[CIFS] work around bug in Samba server handling for posix open

Samba server (version 3.3.1 and earlier, and 3.2.8 and earlier) incorrectly
required the O_CREAT flag on posix open (even when a file was not being
created).  This disables posix open (create is still ok) after the first
attempt returns EINVAL (and logs an error, once, recommending that they
update their server).

Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 7bef4cce572a..81747acca4c4 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -328,7 +328,8 @@ int cifs_open(struct inode *inode, struct file *file)
         else
                 oplock = 0;
 
-        if (tcon->unix_ext && (tcon->ses->capabilities & CAP_UNIX) &&
+        if (!tcon->broken_posix_open && tcon->unix_ext &&
+            (tcon->ses->capabilities & CAP_UNIX) &&
             (CIFS_UNIX_POSIX_PATH_OPS_CAP &
                         le64_to_cpu(tcon->fsUnixInfo.Capability))) {
                 int oflags = (int) cifs_posix_convert_flags(file->f_flags);
@@ -344,11 +345,20 @@ int cifs_open(struct inode *inode, struct file *file)
                         cifs_posix_open_inode_helper(inode, file, pCifsInode,
                                                      pCifsFile, oplock, netfid);
                         goto out;
+                } else if ((rc == -EINVAL) || (rc == -EOPNOTSUPP)) {
+                        if (tcon->ses->serverNOS)
+                                cERROR(1, ("server %s of type %s returned"
+                                           " unexpected error on SMB posix open"
+                                           ", disabling posix open support."
+                                           " Check if server update available.",
+                                           tcon->ses->serverName,
+                                           tcon->ses->serverNOS));
+                        tcon->broken_posix_open = true;
                 } else if ((rc != -EIO) && (rc != -EREMOTE) &&
                          (rc != -EOPNOTSUPP)) /* path not found or net err */
                         goto out;
-                /* fallthrough to retry open the old way on operation
-                   not supported or DFS errors */
+                /* else fallthrough to retry open the old way on network i/o
+                   or DFS errors */
         }
 
         desiredAccess = cifs_convert_flags(file->f_flags);