slot);
>
> This will fit to one line
>
> > +
> > + while (1) {
> > + if (ptr >= end) {
> > + WARN_ON(ptr > end);
>
> Please add some verbose error message or get rid of the WARN_ON
> completely if possible.
>
> > + break;
> > + }
> > +
> > + iref = (struct btrfs_extent_inline_ref *)ptr;
> > + type = btrfs_get_extent_inline_ref_type(l, iref, is_data);
> > + if (type < 0)
> > + return type;
> > +
> > + ptr += btrfs_extent_inline_ref_size(type);
> > + }
> > + return 0;
> > +}
> > +
> > static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
> > struct map_lookup *map,
> > struct btrfs_device *scrub_dev,
> > @@ -3318,6 +3351,16 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
> > goto next;
> > }
> >
> > + /* sanity check for extent inline ref type */
> > + if (check_extent_item(l, slot, extent, key.type)) {
> > + btrfs_err(fs_info,
> > + "scrub: extent %llu(0x%llx) has an invalid extent inline ref type, ignored.",
>
> Strings can be un-indented to the left.
>
> > + key.objectid, key.objectid);
> > + spin_lock(&sctx->stat_lock);
> > + sctx->stat.uncorrectable_errors++;
>
> Yeah, this is an example where the uncorrectable_error would gain a new
> meaning. We'd need to extend the scrub error reporting so the various
> metadata errors get reported properly and not mangled with the rest.
>
> > + spin_unlock(&sctx->stat_lock);
> > + goto next;
> > + }
> > again:
> > extent_logical = key.objectid;
> > extent_len = bytes;
> --
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