[PATCH v2] vfs: Make vfs_get_super() internal

[PATCH v2] vfs: Make vfs_get_super() internal

[Dawei Li]

For now there are no external callers of vfs_get_super(),
so just make it an internal API.

v1: https://lore.kernel.org/all/TYCP286MB2323D37F4F6400FD07D7C7F7CA319@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM/

v2: move vfs_get_super_keying to super.c, as the suggestion
from Christian Brauner.

base-commit: 3aca47127a646165965ff52803e2b269eed91afc

Signed-off-by: Dawei Li <set_pte_at@outlook.com>
---
 fs/super.c                 | 13 +++++++++++--
 include/linux/fs_context.h | 14 --------------
 2 files changed, 11 insertions(+), 16 deletions(-)

diff --git a/fs/super.c b/fs/super.c
index 6a82660e1adb..24e31e458552 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1111,6 +1111,16 @@ static int test_single_super(struct super_block *s, struct fs_context *fc)
 	return 1;
 }
 
+/*
+ * sget() wrappers to be called from the ->get_tree() op.
+ */
+enum vfs_get_super_keying {
+	vfs_get_single_super,	/* Only one such superblock may exist */
+	vfs_get_single_reconf_super, /* As above, but reconfigure if it exists */
+	vfs_get_keyed_super,	/* Superblocks with different s_fs_info keys may exist */
+	vfs_get_independent_super, /* Multiple independent superblocks may exist */
+};
+
 /**
  * vfs_get_super - Get a superblock with a search key set in s_fs_info.
  * @fc: The filesystem context holding the parameters
@@ -1136,7 +1146,7 @@ static int test_single_super(struct super_block *s, struct fs_context *fc)
  * A permissions check is made by sget_fc() unless we're getting a superblock
  * for a kernel-internal mount or a submount.
  */
-int vfs_get_super(struct fs_context *fc,
+static int vfs_get_super(struct fs_context *fc,
 		  enum vfs_get_super_keying keying,
 		  int (*fill_super)(struct super_block *sb,
 				    struct fs_context *fc))
@@ -1189,7 +1199,6 @@ int vfs_get_super(struct fs_context *fc,
 	deactivate_locked_super(sb);
 	return err;
 }
-EXPORT_SYMBOL(vfs_get_super);
 
 int get_tree_nodev(struct fs_context *fc,
 		  int (*fill_super)(struct super_block *sb,
diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h
index 13fa6f3df8e4..87a34f2fa68d 100644
--- a/include/linux/fs_context.h
+++ b/include/linux/fs_context.h
@@ -145,20 +145,6 @@ extern void fc_drop_locked(struct fs_context *fc);
 int reconfigure_single(struct super_block *s,
 		       int flags, void *data);
 
-/*
- * sget() wrappers to be called from the ->get_tree() op.
- */
-enum vfs_get_super_keying {
-	vfs_get_single_super,	/* Only one such superblock may exist */
-	vfs_get_single_reconf_super, /* As above, but reconfigure if it exists */
-	vfs_get_keyed_super,	/* Superblocks with different s_fs_info keys may exist */
-	vfs_get_independent_super, /* Multiple independent superblocks may exist */
-};
-extern int vfs_get_super(struct fs_context *fc,
-			 enum vfs_get_super_keying keying,
-			 int (*fill_super)(struct super_block *sb,
-					   struct fs_context *fc));
-
 extern int get_tree_nodev(struct fs_context *fc,
 			 int (*fill_super)(struct super_block *sb,
 					   struct fs_context *fc));
-- 
2.25.1

Re: [PATCH v2] vfs: Make vfs_get_super() internal

[Al Viro]

On Sun, Oct 30, 2022 at 09:06:08PM +0800, Dawei Li wrote:
> For now there are no external callers of vfs_get_super(),
> so just make it an internal API.
> 
> v1: https://lore.kernel.org/all/TYCP286MB2323D37F4F6400FD07D7C7F7CA319@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM/
> 
> v2: move vfs_get_super_keying to super.c, as the suggestion
> from Christian Brauner.
> 
> base-commit: 3aca47127a646165965ff52803e2b269eed91afc
> 
> Signed-off-by: Dawei Li <set_pte_at@outlook.com>
> ---
>  fs/super.c                 | 13 +++++++++++--
>  include/linux/fs_context.h | 14 --------------
>  2 files changed, 11 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/super.c b/fs/super.c
> index 6a82660e1adb..24e31e458552 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -1111,6 +1111,16 @@ static int test_single_super(struct super_block *s, struct fs_context *fc)
>  	return 1;
>  }
>  
> +/*
> + * sget() wrappers to be called from the ->get_tree() op.
> + */
> +enum vfs_get_super_keying {
> +	vfs_get_single_super,	/* Only one such superblock may exist */
> +	vfs_get_single_reconf_super, /* As above, but reconfigure if it exists */
> +	vfs_get_keyed_super,	/* Superblocks with different s_fs_info keys may exist */
> +	vfs_get_independent_super, /* Multiple independent superblocks may exist */
> +};

I would rather kill the "keying" thing completely.

Seriously, what does it buy us?  Consider e.g.
        return vfs_get_super(fc, vfs_get_independent_super, fill_super);
in get_tree_nodev().  If you expand vfs_get_super() there, you'll get
this:
{
        struct super_block *sb = sget_fc(fc, NULL, set_anon_super_fc);
        if (IS_ERR(sb))
                return PTR_ERR(sb);

        if (!sb->s_root) {
                int err = fill_super(sb, fc);
                if (unlikely(err)) {
                        deactivate_locked_super(sb);
			return err;
		}
                sb->s_flags |= SB_ACTIVE;
        }
	fc->root = dget(sb->s_root);
	return 0;
}

Sure, it's several lines long, but it's much easier to follow than
vfs_get_super().  And duplication between these vfs_get_super()
callers is, IMO, not worth eliminating...

Re: [PATCH v2] vfs: Make vfs_get_super() internal

[Christoph Hellwig]

On Sun, Oct 30, 2022 at 08:28:39PM +0000, Al Viro wrote:
> I would rather kill the "keying" thing completely.

And I replied with a patch doing just that to his v1.  Guess it's time
to resend it formally.