cifs: track writepages in vfs operation counters

mainline inclusion
from mainline-v4.20-rc1
commit 0cb012d1a0a9ead759112da141698a2078fbf2ce
category: bugfix
bugzilla: 12058
CVE: NA

-------------------------------------------------

writepages and readpages operations did not call get/free_xid
so the statistics for file copy could get confusing with "vfs operations"
not increasing.  Add get_xid and free_xid to cifs readpages and
writepages functions.
Signed-off-by: NSteve French <stfrench@microsoft.com>
Reviewed-by: NRonnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: NZhangXiaoxu <zhangxiaoxu5@huawei.com>
Reviewed-by: Nzhengbin <zhengbin13@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/cifs/file.c

@@ -2118,6 +2118,7 @@ static int cifs_writepages(struct address_space *mapping,
 	pgoff_t end, index;
 	struct cifs_writedata *wdata;
 	int rc = 0;
+	unsigned int xid;
 
 	/*
 	 * If wsize is smaller than the page cache size, default to writing
@@ -2126,6 +2127,7 @@ static int cifs_writepages(struct address_space *mapping,
 	if (cifs_sb->wsize < PAGE_SIZE)
 		return generic_writepages(mapping, wbc);
 
+	xid = get_xid();
 	if (wbc->range_cyclic) {
 		index = mapping->writeback_index; /* Start from prev offset */
 		end = -1;
@@ -2219,6 +2221,7 @@ static int cifs_writepages(struct address_space *mapping,
 	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
 		mapping->writeback_index = index;
 
+	free_xid(xid);
 	return rc;
 }
 
@@ -3770,7 +3773,9 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 	struct cifs_sb_info *cifs_sb = CIFS_FILE_SB(file);
 	struct TCP_Server_Info *server;
 	pid_t pid;
+	unsigned int xid;
 
+	xid = get_xid();
 	/*
 	 * Reads as many pages as possible from fscache. Returns -ENOBUFS
 	 * immediately if the cookie is negative
@@ -3780,8 +3785,10 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 	 */
 	rc = cifs_readpages_from_fscache(mapping->host, mapping, page_list,
 					 &num_pages);
-	if (rc == 0)
+	if (rc == 0) {
+		free_xid(xid);
 		return rc;
+	}
 
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RWPIDFORWARD)
 		pid = open_file->pid;
@@ -3825,6 +3832,7 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 		 */
 		if (unlikely(rsize < PAGE_SIZE)) {
 			add_credits_and_wake_if(server, credits, 0);
+			free_xid(xid);
 			return 0;
 		}
 
@@ -3889,6 +3897,7 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
 	 * allocator.
 	 */
 	cifs_fscache_readpages_cancel(mapping->host, page_list);
+	free_xid(xid);
 	return rc;
 }