From mboxrd@z Thu Jan 1 00:00:00 1970 From: KOSAKI Motohiro Subject: [RFC][PATCH v3 5/6] don't use bio-map in read() path Date: Tue, 14 Apr 2009 15:21:51 +0900 (JST) Message-ID: <20090414152020.C656.A69D9226@jp.fujitsu.com> References: <20090414151204.C647.A69D9226@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Cc: kosaki.motohiro@jp.fujitsu.com, Linus Torvalds , Andrew Morton , Nick Piggin , Andrea Arcangeli , Jeff Moyer , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, FUJITA Tomonori , Jens Axboe , James Bottomley To: LKML Return-path: Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:43296 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751263AbZDNGVz (ORCPT ); Tue, 14 Apr 2009 02:21:55 -0400 In-Reply-To: <20090414151204.C647.A69D9226@jp.fujitsu.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Who know proper fixing way? ================= Subject: [Untested][RFC][PATCH] don't use bio-map in read() path __bio_map_user_iov() has wrong usage of get_user_pages_fast(). it doesn't have prevent fork mechanism. then, it sould be used read-side (memory to device transfer) gup only. This patch is obviously temporally fix. we can implement fork safe bio_map_user() the future... Signed-off-by: KOSAKI Motohiro Cc: FUJITA Tomonori Cc: Jens Axboe Cc: James Bottomley --- block/blk-map.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) Index: b/block/blk-map.c =================================================================== --- a/block/blk-map.c 2009-02-21 16:53:21.000000000 +0900 +++ b/block/blk-map.c 2009-04-12 23:36:32.000000000 +0900 @@ -55,7 +55,7 @@ static int __blk_rq_map_user(struct requ * direct dma. else, set up kernel bounce buffers */ uaddr = (unsigned long) ubuf; - if (blk_rq_aligned(q, ubuf, len) && !map_data) + if (blk_rq_aligned(q, ubuf, len) && !map_data && !reading) bio = bio_map_user(q, NULL, uaddr, len, reading, gfp_mask); else bio = bio_copy_user(q, map_data, uaddr, len, reading, gfp_mask); @@ -208,7 +208,7 @@ int blk_rq_map_user_iov(struct request_q } } - if (unaligned || (q->dma_pad_mask & len) || map_data) + if (unaligned || (q->dma_pad_mask & len) || map_data || read) bio = bio_copy_user_iov(q, map_data, iov, iov_count, read, gfp_mask); else