nfs: no PG_private waiters remain, remove waker

Since commit 4f52b6b ("NFS: Don't call COMMIT in ->releasepage()"),
no tasks wait on PagePrivate.

Thus the wake introduced in commit 9590544 ("NFS: avoid deadlocks
with loop-back mounted NFS filesystems.") can be removed.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Nicholas Piggin <[email protected]>
Cc: Trond Myklebust <[email protected]>
Cc: Anna Schumaker <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: npiggin

fs/nfs/write.c

@@ -728,8 +728,6 @@ static void nfs_inode_remove_request(struct nfs_page *req)
 		if (likely(head->wb_page && !PageSwapCache(head->wb_page))) {
 			set_page_private(head->wb_page, 0);
 			ClearPagePrivate(head->wb_page);
-			smp_mb__after_atomic();
-			wake_up_page(head->wb_page, PG_private);
 			clear_bit(PG_MAPPED, &head->wb_flags);
 		}
 		nfsi->nrequests--;