From mboxrd@z Thu Jan 1 00:00:00 1970 In-reply-to: (message from Miklos Szeredi on Wed, 07 May 2008 22:34:38 +0200) Subject: Re: NFS infinite loop in filemap_fault() References: Message-Id: From: Miklos Szeredi Date: Thu, 08 May 2008 08:47:09 +0200 Sender: owner-linux-mm@kvack.org Return-Path: To: trond.myklebust@fys.uio.no, npiggin@suse.de Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org List-ID: > Page fault on NFS apparently goes into an infinite loop if the read on > the server fails. > > I don't understand the NFS readpage code, but the filemap_fault() code > looks somewhat suspicious: > > /* > * Umm, take care of errors if the page isn't up-to-date. > * Try to re-read it _once_. We do this synchronously, > * because there really aren't any performance issues here > * and we need to check for errors. > */ > ClearPageError(page); > error = mapping->a_ops->readpage(file, page); > page_cache_release(page); > > if (!error || error == AOP_TRUNCATED_PAGE) > goto retry_find; > > The comment doesn't seem to match what the it actually does: if > ->readpage() is asynchronous, then this will just repeat everything, > without any guarantee that it will re-read once. This patch fixes it. It's probably wrong in some subtle way though... Miklos --- mm/filemap.c | 6 ++++++ 1 file changed, 6 insertions(+) Index: linux.git/mm/filemap.c =================================================================== --- linux.git.orig/mm/filemap.c 2008-05-08 08:17:22.000000000 +0200 +++ linux.git/mm/filemap.c 2008-05-08 08:19:59.000000000 +0200 @@ -1461,6 +1461,12 @@ page_not_uptodate: */ ClearPageError(page); error = mapping->a_ops->readpage(file, page); + if (!error && !PageUptodate(page)) { + lock_page(page); + if (!PageUptodate(page)) + error = -EIO; + unlock_page(page); + } page_cache_release(page); if (!error || error == AOP_TRUNCATED_PAGE) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org