Re: [PATCH 1/2] md: fix WARN_ON if create symlink fail in bind_rdev_to_array()

[Li Nan]

在 2023/12/22 2:58, Song Liu 写道:
> Hi,
>
> On Wed, Dec 20, 2023 at 11:13 PM <linan666@xxxxxxxxxxxxxxx> wrote:
> > From: Li Nan <linan122@xxxxxxxxxx>
> >
> > Removing a device can trigger WARN_ON in bd_unlink_disk_holder() if creating
> > symlink failed while adding device.
> >
> >    WARNING: CPU: 0 PID: 742 at block/holder.c:145 bd_unlink_disk_holder+0x17b/0x1a0
> >
> > Fix it by adding the flag 'SymlinkCreated', which only be set after
> > creating symlink success.
> >
> > Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
> > ---
> >   drivers/md/md.h | 3 +++
> >   drivers/md/md.c | 8 ++++++--
> >   2 files changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/md/md.h b/drivers/md/md.h
> > index 8d881cc59799..427d17713a8c 100644
> > --- a/drivers/md/md.h
> > +++ b/drivers/md/md.h
> > @@ -207,6 +207,9 @@ enum flag_bits {
> >                                   * check if there is collision between raid1
> >                                   * serial bios.
> >                                   */
> > +       SymlinkCreated,         /* This device has created the symlink
> > +                                * with gendisk.
> > +                                */
>
> In general, I would like to avoid adding flags if possible.

This flag is mainly used to fix deadlock in next patch. Or should we
export bd_find_holder_disk()? Link hodler if it return NULL.
just like:

  rdev_for_each_rcu
    if (!bd_find_holder_disk)
      bd_link_disk_holder


> >   };
> >
> >   static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
> > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > index e05858653a41..d6612b922c76 100644
> > --- a/drivers/md/md.c
> > +++ b/drivers/md/md.c
> > @@ -2526,7 +2526,8 @@ static int bind_rdev_to_array(struct md_rdev *rdev, struct mddev *mddev)
> >                  sysfs_get_dirent_safe(rdev->kobj.sd, "bad_blocks");
> >
> >          list_add_rcu(&rdev->same_set, &mddev->disks);
> > -       bd_link_disk_holder(rdev->bdev, mddev->gendisk);
> > +       if (!bd_link_disk_holder(rdev->bdev, mddev->gendisk))
> > +               set_bit(SymlinkCreated, &rdev->flags);
>
> Shall we just fail bind_rdev_to_array() if bd_link_disk_holder()
> returns non-zero?

I keep this action because of commit 00bcb4ac7ee7 ("md: reduce
dependence on sysfs."). Fail bind_rdev_to_array is good to me.

> Thanks,
> Song
>
> .

--
Thanks,
Nan