From: Lukas Czerner Subject: Re: [PATCH] ext4: Fix max file size of extent format file Date: Fri, 3 Jun 2011 20:08:03 +0200 (CEST) Message-ID: References: <4DCA4406.4030601@sx.jp.nec.com>

Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Lukas Czerner , Theodore Tso , Kazuya Mio , ext4 To: Andreas Dilger Return-path: Received: from mx1.redhat.com ([209.132.183.28]:32448 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754205Ab1FCSIN (ORCPT ); Fri, 3 Jun 2011 14:08:13 -0400 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, 3 Jun 2011, Andreas Dilger wrote: > On 2011-05-13, at 12:34 AM, Lukas Czerner wrote: > > On Wed, 11 May 2011, Kazuya Mio wrote: > >> We hit BUG_ON in ext4_ext_put_gap_in_cache() while creating a file > >> whose size is the max file size of extent format. Because the extent cache > >> length is 0 when we allocate two blocks to the file offset 2^32-2, and then > >> the offset 2^32-1. To fix it, we decrease the max file size to > >> (2^32-2)*blocksize. In this way, we would be able to allocate a block up to > >> the offset 2^32-2. I think there is no data loss because we can read all files > >> created before applying this patch. > >> > >> How to reproduce: > >> I'm running 2.6.39-rc6. Note that i386 architecture and 4KB blocksize cannot > >> reproduce this problem. > >> > >> # dd if=/dev/zero of=/mnt/mp1/file bs= count=1 seek=$((2**32-2)) > >> # sync > >> # dd if=/dev/zero of=/mnt/mp1/file bs= count=1 seek=$((2**32-1)) > > > > Hi Kazuya, > > > > Thanks for the patch, however I think that there is a better solution > > than lowering the max file size, which is not necessary. I would rather > > fix ext4_ext_put_gap_in_cache() and allow to invalidate the cache by > > setting the length to zero. > > > > Please see the following patch, if it works for you. > > This thread has stalled. Until we can come up with a better fix, I think > we should land Kazuya's patch for the current merge window and then worry > about allocating that last 4kB at the end of the 16TB file later (2.3e-6% > of the file :-). Wait just a sec, I am testing new version of my patch. I have tried and failed with my approach. It seems that there is no way to do that without also changing the struct ext4_ext_cache and other structures, resulting in different on-disk format. So I think that Kazuyas fix is good after all, however there is unconsistency in using EXT_MAX_BLOCK and in comments as well. So I fixed that as well. Also I hit another bug, while testing this change so I'll send both as a series shortly. Thanks! -Lukas > > >> Signed-off-by: Kazuya Mio > >> --- > >> fs/ext4/super.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> diff --git a/fs/ext4/super.c b/fs/ext4/super.c > >> index 8553dfb..fce0249 100644 > >> --- a/fs/ext4/super.c > >> +++ b/fs/ext4/super.c > >> @@ -2248,8 +2248,8 @@ static loff_t ext4_max_size(int blkbits, int has_huge_files) > >> > >> /* 32-bit extent-start container, ee_block */ > >> res = 1LL << 32; > >> - res <<= blkbits; > >> res -= 1; > >> + res <<= blkbits; > >> > >> /* Sanity check against vm- & vfs- imposed limits */ > >> if (res > upper_limit) > >> > >> -- > >> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > >> the body of a message to majordomo@vger.kernel.org > >> More majordomo info at http://vger.kernel.org/majordomo-info.html > >> > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > Cheers, Andreas > > > > > > --