[PATCH 2/2] cifs: don't add dot and dotdot entry by default at the start of cifs_readdir

[Namjae Jeon <namjae.jeon-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>]

Currently, dot and dotdot are added by default at the start of cifs_readdir.
This works well for the servers which send dot and dotdot entries at the start
in readdir query response.

For servers which do not send these two entries at the beginning,
this behavior creates 2 problems.
1) adding dot and dotdot increments ctx->pos by 2 hence the valid
   first 2 entries are missed in readdir output at client side.
2) Currently when we encounter dot or dotdot, the entry is simple skipped.

In case of smb2, if some buggy server sends only 1 entry in response per
cifs_query_dir_next request, and if that entry is happen to be dot OR dotdot,
getdents call return 0 bytes to user app making it falsely believe that there
are no more directory entries left.

This patch tries to solve the above issues by processing dot and dotdot entries
when they are encountered. This will have no effect on servers which already
sends these 2 entries at the start.

Signed-off-by: Namjae Jeon <namjae.jeon-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
Signed-off-by: Ashish Sangwan <a.sangwan-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
---
 fs/cifs/cifsglob.h |  2 ++
 fs/cifs/cifssmb.c  |  4 ++--
 fs/cifs/readdir.c  | 43 ++++++++++++++++++++++++++++++++++++++-----
 3 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 6e13911..864ea1a 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -987,6 +987,8 @@ struct cifs_search_info {
 	bool emptyDir:1;
 	bool unicode:1;
 	bool smallBuf:1; /* so we know which buf_release function to call */
+	bool gotdot:1;
+	bool gotdotdot:1;
 };
 
 struct cifs_open_parms {
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index fa13d5e..db49633 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -4475,8 +4475,8 @@ findFirstRetry:
 
 			psrch_inf->entries_in_buffer =
 					le16_to_cpu(parms->SearchCount);
-			psrch_inf->index_of_last_entry = 2 /* skip . and .. */ +
-				psrch_inf->entries_in_buffer;
+			psrch_inf->index_of_last_entry =
+					psrch_inf->entries_in_buffer;
 			lnoff = le16_to_cpu(parms->LastNameOffset);
 			if (CIFSMaxBufSize < lnoff) {
 				cifs_dbg(VFS, "ignoring corrupt resume name\n");
diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index 8eaf20a..ab0639a 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -698,9 +698,26 @@ static int cifs_filldir(char *find_entry, struct file *file,
 		return -EINVAL;
 	}
 
-	/* skip . and .. since we added them first */
-	if (cifs_entry_is_dot(&de, file_info->srch_inf.unicode))
+	if (cifs_entry_is_dot(&de, file_info->srch_inf.unicode) == 1) {
+		if (file_info->srch_inf.gotdot == true)
+			return -EINVAL;
+		if (!dir_emit_dot(file, ctx)) {
+			cifs_dbg(VFS, "Filldir for current dir failed\n");
+			return -ENOMEM;
+		}
+		file_info->srch_inf.gotdot = true;
+		return 0;
+	}
+	if (cifs_entry_is_dot(&de, file_info->srch_inf.unicode) == 2) {
+		if (file_info->srch_inf.gotdotdot == true)
+			return -EINVAL;
+		if (!dir_emit_dotdot(file, ctx)) {
+			cifs_dbg(VFS, "Filldir for parent dir failed\n");
+			return -ENOMEM;
+		}
+		file_info->srch_inf.gotdotdot = true;
 		return 0;
+	}
 
 	if (file_info->srch_inf.unicode) {
 		struct nls_table *nlt = cifs_sb->local_nls;
@@ -786,9 +803,6 @@ int cifs_readdir(struct file *file, struct dir_context *ctx)
 			goto rddir2_exit;
 	}
 
-	if (!dir_emit_dots(file, ctx))
-		goto rddir2_exit;
-
 	/* 1) If search is active,
 		is in current search buffer?
 		if it before then restart search
@@ -864,6 +878,25 @@ int cifs_readdir(struct file *file, struct dir_context *ctx)
 	kfree(tmp_buf);
 
 rddir2_exit:
+	if (cifsFile->srch_inf.endOfSearch) {
+		if (cifsFile->srch_inf.gotdot != true) {
+			if (!dir_emit_dot(file, ctx)) {
+				cifs_dbg(VFS,
+					"Filldir for current dir failed\n");
+				rc = -ENOMEM;
+			}
+			ctx->pos++;
+		}
+
+		if (cifsFile->srch_inf.gotdotdot != true) {
+			if (!dir_emit_dotdot(file, ctx)) {
+				cifs_dbg(VFS,
+					"Filldir for parent dir failed\n");
+				rc = -ENOMEM;
+			}
+			ctx->pos++;
+		}
+	}
 	free_xid(xid);
 	return rc;
 }
-- 
1.7.11-rc0