[PATCH] cifs: use discard iterator to discard unneeded network data more efficiently

Steve French
2021-02-04T06:26:11Z

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(cleanup patch, to make netfs merge easier)

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>
---
fs/cifs/cifsproto.h | 2 ++
fs/cifs/cifssmb.c | 6 +++---
fs/cifs/connect.c | 10 ++++++++++
3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 32f7a013402e..75ce6f742b8d 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -232,6 +232,8 @@ 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 0496934feecb..c279527aae92 100644
--- 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 10fe6d6d2dee..943f4eba027d 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -564,6 +564,16 @@ 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(&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)

--
Thanks,

Steve

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From c3a4621f56db8038b19844fa9d5f3951afaac4fd Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Thu, 4 Feb 2021 00:15:21 -0600
Subject: [PATCH] cifs: use discard iterator to discard unneeded network data
more efficiently

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>
---
fs/cifs/cifsproto.h | 2 ++
fs/cifs/cifssmb.c | 6 +++---
fs/cifs/connect.c | 10 ++++++++++
3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 32f7a013402e..75ce6f742b8d 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -232,6 +232,8 @@ 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 0496934feecb..c279527aae92 100644
--- 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 10fe6d6d2dee..943f4eba027d 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -564,6 +564,16 @@ cifs_read_from_socket(struct TCP_Server_Info *server, char *buf,