[PATCH -V9 0/9] Generic name to handle and open by handle syscalls

[PATCH -V9 0/9] Generic name to handle and open by handle syscalls

[Aneesh Kumar K.V]

Hi,

The below set of patches implement open by handle support using exportfs
operations. This allows user space application to map a file name to file 
handle and later open the file using handle. This should be usable
for userspace NFS [1] and 9P server [2]. XFS already support this with the ioctls
XFS_IOC_PATH_TO_HANDLE and XFS_IOC_OPEN_BY_HANDLE.

[1] http://nfs-ganesha.sourceforge.net/
[2] http://thread.gmane.org/gmane.comp.emulators.qemu/68992

Changes from V8:
a)  exportfs_decode_fh now returns -ESTALE if export operations is not defined.
b)  drop get_fsid super_operations. Instead use superblock to store uuid.

Changes from V7:
a) open_by_handle now use mountdirfd to identify the vfsmount.
b) We don't validate the UUID passed as a part of file handle in open_by_handle.
   UUID is provided as a part of file handle as an easy way for userspace to
   use the kernel returned handle as it is. It also helps in finding the 16 byte
   filessytem UUID in userspace without using file system specific libraries to
   read file system superblock. If a particular file system doesn't support UUID
   or any form of unique id this field in the file handle will be zero filled.
c) drop freadlink syscall. Instead use readlinkat with NULL pathname to indicate
   read the link target name of the link pointed by fd. This is similar to
   sys_utimensat
d) Instead of opencoding all the open flag related check use helper functions.
   Did finish_open_by_handle similar to finish_open.
c) Fix may_open to not return ELOOP for symlink when we are called from handle open.
   open(2) still returns error as expected. 

Changes from V6:
a) Add uuid to vfsmount lookup and drop uuid to superblock lookup
b) Return -EOPNOTSUPP in sys_name_to_handle if the file system returned uuid
   doesn't give the same vfsmount on lookup. This ensure that we fail
   sys_name_to_handle when we have multiple file system returning same UUID.

Changes from V5:
a) added sys_name_to_handle_at syscall which takes AT_SYMLINK_NOFOLLOW flag 
   instead of two syscalls sys_name_to_handle and sys_lname_to_handle.
b) addressed review comments from Niel Brown
c) rebased to b91ce4d14a21fc04d165be30319541e0f9204f15
d) Add compat_sys_open_by_handle

Chages from V4:
a) Changed the syscal arguments so that we don't need compat syscalls
   as suggested by Christoph
c) Added two new syscall sys_lname_to_handle and sys_freadlink to work with
   symlinks
d) Changed open_by_handle to work with all file types
e) Add ext3 support

Changes from V3:
a) Code cleanup suggested by Andreas
b) x86_64 syscall support
c) add compat syscall

Chages from V2:
a) Support system wide unique handle.

Changes from v1:
a) handle size is now specified in bytes
b) returns -EOVERFLOW if the handle size is small
c) dropped open_handle syscall and added open_by_handle_at syscall
   open_by_handle_at takes mount_fd as the directory fd of the mount point
   containing the file
e) handle will only be unique in a given file system. So for an NFS server
   exporting multiple file system, NFS server will have to internally track the
   mount point to which a file handle belongs to. We should be able to do it much
   easily than expecting kernel to give a system wide unique file handle. System
   wide unique file handle would need much larger changes to the exportfs or VFS
   interface and I was not sure whether we really need to do that in the kernel or
   in the user space
f) open_handle_at now only check for DAC_OVERRIDE capability


Example program: (x86_32). (x86_64 would need a different syscall number)
-------
cc <source.c> -luuid
--------
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>

#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <uuid/uuid.h>

struct uuid {
	unsigned char uuid[16];
};

struct file_handle {
        int handle_size;
        int handle_type;
	struct uuid fsid;
        unsigned char handle[0];
};

#define AT_FDCWD		-100
#define AT_SYMLINK_FOLLOW	0x400

static int name_to_handle(const char *name, struct file_handle  *fh)
{
	return syscall(338, AT_FDCWD, name, fh, AT_SYMLINK_FOLLOW);
}

static int lname_to_handle(const char *name, struct file_handle  *fh)
{
	return syscall(338, AT_FDCWD, name, fh, 0);
}

static int open_by_handle(int mountfd, struct file_handle *fh,  int flags)
{
	return syscall(339, mountfd, fh, flags);
}

#define BUFSZ 100
int main(int argc, char *argv[])
{
        int fd;
        int ret;
	int mountfd;
	int handle_sz;
	struct stat bufstat;
        char buf[BUFSZ];
	char uuid[36];
        struct file_handle *fh = NULL;;
	if (argc != 3 ) {
		printf("Usage: %s <filename> <mount-dir-name>\n", argv[0]);
		exit(1);
	}
again:
	if (fh && fh->handle_size) {
		handle_sz = fh->handle_size;
		free(fh);
		fh = malloc(sizeof(struct file_handle) + handle_sz);
		fh->handle_size = handle_sz;
	} else {
		fh = malloc(sizeof(struct file_handle));
		fh->handle_size = 0;
	}
        errno  = 0;
        ret = lname_to_handle(argv[1], fh);
        if (ret && errno == EOVERFLOW) {
		printf("Found the handle size needed to be %d\n", fh->handle_size);
		goto again;
        } else if (ret) {
                perror("Error:");
		exit(1);
	}
	uuid_unparse(fh->fsid.uuid, uuid);
	printf("UUID:%s\n", uuid);
	printf("Waiting for input");
	getchar();
	mountfd = open(argv[2], O_RDONLY | O_DIRECTORY);
	if (mountfd <= 0) {
                perror("Error:");
                exit(1);
        }
        fd = open_by_handle(mountfd, fh, O_RDWR);
        if (fd <= 0 ) {
                perror("Error:");
                exit(1);
        }
	printf("Reading the content now \n");
	fstat(fd, &bufstat);
	ret = S_ISLNK(bufstat.st_mode);
	if (ret) {
		memset(buf, 0 , BUFSZ);
		readlinkat(fd, NULL, buf, BUFSZ);
		printf("%s is a symlink pointing to %s\n", argv[1], buf);
	}
        memset(buf, 0 , BUFSZ);
	while (1) {
		ret = read(fd, buf, BUFSZ -1);
		if (ret <= 0)
			break;
		buf[ret] = '\0';
                printf("%s", buf);
                memset(buf, 0 , BUFSZ);
        }
        return 0;
}

-aneesh

[PATCH -V9 1/9] exportfs: Return the minimum required handle size

[Aneesh Kumar K.V]

The exportfs encode handle function should return the minimum required
handle size. This helps user to find out the handle size by passing 0
handle size in the first step and then redoing to the call again with
the returned handle size value.

Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/btrfs/export.c             |    8 ++++++--
 fs/exportfs/expfs.c           |    9 +++++++--
 fs/fat/inode.c                |    4 +++-
 fs/fuse/inode.c               |    4 +++-
 fs/gfs2/export.c              |    8 ++++++--
 fs/isofs/export.c             |    8 ++++++--
 fs/ocfs2/export.c             |    8 +++++++-
 fs/reiserfs/inode.c           |    7 ++++++-
 fs/udf/namei.c                |    7 ++++++-
 fs/xfs/linux-2.6/xfs_export.c |    4 +++-
 mm/shmem.c                    |    4 +++-
 11 files changed, 56 insertions(+), 15 deletions(-)

diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
index 951ef09..5f8ee5a 100644
--- a/fs/btrfs/export.c
+++ b/fs/btrfs/export.c
@@ -21,9 +21,13 @@ static int btrfs_encode_fh(struct dentry *dentry, u32 *fh, int *max_len,
 	int len = *max_len;
 	int type;
 
-	if ((len < BTRFS_FID_SIZE_NON_CONNECTABLE) ||
-	    (connectable && len < BTRFS_FID_SIZE_CONNECTABLE))
+	if (connectable && (len < BTRFS_FID_SIZE_CONNECTABLE)) {
+		*max_len = BTRFS_FID_SIZE_CONNECTABLE;
 		return 255;
+	} else if (len < BTRFS_FID_SIZE_NON_CONNECTABLE) {
+		*max_len = BTRFS_FID_SIZE_NON_CONNECTABLE;
+		return 255;
+	}
 
 	len  = BTRFS_FID_SIZE_NON_CONNECTABLE;
 	type = FILEID_BTRFS_WITHOUT_PARENT;
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index e9e1759..cfee0f0 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -319,9 +319,14 @@ static int export_encode_fh(struct dentry *dentry, struct fid *fid,
 	struct inode * inode = dentry->d_inode;
 	int len = *max_len;
 	int type = FILEID_INO32_GEN;
-	
-	if (len < 2 || (connectable && len < 4))
+
+	if (connectable && (len < 4)) {
+		*max_len = 4;
+		return 255;
+	} else if (len < 2) {
+		*max_len = 2;
 		return 255;
+	}
 
 	len = 2;
 	fid->i32.ino = inode->i_ino;
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 0ce143b..6f83bc7 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -738,8 +738,10 @@ fat_encode_fh(struct dentry *de, __u32 *fh, int *lenp, int connectable)
 	struct inode *inode =  de->d_inode;
 	u32 ipos_h, ipos_m, ipos_l;
 
-	if (len < 5)
+	if (len < 5) {
+		*lenp = 5;
 		return 255; /* no room */
+	}
 
 	ipos_h = MSDOS_I(inode)->i_pos >> 8;
 	ipos_m = (MSDOS_I(inode)->i_pos & 0xf0) << 24;
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index ec14d19..beaea69 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -638,8 +638,10 @@ static int fuse_encode_fh(struct dentry *dentry, u32 *fh, int *max_len,
 	u64 nodeid;
 	u32 generation;
 
-	if (*max_len < len)
+	if (*max_len < len) {
+		*max_len = len;
 		return  255;
+	}
 
 	nodeid = get_fuse_inode(inode)->nodeid;
 	generation = inode->i_generation;
diff --git a/fs/gfs2/export.c b/fs/gfs2/export.c
index c22c211..d022236 100644
--- a/fs/gfs2/export.c
+++ b/fs/gfs2/export.c
@@ -36,9 +36,13 @@ static int gfs2_encode_fh(struct dentry *dentry, __u32 *p, int *len,
 	struct super_block *sb = inode->i_sb;
 	struct gfs2_inode *ip = GFS2_I(inode);
 
-	if (*len < GFS2_SMALL_FH_SIZE ||
-	    (connectable && *len < GFS2_LARGE_FH_SIZE))
+	if (connectable && (*len < GFS2_LARGE_FH_SIZE)) {
+		*len = GFS2_LARGE_FH_SIZE;
 		return 255;
+	} else if (*len < GFS2_SMALL_FH_SIZE) {
+		*len = GFS2_SMALL_FH_SIZE;
+		return 255;
+	}
 
 	fh[0] = cpu_to_be32(ip->i_no_formal_ino >> 32);
 	fh[1] = cpu_to_be32(ip->i_no_formal_ino & 0xFFFFFFFF);
diff --git a/fs/isofs/export.c b/fs/isofs/export.c
index ed752cb..dd4687f 100644
--- a/fs/isofs/export.c
+++ b/fs/isofs/export.c
@@ -124,9 +124,13 @@ isofs_export_encode_fh(struct dentry *dentry,
 	 * offset of the inode and the upper 16 bits of fh32[1] to
 	 * hold the offset of the parent.
 	 */
-
-	if (len < 3 || (connectable && len < 5))
+	if (connectable && (len < 5)) {
+		*max_len = 5;
+		return 255;
+	} else if (len < 3) {
+		*max_len = 3;
 		return 255;
+	}
 
 	len = 3;
 	fh32[0] = ei->i_iget5_block;
diff --git a/fs/ocfs2/export.c b/fs/ocfs2/export.c
index 19ad145..250a347 100644
--- a/fs/ocfs2/export.c
+++ b/fs/ocfs2/export.c
@@ -201,8 +201,14 @@ static int ocfs2_encode_fh(struct dentry *dentry, u32 *fh_in, int *max_len,
 		   dentry->d_name.len, dentry->d_name.name,
 		   fh, len, connectable);
 
-	if (len < 3 || (connectable && len < 6)) {
+	if (connectable && (len < 6)) {
 		mlog(ML_ERROR, "fh buffer is too small for encoding\n");
+		*max_len = 6;
+		type = 255;
+		goto bail;
+	} else if (len < 3) {
+		mlog(ML_ERROR, "fh buffer is too small for encoding\n");
+		*max_len = 3;
 		type = 255;
 		goto bail;
 	}
diff --git a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c
index dc2c65e..5fff1e2 100644
--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -1588,8 +1588,13 @@ int reiserfs_encode_fh(struct dentry *dentry, __u32 * data, int *lenp,
 	struct inode *inode = dentry->d_inode;
 	int maxlen = *lenp;
 
-	if (maxlen < 3)
+	if (need_parent && (maxlen < 5)) {
+		*lenp = 5;
 		return 255;
+	} else if (maxlen < 3) {
+		*lenp = 3;
+		return 255;
+	}
 
 	data[0] = inode->i_ino;
 	data[1] = le32_to_cpu(INODE_PKEY(inode)->k_dir_id);
diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index 7581602..37ce713 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -1360,8 +1360,13 @@ static int udf_encode_fh(struct dentry *de, __u32 *fh, int *lenp,
 	struct fid *fid = (struct fid *)fh;
 	int type = FILEID_UDF_WITHOUT_PARENT;
 
-	if (len < 3 || (connectable && len < 5))
+	if (connectable && (len < 5)) {
+		*lenp = 5;
+		return 255;
+	} else if (len < 3) {
+		*lenp = 3;
 		return 255;
+	}
 
 	*lenp = 3;
 	fid->udf.block = location.logicalBlockNum;
diff --git a/fs/xfs/linux-2.6/xfs_export.c b/fs/xfs/linux-2.6/xfs_export.c
index 846b75a..82c0553 100644
--- a/fs/xfs/linux-2.6/xfs_export.c
+++ b/fs/xfs/linux-2.6/xfs_export.c
@@ -81,8 +81,10 @@ xfs_fs_encode_fh(
 	 * seven combinations work.  The real answer is "don't use v2".
 	 */
 	len = xfs_fileid_length(fileid_type);
-	if (*max_len < len)
+	if (*max_len < len) {
+		*max_len = len
 		return 255;
+	}
 	*max_len = len;
 
 	switch (fileid_type) {
diff --git a/mm/shmem.c b/mm/shmem.c
index eef4ebe..bbeda1c 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2125,8 +2125,10 @@ static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
 {
 	struct inode *inode = dentry->d_inode;
 
-	if (*len < 3)
+	if (*len < 3) {
+		*len = 3;
 		return 255;
+	}
 
 	if (hlist_unhashed(&inode->i_hash)) {
 		/* Unfortunately insert_inode_hash is not idempotent,
-- 
1.7.1.78.g212f0

[PATCH -V9 2/9] vfs: Add name to file handle conversion support

[Aneesh Kumar K.V]

This patch add a new superblock field unsigned char s_uuid[16]
to store UUID mapping for the file system. The s_uuid[16] is used to
identify the file system apart of file_handle

Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/exportfs/expfs.c |    2 +-
 fs/open.c           |   82 +++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h  |   15 +++++++++
 3 files changed, 98 insertions(+), 1 deletions(-)

diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index cfee0f0..d103c31 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -352,7 +352,7 @@ int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
 	const struct export_operations *nop = dentry->d_sb->s_export_op;
 	int error;
 
-	if (nop->encode_fh)
+	if (nop && nop->encode_fh)
 		error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
 	else
 		error = export_encode_fh(dentry, fid, max_len, connectable);
diff --git a/fs/open.c b/fs/open.c
index 74e5cd9..51aa494 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -30,6 +30,7 @@
 #include <linux/falloc.h>
 #include <linux/fs_struct.h>
 #include <linux/ima.h>
+#include <linux/exportfs.h>
 
 #include "internal.h"
 
@@ -1206,3 +1207,84 @@ int nonseekable_open(struct inode *inode, struct file *filp)
 }
 
 EXPORT_SYMBOL(nonseekable_open);
+
+/* limit the handle size to some value */
+#define MAX_HANDLE_SZ 4096
+static long do_sys_name_to_handle(struct path *path,
+			struct file_handle __user *ufh)
+{
+	int retval;
+	int handle_size;
+	struct super_block *sb;
+	struct file_handle f_handle;
+	struct file_handle *handle = NULL;
+
+	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
+		retval = -EFAULT;
+		goto err_out;
+	}
+	if (f_handle.handle_size > MAX_HANDLE_SZ) {
+		retval = -EINVAL;
+		goto err_out;
+	}
+	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_size,
+			GFP_KERNEL);
+	if (!handle) {
+		retval = -ENOMEM;
+		goto err_out;
+	}
+	handle_size = f_handle.handle_size;
+
+	/* we ask for a non connected handle */
+	retval = exportfs_encode_fh(path->dentry,
+				(struct fid *)handle->f_handle,
+				&handle_size,  0);
+	/* convert handle size to bytes */
+	handle_size *= sizeof(u32);
+	handle->handle_type = retval;
+	handle->handle_size = handle_size;
+	if (handle_size <= f_handle.handle_size) {
+		/* get the uuid */
+		sb = path->mnt->mnt_sb;
+		memcpy(handle->fsid.uuid,
+			sb->s_uuid,
+			sizeof(handle->fsid.uuid));
+		retval = 0;
+	} else {
+		/*
+		 * set the handle_size to zero so we copy only
+		 * non variable part of the file_handle
+		 */
+		handle_size = 0;
+		retval = -EOVERFLOW;
+	}
+	if (copy_to_user(ufh, handle,
+				sizeof(struct file_handle) + handle_size))
+		retval = -EFAULT;
+
+	kfree(handle);
+err_out:
+	return retval;
+}
+
+SYSCALL_DEFINE4(name_to_handle_at, int, dfd, const char __user *, name,
+		struct file_handle __user *, handle, int, flag)
+{
+	int follow;
+	long ret = -EINVAL;
+	struct path path;
+
+	if ((flag & ~AT_SYMLINK_FOLLOW) != 0)
+		goto err_out;
+
+	follow = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
+	ret = user_path_at(dfd, name, follow, &path);
+	if (ret)
+		goto err_out;
+	ret = do_sys_name_to_handle(&path, handle);
+	path_put(&path);
+err_out:
+	/* avoid REGPARM breakage on x86: */
+	asmlinkage_protect(4, ret, dfd, name, handle, flag);
+	return ret;
+}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 44f35ae..961392c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -948,6 +948,20 @@ struct file {
 	unsigned long f_mnt_write_state;
 #endif
 };
+
+struct uuid {
+	unsigned char uuid[16];
+};
+
+struct file_handle {
+	int handle_size;
+	int handle_type;
+	/* File system identifier */
+	struct uuid fsid;
+	/* file identifier */
+	unsigned char f_handle[0];
+};
+
 extern spinlock_t files_lock;
 #define file_list_lock() spin_lock(&files_lock);
 #define file_list_unlock() spin_unlock(&files_lock);
@@ -1358,6 +1372,7 @@ struct super_block {
 	wait_queue_head_t	s_wait_unfrozen;
 
 	char s_id[32];				/* Informational name */
+	unsigned char s_uuid[16];		/* UUID */
 
 	void 			*s_fs_info;	/* Filesystem private info */
 	fmode_t			s_mode;
-- 
1.7.1.78.g212f0

[PATCH -V9 3/9] vfs: Add open by file handle support

[Aneesh Kumar K.V]

Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/exportfs/expfs.c |    2 +
 fs/namei.c          |   50 +++++++++++++++
 fs/open.c           |  171 +++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h  |    3 +-
 4 files changed, 225 insertions(+), 1 deletions(-)

diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index d103c31..e73c0ab 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -373,6 +373,8 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
 	/*
 	 * Try to get any dentry for the given file handle from the filesystem.
 	 */
+	if (!nop || !nop->fh_to_dentry)
+		return ERR_PTR(-ESTALE);
 	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
 	if (!result)
 		result = ERR_PTR(-ESTALE);
diff --git a/fs/namei.c b/fs/namei.c
index b86b96f..21cf0a5 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1556,6 +1556,56 @@ static int open_will_truncate(int flag, struct inode *inode)
 	return (flag & O_TRUNC);
 }
 
+struct file *finish_open_handle(struct path *path,
+			int open_flag, int acc_mode)
+{
+	int error;
+	struct file *filp;
+	int will_truncate;
+
+	will_truncate = open_will_truncate(open_flag, path->dentry->d_inode);
+	if (will_truncate) {
+		error = mnt_want_write(path->mnt);
+		if (error)
+			goto exit;
+	}
+	error = may_open(path, acc_mode, open_flag);
+	if (error) {
+		if (will_truncate)
+			mnt_drop_write(path->mnt);
+		goto exit;
+	}
+	filp = dentry_open(path->dentry, path->mnt, open_flag, current_cred());
+	if (!IS_ERR(filp)) {
+		error = ima_file_check(filp, acc_mode);
+		if (error) {
+			fput(filp);
+			filp = ERR_PTR(error);
+		}
+	}
+	if (!IS_ERR(filp)) {
+		if (will_truncate) {
+			error = handle_truncate(path);
+			if (error) {
+				fput(filp);
+				filp = ERR_PTR(error);
+			}
+		}
+	}
+	/*
+	 * It is now safe to drop the mnt write
+	 * because the filp has had a write taken
+	 * on its behalf.
+	 */
+	if (will_truncate)
+		mnt_drop_write(path->mnt);
+	return filp;
+
+exit:
+	path_put(path);
+	return ERR_PTR(error);
+}
+
 static struct file *finish_open(struct nameidata *nd,
 				int open_flag, int acc_mode)
 {
diff --git a/fs/open.c b/fs/open.c
index 51aa494..c1faf11 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1288,3 +1288,174 @@ err_out:
 	asmlinkage_protect(4, ret, dfd, name, handle, flag);
 	return ret;
 }
+
+static struct vfsmount *get_vfsmount_from_fd(int fd)
+{
+	int fput_needed;
+	struct path *path;
+	struct file *filep;
+
+	if (fd == AT_FDCWD) {
+		struct fs_struct *fs = current->fs;
+		read_lock(&fs->lock);
+		path = &fs->pwd;
+		mntget(path->mnt);
+		read_unlock(&fs->lock);
+	} else {
+		filep = fget_light(fd, &fput_needed);
+		if (!filep)
+			return ERR_PTR(-EBADF);
+		path = &filep->f_path;
+		mntget(path->mnt);
+		fput_light(filep, fput_needed);
+	}
+	return path->mnt;
+}
+
+static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
+{
+	return 1;
+}
+
+static struct path *handle_to_path(int mountdirfd, struct file_handle *handle)
+{
+	int retval;
+	int handle_size;
+	struct path *path;
+
+	path = kmalloc(sizeof(struct path), GFP_KERNEL);
+	if (!path)
+		return ERR_PTR(-ENOMEM);
+
+	path->mnt = get_vfsmount_from_fd(mountdirfd);
+	if (IS_ERR(path->mnt)) {
+		retval = PTR_ERR(path->mnt);
+		goto out_err;
+	}
+	/* change the handle size to multiple of sizeof(u32) */
+	handle_size = handle->handle_size >> 2;
+	path->dentry = exportfs_decode_fh(path->mnt,
+					(struct fid *)handle->f_handle,
+					handle_size, handle->handle_type,
+					vfs_dentry_acceptable, NULL);
+	if (IS_ERR(path->dentry)) {
+		retval = PTR_ERR(path->dentry);
+		goto out_mnt;
+	}
+	return path;
+out_mnt:
+	mntput(path->mnt);
+out_err:
+	kfree(path);
+	return ERR_PTR(retval);
+}
+
+static long do_sys_open_by_handle(int mountdirfd,
+				struct file_handle __user *ufh, int open_flag)
+{
+	int acc_mode;
+	int fd, retval = 0;
+	struct file *filp;
+	struct path *path;
+	struct file_handle f_handle;
+	struct file_handle *handle = NULL;
+
+	/* can't use O_CREATE with open_by_handle */
+	if (open_flag & O_CREAT) {
+		retval = -EINVAL;
+		goto out_err;
+	}
+	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
+		retval = -EFAULT;
+		goto out_err;
+	}
+	if ((f_handle.handle_size > MAX_HANDLE_SZ) ||
+		(f_handle.handle_size <= 0)) {
+		retval =  -EINVAL;
+		goto out_err;
+	}
+	if (!capable(CAP_DAC_OVERRIDE)) {
+		retval = -EPERM;
+		goto out_err;
+	}
+	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_size,
+			GFP_KERNEL);
+	if (!handle) {
+		retval =  -ENOMEM;
+		goto out_err;
+	}
+	/* copy the full handle */
+	if (copy_from_user(handle, ufh,
+				sizeof(struct file_handle) +
+				f_handle.handle_size)) {
+		retval = -EFAULT;
+		goto out_handle;
+	}
+	path = handle_to_path(mountdirfd, handle);
+	if (IS_ERR(path)) {
+		retval = PTR_ERR(path);
+		goto out_handle;
+	}
+	/*
+	 * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
+	 * check for O_DSYNC if the need any syncing at all we enforce it's
+	 * always set instead of having to deal with possibly weird behaviour
+	 * for malicious applications setting only __O_SYNC.
+	 */
+	if (open_flag & __O_SYNC)
+		open_flag |= O_DSYNC;
+
+	acc_mode = MAY_OPEN | ACC_MODE(open_flag);
+
+	/* O_TRUNC implies we need access checks for write permissions */
+	if (open_flag & O_TRUNC)
+		acc_mode |= MAY_WRITE;
+	/*
+	 * Allow the LSM permission hook to distinguish append
+	 * access from general write access.
+	 */
+	if (open_flag & O_APPEND)
+		acc_mode |= MAY_APPEND;
+
+	fd = get_unused_fd_flags(open_flag);
+	if (fd < 0) {
+		retval = fd;
+		goto out_path;
+	}
+	filp = finish_open_handle(path, open_flag, acc_mode);
+	if (IS_ERR(filp)) {
+		put_unused_fd(fd);
+		retval =  PTR_ERR(filp);
+	} else {
+		retval = fd;
+		fsnotify_open(filp->f_path.dentry);
+		fd_install(fd, filp);
+	}
+	kfree(path);
+	kfree(handle);
+	return retval;
+
+out_path:
+	path_put(path);
+	kfree(path);
+out_handle:
+	kfree(handle);
+out_err:
+	return retval;
+}
+
+SYSCALL_DEFINE3(open_by_handle, int, mountdirfd,
+		struct file_handle __user *, handle,
+		int, flags)
+{
+	long ret;
+
+	if (force_o_largefile())
+		flags |= O_LARGEFILE;
+
+	ret = do_sys_open_by_handle(mountdirfd, handle, flags);
+
+	/* avoid REGPARM breakage on x86: */
+	asmlinkage_protect(3, ret, mountdirfd, handle, flags);
+	return ret;
+}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 961392c..1417df5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2144,7 +2144,8 @@ extern int may_open(struct path *, int, int);
 
 extern int kernel_read(struct file *, loff_t, char *, unsigned long);
 extern struct file * open_exec(const char *);
- 
+extern struct file *finish_open_handle(struct path *, int, int);
+
 /* fs/dcache.c -- generic fs support functions */
 extern int is_subdir(struct dentry *, struct dentry *);
 extern int path_is_under(struct path *, struct path *);
-- 
1.7.1.78.g212f0

[PATCH -V9 4/9] vfs: Allow handle based open on symlinks

[Aneesh Kumar K.V]

The patch update may_open to allow handle based open on symlinks.
The file handle based API use file descritor returned from open_by_handle_at
to do different file system operations. To find the link target name we
need to get a file descriptor on symlinks.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/namei.c |   17 ++++++++++++++---
 1 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 21cf0a5..3a93c15 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1421,7 +1421,7 @@ int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
 	return error;
 }
 
-int may_open(struct path *path, int acc_mode, int flag)
+static int __may_open(struct path *path, int acc_mode, int flag, int handle)
 {
 	struct dentry *dentry = path->dentry;
 	struct inode *inode = dentry->d_inode;
@@ -1432,7 +1432,13 @@ int may_open(struct path *path, int acc_mode, int flag)
 
 	switch (inode->i_mode & S_IFMT) {
 	case S_IFLNK:
-		return -ELOOP;
+		/*
+		 * For file handle based open we should allow
+		 * open of symlink.
+		 */
+		if (!handle)
+			return -ELOOP;
+		break;
 	case S_IFDIR:
 		if (acc_mode & MAY_WRITE)
 			return -EISDIR;
@@ -1472,6 +1478,11 @@ int may_open(struct path *path, int acc_mode, int flag)
 	return break_lease(inode, flag);
 }
 
+int may_open(struct path *path, int acc_mode, int flag)
+{
+	return __may_open(path, acc_mode, flag, 0);
+}
+
 static int handle_truncate(struct path *path)
 {
 	struct inode *inode = path->dentry->d_inode;
@@ -1569,7 +1580,7 @@ struct file *finish_open_handle(struct path *path,
 		if (error)
 			goto exit;
 	}
-	error = may_open(path, acc_mode, open_flag);
+	error = __may_open(path, acc_mode, open_flag, 1);
 	if (error) {
 		if (will_truncate)
 			mnt_drop_write(path->mnt);
-- 
1.7.1.78.g212f0

[PATCH -V9 5/9] vfs: Support null pathname in readlink

[Aneesh Kumar K.V]

From: NeilBrown <neilb@suse.de>

This enables to use readlink to get the link target name
from a file descriptor point to the link. This can be used
with open_by_handle syscall that returns a file descriptor for a link.
We can then use this file descriptor to get the target name.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/stat.c |   30 ++++++++++++++++++++++--------
 1 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/fs/stat.c b/fs/stat.c
index c4ecd52..49b95a7 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -284,26 +284,40 @@ SYSCALL_DEFINE2(newfstat, unsigned int, fd, struct stat __user *, statbuf)
 SYSCALL_DEFINE4(readlinkat, int, dfd, const char __user *, pathname,
 		char __user *, buf, int, bufsiz)
 {
-	struct path path;
-	int error;
+	int error = 0;
+	struct path path, *pp;
+	struct file *file = NULL;
 
 	if (bufsiz <= 0)
 		return -EINVAL;
 
-	error = user_path_at(dfd, pathname, 0, &path);
+	if (pathname == NULL && dfd != AT_FDCWD) {
+		file = fget(dfd);
+
+		if (file)
+			pp = &file->f_path;
+		else
+			error = -EBADF;
+	} else {
+		error = user_path_at(dfd, pathname, 0, &path);
+		pp = &path;
+	}
 	if (!error) {
-		struct inode *inode = path.dentry->d_inode;
+		struct inode *inode = pp->dentry->d_inode;
 
 		error = -EINVAL;
 		if (inode->i_op->readlink) {
-			error = security_inode_readlink(path.dentry);
+			error = security_inode_readlink(pp->dentry);
 			if (!error) {
-				touch_atime(path.mnt, path.dentry);
-				error = inode->i_op->readlink(path.dentry,
+				touch_atime(pp->mnt, pp->dentry);
+				error = inode->i_op->readlink(pp->dentry,
 							      buf, bufsiz);
 			}
 		}
-		path_put(&path);
+		if (file)
+			fput(file);
+		else
+			path_put(&path);
 	}
 	return error;
 }
-- 
1.7.1.78.g212f0

[PATCH -V9 6/9] ext4: Copy fs UUID to superblock

[Aneesh Kumar K.V]

This enables userspace application to find the file system
UUID using sys_name_to_handle_at syscall

Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/ext4/super.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e14d22c..02ba21b 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2828,6 +2828,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_qcop = &ext4_qctl_operations;
 	sb->dq_op = &ext4_quota_operations;
 #endif
+	memcpy(sb->s_uuid, es->s_uuid, sizeof(es->s_uuid));
+
 	INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */
 	mutex_init(&sbi->s_orphan_lock);
 	mutex_init(&sbi->s_resize_lock);
-- 
1.7.1.78.g212f0

[PATCH -V9 7/9] x86: Add new syscalls for x86_32

[Aneesh Kumar K.V]

This patch adds sys_name_to_handle_at and sys_open_by_handle_at
syscalls to x86_32

Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/x86/include/asm/unistd_32.h   |    4 +++-
 arch/x86/kernel/syscall_table_32.S |    2 ++
 2 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/unistd_32.h b/arch/x86/include/asm/unistd_32.h
index beb9b5f..ca792fb 100644
--- a/arch/x86/include/asm/unistd_32.h
+++ b/arch/x86/include/asm/unistd_32.h
@@ -343,10 +343,12 @@
 #define __NR_rt_tgsigqueueinfo	335
 #define __NR_perf_event_open	336
 #define __NR_recvmmsg		337
+#define __NR_name_to_handle_at	338
+#define __NR_open_by_handle     339
 
 #ifdef __KERNEL__
 
-#define NR_syscalls 338
+#define NR_syscalls 340
 
 #define __ARCH_WANT_IPC_PARSE_VERSION
 #define __ARCH_WANT_OLD_READDIR
diff --git a/arch/x86/kernel/syscall_table_32.S b/arch/x86/kernel/syscall_table_32.S
index 8b37293..399b49e 100644
--- a/arch/x86/kernel/syscall_table_32.S
+++ b/arch/x86/kernel/syscall_table_32.S
@@ -337,3 +337,5 @@ ENTRY(sys_call_table)
 	.long sys_rt_tgsigqueueinfo	/* 335 */
 	.long sys_perf_event_open
 	.long sys_recvmmsg
+	.long sys_name_to_handle_at
+	.long sys_open_by_handle	/* 339 */
-- 
1.7.1.78.g212f0

[PATCH -V9 8/9] x86: Add new syscalls for x86_64

[Aneesh Kumar K.V]

Add sys_name_to_handle_at and sys_open_by_handle_at syscalls
for x86_64

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/x86/ia32/ia32entry.S        |    2 ++
 arch/x86/include/asm/unistd_64.h |    4 ++++
 fs/compat.c                      |   11 +++++++++++
 fs/open.c                        |    4 ++--
 include/linux/fs.h               |    1 +
 5 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index e790bc1..74552bc 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -842,4 +842,6 @@ ia32_sys_call_table:
 	.quad compat_sys_rt_tgsigqueueinfo	/* 335 */
 	.quad sys_perf_event_open
 	.quad compat_sys_recvmmsg
+	.quad sys_name_to_handle_at
+	.quad compat_sys_open_by_handle		/* 339 */
 ia32_syscall_end:
diff --git a/arch/x86/include/asm/unistd_64.h b/arch/x86/include/asm/unistd_64.h
index ff4307b..a5c3622 100644
--- a/arch/x86/include/asm/unistd_64.h
+++ b/arch/x86/include/asm/unistd_64.h
@@ -663,6 +663,10 @@ __SYSCALL(__NR_rt_tgsigqueueinfo, sys_rt_tgsigqueueinfo)
 __SYSCALL(__NR_perf_event_open, sys_perf_event_open)
 #define __NR_recvmmsg				299
 __SYSCALL(__NR_recvmmsg, sys_recvmmsg)
+#define __NR_name_to_handle_at			300
+__SYSCALL(__NR_name_to_handle, sys_name_to_handle)
+#define __NR_open_by_handle			301
+__SYSCALL(__NR_open_by_handle, sys_open_by_handle)
 
 #ifndef __NO_STUBS
 #define __ARCH_WANT_OLD_READDIR
diff --git a/fs/compat.c b/fs/compat.c
index 0544873..f46d2d6 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -2308,3 +2308,14 @@ asmlinkage long compat_sys_timerfd_gettime(int ufd,
 }
 
 #endif /* CONFIG_TIMERFD */
+
+/*
+ * Exactly like fs/open.c:sys_open_by_handle_at(), except that it
+ * doesn't set the O_LARGEFILE flag.
+ */
+asmlinkage long
+compat_sys_open_by_handle(int mountdirfd,
+			struct file_handle __user *handle, int flags)
+{
+	return do_sys_open_by_handle(mountdirfd, handle, flags);
+}
diff --git a/fs/open.c b/fs/open.c
index c1faf11..7450e0e 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1350,8 +1350,8 @@ out_err:
 	return ERR_PTR(retval);
 }
 
-static long do_sys_open_by_handle(int mountdirfd,
-				struct file_handle __user *ufh, int open_flag)
+long do_sys_open_by_handle(int mountdirfd,
+			struct file_handle __user *ufh, int open_flag)
 {
 	int acc_mode;
 	int fd, retval = 0;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1417df5..c921000 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1933,6 +1933,7 @@ extern struct file * dentry_open(struct dentry *, struct vfsmount *, int,
 				 const struct cred *);
 extern int filp_close(struct file *, fl_owner_t id);
 extern char * getname(const char __user *);
+extern long do_sys_open_by_handle(int, struct file_handle __user *, int);
 
 /* fs/ioctl.c */
 
-- 
1.7.1.78.g212f0

[PATCH -V9 9/9] ext3: Copy fs UUID to superblock.

[Aneesh Kumar K.V]

This enable user space application to get the file system UUID
using sys_name_to_handle_at syscall

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/ext3/super.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 1bee604..7c304e7 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -1928,6 +1928,7 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent)
 	sb->s_qcop = &ext3_qctl_operations;
 	sb->dq_op = &ext3_quota_operations;
 #endif
+	memcpy(sb->s_uuid, es->s_uuid, sizeof(es->s_uuid));
 	INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */
 	mutex_init(&sbi->s_orphan_lock);
 	mutex_init(&sbi->s_resize_lock);
-- 
1.7.1.78.g212f0

Re: [PATCH -V9 2/9] vfs: Add name to file handle conversion support

[Aneesh Kumar K. V]

Updated patch below. 

-aneesh

>From 2c65b0657c914e38d049928e89538a9003715786 Mon Sep 17 00:00:00 2001
From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Date: Tue, 18 May 2010 14:51:34 +0530
Subject: [PATCH -V9 2/9] vfs: Add name to file handle conversion support

This patch add a new superblock field unsigned char s_uuid[16]
to store UUID mapping for the file system. The s_uuid[16] is used to
identify the file system apart of file_handle

Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/exportfs/expfs.c |    2 +-
 fs/open.c           |   82 +++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h  |   11 +++++++
 3 files changed, 94 insertions(+), 1 deletions(-)

diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index cfee0f0..d103c31 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -352,7 +352,7 @@ int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
 	const struct export_operations *nop = dentry->d_sb->s_export_op;
 	int error;
 
-	if (nop->encode_fh)
+	if (nop && nop->encode_fh)
 		error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
 	else
 		error = export_encode_fh(dentry, fid, max_len, connectable);
diff --git a/fs/open.c b/fs/open.c
index 74e5cd9..8091bcc 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -30,6 +30,7 @@
 #include <linux/falloc.h>
 #include <linux/fs_struct.h>
 #include <linux/ima.h>
+#include <linux/exportfs.h>
 
 #include "internal.h"
 
@@ -1206,3 +1207,84 @@ int nonseekable_open(struct inode *inode, struct file *filp)
 }
 
 EXPORT_SYMBOL(nonseekable_open);
+
+/* limit the handle size to some value */
+#define MAX_HANDLE_SZ 4096
+static long do_sys_name_to_handle(struct path *path,
+			struct file_handle __user *ufh)
+{
+	int retval;
+	int handle_size;
+	struct super_block *sb;
+	struct file_handle f_handle;
+	struct file_handle *handle = NULL;
+
+	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
+		retval = -EFAULT;
+		goto err_out;
+	}
+	if (f_handle.handle_size > MAX_HANDLE_SZ) {
+		retval = -EINVAL;
+		goto err_out;
+	}
+	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_size,
+			GFP_KERNEL);
+	if (!handle) {
+		retval = -ENOMEM;
+		goto err_out;
+	}
+	handle_size = f_handle.handle_size;
+
+	/* we ask for a non connected handle */
+	retval = exportfs_encode_fh(path->dentry,
+				(struct fid *)handle->f_handle,
+				&handle_size,  0);
+	/* convert handle size to bytes */
+	handle_size *= sizeof(u32);
+	handle->handle_type = retval;
+	handle->handle_size = handle_size;
+	if (handle_size <= f_handle.handle_size) {
+		/* get the uuid */
+		sb = path->mnt->mnt_sb;
+		memcpy(handle->fs_uuid,
+			sb->s_uuid,
+			sizeof(handle->fs_uuid));
+		retval = 0;
+	} else {
+		/*
+		 * set the handle_size to zero so we copy only
+		 * non variable part of the file_handle
+		 */
+		handle_size = 0;
+		retval = -EOVERFLOW;
+	}
+	if (copy_to_user(ufh, handle,
+				sizeof(struct file_handle) + handle_size))
+		retval = -EFAULT;
+
+	kfree(handle);
+err_out:
+	return retval;
+}
+
+SYSCALL_DEFINE4(name_to_handle_at, int, dfd, const char __user *, name,
+		struct file_handle __user *, handle, int, flag)
+{
+	int follow;
+	long ret = -EINVAL;
+	struct path path;
+
+	if ((flag & ~AT_SYMLINK_FOLLOW) != 0)
+		goto err_out;
+
+	follow = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
+	ret = user_path_at(dfd, name, follow, &path);
+	if (ret)
+		goto err_out;
+	ret = do_sys_name_to_handle(&path, handle);
+	path_put(&path);
+err_out:
+	/* avoid REGPARM breakage on x86: */
+	asmlinkage_protect(4, ret, dfd, name, handle, flag);
+	return ret;
+}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 44f35ae..d428b1a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -948,6 +948,16 @@ struct file {
 	unsigned long f_mnt_write_state;
 #endif
 };
+
+struct file_handle {
+	int handle_size;
+	int handle_type;
+	/* File system UUID identifier */
+	u8 fs_uuid[16];
+	/* file identifier */
+	unsigned char f_handle[0];
+};
+
 extern spinlock_t files_lock;
 #define file_list_lock() spin_lock(&files_lock);
 #define file_list_unlock() spin_unlock(&files_lock);
@@ -1358,6 +1368,7 @@ struct super_block {
 	wait_queue_head_t	s_wait_unfrozen;
 
 	char s_id[32];				/* Informational name */
+	u8 s_uuid[16];				/* UUID */
 
 	void 			*s_fs_info;	/* Filesystem private info */
 	fmode_t			s_mode;
-- 
1.7.1.78.g212f0