[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>

4 files changed, 16 insertions, 11 deletions

diff --git a/include/linux/coda_psdev.h b/include/linux/coda_psdev.h
index d539262a8f89..98f6c52c152b 100644
--- a/include/linux/coda_psdev.h
+++ b/include/linux/coda_psdev.h
@@ -70,7 +70,7 @@ int venus_pioctl(struct super_block *sb, struct CodaFid *fid,
                  unsigned int cmd, struct PioctlData *data);
 int coda_downcall(int opcode, union outputArgs *out, struct super_block *sb);
 int venus_fsync(struct super_block *sb, struct CodaFid *fid);
-int venus_statfs(struct super_block *sb, struct kstatfs *sfs);
+int venus_statfs(struct dentry *dentry, struct kstatfs *sfs);
 
 
 /* messages between coda filesystem in kernel and Venus */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3e50dd24af87..c823a3815e24 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1096,7 +1096,7 @@ struct super_operations {
         int (*sync_fs)(struct super_block *sb, int wait);
         void (*write_super_lockfs) (struct super_block *);
         void (*unlockfs) (struct super_block *);
-        int (*statfs) (struct super_block *, struct kstatfs *);
+        int (*statfs) (struct dentry *, struct kstatfs *);
         int (*remount_fs) (struct super_block *, int *, char *);
         void (*clear_inode) (struct inode *);
         void (*umount_begin) (struct super_block *);
@@ -1325,7 +1325,7 @@ extern struct vfsmount *copy_tree(struct vfsmount *, struct dentry *, int);
 extern void mnt_set_mountpoint(struct vfsmount *, struct dentry *,
                                   struct vfsmount *);
 
-extern int vfs_statfs(struct super_block *, struct kstatfs *);
+extern int vfs_statfs(struct dentry *, struct kstatfs *);
 
 /* /sys/fs */
 extern struct subsystem fs_subsys;
@@ -1746,7 +1746,7 @@ extern int dcache_dir_close(struct inode *, struct file *);
 extern loff_t dcache_dir_lseek(struct file *, loff_t, int);
 extern int dcache_readdir(struct file *, void *, filldir_t);
 extern int simple_getattr(struct vfsmount *, struct dentry *, struct kstat *);
-extern int simple_statfs(struct super_block *, struct kstatfs *);
+extern int simple_statfs(struct dentry *, struct kstatfs *);
 extern int simple_link(struct dentry *, struct inode *, struct dentry *);
 extern int simple_unlink(struct inode *, struct dentry *);
 extern int simple_rmdir(struct inode *, struct dentry *);
diff --git a/include/linux/mount.h b/include/linux/mount.h
index b7472ae91fa4..60718f12caa9 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -17,6 +17,11 @@
 #include <linux/spinlock.h>
 #include <asm/atomic.h>
 
+struct super_block;
+struct vfsmount;
+struct dentry;
+struct namespace;
+
 #define MNT_NOSUID      0x01
 #define MNT_NODEV       0x02
 #define MNT_NOEXEC      0x04
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;
 }