[PATCH -V20 04/12] vfs: Add handle based readlink syscall

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

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 89a0ade..bf03e4a 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