[CIFS] [PATCH] warn on EINVAL error on posix open, and turn off posix open if server broken for this call

[Steve French <smfrench@gmail.com>]

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Attached is patch to workaround the problem found in posix open to
Samba versions 3.3.1 and earlier
(create works, but open would fail with invalid parameter) - it
disables requests to try posix open after
a first failure.



-- 
Thanks,

Steve

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diff --git a/fs/cifs/CHANGES b/fs/cifs/CHANGES
index b33c841..fc977df 100644
--- a/fs/cifs/CHANGES
+++ b/fs/cifs/CHANGES
@@ -11,6 +11,8 @@ to better ensure that we wait for server to write all of the data to
 server disk (not just write it over the network).  Add new mount
 parameter to allow user to disable sending the (slow) SMB flush on
 fsync if desired (fsync still flushes all cached write data to the server).
+Posix file open support added (turned off after one attempt if server
+fails to support it properly, as with Samba server versions prior to 3.3.2)
 
 Version 1.56
 ------------
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 44ff94d..9fbf4df 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -299,6 +299,7 @@ struct cifsTconInfo {
 	bool unix_ext:1;  /* if false disable Linux extensions to CIFS protocol
 				for this mount even if server would support */
 	bool local_lease:1; /* check leases (only) on local system not remote */
+	bool broken_posix_open; /* e.g. Samba server versions < 3.3.2, 3.2.9 */
 	bool need_reconnect:1; /* connection reset, tid now invalid */
 	/* BB add field for back pointer to sb struct(s)? */
 };
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 7bef4cc..b877f9a 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 +345,19 @@ 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 of type %s returned"
+					   " unexpected error on SMB posix open"
+					   ", disabling posix open support."
+					   " Check if server update available.",
+					   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);