Re: [PATCH] nilfs2: fix backing_dev_info reference leak

[Ryusuke Konishi]

On Fri, May 8, 2026 at 6:41 AM Viacheslav Dubeyko wrote:
>
> On Thu, 2026-05-07 at 11:50 -0400, Shuangpeng Bai wrote:
> > setup_bdev_super() already initializes sb->s_bdev and takes a
> > reference on the block device backing_dev_info when assigning sb->s_bdi.
> >
> > nilfs_fill_super() takes another reference to the same
> > backing_dev_info and stores it in sb->s_bdi again. The extra
> > reference is not paired with a matching bdi_put(), since
> > generic_shutdown_super() releases sb->s_bdi only once.
> >
> > Drop the redundant bdi_get() in nilfs_fill_super(). The single
> > reference taken by setup_bdev_super() is enough and is released
> > during superblock shutdown.
> >
> > Fixes: c1e012ea9e83 ("nilfs2: use setup_bdev_super to de-duplicate the mount code")
> > Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@xxxxxxxxx>
> > ---
> >  fs/nilfs2/super.c | 2 --
> >  1 file changed, 2 deletions(-)

Acked-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>

Viacheslav,

Could you please apply this directly?
I have also verified the fix and confirmed that the Fixes tag
correctly identifies the origin of the leak for backporting.

Thanks,
Ryusuke Konishi

> >
> > diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
> > index 7aa5ef8606cd..893a504cb80c 100644
> > --- a/fs/nilfs2/super.c
> > +++ b/fs/nilfs2/super.c
> > @@ -1070,8 +1070,6 @@ nilfs_fill_super(struct super_block *sb, struct fs_context *fc)
> >       sb->s_time_gran = 1;
> >       sb->s_max_links = NILFS_LINK_MAX;
> >
> > -     sb->s_bdi = bdi_get(sb->s_bdev->bd_disk->bdi);
> > -
> >       err = load_nilfs(nilfs, sb);
> >       if (err)
> >               goto failed_nilfs;
>
> Makes sense to me.
>
> Reviewed-by: Viacheslav Dubeyko <slava@xxxxxxxxxxx>
>
> Thanks,
> Slava.
>