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Commit 43ce4c1f authored by David Howells's avatar David Howells Committed by Al Viro
Browse files

vfs: Add a single-or-reconfig keying to vfs_get_super() 



Add an additional keying mode to vfs_get_super() to indicate that only a
single superblock should exist in the system, and that, if it does, further
mounts should invoke reconfiguration upon it.

This allows mount_single() to be replaced.

[Fix by Eric Biggers folded in]

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 0f071004

fs/super.c

+28 −7
Original line number Diff line number Diff line
@@ -1160,9 +1160,11 @@ int vfs_get_super(struct fs_context *fc, 
{

	int (*test)(struct super_block *, struct fs_context *);

	struct super_block *sb;

	int err;



	switch (keying) {

	case vfs_get_single_super:

	case vfs_get_single_reconf_super:

		test = test_single_super;

		break;

	case vfs_get_keyed_super:
@@ -1180,18 +1182,29 @@ int vfs_get_super(struct fs_context *fc, 
		return PTR_ERR(sb);



	if (!sb->s_root) {

		int err = fill_super(sb, fc);

		if (err) {

			deactivate_locked_super(sb);

			return err;

		}

		err = fill_super(sb, fc);

		if (err)

			goto error;



		sb->s_flags |= SB_ACTIVE;

		fc->root = dget(sb->s_root);

	} else {

		fc->root = dget(sb->s_root);

		if (keying == vfs_get_single_reconf_super) {

			err = reconfigure_super(fc);

			if (err < 0) {

				dput(fc->root);

				fc->root = NULL;

				goto error;

			}

		}

	}



	BUG_ON(fc->root);

	fc->root = dget(sb->s_root);

	return 0;



error:

	deactivate_locked_super(sb);

	return err;

}

EXPORT_SYMBOL(vfs_get_super);
@@ -1211,6 +1224,14 @@ int get_tree_single(struct fs_context *fc, 
}

EXPORT_SYMBOL(get_tree_single);



int get_tree_single_reconf(struct fs_context *fc,

		  int (*fill_super)(struct super_block *sb,

				    struct fs_context *fc))

{

	return vfs_get_super(fc, vfs_get_single_reconf_super, fill_super);

}

EXPORT_SYMBOL(get_tree_single_reconf);



int get_tree_keyed(struct fs_context *fc,

		  int (*fill_super)(struct super_block *sb,

				    struct fs_context *fc),

include/linux/fs_context.h

+4 −0
Original line number Diff line number Diff line
@@ -141,6 +141,7 @@ extern void put_fs_context(struct fs_context *fc); 
 */

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 */

};
@@ -155,6 +156,9 @@ extern int get_tree_nodev(struct fs_context *fc, 
extern int get_tree_single(struct fs_context *fc,

			 int (*fill_super)(struct super_block *sb,

					   struct fs_context *fc));

extern int get_tree_single_reconf(struct fs_context *fc,

			 int (*fill_super)(struct super_block *sb,

					   struct fs_context *fc));

extern int get_tree_keyed(struct fs_context *fc,

			 int (*fill_super)(struct super_block *sb,

					   struct fs_context *fc),