cifs: wait for writeback to complete in cifs_flush

The f_op->flush operation is the last chance to return a writeback
related error when closing a file. Ensure that we don't miss reporting
any errors by waiting for writeback to complete in cifs_flush before
proceeding.

There's no reason to do this when the file isn't open for write
however.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: David Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 7 insertions, 14 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index baf4b5067ff9..128e07b85d6c 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1688,20 +1688,13 @@ int cifs_flush(struct file *file, fl_owner_t id)
         struct inode *inode = file->f_path.dentry->d_inode;
         int rc = 0;
 
-        /* Rather than do the steps manually:
-           lock the inode for writing
-           loop through pages looking for write behind data (dirty pages)
-           coalesce into contiguous 16K (or smaller) chunks to write to server
-           send to server (prefer in parallel)
-           deal with writebehind errors
-           unlock inode for writing
-           filemapfdatawrite appears easier for the time being */
-
-        rc = filemap_fdatawrite(inode->i_mapping);
-        /* reset wb rc if we were able to write out dirty pages */
-        if (!rc) {
-                rc = CIFS_I(inode)->write_behind_rc;
-                CIFS_I(inode)->write_behind_rc = 0;
+        if (file->f_mode & FMODE_WRITE) {
+                rc = filemap_write_and_wait(inode->i_mapping);
+                /* reset wb rc if we were able to write out dirty pages */
+                if (!rc) {
+                        rc = CIFS_I(inode)->write_behind_rc;
+                        CIFS_I(inode)->write_behind_rc = 0;
+                }
         }
 
         cFYI(1, "Flush inode %p file %p rc %d", inode, file, rc);