Re: [PATCH v2 1/6] fs: enhance and rename shutdown() callback to remove_bdev()

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Jul 01, 2025 at 03:02:34PM +0930, Qu Wenruo wrote:
> Currently all the filesystems implementing the
> super_opearations::shutdown() call back can not afford losing a device.
> 
> Thus fs_bdev_mark_dead() will just call the shutdown() callback for the
> involved filesystem.
> 
> But it will no longer be the case, with multi-device filesystems like
> btrfs and bcachefs the filesystem can handle certain device loss without
> shutting down the whole filesystem.
> 
> To allow those multi-device filesystems to be integrated to use
> fs_holder_ops:
> 
> - Rename shutdown() call back to remove_bdev()
>   To better describe when the call back is called.
> 
> - Add a new @bdev parameter to remove_bdev() callback
>   To allow the fs to determine which device is missing, and do the
>   proper handling when needed.
> 
> For the existing shutdown callback users, the change is minimal.
> 
> They only need to follow the rename and the new parameter list.
> Since the behavior is still to shutdown the fs, they shouldn't change
> their function names.
> 
> This has a good side effect that, a single line like
> ".remove_bdev = ext4_shutdown," will easily show the fs behavior and
> indicate the fs will shutdown when a device went missing.
> 
> Btrfs is going to implement the callback soon, which will either
> shutdown the fs or continue read-write operations.

Hrmm, this could be useful for xfs rt devices, if we could some day
reattach a resurrected bdev to a still-running filesystem....

Looks good to me,
Acked-by: "Darrick J. Wong" <djwong@kernel.org>

--D


> Cc: linux-fsdevel@vger.kernel.org
> Cc: linux-ext4@vger.kernel.org
> Cc: linux-f2fs-devel@lists.sourceforge.net
> Cc: ntfs3@lists.linux.dev
> Cc: linux-xfs@vger.kernel.org
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>  fs/exfat/super.c   | 4 ++--
>  fs/ext4/super.c    | 4 ++--
>  fs/f2fs/super.c    | 4 ++--
>  fs/ntfs3/super.c   | 4 ++--
>  fs/super.c         | 4 ++--
>  fs/xfs/xfs_super.c | 5 +++--
>  include/linux/fs.h | 7 ++++++-
>  7 files changed, 19 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/exfat/super.c b/fs/exfat/super.c
> index 7ed858937d45..5773026be84c 100644
> --- a/fs/exfat/super.c
> +++ b/fs/exfat/super.c
> @@ -172,7 +172,7 @@ int exfat_force_shutdown(struct super_block *sb, u32 flags)
>  	return 0;
>  }
>  
> -static void exfat_shutdown(struct super_block *sb)
> +static void exfat_shutdown(struct super_block *sb, struct block_device *bdev)
>  {
>  	exfat_force_shutdown(sb, EXFAT_GOING_DOWN_NOSYNC);
>  }
> @@ -202,7 +202,7 @@ static const struct super_operations exfat_sops = {
>  	.put_super	= exfat_put_super,
>  	.statfs		= exfat_statfs,
>  	.show_options	= exfat_show_options,
> -	.shutdown	= exfat_shutdown,
> +	.remove_bdev	= exfat_shutdown,
>  };
>  
>  enum {
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index c7d39da7e733..8724f89d20d8 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1456,7 +1456,7 @@ static void ext4_destroy_inode(struct inode *inode)
>  			 EXT4_I(inode)->i_reserved_data_blocks);
>  }
>  
> -static void ext4_shutdown(struct super_block *sb)
> +static void ext4_shutdown(struct super_block *sb, struct block_device *bdev)
>  {
>         ext4_force_shutdown(sb, EXT4_GOING_FLAGS_NOLOGFLUSH);
>  }
> @@ -1620,7 +1620,7 @@ static const struct super_operations ext4_sops = {
>  	.unfreeze_fs	= ext4_unfreeze,
>  	.statfs		= ext4_statfs,
>  	.show_options	= ext4_show_options,
> -	.shutdown	= ext4_shutdown,
> +	.remove_bdev	= ext4_shutdown,
>  #ifdef CONFIG_QUOTA
>  	.quota_read	= ext4_quota_read,
>  	.quota_write	= ext4_quota_write,
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index bbf1dad6843f..51c60b429a31 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -2640,7 +2640,7 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>  	return err;
>  }
>  
> -static void f2fs_shutdown(struct super_block *sb)
> +static void f2fs_shutdown(struct super_block *sb, struct block_device *bdev)
>  {
>  	f2fs_do_shutdown(F2FS_SB(sb), F2FS_GOING_DOWN_NOSYNC, false, false);
>  }
> @@ -3264,7 +3264,7 @@ static const struct super_operations f2fs_sops = {
>  	.unfreeze_fs	= f2fs_unfreeze,
>  	.statfs		= f2fs_statfs,
>  	.remount_fs	= f2fs_remount,
> -	.shutdown	= f2fs_shutdown,
> +	.remove_bdev	= f2fs_shutdown,
>  };
>  
>  #ifdef CONFIG_FS_ENCRYPTION
> diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
> index 920a1ab47b63..5e422543b851 100644
> --- a/fs/ntfs3/super.c
> +++ b/fs/ntfs3/super.c
> @@ -764,7 +764,7 @@ static int ntfs_show_options(struct seq_file *m, struct dentry *root)
>  /*
>   * ntfs_shutdown - super_operations::shutdown
>   */
> -static void ntfs_shutdown(struct super_block *sb)
> +static void ntfs_shutdown(struct super_block *sb, struct block_device *bdev)
>  {
>  	set_bit(NTFS_FLAGS_SHUTDOWN_BIT, &ntfs_sb(sb)->flags);
>  }
> @@ -821,7 +821,7 @@ static const struct super_operations ntfs_sops = {
>  	.put_super = ntfs_put_super,
>  	.statfs = ntfs_statfs,
>  	.show_options = ntfs_show_options,
> -	.shutdown = ntfs_shutdown,
> +	.remove_bdev = ntfs_shutdown,
>  	.sync_fs = ntfs_sync_fs,
>  	.write_inode = ntfs3_write_inode,
>  };
> diff --git a/fs/super.c b/fs/super.c
> index 80418ca8e215..c972efb38f6a 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -1463,8 +1463,8 @@ static void fs_bdev_mark_dead(struct block_device *bdev, bool surprise)
>  		sync_filesystem(sb);
>  	shrink_dcache_sb(sb);
>  	evict_inodes(sb);
> -	if (sb->s_op->shutdown)
> -		sb->s_op->shutdown(sb);
> +	if (sb->s_op->remove_bdev)
> +		sb->s_op->remove_bdev(sb, bdev);
>  
>  	super_unlock_shared(sb);
>  }
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 0bc4b5489078..e47d427f4416 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -1277,7 +1277,8 @@ xfs_fs_free_cached_objects(
>  
>  static void
>  xfs_fs_shutdown(
> -	struct super_block	*sb)
> +	struct super_block	*sb,
> +	struct block_device	*bdev)
>  {
>  	xfs_force_shutdown(XFS_M(sb), SHUTDOWN_DEVICE_REMOVED);
>  }
> @@ -1308,7 +1309,7 @@ static const struct super_operations xfs_super_operations = {
>  	.show_options		= xfs_fs_show_options,
>  	.nr_cached_objects	= xfs_fs_nr_cached_objects,
>  	.free_cached_objects	= xfs_fs_free_cached_objects,
> -	.shutdown		= xfs_fs_shutdown,
> +	.remove_bdev		= xfs_fs_shutdown,
>  	.show_stats		= xfs_fs_show_stats,
>  };
>  
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index b085f161ed22..b08af63d2d4f 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2367,7 +2367,12 @@ struct super_operations {
>  				  struct shrink_control *);
>  	long (*free_cached_objects)(struct super_block *,
>  				    struct shrink_control *);
> -	void (*shutdown)(struct super_block *sb);
> +	/*
> +	 * Called when block device @bdev belonging to @sb is removed.
> +	 *
> +	 * If the fs can't afford the device loss, it should be shutdown.
> +	 */
> +	void (*remove_bdev)(struct super_block *sb, struct block_device *bdev);
>  };
>  
>  /*
> -- 
> 2.50.0
> 
>