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 6f38b134a346851bb07fe72653571680211ff7e0..7d756721e1a68b0459c27efdfc29fd26e67b7522 100644 (file)
--- 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);