[PATCH 5.19 017/717] cifs: destage dirty pages before re-reading them for cache=none

Greg Kroah-Hartman
2022-10-22T07:34:58Z

From: Ronnie Sahlberg <lsahlber@redhat.com>

commit bb44c31cdcac107344dd2fcc3bd0504a53575c51 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/cifs/file.c | 9 +++++++++
1 file changed, 9 insertions(+)

--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4024,6 +4024,15 @@ 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);