[PATCH 3/7] vfs: vfs_lookup_open() should only return -EFTYPE for non-regular files

[NeilBrown <neilb@ownmail.net>]

From: NeilBrown <neil@brown.name>

Decoding the non-regular type into over-loaded error codes doesn't
really help nfsd much and it isn't particularly elegant.
It also isn't reliable as some filesystems may return -EFTYPE
from their atomic_open() for any non-regular file, given that
__O_REGULAR was passed.

So change to only return -EFTYPE for non-regular files.
Also use d_is_reg() to detect this case.

Caller can repeat the lookup in the dcache to determine what sort of
object was there.  This might find a different dentry if there is a
race, but that is not significant.

Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/namei.c | 30 ++++--------------------------
 1 file changed, 4 insertions(+), 26 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index c4be59213352..0c787363b101 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4616,14 +4616,8 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
  * nfsd.
  * It uses ->atomic_open or ->lookup / ->create / ->open as appropriate.
  *
- * If the fs object found is not a regular file then an error is returned.
- * In some cases, related errors are repurposed so that the caller can
- * 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.
+ * If the fs object found is not a regular file then -EFTYPE is
+ * returned.
  *
  * Returns: the opened struct file, or an error.
  */
@@ -4671,24 +4665,8 @@ 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:
-			error = -EISDIR;
-			break;
-		case S_IFLNK:
-			error = -ELOOP;
-			break;
-		case S_IFBLK:
-		case S_IFCHR:
-			error = -ENODEV;
-			break;
-		case S_IFIFO:
-		case S_IFSOCK:
-		default:
-			error = -EFTYPE;
-			break;
-		}
+	} else if (!d_is_reg(dentry)) {
+		error = -EFTYPE;
 	} else if (!(file->f_mode & FMODE_OPENED)) {
 		nd.path.dentry = dentry;
 		error = vfs_open(&nd.path, file);
-- 
2.50.0.107.gf914562f5916.dirty