Commit 0522f6ad authored May 26, 2010 by Trond Myklebust

NFS: Fix another nfs_wb_page() deadlock



J.R. Okajima reports that the call to sync_inode() in nfs_wb_page() can
deadlock with other writeback flush calls. It boils down to the fact
that we cannot ever call writeback_single_inode() while holding a page
lock (even if we do set nr_to_write to zero) since another process may
already be waiting in the call to do_writepages(), and so will deny us
the I_SYNC lock.

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

parent c5efa5fc

fs/nfs/write.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -1518,14 +1518,17 @@ int nfs_wb_page(struct inode inode, struct page page)
		};
		int ret;

		while(PagePrivate(page)) {
		for (;;) {
		wait_on_page_writeback(page);
		if (clear_page_dirty_for_io(page)) {
		ret = nfs_writepage_locked(page, &wbc);
		if (ret < 0)
		goto out_error;
		continue;
		}
		ret = sync_inode(inode, &wbc);
		if (!PagePrivate(page))
		break;
		ret = nfs_commit_inode(inode, FLUSH_SYNC);
		if (ret < 0)
		goto out_error;
		}