[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>

Documentation/filesystems/Locking

@@ -99,7 +99,7 @@ prototypes:
 	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 *);

Documentation/filesystems/vfs.txt

@@ -211,7 +211,7 @@ 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 *);

arch/alpha/kernel/osf_sys.c

@@ -244,7 +244,7 @@ do_osf_statfs(struct dentry * dentry, struct osf_statfs __user *buffer,
 	      unsigned long bufsiz)
 {
 	struct kstatfs linux_stat;
-	int error = vfs_statfs(dentry->d_inode->i_sb, &linux_stat);
+	int error = vfs_statfs(dentry, &linux_stat);
 	if (!error)
 		error = linux_to_osf_statfs(&linux_stat, buffer, bufsiz);
 	return error;	

arch/mips/kernel/sysirix.c

@@ -694,7 +694,7 @@ asmlinkage int irix_statfs(const char __user *path,
 	if (error)
 		goto out;
 
-	error = vfs_statfs(nd.dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(nd.dentry, &kbuf);
 	if (error)
 		goto dput_and_out;
 
@@ -732,7 +732,7 @@ asmlinkage int irix_fstatfs(unsigned int fd, struct irix_statfs __user *buf)
 		goto out;
 	}
 
-	error = vfs_statfs(file->f_dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(file->f_dentry, &kbuf);
 	if (error)
 		goto out_f;
 
@@ -1360,7 +1360,7 @@ asmlinkage int irix_statvfs(char __user *fname, struct irix_statvfs __user *buf)
 	error = user_path_walk(fname, &nd);
 	if (error)
 		goto out;
-	error = vfs_statfs(nd.dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(nd.dentry, &kbuf);
 	if (error)
 		goto dput_and_out;
 
@@ -1406,7 +1406,7 @@ asmlinkage int irix_fstatvfs(int fd, struct irix_statvfs __user *buf)
 		error = -EBADF;
 		goto out;
 	}
-	error = vfs_statfs(file->f_dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(file->f_dentry, &kbuf);
 	if (error)
 		goto out_f;
 
@@ -1611,7 +1611,7 @@ asmlinkage int irix_statvfs64(char __user *fname, struct irix_statvfs64 __user *
 	error = user_path_walk(fname, &nd);
 	if (error)
 		goto out;
-	error = vfs_statfs(nd.dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(nd.dentry, &kbuf);
 	if (error)
 		goto dput_and_out;
 
@@ -1658,7 +1658,7 @@ asmlinkage int irix_fstatvfs64(int fd, struct irix_statvfs __user *buf)
 		error = -EBADF;
 		goto out;
 	}
-	error = vfs_statfs(file->f_dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(file->f_dentry, &kbuf);
 	if (error)
 		goto out_f;
 

arch/parisc/hpux/sys_hpux.c

@@ -145,7 +145,7 @@ static int hpux_ustat(dev_t dev, struct hpux_ustat __user *ubuf)
 	s = user_get_super(dev);
 	if (s == NULL)
 		goto out;
-	err = vfs_statfs(s, &sbuf);
+	err = vfs_statfs(s->s_root, &sbuf);
 	drop_super(s);
 	if (err)
 		goto out;
@@ -186,12 +186,12 @@ struct hpux_statfs {
      int16_t f_pad;
 };
 
-static int vfs_statfs_hpux(struct super_block *sb, struct hpux_statfs *buf)
+static int vfs_statfs_hpux(struct dentry *dentry, struct hpux_statfs *buf)
 {
 	struct kstatfs st;
 	int retval;
 	
-	retval = vfs_statfs(sb, &st);
+	retval = vfs_statfs(dentry, &st);
 	if (retval)
 		return retval;
 
@@ -219,7 +219,7 @@ asmlinkage long hpux_statfs(const char __user *path,
 	error = user_path_walk(path, &nd);
 	if (!error) {
 		struct hpux_statfs tmp;
-		error = vfs_statfs_hpux(nd.dentry->d_inode->i_sb, &tmp);
+		error = vfs_statfs_hpux(nd.dentry, &tmp);
 		if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
 			error = -EFAULT;
 		path_release(&nd);
@@ -237,7 +237,7 @@ asmlinkage long hpux_fstatfs(unsigned int fd, struct hpux_statfs __user * buf)
 	file = fget(fd);
 	if (!file)
 		goto out;
-	error = vfs_statfs_hpux(file->f_dentry->d_inode->i_sb, &tmp);
+	error = vfs_statfs_hpux(file->f_dentry, &tmp);
 	if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
 		error = -EFAULT;
 	fput(file);

arch/sparc64/solaris/fs.c

@@ -356,7 +356,7 @@ static int report_statvfs(struct vfsmount *mnt, struct inode *inode, u32 buf)
 	int error;
 	struct sol_statvfs __user *ss = A(buf);
 
-	error = vfs_statfs(mnt->mnt_sb, &s);
+	error = vfs_statfs(mnt->mnt_root, &s);
 	if (!error) {
 		const char *p = mnt->mnt_sb->s_type->name;
 		int i = 0;
@@ -392,7 +392,7 @@ static int report_statvfs64(struct vfsmount *mnt, struct inode *inode, u32 buf)
 	int error;
 	struct sol_statvfs64 __user *ss = A(buf);
 			
-	error = vfs_statfs(mnt->mnt_sb, &s);
+	error = vfs_statfs(mnt->mnt_root, &s);
 	if (!error) {
 		const char *p = mnt->mnt_sb->s_type->name;
 		int i = 0;

fs/adfs/super.c

@@ -196,17 +196,17 @@ static int adfs_remount(struct super_block *sb, int *flags, char *data)
 	return parse_options(sb, data);
 }
 
-static int adfs_statfs(struct super_block *sb, struct kstatfs *buf)
+static int adfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
-	struct adfs_sb_info *asb = ADFS_SB(sb);
+	struct adfs_sb_info *asb = ADFS_SB(dentry->d_sb);
 
 	buf->f_type    = ADFS_SUPER_MAGIC;
 	buf->f_namelen = asb->s_namelen;
-	buf->f_bsize   = sb->s_blocksize;
+	buf->f_bsize   = dentry->d_sb->s_blocksize;
 	buf->f_blocks  = asb->s_size;
 	buf->f_files   = asb->s_ids_per_zone * asb->s_map_size;
 	buf->f_bavail  =
-	buf->f_bfree   = adfs_map_free(sb);
+	buf->f_bfree   = adfs_map_free(dentry->d_sb);
 	buf->f_ffree   = (long)(buf->f_bfree * buf->f_files) / (long)buf->f_blocks;
 
 	return 0;

fs/affs/super.c

@@ -18,7 +18,7 @@
 
 extern struct timezone sys_tz;
 
-static int affs_statfs(struct super_block *sb, struct kstatfs *buf);
+static int affs_statfs(struct dentry *dentry, struct kstatfs *buf);
 static int affs_remount (struct super_block *sb, int *flags, char *data);
 
 static void
@@ -508,8 +508,9 @@ affs_remount(struct super_block *sb, int *flags, char *data)
 }
 
 static int
-affs_statfs(struct super_block *sb, struct kstatfs *buf)
+affs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
+	struct super_block *sb = dentry->d_sb;
 	int		 free;
 
 	pr_debug("AFFS: statfs() partsize=%d, reserved=%d\n",AFFS_SB(sb)->s_partition_size,

fs/befs/linuxvfs.c

@@ -49,7 +49,7 @@ static int befs_nls2utf(struct super_block *sb, const char *in, int in_len,
 			char **out, int *out_len);
 static void befs_put_super(struct super_block *);
 static int befs_remount(struct super_block *, int *, char *);
-static int befs_statfs(struct super_block *, struct kstatfs *);
+static int befs_statfs(struct dentry *, struct kstatfs *);
 static int parse_options(char *, befs_mount_options *);
 
 static const struct super_operations befs_sops = {
@@ -880,8 +880,9 @@ befs_remount(struct super_block *sb, int *flags, char *data)
 }
 
 static int
-befs_statfs(struct super_block *sb, struct kstatfs *buf)
+befs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
+	struct super_block *sb = dentry->d_sb;
 
 	befs_debug(sb, "---> befs_statfs()");
 

fs/bfs/inode.c

@@ -203,8 +203,9 @@ static void bfs_put_super(struct super_block *s)
 	s->s_fs_info = NULL;
 }
 
-static int bfs_statfs(struct super_block *s, struct kstatfs *buf)
+static int bfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
+	struct super_block *s = dentry->d_sb;
 	struct bfs_sb_info *info = BFS_SB(s);
 	u64 id = huge_encode_dev(s->s_bdev->bd_dev);
 	buf->f_type = BFS_MAGIC;

fs/cifs/cifsfs.c

@@ -166,8 +166,9 @@ cifs_put_super(struct super_block *sb)
 }
 
 static int
-cifs_statfs(struct super_block *sb, struct kstatfs *buf)
+cifs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
+	struct super_block *sb = dentry->d_sb;
 	int xid; 
 	int rc = -EOPNOTSUPP;
 	struct cifs_sb_info *cifs_sb;

fs/coda/inode.c

@@ -36,7 +36,7 @@
 /* VFS super_block ops */
 static void coda_clear_inode(struct inode *);
 static void coda_put_super(struct super_block *);
-static int coda_statfs(struct super_block *sb, struct kstatfs *buf);
+static int coda_statfs(struct dentry *dentry, struct kstatfs *buf);
 
 static kmem_cache_t * coda_inode_cachep;
 
@@ -278,13 +278,13 @@ struct inode_operations coda_file_inode_operations = {
 	.setattr	= coda_setattr,
 };
 
-static int coda_statfs(struct super_block *sb, struct kstatfs *buf)
+static int coda_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	int error;
 	
 	lock_kernel();
 
-	error = venus_statfs(sb, buf);
+	error = venus_statfs(dentry, buf);
 
 	unlock_kernel();
 

fs/coda/upcall.c

@@ -611,7 +611,7 @@ int venus_pioctl(struct super_block *sb, struct CodaFid *fid,
 	return error;
 }
 
-int venus_statfs(struct super_block *sb, struct kstatfs *sfs) 
+int venus_statfs(struct dentry *dentry, struct kstatfs *sfs)
 { 
         union inputArgs *inp;
         union outputArgs *outp;
@@ -620,7 +620,7 @@ int venus_statfs(struct super_block *sb, struct kstatfs *sfs)
 	insize = max_t(unsigned int, INSIZE(statfs), OUTSIZE(statfs));
 	UPARG(CODA_STATFS);
 
-        error = coda_upcall(coda_sbp(sb), insize, &outsize, inp);
+        error = coda_upcall(coda_sbp(dentry->d_sb), insize, &outsize, inp);
 	
         if (!error) {
 		sfs->f_blocks = outp->coda_statfs.stat.f_blocks;

fs/compat.c

@@ -197,7 +197,7 @@ asmlinkage long compat_sys_statfs(const char __user *path, struct compat_statfs
 	error = user_path_walk(path, &nd);
 	if (!error) {
 		struct kstatfs tmp;
-		error = vfs_statfs(nd.dentry->d_inode->i_sb, &tmp);
+		error = vfs_statfs(nd.dentry, &tmp);
 		if (!error)
 			error = put_compat_statfs(buf, &tmp);
 		path_release(&nd);
@@ -215,7 +215,7 @@ asmlinkage long compat_sys_fstatfs(unsigned int fd, struct compat_statfs __user
 	file = fget(fd);
 	if (!file)
 		goto out;
-	error = vfs_statfs(file->f_dentry->d_inode->i_sb, &tmp);
+	error = vfs_statfs(file->f_dentry, &tmp);
 	if (!error)
 		error = put_compat_statfs(buf, &tmp);
 	fput(file);
@@ -265,7 +265,7 @@ asmlinkage long compat_sys_statfs64(const char __user *path, compat_size_t sz, s
 	error = user_path_walk(path, &nd);
 	if (!error) {
 		struct kstatfs tmp;
-		error = vfs_statfs(nd.dentry->d_inode->i_sb, &tmp);
+		error = vfs_statfs(nd.dentry, &tmp);
 		if (!error)
 			error = put_compat_statfs64(buf, &tmp);
 		path_release(&nd);
@@ -286,7 +286,7 @@ asmlinkage long compat_sys_fstatfs64(unsigned int fd, compat_size_t sz, struct c
 	file = fget(fd);
 	if (!file)
 		goto out;
-	error = vfs_statfs(file->f_dentry->d_inode->i_sb, &tmp);
+	error = vfs_statfs(file->f_dentry, &tmp);
 	if (!error)
 		error = put_compat_statfs64(buf, &tmp);
 	fput(file);

fs/cramfs/inode.c

@@ -322,8 +322,10 @@ out:
 	return -EINVAL;
 }
 
-static int cramfs_statfs(struct super_block *sb, struct kstatfs *buf)
+static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
+	struct super_block *sb = dentry->d_sb;
+
 	buf->f_type = CRAMFS_MAGIC;
 	buf->f_bsize = PAGE_CACHE_SIZE;
 	buf->f_blocks = CRAMFS_SB(sb)->blocks;

fs/efs/super.c

@@ -15,7 +15,7 @@
 #include <linux/buffer_head.h>
 #include <linux/vfs.h>
 
-static int efs_statfs(struct super_block *s, struct kstatfs *buf);
+static int efs_statfs(struct dentry *dentry, struct kstatfs *buf);
 static int efs_fill_super(struct super_block *s, void *d, int silent);
 
 static int efs_get_sb(struct file_system_type *fs_type,
@@ -322,8 +322,8 @@ out_no_fs:
 	return -EINVAL;
 }
 
-static int efs_statfs(struct super_block *s, struct kstatfs *buf) {
-	struct efs_sb_info *sb = SUPER_INFO(s);
+static int efs_statfs(struct dentry *dentry, struct kstatfs *buf) {
+	struct efs_sb_info *sb = SUPER_INFO(dentry->d_sb);
 
 	buf->f_type    = EFS_SUPER_MAGIC;	/* efs magic number */
 	buf->f_bsize   = EFS_BLOCKSIZE;		/* blocksize */

fs/ext2/super.c

@@ -39,7 +39,7 @@
 static void ext2_sync_super(struct super_block *sb,
 			    struct ext2_super_block *es);
 static int ext2_remount (struct super_block * sb, int * flags, char * data);
-static int ext2_statfs (struct super_block * sb, struct kstatfs * buf);
+static int ext2_statfs (struct dentry * dentry, struct kstatfs * buf);
 
 void ext2_error (struct super_block * sb, const char * function,
 		 const char * fmt, ...)
@@ -1038,8 +1038,9 @@ restore_opts:
 	return err;
 }
 
-static int ext2_statfs (struct super_block * sb, struct kstatfs * buf)
+static int ext2_statfs (struct dentry * dentry, struct kstatfs * buf)
 {
+	struct super_block *sb = dentry->d_sb;
 	struct ext2_sb_info *sbi = EXT2_SB(sb);
 	unsigned long overhead;
 	int i;

fs/ext3/super.c

@@ -58,7 +58,7 @@ static int ext3_sync_fs(struct super_block *sb, int wait);
 static const char *ext3_decode_error(struct super_block * sb, int errno,
 				     char nbuf[16]);
 static int ext3_remount (struct super_block * sb, int * flags, char * data);
-static int ext3_statfs (struct super_block * sb, struct kstatfs * buf);
+static int ext3_statfs (struct dentry * dentry, struct kstatfs * buf);
 static void ext3_unlockfs(struct super_block *sb);
 static void ext3_write_super (struct super_block * sb);
 static void ext3_write_super_lockfs(struct super_block *sb);
@@ -2318,8 +2318,9 @@ restore_opts:
 	return err;
 }
 
-static int ext3_statfs (struct super_block * sb, struct kstatfs * buf)
+static int ext3_statfs (struct dentry * dentry, struct kstatfs * buf)
 {
+	struct super_block *sb = dentry->d_sb;
 	struct ext3_sb_info *sbi = EXT3_SB(sb);
 	struct ext3_super_block *es = sbi->s_es;
 	unsigned long overhead;

fs/fat/inode.c

@@ -539,18 +539,18 @@ static int fat_remount(struct super_block *sb, int *flags, char *data)
 	return 0;
 }
 
-static int fat_statfs(struct super_block *sb, struct kstatfs *buf)
+static int fat_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
-	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 
 	/* If the count of free cluster is still unknown, counts it here. */
 	if (sbi->free_clusters == -1) {
-		int err = fat_count_free_clusters(sb);
+		int err = fat_count_free_clusters(dentry->d_sb);
 		if (err)
 			return err;
 	}
 
-	buf->f_type = sb->s_magic;
+	buf->f_type = dentry->d_sb->s_magic;
 	buf->f_bsize = sbi->cluster_size;
 	buf->f_blocks = sbi->max_cluster - FAT_START_ENT;
 	buf->f_bfree = sbi->free_clusters;

fs/freevxfs/vxfs_super.c

@@ -40,6 +40,7 @@
 #include <linux/slab.h>
 #include <linux/stat.h>
 #include <linux/vfs.h>
+#include <linux/mount.h>
 
 #include "vxfs.h"
 #include "vxfs_extern.h"
@@ -55,7 +56,7 @@ MODULE_ALIAS("vxfs"); /* makes mount -t vxfs autoload the module */
 
 
 static void		vxfs_put_super(struct super_block *);
-static int		vxfs_statfs(struct super_block *, struct kstatfs *);
+static int		vxfs_statfs(struct dentry *, struct kstatfs *);
 static int		vxfs_remount(struct super_block *, int *, char *);
 
 static struct super_operations vxfs_super_ops = {
@@ -90,12 +91,12 @@ vxfs_put_super(struct super_block *sbp)
 
 /**
  * vxfs_statfs - get filesystem information
- * @sbp:	VFS superblock
+ * @dentry:	VFS dentry to locate superblock
  * @bufp:	output buffer
  *
  * Description:
  *   vxfs_statfs fills the statfs buffer @bufp with information
- *   about the filesystem described by @sbp.
+ *   about the filesystem described by @dentry.
  *
  * Returns:
  *   Zero.
@@ -107,12 +108,12 @@ vxfs_put_super(struct super_block *sbp)
  *   This is everything but complete...
  */
 static int
-vxfs_statfs(struct super_block *sbp, struct kstatfs *bufp)
+vxfs_statfs(struct dentry *dentry, struct kstatfs *bufp)
 {
-	struct vxfs_sb_info		*infp = VXFS_SBI(sbp);
+	struct vxfs_sb_info		*infp = VXFS_SBI(dentry->d_sb);
 
 	bufp->f_type = VXFS_SUPER_MAGIC;
-	bufp->f_bsize = sbp->s_blocksize;
+	bufp->f_bsize = dentry->d_sb->s_blocksize;
 	bufp->f_blocks = infp->vsi_raw->vs_dsize;
 	bufp->f_bfree = infp->vsi_raw->vs_free;
 	bufp->f_bavail = 0;