cifs: use discard iterator to discard unneeded network data more efficiently

[ Upstream commit cf0604a686b11175d8beae60281c4ccc95aaa5c2 ]

The iterator, ITER_DISCARD, that can only be used in READ mode and
just discards any data copied to it, was added to allow a network
filesystem to discard any unwanted data sent by a server.
Convert cifs_discard_from_socket() to use this.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Stable-dep-of: bedc8f76b353 ("cifs: always initialize struct msghdr smb_msg completely")
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 24c6f36177bac396e9271f13f5a250fbec68f641..a6ca4eda9a5ae062e59ca801d2161fac8ad64320 100644 (file)
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -230,6 +230,8 @@ extern unsigned int setup_special_user_owner_ACE(struct cifs_ace *pace);
 extern void dequeue_mid(struct mid_q_entry *mid, bool malformed);
 extern int cifs_read_from_socket(struct TCP_Server_Info *server, char *buf,
                                 unsigned int to_read);
+extern ssize_t cifs_discard_from_socket(struct TCP_Server_Info *server,
+                                       size_t to_read);
 extern int cifs_read_page_from_socket(struct TCP_Server_Info *server,
                                        struct page *page,
                                        unsigned int page_offset,

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 0496934feecb777b6a7ae53a00003278f23517ea..c279527aae92d382af7ac5aa1c3a718e2d7f8306 100644 (file)
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -1451,9 +1451,9 @@ cifs_discard_remaining_data(struct TCP_Server_Info *server)
        while (remaining > 0) {
                int length;
 
-               length = cifs_read_from_socket(server, server->bigbuf,
-                               min_t(unsigned int, remaining,
-                                   CIFSMaxBufSize + MAX_HEADER_SIZE(server)));
+               length = cifs_discard_from_socket(server,
+                               min_t(size_t, remaining,
+                                     CIFSMaxBufSize + MAX_HEADER_SIZE(server)));
                if (length < 0)
                        return length;
                server->total_read += length;

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 7f5d173760cfc745245ef707011e38edc751c38a..6e7d5b9e84b8ffa6b89bd140c8f74455e0357807 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -755,6 +755,23 @@ cifs_read_from_socket(struct TCP_Server_Info *server, char *buf,
        return cifs_readv_from_socket(server, &smb_msg);
 }
 
+ssize_t
+cifs_discard_from_socket(struct TCP_Server_Info *server, size_t to_read)
+{
+       struct msghdr smb_msg;
+
+       /*
+        *  iov_iter_discard already sets smb_msg.type and count and iov_offset
+        *  and cifs_readv_from_socket sets msg_control and msg_controllen
+        *  so little to initialize in struct msghdr
+        */
+       smb_msg.msg_name = NULL;
+       smb_msg.msg_namelen = 0;
+       iov_iter_discard(&smb_msg.msg_iter, READ, to_read);
+
+       return cifs_readv_from_socket(server, &smb_msg);
+}
+
 int
 cifs_read_page_from_socket(struct TCP_Server_Info *server, struct page *page,
        unsigned int page_offset, unsigned int to_read)