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

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

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