cifs: reduce roundtrips on create/qinfo requests

To work around some Window servers that return
STATUS_OBJECT_NAME_INVALID on query infos under DFS namespaces that
contain non-ASCII characters, we started checking for -ENOENT on every
file open, and if so, then send additional requests to figure out
whether it is a DFS link or not.  It means that all those requests
will be sent to every non-existing file.

So, in order to reduce the number of roundtrips, check earlier whether
status code is STATUS_OBJECT_NAME_INVALID and tcon supports dfs, and
if so, then map -ENOENT to -EREMOTE so mount or automount will take
care of chasing the DFS link -- if it isn't an DFS link, then -ENOENT
will be returned appropriately.

Before patch

  SMB2 438 Create Request File: ada.test\dfs\foo;GetInfo Request...
  SMB2 310 Create Response, Error: STATUS_OBJECT_NAME_NOT_FOUND;...
  SMB2 228 Ioctl Request FSCTL_DFS_GET_REFERRALS, File: \ada.test\dfs\foo
  SMB2 143 Ioctl Response, Error: STATUS_OBJECT_PATH_NOT_FOUND
  SMB2 438 Create Request File: ada.test\dfs\foo;GetInfo Request...
  SMB2 310 Create Response, Error: STATUS_OBJECT_NAME_NOT_FOUND;...
  SMB2 228 Ioctl Request FSCTL_DFS_GET_REFERRALS, File: \ada.test\dfs\foo
  SMB2 143 Ioctl Response, Error: STATUS_OBJECT_PATH_NOT_FOUND

After patch

  SMB2 438 Create Request File: ada.test\dfs\foo;GetInfo Request...
  SMB2 310 Create Response, Error: STATUS_OBJECT_NAME_NOT_FOUND;...
  SMB2 438 Create Request File: ada.test\dfs\foo;GetInfo Request...
  SMB2 310 Create Response, Error: STATUS_OBJECT_NAME_NOT_FOUND;...

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 0 insertions, 45 deletions

diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 1cbecd64d697..062175994e87 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -1314,49 +1314,4 @@ int cifs_update_super_prepath(struct cifs_sb_info *cifs_sb, char *prefix)
 	cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH;
 	return 0;
 }
-
-/** cifs_dfs_query_info_nonascii_quirk
- * Handle weird Windows SMB server behaviour. It responds with
- * STATUS_OBJECT_NAME_INVALID code to SMB2 QUERY_INFO request
- * for "\<server>\<dfsname>\<linkpath>" DFS reference,
- * where <dfsname> contains non-ASCII unicode symbols.
- *
- * Check such DFS reference.
- */
-int cifs_dfs_query_info_nonascii_quirk(const unsigned int xid,
-				       struct cifs_tcon *tcon,
-				       struct cifs_sb_info *cifs_sb,
-				       const char *linkpath)
-{
-	char *treename, *dfspath, sep;
-	int treenamelen, linkpathlen, rc;
-
-	treename = tcon->tree_name;
-	/* MS-DFSC: All paths in REQ_GET_DFS_REFERRAL and RESP_GET_DFS_REFERRAL
-	 * messages MUST be encoded with exactly one leading backslash, not two
-	 * leading backslashes.
-	 */
-	sep = CIFS_DIR_SEP(cifs_sb);
-	if (treename[0] == sep && treename[1] == sep)
-		treename++;
-	linkpathlen = strlen(linkpath);
-	treenamelen = strnlen(treename, MAX_TREE_SIZE + 1);
-	dfspath = kzalloc(treenamelen + linkpathlen + 1, GFP_KERNEL);
-	if (!dfspath)
-		return -ENOMEM;
-	if (treenamelen)
-		memcpy(dfspath, treename, treenamelen);
-	memcpy(dfspath + treenamelen, linkpath, linkpathlen);
-	rc = dfs_cache_find(xid, tcon->ses, cifs_sb->local_nls,
-			    cifs_remap(cifs_sb), dfspath, NULL, NULL);
-	if (rc == 0) {
-		cifs_dbg(FYI, "DFS ref '%s' is found, emulate -EREMOTE\n",
-			 dfspath);
-		rc = -EREMOTE;
-	} else {
-		cifs_dbg(FYI, "%s: dfs_cache_find returned %d\n", __func__, rc);
-	}
-	kfree(dfspath);
-	return rc;
-}
 #endif