FAILED: patch "[PATCH] cifs: destage dirty pages before re-reading them for" failed to apply to 4.19-stable tree

FAILED: patch "[PATCH] cifs: destage dirty pages before re-reading them for" failed to apply to 4.19-stable tree

[gregkh]

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

Possible dependencies:

bb44c31cdcac ("cifs: destage dirty pages before re-reading them for cache=none")
6e6e2b86c29c ("CIFS: Add support for direct I/O read")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From bb44c31cdcac107344dd2fcc3bd0504a53575c51 Mon Sep 17 00:00:00 2001
From: Ronnie Sahlberg <lsahlber@redhat.com>
Date: Tue, 20 Sep 2022 14:32:02 +1000
Subject: [PATCH] cifs: destage dirty pages before re-reading them for
 cache=none

This is the opposite case of kernel bugzilla 216301.
If we mmap a file using cache=none and then proceed to update the mmapped
area these updates are not reflected in a later pread() of that part of the
file.
To fix this we must first destage any dirty pages in the range before
we allow the pread() to proceed.

Cc: stable@vger.kernel.org
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Reviewed-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 6f38b134a346..7d756721e1a6 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4271,6 +4271,15 @@ static ssize_t __cifs_readv(
 		len = ctx->len;
 	}
 
+	if (direct) {
+		rc = filemap_write_and_wait_range(file->f_inode->i_mapping,
+						  offset, offset + len - 1);
+		if (rc) {
+			kref_put(&ctx->refcount, cifs_aio_ctx_release);
+			return -EAGAIN;
+		}
+	}
+
 	/* grab a lock here due to read response handlers can access ctx */
 	mutex_lock(&ctx->aio_mutex);