NFS: Ensure that nfs_wb_page() waits for Pg_writeback to clear

Neil Brown reports that he is seeing the BUG_ON(ret == 0) trigger in
nfs_page_async_flush. According to the trace in
     https://bugzilla.novell.com/show_bug.cgi?id=599628
the problem appears to be due to nfs_wb_page() not waiting for the
PG_writeback flag to clear.

There is a ditto problem in nfs_wb_page_cancel()

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index ccde2ae..3aea3ca 100644 (file)
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1472,6 +1472,7 @@ int nfs_wb_page_cancel(struct inode *inode, struct page *page)
 
        BUG_ON(!PageLocked(page));
        for (;;) {
+               wait_on_page_writeback(page);
                req = nfs_page_find_request(page);
                if (req == NULL)
                        break;
@@ -1506,30 +1507,18 @@ int nfs_wb_page(struct inode *inode, struct page *page)
                .range_start = range_start,
                .range_end = range_end,
        };
-       struct nfs_page *req;
-       int need_commit;
        int ret;
 
        while(PagePrivate(page)) {
+               wait_on_page_writeback(page);
                if (clear_page_dirty_for_io(page)) {
                        ret = nfs_writepage_locked(page, &wbc);
                        if (ret < 0)
                                goto out_error;
                }
-               req = nfs_find_and_lock_request(page);
-               if (!req)
-                       break;
-               if (IS_ERR(req)) {
-                       ret = PTR_ERR(req);
+               ret = sync_inode(inode, &wbc);
+               if (ret < 0)
                        goto out_error;
-               }
-               need_commit = test_bit(PG_CLEAN, &req->wb_flags);
-               nfs_clear_page_tag_locked(req);
-               if (need_commit) {
-                       ret = nfs_commit_inode(inode, FLUSH_SYNC);
-                       if (ret < 0)
-                               goto out_error;
-               }
        }
        return 0;
 out_error: