[PATCH v2 08/14] vfs: don't return -ENODEV from vfs_lookup_open()

[NeilBrown <neilb@ownmail.net>]

From: NeilBrown <neil@brown.name>

-ENODEV is not generally an error meaning "the object is a device"
and nfsd - the only intended caller of vfs_lookup_open() - does not
benefit from knowing it was a device file.  So return -EFTYPE in
that case.
Also switch to testing the dentry type rather than dereferencing the
inode to get the type.

-EISDIR is widely used to mean "the object is a directory which is
   not what is wanted".
-ELOOP is sometimes used elsewhere to mean "a symlink was found but
   cannot be handled".

Also remove note about ->atomic_open returning -EFTYPE as that now only
happens for non regular/dir/symlink.

Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/namei.c | 24 +++++-------------------
 1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index b9fca38ad489..ba3e7e4b5fdb 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4621,9 +4621,7 @@ out_dput:
  * determine the type of file found from the error.
  * -EISDIR : a directory was found
  * -ELOOP  : a symlink was found
- * -ENODEV : a block or character device special file was found
- * -EFTYPE : any other non-regular file was found, such as FIFO or SOCK.
- *           or ->atomic_open responded to __O_REGULAR.
+ * -EFTYPE : any other non-regular file was found, device-special, FIFO or SOCK
  *
  * Returns: the opened struct file, or an error.
  */
@@ -4671,24 +4669,12 @@ struct file *vfs_lookup_open(struct path *parent, struct qstr *last,
 		error = -ENOENT;
 	} else if (!(file->f_mode & FMODE_CREATED) && (open_flag & O_EXCL)) {
 		error = -EEXIST;
-	} else if ((dentry->d_inode->i_mode & S_IFMT) != S_IFREG) {
-		switch (dentry->d_inode->i_mode & S_IFMT) {
-		case S_IFDIR:
+	} else if (!d_is_reg(dentry)) {
+		error = -EFTYPE;
+		if (d_is_dir(dentry))
 			error = -EISDIR;
-			break;
-		case S_IFLNK:
+		if (d_is_symlink(dentry))
 			error = -ELOOP;
-			break;
-		case S_IFBLK:
-		case S_IFCHR:
-			error = -ENODEV;
-			break;
-		case S_IFIFO:
-		case S_IFSOCK:
-		default:
-			error = -EFTYPE;
-			break;
-		}
 	} else if (!(file->f_mode & FMODE_OPENED)) {
 		nd.path.dentry = dentry;
 		error = vfs_open(&nd.path, file);
-- 
2.50.0.107.gf914562f5916.dirty