From: Ronnie Sahlberg <lsahlber@redhat.com>
Date: Fri, 19 Jul 2019 08:12:11 +1000
Subject: [PATCH] cifs: flush before set-info if we have writeable handles
Git-commit: aa081859b10c5d8b19f5c525c78883a59d73c2b8
Patch-mainline: v5.3-rc1
References: bsc#1144333

Servers can defer destaging any data and updating the mtime until close().
This means that if we do a setinfo to modify the mtime while other handles
are open for write the server may overwrite our setinfo timestamps when
if flushes the file on close() of the writeable handle.

To solve this we add an explicit flush when the mtime is about to
be updated.

This fixes "cp -p" to preserve mtime when copying a file onto an SMB2 share.

CC: Stable <stable@vger.kernel.org>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Acked-by: Paulo Alcantara <palcantara@suse.de>
---
 fs/cifs/inode.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 1bffe029fb66..56ca4b8ccaba 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -2406,6 +2406,8 @@ cifs_setattr_nounix(struct dentry *direntry, struct iattr *attrs)
 	struct inode *inode = d_inode(direntry);
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 	struct cifsInodeInfo *cifsInode = CIFS_I(inode);
+	struct cifsFileInfo *wfile;
+	struct cifs_tcon *tcon;
 	char *full_path = NULL;
 	int rc = -EACCES;
 	__u32 dosattr = 0;
@@ -2452,6 +2454,20 @@ cifs_setattr_nounix(struct dentry *direntry, struct iattr *attrs)
 	mapping_set_error(inode->i_mapping, rc);
 	rc = 0;
 
+	if (attrs->ia_valid & ATTR_MTIME) {
+		rc = cifs_get_writable_file(cifsInode, false, &wfile);
+		if (!rc) {
+			tcon = tlink_tcon(wfile->tlink);
+			rc = tcon->ses->server->ops->flush(xid, tcon, &wfile->fid);
+			cifsFileInfo_put(wfile);
+			if (rc)
+				return rc;
+		} else if (rc != -EBADF)
+			return rc;
+		else
+			rc = 0;
+	}
+
 	if (attrs->ia_valid & ATTR_SIZE) {
 		rc = cifs_set_file_size(inode, attrs, xid, full_path);
 		if (rc != 0)
-- 
2.22.0