From: Badari Pulavarty Subject: Re: pagefault in generic_file_buffered_write() causing deadlock Date: Wed, 15 Nov 2006 10:20:43 -0800 Message-ID: <455B5A7B.6010807@us.ibm.com> References: <1163606265.7662.8.camel@dyn9047017100.beaverton.ibm.com> <20061115090005.c9ec6db5.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-mm , ext4 , lkml Return-path: Received: from e6.ny.us.ibm.com ([32.97.182.146]:37609 "EHLO e6.ny.us.ibm.com") by vger.kernel.org with ESMTP id S1030799AbWKOSUr (ORCPT ); Wed, 15 Nov 2006 13:20:47 -0500 To: Andrew Morton In-Reply-To: <20061115090005.c9ec6db5.akpm@osdl.org> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Andrew Morton wrote: > On Wed, 15 Nov 2006 07:57:45 -0800 > Badari Pulavarty wrote: > > >> We are looking at a customer situation (on 2.6.16-based distro) - where >> system becomes almost useless while running some java & stress tests. >> >> Root cause seems to be taking a pagefault in generic_file_buffered_write >> () after calling prepare_write. I am wondering >> >> 1) Why & How this can happen - since we made sure to fault the user >> buffer before prepare write. >> > > When using writev() we only fault in the first segment of the iovec. If > the second or succesive segment isn't mapped into pagetables we're > vulnerable to the deadlock. > > Hmm.. Not it :( Its coming from write() not writev(). [C00000002ABBF290] [C00000000039D58C] .do_page_fault+0x2e4/0x75c [C00000002ABBF460] [C000000000004860] .handle_page_fault+0x20/0x54 --- Exception: 301 at .__copy_tofrom_user+0x11c/0x580 LR = .generic_file_buffered_write+0x39c/0x7c8 [C00000002ABBF750] [C000000000095A94] .generic_file_buffered_write+0x2c0/0x7c8 ( unreliable) [C00000002ABBF8F0] [C0000000000962EC] .__generic_file_aio_write_nolock+0x350/0x3 e0 [C00000002ABBFA20] [C000000000096908] .generic_file_aio_write+0x78/0x104 [C00000002ABBFAE0] [C0000000001649F0] .ext3_file_write+0x2c/0xd4 [C00000002ABBFB70] [C0000000000C5168] .do_sync_write+0xd4/0x130 [C00000002ABBFCF0] [C0000000000C5ED4] .vfs_write+0x128/0x20c [C00000002ABBFD90] [C0000000000C664C] .sys_write+0x4c/0x8c [C00000002ABBFE30] [C00000000000871C] syscall_exit+0x0/0x40 Thanks, Badari