[PATCH] VFS: Permit filesystem to perform statfs with a known root dentry

Give the statfs superblock operation a dentry pointer rather than a superblock
pointer.

This complements the get_sb() patch.  That reduced the significance of
sb->s_root, allowing NFS to place a fake root there.  However, NFS does
require a dentry to use as a target for the statfs operation.  This permits
the root in the vfsmount to be used instead.

linux/mount.h has been added where necessary to make allyesconfig build
successfully.

Interest has also been expressed for use with the FUSE and XFS filesystems.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Nathan Scott <nathans@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 7 deletions

diff --git a/include/linux/security.h b/include/linux/security.h
index 47722d355532..383c320fc834 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -171,9 +171,9 @@ struct swap_info_struct;
  *      Deallocate and clear the sb->s_security field.
  *      @sb contains the super_block structure to be modified.
  * @sb_statfs:
- *      Check permission before obtaining filesystem statistics for the @sb
- *      filesystem.
- *      @sb contains the super_block structure for the filesystem.
+ *      Check permission before obtaining filesystem statistics for the @mnt
+ *      mountpoint.
+ *      @dentry is a handle on the superblock for the filesystem.
  *      Return 0 if permission is granted.  
  * @sb_mount:
  *      Check permission before an object specified by @dev_name is mounted on
@@ -1127,7 +1127,7 @@ struct security_operations {
         int (*sb_copy_data)(struct file_system_type *type,
                             void *orig, void *copy);
         int (*sb_kern_mount) (struct super_block *sb, void *data);
-        int (*sb_statfs) (struct super_block * sb);
+        int (*sb_statfs) (struct dentry *dentry);
         int (*sb_mount) (char *dev_name, struct nameidata * nd,
                          char *type, unsigned long flags, void *data);
         int (*sb_check_sb) (struct vfsmount * mnt, struct nameidata * nd);
@@ -1450,9 +1450,9 @@ static inline int security_sb_kern_mount (struct super_block *sb, void *data)
         return security_ops->sb_kern_mount (sb, data);
 }
 
-static inline int security_sb_statfs (struct super_block *sb)
+static inline int security_sb_statfs (struct dentry *dentry)
 {
-        return security_ops->sb_statfs (sb);
+        return security_ops->sb_statfs (dentry);
 }
 
 static inline int security_sb_mount (char *dev_name, struct nameidata *nd,
@@ -2162,7 +2162,7 @@ static inline int security_sb_kern_mount (struct super_block *sb, void *data)
         return 0;
 }
 
-static inline int security_sb_statfs (struct super_block *sb)
+static inline int security_sb_statfs (struct dentry *dentry)
 {
         return 0;
 }