Re: [PATCH RFC 7/8] erofs: open via dedicated fs bdev helpers

[Gao Xiang]

On 2026/6/2 18:10, Christian Brauner wrote:
> Route opens through fs_bdev_file_open_by_path() so each external device
> is registered against the correct superblock, and convert the matching
> releases.
>
> Signed-off-by: Christian Brauner (Amutable) <brauner@xxxxxxxxxx>
> ---
>   fs/erofs/data.c     |  6 +++++
>   fs/erofs/internal.h | 10 ++++++++
>   fs/erofs/super.c    | 66 +++++++++++++++++++++++++++++++++++++++++++----------
>   fs/erofs/zdata.c    | 10 +++++---
>   4 files changed, 77 insertions(+), 15 deletions(-)
>
> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> index 44da21c9d777..5220585293df 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -69,6 +69,9 @@ int erofs_init_metabuf(struct erofs_buf *buf, struct super_block *sb,
>   {
>   	struct erofs_sb_info *sbi = EROFS_SB(sb);
>   
> +	if (erofs_is_shutdown(sb))
> +		return -EIO;
> +
>   	buf->file = NULL;
>   	if (in_metabox) {
>   		if (unlikely(!sbi->metabox_inode))
> @@ -236,6 +239,9 @@ int erofs_map_dev(struct super_block *sb, struct erofs_map_dev *map)
>   		}
>   		up_read(&devs->rwsem);
>   	}
> +	if (erofs_is_shutdown(sb) ||
> +	    (map->m_dif && READ_ONCE(map->m_dif->dead)))
> +		return -EIO;

Take a quick look at the code, maybe we can just add
the SHUTDOWN status only since I don't think remove an
individual blob device is useful for the typical image
use cases, so there is no need adding `dead` for each
individual extra device.

and just bail out if erofs_is_shutdown() at the very
beginning of erofs_map_dev()?

>   	return 0;
>   }
>   

...

> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index 43bb5a6a9924..89ae91935364 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -1697,11 +1697,15 @@ static void z_erofs_submit_queue(struct z_erofs_frontend *f,
>   			continue;
>   		}
>   
> -		/* no device id here, thus it will always succeed */
>   		mdev = (struct erofs_map_dev) {
>   			.m_pa = round_down(pcl->pos, sb->s_blocksize),
>   		};
> -		(void)erofs_map_dev(sb, &mdev);
> +		if (erofs_map_dev(sb, &mdev)) {
> +			/* the backing device is gone; fail the batch */
> +			q[JQ_SUBMIT]->eio = true;
> +			qtail[JQ_SUBMIT] = &pcl->next;
> +			continue;
> +		}

It needs some injection tests anyway.

May I ask if it's an urgent 7.2 work? If not, I could
make a preparation patch for the upcoming 7.2 cycle
to handle erofs_map_dev() failure here so you don't
need to bother with this in this patchset.

I will seek more time to resolve the recent todos
yet always intercepted by other unrelated stuffs.

Thanks,
Gao Xaing