From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tao Ma Subject: Re: [PATCH v2] ext4: Fix a kernel panic in mb_mark_used during trim. Date: Wed, 16 Mar 2011 23:20:01 +0800 Message-ID: <4D80D521.8050506@tao.ma> References: <1299160774-2337-1-git-send-email-tm@tao.ma> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Lukas Czerner , Theodore Ts'o To: linux-ext4@vger.kernel.org Return-path: Received: from cpoproxy3-pub.bluehost.com ([67.222.54.6]:56975 "HELO cpoproxy3-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752102Ab1CPPUT (ORCPT ); Wed, 16 Mar 2011 11:20:19 -0400 In-Reply-To: <1299160774-2337-1-git-send-email-tm@tao.ma> Sender: linux-ext4-owner@vger.kernel.org List-ID: Hi Ted, This is a fix for kernel panic in ext4. So any comment for it? Regards, Tao On 03/03/2011 09:59 PM, Tao Ma wrote: > From: Tao Ma > > In a bs=4096 volume, if we call FITRIM with the following parameter as > fstrim_range(start = 102400, len = 134144000, minlen = 10240), > we will trigger a BUG_ON. > BUG_ON(start + len > (e4b->bd_sb->s_blocksize << 3)); > > Mar 4 00:55:52 boyu-tm kernel: ------------[ cut here ]------------ > Mar 4 00:55:52 boyu-tm kernel: kernel BUG at fs/ext4/mballoc.c:1506! > Mar 4 01:21:09 boyu-tm kernel: Code: d4 00 00 00 00 49 89 fe 8b 56 0c 44 8b 7e 04 89 55 c4 48 8b 4f 28 89 d6 44 01 fe 48 63 d6 48 8b 41 18 48 c1 e0 03 48 39 c2 76 04 <0f> 0b eb fe 48 8b 55 b0 8b 47 34 3b 42 08 74 04 0f 0b eb fe 48 > Mar 4 01:21:09 boyu-tm kernel: RIP [] mb_mark_used+0x47/0x26c [ext4] > Mar 4 01:21:09 boyu-tm kernel: RSP > Mar 4 01:21:09 boyu-tm kernel: ---[ end trace 9f461696f6a9dcf2 ]--- > > The reason is that in ext4_trim_fs, the last_block is checked wrongly. > if (len >= EXT4_BLOCKS_PER_GROUP(sb)) > len -= (EXT4_BLOCKS_PER_GROUP(sb) - first_block); > else > last_block = first_block + len; > > So if len < EXT4_BLOCKS_PER_GROUP while first_block + len > EXT4_BLOCKS_PER_GROUP, > last_block will be set to a overflow value which exceeds EXT4_BLOCKS_PER_GROUP. > > This patch fixes it and adjusts len accordingly. > > Cc: Lukas Czerner > Cc: "Theodore Ts'o" > Signed-off-by: Tao Ma > --- > fs/ext4/mballoc.c | 11 ++++++++--- > 1 files changed, 8 insertions(+), 3 deletions(-) > > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c > index 29d7d17..290b36c 100644 > --- a/fs/ext4/mballoc.c > +++ b/fs/ext4/mballoc.c > @@ -4889,10 +4889,15 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range) > break; > } > > - if (len >= EXT4_BLOCKS_PER_GROUP(sb)) > - len -= (EXT4_BLOCKS_PER_GROUP(sb) - first_block); > - else > + /* > + * For all the groups except the last one, last block will > + * always be EXT4_BLOCKS_PER_GROUP(sb), so we only need to > + * change it for the last group in which case start + > + * len < EXT4_BLOCKS_PER_GROUP(sb). > + */ > + if (first_block + len < EXT4_BLOCKS_PER_GROUP(sb)) > last_block = first_block + len; > + len -= last_block - first_block; > > if (e4b.bd_info->bb_free >= minlen) { > cnt = ext4_trim_all_free(sb, &e4b, first_block,