[PATCH] nilfs2: fix backing_dev_info reference leak

[PATCH] nilfs2: fix backing_dev_info reference leak

[Shuangpeng Bai]

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@gmail.com>
---
 fs/nilfs2/super.c | 2 --
 1 file changed, 2 deletions(-)

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;
-- 
2.34.1

Re: [PATCH] nilfs2: fix backing_dev_info reference leak

[Viacheslav Dubeyko]

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@gmail.com>
> ---
>  fs/nilfs2/super.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> 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@dubeyko.com>

Thanks,
Slava.

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@gmail.com>
> > ---
> >  fs/nilfs2/super.c | 2 --
> >  1 file changed, 2 deletions(-)

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

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@dubeyko.com>
>
> Thanks,
> Slava.
>

Re: [PATCH] nilfs2: fix backing_dev_info reference leak

[Viacheslav Dubeyko]

On Fri, 2026-05-08 at 11:05 +0900, Ryusuke Konishi wrote:
> 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@gmail.com>
> > > ---
> > >  fs/nilfs2/super.c | 2 --
> > >  1 file changed, 2 deletions(-)
> 
> Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
> 
> 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.
> 

Applied.

Thanks,
Slava.