FAILED: patch "[PATCH] cifs: destage dirty pages before re-reading them for" failed to apply to 4.14-stable tree

The patch below does not apply to the 4.14-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 <[email protected]>.

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 <[email protected]>
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.

index 6f38b134a346..7d756721e1a6 100644
@@ -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);