[PATCH -V19 00/15] Generic name to handle and open by handle syscalls

[PATCH -V19 00/15] 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

git repo for the patchset at:
git://git.kernel.org/pub/scm/linux/kernel/git/kvaneesh/linux-open-handle.git open-by-handle

Test case can be found at
http://git.kernel.org/?p=fs/ext2/kvaneesh/handle-test.git
git://git.kernel.org/pub/scm/fs/ext2/kvaneesh/handle-test.git

Changes from V18:
a) Drop open on symlink patch
b) Drop other patches that added support for NULL pathname in *at syscalls
c) Add new handle based syscalls. All of them are restricted to CAP_DAC_READ_SEARCH


-aneesh

[PATCH -V19 01/15] 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 +++-
 include/linux/exportfs.h      |    6 ++++--
 mm/shmem.c                    |    4 +++-
 12 files changed, 60 insertions(+), 17 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 8300580..0812d29 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -759,8 +759,10 @@ 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 da9e6e1..52adfcd 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -640,8 +640,10 @@ 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 dfe237a..bd0fd68 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 ae35413..e6c336b 100644
--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -1594,8 +1594,13 @@ 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 bf5fc67..20db42f 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -1336,8 +1336,13 @@ 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 3764d74..7132d7c 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/include/linux/exportfs.h b/include/linux/exportfs.h
index a9cd507..acd0b2d 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -108,8 +108,10 @@ struct fid {
  *    set, the encode_fh() should store sufficient information so that a good
  *    attempt can be made to find not only the file but also it's place in the
  *    filesystem.   This typically means storing a reference to de->d_parent in
- *    the filehandle fragment.  encode_fh() should return the number of bytes
- *    stored or a negative error code such as %-ENOSPC
+ *    the filehandle fragment.  encode_fh() should return the fileid_type on
+ *    success and on error returns 255 (if the space needed to encode fh is
+ *    greater than @max_len*4 bytes). On error @max_len contain the minimum
+ *    size(in 4 byte unit) needed to encode the file handle.
  *
  * fh_to_dentry:
  *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
diff --git a/mm/shmem.c b/mm/shmem.c
index dfaa0f4..47e58af 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2143,8 +2143,10 @@ 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,
-- 
1.7.0.4

[PATCH -V19 02/15] vfs: Add name to file handle conversion support

[Aneesh Kumar K.V]

The syscall also return mount id which can be used
to lookup file system specific information such as uuid
in /proc/<pid>/mountinfo

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/open.c                |  129 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/exportfs.h |    3 +
 include/linux/fs.h       |    8 +++
 include/linux/syscalls.h |    5 ++-
 4 files changed, 144 insertions(+), 1 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index 630715f..efb1806 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -30,6 +30,7 @@
 #include <linux/fs_struct.h>
 #include <linux/ima.h>
 #include <linux/dnotify.h>
+#include <linux/exportfs.h>
 
 #include "internal.h"
 
@@ -1042,3 +1043,131 @@ int nonseekable_open(struct inode *inode, struct file *filp)
 }
 
 EXPORT_SYMBOL(nonseekable_open);
+
+#ifdef CONFIG_EXPORTFS
+static long do_sys_name_to_handle(struct path *path,
+				  struct file_handle __user *ufh,
+				  int __user *mnt_id)
+{
+	long retval;
+	int handle_size;
+	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;
+	}
+
+	/* convert handle size to  multiple of sizeof(u32) */
+	handle_size = f_handle.handle_size >> 2;
+
+	/* 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) {
+		/*
+		 * set the handle_size to zero so we copy only
+		 * non variable part of the file_handle
+		 */
+		handle_size = 0;
+		retval = -EOVERFLOW;
+	} else
+		retval = 0;
+	/* copy the mount id */
+	if (copy_to_user(mnt_id, &path->mnt->mnt_id, sizeof(*mnt_id))) {
+		retval = -EFAULT;
+		goto err_free_out;
+	}
+	if (copy_to_user(ufh, handle,
+			 sizeof(struct file_handle) + handle_size))
+		retval = -EFAULT;
+err_free_out:
+	kfree(handle);
+err_out:
+	return retval;
+}
+
+/**
+ * sys_name_to_handle_at: convert name to handle
+ * @dfd: directory relative to which name is interpreted if not absolute
+ * @name: name that should be converted to handle.
+ * @handle: resulting file handle
+ * @mnt_id: mount id of the file system containing the file
+ * @flag: flag value to indicate whether to follow symlink or not
+ *
+ * @handle->handle_size indicate the space available to store the
+ * variable part of the file handle in bytes. If there is not
+ * enough space, the field is updated to return the minimum
+ * value required.
+ */
+SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
+		struct file_handle __user *, handle, int __user*, mnt_id,
+		int, flag)
+{
+
+	int follow;
+	int fput_needed;
+	long ret = -EINVAL;
+	struct path path, *pp;
+	struct file *file = NULL;
+
+	if ((flag & ~AT_SYMLINK_FOLLOW) != 0)
+		goto err_out;
+
+	if (name == NULL && dfd != AT_FDCWD) {
+		file = fget_light(dfd, &fput_needed);
+		if (file) {
+			pp = &file->f_path;
+			ret = 0;
+		} else
+			ret = -EBADF;
+	} else {
+		follow = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
+		ret = user_path_at(dfd, name, follow, &path);
+		pp = &path;
+	}
+	if (ret)
+		goto err_out;
+	/*
+	 * We need t make sure wether the file system
+	 * support decoding of the file handle
+	 */
+	if (!pp->mnt->mnt_sb->s_export_op ||
+	    !pp->mnt->mnt_sb->s_export_op->fh_to_dentry) {
+		ret = -EOPNOTSUPP;
+		goto out_path;
+	}
+	ret = do_sys_name_to_handle(pp, handle, mnt_id);
+
+out_path:
+	if (file)
+		fput_light(file, fput_needed);
+	else
+		path_put(&path);
+err_out:
+	return ret;
+}
+#else
+SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
+		struct file_handle __user *, handle, int __user *, mnt_id,
+		int, flag)
+{
+	return -ENOSYS;
+}
+#endif
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index acd0b2d..1a6d72f 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -8,6 +8,9 @@ struct inode;
 struct super_block;
 struct vfsmount;
 
+/* limit the handle size to some value */
+#define MAX_HANDLE_SZ 4096
+
 /*
  * The fileid_type identifies how the file within the filesystem is encoded.
  * In theory this is freely set and parsed by the filesystem, but we try to
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9a96b4d..f2f7ad3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -953,6 +953,14 @@ struct file {
 	unsigned long f_mnt_write_state;
 #endif
 };
+
+struct file_handle {
+	int handle_size;
+	int handle_type;
+	/* 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);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 6e5d197..f7aba76 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -62,6 +62,7 @@ struct robust_list_head;
 struct getcpu_cache;
 struct old_linux_dirent;
 struct perf_event_attr;
+struct file_handle;
 
 #include <linux/types.h>
 #include <linux/aio_abi.h>
@@ -831,5 +832,7 @@ asmlinkage long sys_mmap_pgoff(unsigned long addr, unsigned long len,
 			unsigned long prot, unsigned long flags,
 			unsigned long fd, unsigned long pgoff);
 asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg);
-
+asmlinkage long sys_name_to_handle_at(int dfd, const char __user *name,
+				      struct file_handle __user *handle,
+				      int __user *mnt_id, int flag);
 #endif
-- 
1.7.0.4

[PATCH -V19 03/15] vfs: Add open by file handle support

[Aneesh Kumar K.V]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/compat.c              |   11 +++
 fs/exportfs/expfs.c      |    2 +
 fs/namei.c               |  223 +++++++++++++++++++++++++++++++++++++++++++---
 fs/open.c                |   32 ++++++-
 include/linux/fs.h       |   10 ++-
 include/linux/namei.h    |    1 +
 include/linux/syscalls.h |    3 +
 7 files changed, 263 insertions(+), 19 deletions(-)

diff --git a/fs/compat.c b/fs/compat.c
index 718c706..c4037fd 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -2334,3 +2334,14 @@ 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_at(int mountdirfd,
+			     struct file_handle __user *handle, int flags)
+{
+	return do_handle_open(mountdirfd, handle, flags);
+}
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index cfee0f0..05a1179 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 17ea76b..4718802 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -32,6 +32,7 @@
 #include <linux/fcntl.h>
 #include <linux/device_cgroup.h>
 #include <linux/fs_struct.h>
+#include <linux/exportfs.h>
 #include <asm/uaccess.h>
 
 #include "internal.h"
@@ -1042,6 +1043,29 @@ out_fail:
 	return retval;
 }
 
+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;
+}
+
 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
 static int do_path_lookup(int dfd, const char *name,
 				unsigned int flags, struct nameidata *nd)
@@ -1546,26 +1570,30 @@ static int open_will_truncate(int flag, struct inode *inode)
 	return (flag & O_TRUNC);
 }
 
-static struct file *finish_open(struct nameidata *nd,
+static struct file *finish_open(struct file *filp, struct path *path,
 				int open_flag, int acc_mode)
 {
-	struct file *filp;
-	int will_truncate;
 	int error;
+	int will_truncate;
 
-	will_truncate = open_will_truncate(open_flag, nd->path.dentry->d_inode);
+	will_truncate = open_will_truncate(open_flag, path->dentry->d_inode);
 	if (will_truncate) {
-		error = mnt_want_write(nd->path.mnt);
+		error = mnt_want_write(path->mnt);
 		if (error)
 			goto exit;
 	}
-	error = may_open(&nd->path, acc_mode, open_flag);
+	error = may_open(path, acc_mode, open_flag);
 	if (error) {
 		if (will_truncate)
-			mnt_drop_write(nd->path.mnt);
+			mnt_drop_write(path->mnt);
 		goto exit;
 	}
-	filp = nameidata_to_filp(nd);
+	/* Has the filesystem initialised the file for us? */
+	if (filp->f_path.dentry == NULL)
+		filp = __dentry_open(path->dentry, path->mnt, filp,
+				     NULL, current_cred());
+	else
+		path_put(path);
 	if (!IS_ERR(filp)) {
 		error = ima_file_check(filp, acc_mode);
 		if (error) {
@@ -1575,7 +1603,7 @@ static struct file *finish_open(struct nameidata *nd,
 	}
 	if (!IS_ERR(filp)) {
 		if (will_truncate) {
-			error = handle_truncate(&nd->path);
+			error = handle_truncate(path);
 			if (error) {
 				fput(filp);
 				filp = ERR_PTR(error);
@@ -1588,13 +1616,17 @@ static struct file *finish_open(struct nameidata *nd,
 	 * on its behalf.
 	 */
 	if (will_truncate)
-		mnt_drop_write(nd->path.mnt);
+		mnt_drop_write(path->mnt);
 	return filp;
 
 exit:
-	if (!IS_ERR(nd->intent.open.file))
-		release_open_intent(nd);
-	path_put(&nd->path);
+	if (!IS_ERR(filp)) {
+		if (filp->f_path.dentry == NULL)
+			put_filp(filp);
+		else
+			fput(filp);
+	}
+	path_put(path);
 	return ERR_PTR(error);
 }
 
@@ -1728,7 +1760,9 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
 	if (S_ISDIR(path->dentry->d_inode->i_mode))
 		goto exit;
 ok:
-	filp = finish_open(nd, open_flag, acc_mode);
+	filp = finish_open(nd->intent.open.file, &nd->path,
+			   open_flag, acc_mode);
+
 	return filp;
 
 exit_mutex_unlock:
@@ -1901,6 +1935,167 @@ struct file *filp_open(const char *filename, int flags, int mode)
 }
 EXPORT_SYMBOL(filp_open);
 
+#ifdef CONFIG_EXPORTFS
+static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
+{
+	return 1;
+}
+
+static int do_handle_to_path(int mountdirfd, struct file_handle *handle,
+			     struct path *path)
+{
+	int retval = 0;
+	int handle_size;
+
+	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 0;
+out_mnt:
+	mntput(path->mnt);
+out_err:
+	return retval;
+}
+
+int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
+		   struct path *path)
+{
+	int retval = 0;
+	struct file_handle f_handle;
+	struct file_handle *handle = NULL;
+
+	/*
+	 * With handle we don't look at the execute bit on the
+	 * the directory. Ideally we would like CAP_DAC_SEARCH.
+	 * But we don't have that
+	 */
+	if (!capable(CAP_DAC_READ_SEARCH)) {
+		retval = -EPERM;
+		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;
+	}
+	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;
+	}
+
+	retval = do_handle_to_path(mountdirfd, handle, path);
+
+out_handle:
+	kfree(handle);
+out_err:
+	return retval;
+}
+#else
+int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
+		   struct path *path)
+{
+	return -ENOSYS;
+}
+#endif
+
+long do_handle_open(int mountdirfd,
+		    struct file_handle __user *ufh, int open_flag)
+{
+	long retval = 0;
+	int fd, acc_mode;
+	struct path path;
+	struct file *filp;
+
+	/* can't use O_CREATE with open_by_handle */
+	if (open_flag & O_CREAT) {
+		retval = -EINVAL;
+		goto out_err;
+	}
+	retval = handle_to_path(mountdirfd, ufh, &path);
+	if (retval)
+		goto out_err;
+
+	if ((open_flag & O_DIRECTORY) &&
+	    !S_ISDIR(path.dentry->d_inode->i_mode)) {
+		retval = -ENOTDIR;
+		goto out_path;
+	}
+	/*
+	 * 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 = get_empty_filp();
+	if (!filp) {
+		retval = -ENFILE;
+		goto out_free_fd;
+	}
+	filp->f_flags = open_flag;
+	filp = finish_open(filp, &path, open_flag, acc_mode);
+	if (IS_ERR(filp)) {
+		put_unused_fd(fd);
+		retval =  PTR_ERR(filp);
+	} else {
+		retval = fd;
+		fsnotify_open(filp);
+		fd_install(fd, filp);
+	}
+	return retval;
+
+out_free_fd:
+	put_unused_fd(fd);
+out_path:
+	path_put(&path);
+out_err:
+	return retval;
+}
+
 /**
  * lookup_create - lookup a dentry, creating it if it doesn't exist
  * @nd: nameidata info
diff --git a/fs/open.c b/fs/open.c
index efb1806..7abdcba 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -652,10 +652,10 @@ static inline int __get_file_write_access(struct inode *inode,
 	return error;
 }
 
-static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
-					struct file *f,
-					int (*open)(struct inode *, struct file *),
-					const struct cred *cred)
+struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
+			   struct file *f,
+			   int (*open)(struct inode *, struct file *),
+			   const struct cred *cred)
 {
 	struct inode *inode;
 	int error;
@@ -1171,3 +1171,27 @@ SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
 	return -ENOSYS;
 }
 #endif
+
+/**
+ * sys_open_by_handle_at: Open the file handle
+ * @mountdirfd: directory file descriptor
+ * @handle: file handle to be opened
+ * @flag: open flags.
+ *
+ * @mountdirfd indicate the directory file descriptor
+ * of the mount point. file handle is decoded relative
+ * to the vfsmount pointed by the @mountdirfd. @flags
+ * value is same as the open(2) flags.
+ */
+SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
+		struct file_handle __user *, handle,
+		int, flags)
+{
+	long ret;
+
+	if (force_o_largefile())
+		flags |= O_LARGEFILE;
+
+	ret = do_handle_open(mountdirfd, handle, flags);
+	return ret;
+}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f2f7ad3..134f97a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1939,6 +1939,10 @@ extern int do_fallocate(struct file *file, int mode, loff_t offset,
 extern long do_sys_open(int dfd, const char __user *filename, int flags,
 			int mode);
 extern struct file *filp_open(const char *, int, int);
+struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
+			   struct file *f,
+			   int (*open)(struct inode *, struct file *),
+			   const struct cred *cred);
 extern struct file * dentry_open(struct dentry *, struct vfsmount *, int,
 				 const struct cred *);
 extern int filp_close(struct file *, fl_owner_t id);
@@ -2150,11 +2154,15 @@ extern void free_write_pipe(struct file *);
 
 extern struct file *do_filp_open(int dfd, const char *pathname,
 		int open_flag, int mode, int acc_mode);
+extern int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
+			  struct path *path);
+extern long do_handle_open(int mountdirfd,
+			   struct file_handle __user *ufh, int open_flag);
 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 *);
- 
+
 /* fs/dcache.c -- generic fs support functions */
 extern int is_subdir(struct dentry *, struct dentry *);
 extern int path_is_under(struct path *, struct path *);
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 05b441d..827aef0 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -64,6 +64,7 @@ extern int user_path_at(int, const char __user *, unsigned, struct path *);
 #define user_path_dir(name, path) \
 	user_path_at(AT_FDCWD, name, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, path)
 
+extern struct vfsmount *get_vfsmount_from_fd(int);
 extern int kern_path(const char *, unsigned, struct path *);
 
 extern int path_lookup(const char *, unsigned, struct nameidata *);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index f7aba76..4dc527c 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -835,4 +835,7 @@ asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg);
 asmlinkage long sys_name_to_handle_at(int dfd, const char __user *name,
 				      struct file_handle __user *handle,
 				      int __user *mnt_id, int flag);
+asmlinkage long sys_open_by_handle_at(int mountdirfd,
+				      struct file_handle __user *handle,
+				      int flags);
 #endif
-- 
1.7.0.4

[PATCH -V19 04/15] vfs: Add handle based readlink syscall

[Aneesh Kumar K.V]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/stat.c                |   28 ++++++++++++++++++++++++++++
 include/linux/syscalls.h |    3 +++
 2 files changed, 31 insertions(+), 0 deletions(-)

diff --git a/fs/stat.c b/fs/stat.c
index 12e90e2..29052eb 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -319,6 +319,34 @@ SYSCALL_DEFINE3(readlink, const char __user *, path, char __user *, buf,
 	return sys_readlinkat(AT_FDCWD, path, buf, bufsiz);
 }
 
+SYSCALL_DEFINE4(handle_readlink, int, mountdirfd,
+		struct file_handle __user *, ufh,
+		char __user *, buf, int, bufsiz)
+{
+	long retval = 0;
+	struct path path;
+	struct inode *inode;
+
+	if (bufsiz <= 0)
+		return -EINVAL;
+	retval = handle_to_path(mountdirfd, ufh, &path);
+	if (retval)
+		goto out_err;
+
+	inode = path.dentry->d_inode;
+	retval = -EINVAL;
+	if (inode->i_op->readlink) {
+		retval = security_inode_readlink(path.dentry);
+		if (!retval) {
+			touch_atime(path.mnt, path.dentry);
+			retval = inode->i_op->readlink(path.dentry,
+						       buf, bufsiz);
+		}
+	}
+	path_put(&path);
+out_err:
+	return retval;
+}
 
 /* ---------- LFS-64 ----------- */
 #ifdef __ARCH_WANT_STAT64
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 4dc527c..35ecae3 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -838,4 +838,7 @@ asmlinkage long sys_name_to_handle_at(int dfd, const char __user *name,
 asmlinkage long sys_open_by_handle_at(int mountdirfd,
 				      struct file_handle __user *handle,
 				      int flags);
+asmlinkage long sys_handle_readlink(int mountdirfd,
+				    struct file_handle __user *ufh,
+				    char __user *buf, int bufsiz);
 #endif
-- 
1.7.0.4

[PATCH -V19 05/15] vfs: Add handle based stat syscall

[Aneesh Kumar K.V]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/x86/ia32/sys_ia32.c |   13 +++++++++++++
 fs/stat.c                |   42 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h       |    3 +++
 include/linux/syscalls.h |    9 +++++++++
 4 files changed, 67 insertions(+), 0 deletions(-)

diff --git a/arch/x86/ia32/sys_ia32.c b/arch/x86/ia32/sys_ia32.c
index 849813f..7f679e4 100644
--- a/arch/x86/ia32/sys_ia32.c
+++ b/arch/x86/ia32/sys_ia32.c
@@ -138,6 +138,19 @@ asmlinkage long sys32_fstatat(unsigned int dfd, const char __user *filename,
 	return cp_stat64(statbuf, &stat);
 }
 
+asmlinkage long sys32_handle_stat64(int mountdirfd,
+				    struct file_handle __user *ufh,
+				    struct stat64 __user *statbuf)
+{
+	struct kstat stat;
+	int error;
+
+	error = do_handle_stat(mountdirfd, ufh, &stat);
+	if (error)
+		return error;
+	return cp_stat64(statbuf, &stat);
+}
+
 /*
  * Linux/i386 didn't use to be able to handle more than
  * 4 system call parameters, so these system calls used a memory
diff --git a/fs/stat.c b/fs/stat.c
index 29052eb..d448876 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -286,6 +286,35 @@ SYSCALL_DEFINE2(newfstat, unsigned int, fd, struct stat __user *, statbuf)
 	return error;
 }
 
+int do_handle_stat(int mountdirfd, struct file_handle __user *ufh,
+		   struct kstat *stat)
+{
+	struct path path;
+	int error = -EINVAL;
+
+	error = handle_to_path(mountdirfd, ufh, &path);
+	if (error)
+		goto out;
+
+	error = vfs_getattr(path.mnt, path.dentry, stat);
+	path_put(&path);
+out:
+	return error;
+}
+
+SYSCALL_DEFINE3(handle_stat, int, mountdirfd,
+		struct file_handle __user *, ufh,
+		struct stat __user *, statbuf)
+{
+	struct kstat stat;
+	int error;
+
+	error = do_handle_stat(mountdirfd, ufh, &stat);
+	if (error)
+		return error;
+	return cp_new_stat(&stat, statbuf);
+}
+
 SYSCALL_DEFINE4(readlinkat, int, dfd, const char __user *, pathname,
 		char __user *, buf, int, bufsiz)
 {
@@ -434,6 +463,19 @@ SYSCALL_DEFINE4(fstatat64, int, dfd, const char __user *, filename,
 		return error;
 	return cp_new_stat64(&stat, statbuf);
 }
+
+SYSCALL_DEFINE3(handle_stat64, int, mountdirfd,
+		struct file_handle __user *, ufh,
+		struct stat64 __user *, statbuf)
+{
+	struct kstat stat;
+	int error;
+
+	error = do_handle_stat(mountdirfd, ufh, &stat);
+	if (error)
+		return error;
+	return cp_new_stat64(&stat, statbuf);
+}
 #endif /* __ARCH_WANT_STAT64 */
 
 /* Caller is here responsible for sufficient locking (ie. inode->i_lock) */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 134f97a..8dde859 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2339,6 +2339,9 @@ extern int vfs_stat(const char __user *, struct kstat *);
 extern int vfs_lstat(const char __user *, struct kstat *);
 extern int vfs_fstat(unsigned int, struct kstat *);
 extern int vfs_fstatat(int , const char __user *, struct kstat *, int);
+extern int do_handle_stat(int mountdirfd,
+			  struct file_handle __user *ufh,
+			  struct kstat *stat);
 
 extern int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
 		    unsigned long arg);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 35ecae3..e45ef50 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -841,4 +841,13 @@ asmlinkage long sys_open_by_handle_at(int mountdirfd,
 asmlinkage long sys_handle_readlink(int mountdirfd,
 				    struct file_handle __user *ufh,
 				    char __user *buf, int bufsiz);
+#if BITS_PER_LONG == 32
+asmlinkage long sys_handle_stat64(int mountdirfd,
+				  struct file_handle __user *ufh,
+				  struct stat64 __user *statbuf);
+#else
+asmlinkage long sys_handle_stat(int mountdirfd,
+				struct file_handle __user *ufh,
+				struct stat __user *statbuf);
+#endif
 #endif
-- 
1.7.0.4

[PATCH -V19 06/15] vfs: Add handle based link syscall

[Aneesh Kumar K.V]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/namei.c               |   45 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/syscalls.h |    2 ++
 2 files changed, 47 insertions(+), 0 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 4718802..304b187 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2706,6 +2706,51 @@ SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname
 	return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
 }
 
+SYSCALL_DEFINE4(handle_link, int, mountdirfd, struct file_handle __user *, uofh,
+		int, newdfd, const char __user *, newname)
+{
+	char *to;
+	int error;
+	struct dentry *new_dentry;
+	struct nameidata nd;
+	struct path old_path;
+
+	error = handle_to_path(mountdirfd, uofh, &old_path);
+	if (error)
+		return error;
+
+	error = user_path_parent(newdfd, newname, &nd, &to);
+	if (error)
+		goto out;
+	error = -EXDEV;
+	if (old_path.mnt != nd.path.mnt)
+		goto out_release;
+	new_dentry = lookup_create(&nd, 0);
+	error = PTR_ERR(new_dentry);
+	if (IS_ERR(new_dentry))
+		goto out_unlock;
+	error = mnt_want_write(nd.path.mnt);
+	if (error)
+		goto out_dput;
+	error = security_path_link(old_path.dentry, &nd.path, new_dentry);
+	if (error)
+		goto out_drop_write;
+	error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
+out_drop_write:
+	mnt_drop_write(nd.path.mnt);
+out_dput:
+	dput(new_dentry);
+out_unlock:
+	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+out_release:
+	path_put(&nd.path);
+	putname(to);
+out:
+	path_put(&old_path);
+
+	return error;
+}
+
 /*
  * The worst of all namespace operations - renaming directory. "Perverted"
  * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index e45ef50..9c82364 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -850,4 +850,6 @@ asmlinkage long sys_handle_stat(int mountdirfd,
 				struct file_handle __user *ufh,
 				struct stat __user *statbuf);
 #endif
+asmlinkage long sys_handle_link(int mountdirfd, struct file_handle __user *uofh,
+				int newfd, const char __user *newname);
 #endif
-- 
1.7.0.4

[PATCH -V19 07/15] vfs: Add handle based chown syscall

[Aneesh Kumar K.V]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/open.c                |   20 ++++++++++++++++++++
 include/linux/syscalls.h |    2 ++
 2 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index 7abdcba..5e06c12 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -623,6 +623,26 @@ out:
 	return error;
 }
 
+SYSCALL_DEFINE4(handle_chown, int, mountdirfd, struct file_handle __user *, ufh,
+		uid_t, user, gid_t, group)
+{
+	struct path path;
+	int error = -EINVAL;
+
+	error = handle_to_path(mountdirfd, ufh, &path);
+	if (error)
+		goto out;
+	error = mnt_want_write(path.mnt);
+	if (error)
+		goto out_release;
+	error = chown_common(&path, user, group);
+	mnt_drop_write(path.mnt);
+out_release:
+	path_put(&path);
+out:
+	return error;
+}
+
 /*
  * You have to be very careful that these write
  * counts get cleaned up in error cases and
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 9c82364..6dab72b 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -852,4 +852,6 @@ asmlinkage long sys_handle_stat(int mountdirfd,
 #endif
 asmlinkage long sys_handle_link(int mountdirfd, struct file_handle __user *uofh,
 				int newfd, const char __user *newname);
+asmlinkage long sys_handle_chown(int mountdirfd, struct file_handle __user *ufh,
+				 uid_t user, gid_t group);
 #endif
-- 
1.7.0.4

[PATCH -V19 08/15] vfs: Add handle based xattr syscalls

[Aneesh Kumar K.V]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/xattr.c               |   70 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/syscalls.h |   15 ++++++++++
 2 files changed, 85 insertions(+), 0 deletions(-)

diff --git a/fs/xattr.c b/fs/xattr.c
index 01bb813..1d236c9 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -335,6 +335,26 @@ SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 	return error;
 }
 
+SYSCALL_DEFINE6(handle_setxattr, int, mountdirfd,
+		struct file_handle __user *, ufh,
+		const char __user *, name, const void __user *, value,
+		size_t, size, int, flags)
+{
+	struct path path;
+	int error;
+
+	error = handle_to_path(mountdirfd, ufh, &path);
+	if (error)
+		return error;
+	error = mnt_want_write(path.mnt);
+	if (!error) {
+		error = setxattr(path.dentry, name, value, size, flags);
+		mnt_drop_write(path.mnt);
+	}
+	path_put(&path);
+	return error;
+}
+
 /*
  * Extended attribute GET operations
  */
@@ -416,6 +436,22 @@ SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 	return error;
 }
 
+SYSCALL_DEFINE5(handle_getxattr, int, mountdirfd,
+		struct file_handle __user *, ufh,
+		const char __user *, name,
+		void __user *, value, size_t, size)
+{
+	struct path path;
+	ssize_t error;
+
+	error = handle_to_path(mountdirfd, ufh, &path);
+	if (error)
+		return error;
+	error = getxattr(path.dentry, name, value, size);
+	path_put(&path);
+	return error;
+}
+
 /*
  * Extended attribute LIST operations
  */
@@ -488,6 +524,21 @@ SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 	return error;
 }
 
+SYSCALL_DEFINE4(handle_listxattr, int, mountdirfd,
+		struct file_handle __user *, ufh,
+		char __user *, list, size_t, size)
+{
+	struct path path;
+	ssize_t error;
+
+	error = handle_to_path(mountdirfd, ufh, &path);
+	if (error)
+		return error;
+	error = listxattr(path.dentry, list, size);
+	path_put(&path);
+	return error;
+}
+
 /*
  * Extended attribute REMOVE operations
  */
@@ -562,6 +613,25 @@ SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 	return error;
 }
 
+SYSCALL_DEFINE3(handle_removexattr, int, mountdirfd,
+		struct file_handle __user *, ufh,
+		const char __user *, name)
+{
+	struct path path;
+	int error;
+
+	error = handle_to_path(mountdirfd, ufh, &path);
+	if (error)
+		return error;
+	error = mnt_want_write(path.mnt);
+	if (!error) {
+		error = removexattr(path.dentry, name);
+		mnt_drop_write(path.mnt);
+	}
+	path_put(&path);
+	return error;
+}
+
 
 static const char *
 strcmp_prefix(const char *a, const char *a_prefix)
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 6dab72b..4c7e922 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -854,4 +854,19 @@ asmlinkage long sys_handle_link(int mountdirfd, struct file_handle __user *uofh,
 				int newfd, const char __user *newname);
 asmlinkage long sys_handle_chown(int mountdirfd, struct file_handle __user *ufh,
 				 uid_t user, gid_t group);
+asmlinkage long sys_handle_setxattr(int mountdirfd,
+				    struct file_handle __user *ufh,
+				    const char __user *name,
+				    const void __user *value,
+				    size_t size, int flags);
+asmlinkage long sys_handle_getxattr(int mountdirfd,
+				    struct file_handle __user *ufh,
+				    const char __user *name,
+				    void __user *value, size_t size);
+asmlinkage long sys_handle_listxattr(int mountdirfd,
+				     struct file_handle __user *ufh,
+				     char __user *list, size_t size);
+asmlinkage long sys_handle_removexattr(int mountdirfd,
+				       struct file_handle __user *ufh,
+				       const char __user *name);
 #endif
-- 
1.7.0.4

[PATCH -V19 09/15] vfs: Add file access and modification time update via handle syscall

[Aneesh Kumar K.V]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/compat.c              |   20 ++++++++++++++++++
 fs/utimes.c              |   49 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/syscalls.h |    3 ++
 include/linux/time.h     |    3 ++
 4 files changed, 75 insertions(+), 0 deletions(-)

diff --git a/fs/compat.c b/fs/compat.c
index c4037fd..29c4cb4 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -131,6 +131,26 @@ asmlinkage long compat_sys_utimes(const char __user *filename, struct compat_tim
 	return compat_sys_futimesat(AT_FDCWD, filename, t);
 }
 
+asmlinkage long compat_sys_handle_utimes(unsigned int mountdirfd,
+					 struct file_handle __user *ufh,
+					 struct compat_timeval __user *t)
+{
+	struct timespec tv[2];
+	if (t) {
+		if (get_user(tv[0].tv_sec, &t[0].tv_sec) ||
+		    get_user(tv[0].tv_nsec, &t[0].tv_usec) ||
+		    get_user(tv[1].tv_sec, &t[1].tv_sec) ||
+		    get_user(tv[1].tv_nsec, &t[1].tv_usec))
+			return -EFAULT;
+		if (tv[0].tv_nsec >= 1000000 || tv[0].tv_nsec < 0 ||
+		    tv[1].tv_nsec >= 1000000 || tv[1].tv_nsec < 0)
+			return -EINVAL;
+		tv[0].tv_nsec *= 1000;
+		tv[1].tv_nsec *= 1000;
+	}
+	return do_handle_utimes(mountdirfd, ufh, t ? tv : NULL);
+}
+
 static int cp_compat_stat(struct kstat *stat, struct compat_stat __user *ubuf)
 {
 	compat_ino_t ino = stat->ino;
diff --git a/fs/utimes.c b/fs/utimes.c
index 179b586..df241a1 100644
--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -222,3 +222,52 @@ SYSCALL_DEFINE2(utimes, char __user *, filename,
 {
 	return sys_futimesat(AT_FDCWD, filename, utimes);
 }
+
+long do_handle_utimes(int mountdirfd, struct file_handle __user *ufh,
+		      struct timespec *times)
+{
+	struct path path;
+	int error = -EINVAL;
+
+	if (times && (!nsec_valid(times[0].tv_nsec) ||
+		      !nsec_valid(times[1].tv_nsec))) {
+		goto out;
+	}
+	error = handle_to_path(mountdirfd, ufh, &path);
+	if (error)
+		goto out;
+
+	error = utimes_common(&path, times);
+	path_put(&path);
+out:
+	return error;
+}
+
+SYSCALL_DEFINE3(handle_utimes, int, mountdirfd,
+		struct file_handle __user *, ufh,
+		struct timeval __user *, utimes)
+{
+	struct timeval times[2];
+	struct timespec tstimes[2];
+
+	if (utimes) {
+		if (copy_from_user(&times, utimes, sizeof(times)))
+			return -EFAULT;
+
+		/* This test is needed to catch all invalid values.  If we
+		   would test only in do_utimes we would miss those invalid
+		   values truncated by the multiplication with 1000.  Note
+		   that we also catch UTIME_{NOW,OMIT} here which are only
+		   valid for utimensat.  */
+		if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
+		    times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
+			return -EINVAL;
+
+		tstimes[0].tv_sec = times[0].tv_sec;
+		tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
+		tstimes[1].tv_sec = times[1].tv_sec;
+		tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
+	}
+
+	return do_handle_utimes(mountdirfd, ufh, utimes ? tstimes : NULL);
+}
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 4c7e922..411a450 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -869,4 +869,7 @@ asmlinkage long sys_handle_listxattr(int mountdirfd,
 asmlinkage long sys_handle_removexattr(int mountdirfd,
 				       struct file_handle __user *ufh,
 				       const char __user *name);
+asmlinkage long sys_handle_utimes(int mountdirfd,
+				  struct file_handle __user *ufh,
+				  struct timeval __user *utimes);
 #endif
diff --git a/include/linux/time.h b/include/linux/time.h
index 9f15ac7..ce84274 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -151,6 +151,9 @@ extern int do_settimeofday(struct timespec *tv);
 extern int do_sys_settimeofday(struct timespec *tv, struct timezone *tz);
 #define do_posix_clock_monotonic_gettime(ts) ktime_get_ts(ts)
 extern long do_utimes(int dfd, const char __user *filename, struct timespec *times, int flags);
+struct file_handle;
+extern long do_handle_utimes(int mountdirfd, struct file_handle __user *ufh,
+			     struct timespec *times);
 struct itimerval;
 extern int do_setitimer(int which, struct itimerval *value,
 			struct itimerval *ovalue);
-- 
1.7.0.4

[PATCH -V19 10/15] x86: Add new syscalls for x86_32

[Aneesh Kumar K.V]

This patch adds new syscalls to x86_32

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/x86/include/asm/unistd_32.h   |   14 +++++++++++++-
 arch/x86/kernel/syscall_table_32.S |   11 +++++++++++
 2 files changed, 24 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/unistd_32.h b/arch/x86/include/asm/unistd_32.h
index b766a5e..75c26e7 100644
--- a/arch/x86/include/asm/unistd_32.h
+++ b/arch/x86/include/asm/unistd_32.h
@@ -346,10 +346,22 @@
 #define __NR_fanotify_init	338
 #define __NR_fanotify_mark	339
 #define __NR_prlimit64		340
+#define __NR_name_to_handle_at	341
+#define __NR_open_by_handle_at  342
+#define __NR_readlink_by_handle 343
+#define __NR_stat64_by_handle   344
+#define __NR_link_by_handle     345
+#define __NR_chown_by_handle    346
+#define __NR_setxattr_by_handle 347
+#define __NR_getxattr_by_handle 348
+#define __NR_listxattr_by_handle	349
+#define __NR_removexattr_by_handle	350
+#define __NR_utimes_by_handle	351
+
 
 #ifdef __KERNEL__
 
-#define NR_syscalls 341
+#define NR_syscalls 352
 
 #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 b35786d..e8721fe 100644
--- a/arch/x86/kernel/syscall_table_32.S
+++ b/arch/x86/kernel/syscall_table_32.S
@@ -340,3 +340,14 @@ ENTRY(sys_call_table)
 	.long sys_fanotify_init
 	.long sys_fanotify_mark
 	.long sys_prlimit64		/* 340 */
+	.long sys_name_to_handle_at
+	.long sys_open_by_handle_at
+	.long sys_handle_readlink
+	.long sys_handle_stat64
+	.long sys_handle_link		/* 345 */
+	.long sys_handle_chown
+	.long sys_handle_setxattr
+	.long sys_handle_getxattr
+	.long sys_handle_listxattr
+	.long sys_handle_removexattr	/* 350 */
+	.long sys_handle_utimes
-- 
1.7.0.4

[PATCH -V19 11/15] x86: Add new syscalls for x86_64

[Aneesh Kumar K.V]

This patch add new syscalls to x86_64

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/x86/ia32/ia32entry.S        |   11 +++++++++++
 arch/x86/include/asm/unistd_64.h |   24 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index b86feab..7b6c67d 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -845,4 +845,15 @@ ia32_sys_call_table:
 	.quad sys_fanotify_init
 	.quad sys32_fanotify_mark
 	.quad sys_prlimit64		/* 340 */
+	.quad sys_name_to_handle_at
+	.quad compat_sys_open_by_handle_at
+	.quad sys_handle_readlink
+	.quad sys32_handle_stat64
+	.quad sys_handle_link		/* 345 */
+	.quad sys_handle_chown
+	.quad sys_handle_setxattr
+	.quad sys_handle_getxattr
+	.quad sys_handle_listxattr
+	.quad sys_handle_removexattr	/* 350 */
+	.quad compat_sys_handle_utimes
 ia32_syscall_end:
diff --git a/arch/x86/include/asm/unistd_64.h b/arch/x86/include/asm/unistd_64.h
index 363e9b8..09ee835 100644
--- a/arch/x86/include/asm/unistd_64.h
+++ b/arch/x86/include/asm/unistd_64.h
@@ -669,6 +669,30 @@ __SYSCALL(__NR_fanotify_init, sys_fanotify_init)
 __SYSCALL(__NR_fanotify_mark, sys_fanotify_mark)
 #define __NR_prlimit64				302
 __SYSCALL(__NR_prlimit64, sys_prlimit64)
+#define __NR_name_to_handle_at			303
+__SYSCALL(__NR_name_to_handle_at, sys_name_to_handle_at)
+#define __NR_open_by_handle_at			304
+__SYSCALL(__NR_open_by_handle_at, sys_open_by_handle_at)
+#define __NR_readlink_by_handle			305
+__SYSCALL(__NR_readlink_by_handle, sys_handle_readlink)
+#define __NR_stat_by_handle			306
+__SYSCALL(__NR_stat_by_handle, sys_handle_stat)
+#define __NR_link_by_handle			307
+__SYSCALL(__NR_link_by_handle, sys_handle_link)
+#define __NR_chown_by_handle			308
+__SYSCALL(__NR_chown_by_handle, sys_handle_chown)
+#define __NR_setxattr_by_handle			309
+__SYSCALL(__NR_setxattr_by_handle, sys_handle_setxattr)
+#define __NR_getxattr_by_handle			310
+__SYSCALL(__NR_getxattr_by_handle, sys_handle_getxattr)
+#define __NR_listxattr_by_handle		311
+__SYSCALL(__NR_listxattr_by_handle, sys_handle_listxattr)
+#define __NR_removexattr_by_handle		312
+__SYSCALL(__NR_removexattr_by_handle, sys_handle_removexattr)
+#define __NR_utimes_by_handle			313
+__SYSCALL(__NR_utimes_by_handle, sys_handle_utimes)
+
+
 
 #ifndef __NO_STUBS
 #define __ARCH_WANT_OLD_READDIR
-- 
1.7.0.4

[PATCH -V19 12/15] unistd.h: Add new syscalls numbers to asm-generic

[Aneesh Kumar K.V]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 include/asm-generic/unistd.h |   25 ++++++++++++++++++++++++-
 1 files changed, 24 insertions(+), 1 deletions(-)

diff --git a/include/asm-generic/unistd.h b/include/asm-generic/unistd.h
index b969770..3efb463 100644
--- a/include/asm-generic/unistd.h
+++ b/include/asm-generic/unistd.h
@@ -646,9 +646,32 @@ __SYSCALL(__NR_prlimit64, sys_prlimit64)
 __SYSCALL(__NR_fanotify_init, sys_fanotify_init)
 #define __NR_fanotify_mark 263
 __SYSCALL(__NR_fanotify_mark, sys_fanotify_mark)
+#define __NR_name_to_handle_at		264
+__SYSCALL(__NR_name_to_handle_at, sys_name_to_handle_at)
+#define __NR_open_by_handle_at		265
+__SYSCALL(__NR_open_by_handle_at, sys_open_by_handle_at)
+#define __NR_readlink_by_handle		266
+__SYSCALL(__NR_readlink_by_handle, sys_handle_readlink)
+#define __NR_stat64_by_handle		267
+__SYSCALL(__NR_stat64_by_handle, sys_handle_stat64)
+#define __NR_link_by_handle		268
+__SYSCALL(__NR_link_by_handle, sys_handle_link)
+#define __NR_chown_by_handle		269
+__SYSCALL(__NR_chown_by_handle, sys_handle_chown)
+#define __NR_setxattr_by_handle		270
+__SYSCALL(__NR_setxattr_by_handle, sys_handle_setxattr)
+#define __NR_getxattr_by_handle		271
+__SYSCALL(__NR_getxattr_by_handle, sys_handle_getxattr)
+#define __NR_listxattr_by_handle	272
+__SYSCALL(__NR_listxattr_by_handle, sys_handle_listxattr)
+#define __NR_removexattr_by_handle	273
+__SYSCALL(__NR_removexattr_by_handle, sys_handle_removexattr)
+#define __NR_utimes_by_handle		274
+__SYSCALL(__NR_utimes_by_handle, sys_handle_utimes)
+
 
 #undef __NR_syscalls
-#define __NR_syscalls 264
+#define __NR_syscalls 275
 
 /*
  * All syscalls below here should go away really,
-- 
1.7.0.4

[PATCH -V19 13/15] vfs: Export file system uuid via /proc/<pid>/mountinfo

[Aneesh Kumar K.V]

We add a per superblock uuid field. File systems should
update the uuid in the fill_super callback

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/namespace.c     |   16 ++++++++++++++++
 include/linux/fs.h |    1 +
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 2e10cb1..041645a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -837,6 +837,18 @@ const struct seq_operations mounts_op = {
 	.show	= show_vfsmnt
 };
 
+static int uuid_is_nil(u8 *uuid)
+{
+	int i;
+	u8  *cp = (u8 *)uuid;
+
+	for (i = 0; i < 16; i++) {
+		if (*cp++)
+			return 0;
+	}
+	return 1;
+}
+
 static int show_mountinfo(struct seq_file *m, void *v)
 {
 	struct proc_mounts *p = m->private;
@@ -875,6 +887,10 @@ static int show_mountinfo(struct seq_file *m, void *v)
 	if (IS_MNT_UNBINDABLE(mnt))
 		seq_puts(m, " unbindable");
 
+	if (!uuid_is_nil(mnt->mnt_sb->s_uuid))
+		/* print the uuid */
+		seq_printf(m, " uuid:%pU", mnt->mnt_sb->s_uuid);
+
 	/* Filesystem specific data */
 	seq_puts(m, " - ");
 	show_type(m, sb);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 8dde859..0f348f9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1369,6 +1369,7 @@ 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;
-- 
1.7.0.4

[PATCH -V19 14/15] ext3: Copy fs UUID to superblock.

[Aneesh Kumar K.V]

File system UUID is made available to application
via  /proc/<pid>/mountinfo

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 5dbf4db..6dda322 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -1918,6 +1918,7 @@ 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);
-- 
1.7.0.4

[PATCH -V19 15/15] ext4: Copy fs UUID to superblock

[Aneesh Kumar K.V]

File system UUID is made available to application
via  /proc/<pid>/mountinfo

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 2614774..b46a78c 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2941,6 +2941,8 @@ 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);
-- 
1.7.0.4

Re: [PATCH -V19 00/15] Generic name to handle and open by handle syscalls

[Aneesh Kumar K. V]

On Fri, 27 Aug 2010 16:32:47 +0530, "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:
> 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
> 
> git repo for the patchset at:
> git://git.kernel.org/pub/scm/linux/kernel/git/kvaneesh/linux-open-handle.git open-by-handle
> 
> Test case can be found at
> http://git.kernel.org/?p=fs/ext2/kvaneesh/handle-test.git
> git://git.kernel.org/pub/scm/fs/ext2/kvaneesh/handle-test.git
> 
> Changes from V18:
> a) Drop open on symlink patch
> b) Drop other patches that added support for NULL pathname in *at syscalls
> c) Add new handle based syscalls. All of them are restricted to CAP_DAC_READ_SEARCH
> 

Hi Al,

Any update on this. Are you ok with syscall approach which is limitted to
CAP_DAC_READ_SEARCH  ?

-aneesh

Re: [PATCH -V19 00/15] Generic name to handle and open by handle syscalls

[Miklos Szeredi]

On Tue, 07 Sep 2010, Aneesh Kumar K. V wrote:
> Any update on this. Are you ok with syscall approach which is limitted to
> CAP_DAC_READ_SEARCH  ?

My gut reaction is: "not another bunch of xattr syscalls!".  It
doesn't feel right, this interface is too specialized to warrant a
full set of filesystem syscalls.

Al Viro is right that there are problems with symlinks.  What we
really want here is a sort of symlink that doesn't get followed.  One
way to provide that is to create a kernel internal "handle" filesystem
and direct open_by_handle() to that for anything not a directory or a
regular file.

Thanks,
Miklos

Re: [PATCH -V19 00/15] Generic name to handle and open by handle syscalls

[Aneesh Kumar K. V]

On Tue, 07 Sep 2010 13:36:03 +0200, Miklos Szeredi <miklos@szeredi.hu> wrote:
> On Tue, 07 Sep 2010, Aneesh Kumar K. V wrote:
> > Any update on this. Are you ok with syscall approach which is limitted to
> > CAP_DAC_READ_SEARCH  ?
> 
> My gut reaction is: "not another bunch of xattr syscalls!".  It
> doesn't feel right, this interface is too specialized to warrant a
> full set of filesystem syscalls.


Are you ok with rest of syscalls other than the handle based xattr one ?
In that case can we get rest of the patches merged and rework xattr patches
later ?. That is xattr support for symlink can follow as a separate patch
series ?


> 
> Al Viro is right that there are problems with symlinks.  What we
> really want here is a sort of symlink that doesn't get followed.  One
> way to provide that is to create a kernel internal "handle" filesystem
> and direct open_by_handle() to that for anything not a directory or a
> regular file.
> 

-aneesh

Re: [PATCH -V19 00/15] Generic name to handle and open by handle syscalls

[Miklos Szeredi]

On Tue, 07 Sep 2010, Aneesh Kumar K. V wrote:
> On Tue, 07 Sep 2010 13:36:03 +0200, Miklos Szeredi <miklos@szeredi.hu> wrote:
> > On Tue, 07 Sep 2010, Aneesh Kumar K. V wrote:
> > > Any update on this. Are you ok with syscall approach which is limitted to
> > > CAP_DAC_READ_SEARCH  ?
> > 
> > My gut reaction is: "not another bunch of xattr syscalls!".  It
> > doesn't feel right, this interface is too specialized to warrant a
> > full set of filesystem syscalls.
> 
> 
> Are you ok with rest of syscalls other than the handle based xattr one ?

No, not really.  Only xattrs stand out from the rest as the "API that
shouldn't be" and adding more to that pile makes me feel especially
bad.

But xattrs aside, I still don't think we need another interface for
file handles that duplicates the existing filesystem APIs.

Thanks,
Miklos

Re: [PATCH -V19 00/15] Generic name to handle and open by handle syscalls

[Aneesh Kumar K. V]

On Tue, 07 Sep 2010 15:24:29 +0200, Miklos Szeredi <miklos@szeredi.hu> wrote:
> On Tue, 07 Sep 2010, Aneesh Kumar K. V wrote:
> > On Tue, 07 Sep 2010 13:36:03 +0200, Miklos Szeredi <miklos@szeredi.hu> wrote:
> > > On Tue, 07 Sep 2010, Aneesh Kumar K. V wrote:
> > > > Any update on this. Are you ok with syscall approach which is limitted to
> > > > CAP_DAC_READ_SEARCH  ?
> > > 
> > > My gut reaction is: "not another bunch of xattr syscalls!".  It
> > > doesn't feel right, this interface is too specialized to warrant a
> > > full set of filesystem syscalls.
> > 
> > 
> > Are you ok with rest of syscalls other than the handle based xattr one ?
> 
> No, not really.  Only xattrs stand out from the rest as the "API that
> shouldn't be" and adding more to that pile makes me feel especially
> bad.
> 
> But xattrs aside, I still don't think we need another interface for
> file handles that duplicates the existing filesystem APIs.
> 

As per your suggestion i started looking at handlefs details and below
is my take on the approach.

handlefs would be an internal kernel mount like pipefs and would have
inode object mapping to the returned file descriptor of
open_by_handle_at syscall for symlinks. For regular files we can do what
we already does and for symlinks we will create inodes in handlefs and
their inode operation will in turn result in call out of inode operations
of the actual symlinks. Based on the above

a) We still need open_by_handle_at syscall
b) We still need handle based link syscall, because we need to support
   creating hardlinks based on handle, and the existing linkat syscall
   takes the oldpath name.
c) We still need handle based readlink syscall, because the existing
   readlinkat syscall takes pathname.
d) we can drop stat, chown and xattr syscall because they are introduced
   specially for symlinks as we don't allow open on symlinks.
e) It would be nice to have handle based stat syscall to avoid two
   syscall overhead for fetching file attributes when implementing a
   file server, where fetching file attribute is a common operation. 

With the above from the current patch series we can drop chown and
xattr syscalls. Would it be ok if we get the series with the those two
syscall patches dropped upstream as i work on supporting symlinks with
handlefs approach ?

-aneesh

Re: [PATCH -V19 00/15] Generic name to handle and open by handle syscalls

[Miklos Szeredi]

On Mon, 13 Sep 2010, Aneesh Kumar K. V wrote:
> As per your suggestion i started looking at handlefs details and below
> is my take on the approach.
> 
> handlefs would be an internal kernel mount like pipefs and would have
> inode object mapping to the returned file descriptor of
> open_by_handle_at syscall for symlinks. For regular files we can do what
> we already does and for symlinks we will create inodes in handlefs and
> their inode operation will in turn result in call out of inode operations
> of the actual symlinks. Based on the above
> 
> a) We still need open_by_handle_at syscall
> b) We still need handle based link syscall, because we need to support
>    creating hardlinks based on handle, and the existing linkat syscall
>    takes the oldpath name.
> c) We still need handle based readlink syscall, because the existing
>    readlinkat syscall takes pathname.

You can implement ->read() on the symlink file instead.

> d) we can drop stat, chown and xattr syscall because they are introduced
>    specially for symlinks as we don't allow open on symlinks.
> e) It would be nice to have handle based stat syscall to avoid two
>    syscall overhead for fetching file attributes when implementing a
>    file server, where fetching file attribute is a common operation. 

Syscall overhead is generally insignificant compared to other effects.
The server can also cache open files for commonly used handles.

> 
> With the above from the current patch series we can drop chown and
> xattr syscalls. Would it be ok if we get the series with the those two
> syscall patches dropped upstream as i work on supporting symlinks with
> handlefs approach ?

Try it.

Al seems to only be active to the outside world around the merge
window, so that's the best time to ask him to pull.

Thanks,
Miklos

Re: [PATCH -V19 00/15] Generic name to handle and open by handle syscalls

[Neil Brown]

On Mon, 13 Sep 2010 08:01:18 +0200
Miklos Szeredi <miklos@szeredi.hu> wrote:

> On Mon, 13 Sep 2010, Aneesh Kumar K. V wrote:
> > As per your suggestion i started looking at handlefs details and below
> > is my take on the approach.
> > 
> > handlefs would be an internal kernel mount like pipefs and would have
> > inode object mapping to the returned file descriptor of
> > open_by_handle_at syscall for symlinks. For regular files we can do what
> > we already does and for symlinks we will create inodes in handlefs and
> > their inode operation will in turn result in call out of inode operations
> > of the actual symlinks. Based on the above
> > 
> > a) We still need open_by_handle_at syscall
> > b) We still need handle based link syscall, because we need to support
> >    creating hardlinks based on handle, and the existing linkat syscall
> >    takes the oldpath name.
> > c) We still need handle based readlink syscall, because the existing
> >    readlinkat syscall takes pathname.
> 
> You can implement ->read() on the symlink file instead.

I would suggest that is a much uglier hack than changed readlinkat to accept
a NULL pathname.

NeilBrown


> 
> > d) we can drop stat, chown and xattr syscall because they are introduced
> >    specially for symlinks as we don't allow open on symlinks.
> > e) It would be nice to have handle based stat syscall to avoid two
> >    syscall overhead for fetching file attributes when implementing a
> >    file server, where fetching file attribute is a common operation. 
> 
> Syscall overhead is generally insignificant compared to other effects.
> The server can also cache open files for commonly used handles.
> 
> > 
> > With the above from the current patch series we can drop chown and
> > xattr syscalls. Would it be ok if we get the series with the those two
> > syscall patches dropped upstream as i work on supporting symlinks with
> > handlefs approach ?
> 
> Try it.
> 
> Al seems to only be active to the outside world around the merge
> window, so that's the best time to ask him to pull.
> 
> Thanks,
> Miklos

Re: [PATCH -V19 00/15] Generic name to handle and open by handle syscalls

[Miklos Szeredi]

On Mon, 13 Sep 2010, Neil Brown wrote:
> > You can implement ->read() on the symlink file instead.
> 
> I would suggest that is a much uglier hack than changed readlinkat to accept
> a NULL pathname.

I think read(2) is a natural interface for reading symlinks and would
have been a perfectly fine API to choose instead of a specialized
syscall.

Thanks,
Miklos

Re: [PATCH -V19 00/15] Generic name to handle and open by handle syscalls

[Aneesh Kumar K. V]

On Mon, 13 Sep 2010 08:01:18 +0200, Miklos Szeredi <miklos@szeredi.hu> wrote:
> On Mon, 13 Sep 2010, Aneesh Kumar K. V wrote:
> > d) we can drop stat, chown and xattr syscall because they are introduced
> >    specially for symlinks as we don't allow open on symlinks.
> > e) It would be nice to have handle based stat syscall to avoid two
> >    syscall overhead for fetching file attributes when implementing a
> >    file server, where fetching file attribute is a common operation. 
> 
> Syscall overhead is generally insignificant compared to other effects.
> The server can also cache open files for commonly used handles.
> 

For some client/server file system an open would require communication to
the server where as we can get stat result based on the values
cached on the client if we support handle based stat.

-aneesh