From 9b7af89ee823b2a95c2d1dd7ca70b02d8ce792d7 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Mon, 24 Feb 2020 17:37:39 -0600
Subject: [PATCH] smb3: fix performance regression with setting mtime
Patch-mainline: Not yet, in for-next branch
References: bsc#1144333

There are cases when we don't want to send the SMB2 flush operation
(e.g. when user specifies mount parm "nostrictsync") and it can be
a very expensive operation on the server.  In most cases in order
to set mtime, we simply need to flush (write) the dirtry pages from
the client and send the writes to the server not also send a flush
protocol operation to the server.

Fixes: aa081859b10c ("cifs: flush before set-info if we have writeable handles")
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Acked-by: Paulo Alcantara <palcantara@suse.de>
---
 fs/cifs/inode.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index aad7d2cad9a0..e6d66977a81d 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -2528,25 +2528,26 @@ cifs_setattr_nounix(struct dentry *direntry, struct iattr *attrs)
 
 	/*
 	 * Attempt to flush data before changing attributes. We need to do
-	 * this for ATTR_SIZE and ATTR_MTIME for sure, and if we change the
-	 * ownership or mode then we may also need to do this. Here, we take
-	 * the safe way out and just do the flush on all setattr requests. If
-	 * the flush returns error, store it to report later and continue.
+	 * this for ATTR_SIZE and ATTR_MTIME.  If the flush of the data
+	 * returns error, store it to report later and continue.
 	 *
 	 * BB: This should be smarter. Why bother flushing pages that
 	 * will be truncated anyway? Also, should we error out here if
-	 * the flush returns error?
+	 * the flush returns error? Do we need to check for ATTR_MTIME_SET flag?
 	 */
-	rc = filemap_write_and_wait(inode->i_mapping);
-	if (is_interrupt_error(rc)) {
-		rc = -ERESTARTSYS;
-		goto cifs_setattr_exit;
+	if (attrs->ia_valid & (ATTR_MTIME | ATTR_SIZE | ATTR_CTIME)) {
+		rc = filemap_write_and_wait(inode->i_mapping);
+		if (is_interrupt_error(rc)) {
+			rc = -ERESTARTSYS;
+			goto cifs_setattr_exit;
+		}
+		mapping_set_error(inode->i_mapping, rc);
 	}
 
-	mapping_set_error(inode->i_mapping, rc);
 	rc = 0;
 
-	if (attrs->ia_valid & ATTR_MTIME) {
+	if ((attrs->ia_valid & ATTR_MTIME) &&
+	    !(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOSSYNC)) {
 		rc = cifs_get_writable_file(cifsInode, FIND_WR_ANY, &wfile);
 		if (!rc) {
 			tcon = tlink_tcon(wfile->tlink);
-- 
2.25.1