Re: [PATCH v2 1/2] Btrfs: add missing error handling after doing leaf/node binary search

[Filipe Manana <fdmanana@kernel.org>]

On Mon, Feb 18, 2019 at 5:11 PM Nikolay Borisov <nborisov@suse.com> wrote:
>
>
>
> On 18.02.19 г. 19:07 ч., fdmanana@kernel.org wrote:
> > From: Filipe Manana <fdmanana@suse.com>
> >
> > The function map_private_extent_buffer() can return an -EINVAL error, and
> > it is called by generic_bin_search() which will return back the error. The
> > btrfs_bin_search() function in turn calls generic_bin_search() and the
> > key_search() function calls btrfs_bin_search(), so both can return the
> > -EINVAL error coming from the map_private_extent_buffer() function. Some
> > callers of these functions were ignoring that these functions can return
> > an error, so fix them to deal with error return values.
> >
> > Signed-off-by: Filipe Manana <fdmanana@suse.com>
>
> Reviewed-by: Nikolay Borisov <nborisov@suse.com>
>
> > ---
> >
> > V2: Fixed error handling in relocation, missed assignment of ret to err.
> >
> >  fs/btrfs/ctree.c      |  6 ++++++
> >  fs/btrfs/relocation.c | 10 ++++++++++
> >  fs/btrfs/tree-log.c   |  2 ++
> >  3 files changed, 18 insertions(+)
> >
> > diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
> > index 5a6c39b44c84..5b9f602fb9e2 100644
> > --- a/fs/btrfs/ctree.c
> > +++ b/fs/btrfs/ctree.c
> > @@ -3005,6 +3005,8 @@ int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key,
> >                */
> >               prev_cmp = -1;
> >               ret = key_search(b, key, level, &prev_cmp, &slot);
> > +             if (ret < 0)
> > +                     goto done;
> >
> >               if (level != 0) {
> >                       int dec = 0;
> > @@ -5156,6 +5158,10 @@ int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
> >               nritems = btrfs_header_nritems(cur);
> >               level = btrfs_header_level(cur);
> >               sret = btrfs_bin_search(cur, min_key, level, &slot);
> > +             if (sret < 0) {
> > +                     ret = sret;
> > +                     goto out;
> > +             }>
> >               /* at the lowest level, we're done, setup the path and exit */
> >               if (level == path->lowest_level) {
> > diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> > index 272b287f8cf0..628ba528516d 100644
> > --- a/fs/btrfs/relocation.c
> > +++ b/fs/btrfs/relocation.c
> > @@ -1802,6 +1802,8 @@ int replace_path(struct btrfs_trans_handle *trans, struct reloc_control *rc,
> >               BUG_ON(level < lowest_level);
> >
> >               ret = btrfs_bin_search(parent, &key, level, &slot);
> > +             if (ret < 0)
> > +                     break;
> >               if (ret && slot > 0)
> >                       slot--;
> >
> > @@ -2685,6 +2687,10 @@ static int do_relocation(struct btrfs_trans_handle *trans,
> >                       if (!lowest) {
> >                               ret = btrfs_bin_search(upper->eb, key,
> >                                                      upper->level, &slot);
> > +                             if (ret < 0) {
> > +                                     err = ret;
> > +                                     goto next;
> > +                             }
> >                               BUG_ON(ret);
> >                               bytenr = btrfs_node_blockptr(upper->eb, slot);
> >                               if (node->eb->start == bytenr)
> > @@ -2720,6 +2726,10 @@ static int do_relocation(struct btrfs_trans_handle *trans,
> >               } else {
> >                       ret = btrfs_bin_search(upper->eb, key, upper->level,
> >                                              &slot);
> > +                     if (ret < 0) {
> > +                             err = ret;
> > +                             goto next;
> > +                     }
> >                       BUG_ON(ret);
>
> Ideally those BUG_ON should disappear and be replaced with, perhahps
> -EUCLEAN or somesuch?

Different problem. Those assert the impossibility of the search
returning 1 (key not found), which would happen due to a relocation
algorithm flaw.
I'm dealing with missing error handling only, therefore won't do such
thing in this patch.

>
> >               }
> >
> > diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
> > index 8c9e87f5ec58..81a357a32837 100644
> > --- a/fs/btrfs/tree-log.c
> > +++ b/fs/btrfs/tree-log.c
> > @@ -3772,6 +3772,8 @@ static int drop_objectid_items(struct btrfs_trans_handle *trans,
> >               found_key.type = 0;
> >               ret = btrfs_bin_search(path->nodes[0], &found_key, 0,
> >                                      &start_slot);
> > +             if (ret < 0)
> > +                     break;
> >
> >               ret = btrfs_del_items(trans, log, path, start_slot,
> >                                     path->slots[0] - start_slot + 1);
> >