NFS: Fix an I/O request leakage in nfs_do_recoalesce

BugLink: https://bugs.launchpad.net/bugs/1822271

commit 4d91969e upstream.

Whether we need to exit early, or just reprocess the list, we
must not lost track of the request which failed to get recoalesced.

Fixes: 03d5eb65 ("NFS: Fix a memory leak in nfs_do_recoalesce")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: stable@vger.kernel.org # v4.0+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/nfs/pagelist.c

@@ -1115,7 +1115,6 @@ static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
 			struct nfs_page *req;
 
 			req = list_first_entry(&head, struct nfs_page, wb_list);
-			nfs_list_remove_request(req);
 			if (__nfs_pageio_add_request(desc, req))
 				continue;
 			if (desc->pg_error < 0) {