From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3362921352; Thu, 4 Jan 2024 12:14:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.162.254]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4T5QVg3rS9z1Q6yM; Thu, 4 Jan 2024 20:14:03 +0800 (CST) Received: from dggpeml500021.china.huawei.com (unknown [7.185.36.21]) by mail.maildlp.com (Postfix) with ESMTPS id 2196F18001C; Thu, 4 Jan 2024 20:14:40 +0800 (CST) Received: from [10.174.177.174] (10.174.177.174) by dggpeml500021.china.huawei.com (7.185.36.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Thu, 4 Jan 2024 20:14:39 +0800 Message-ID: Date: Thu, 4 Jan 2024 20:14:39 +0800 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.1.2 Subject: Re: [PATCH v2 8/8] ext4: mark the group block bitmap as corrupted before reporting an error Content-Language: en-US To: Jan Kara CC: , , , , , , , , Baokun Li References: <20231221150558.2740823-1-libaokun1@huawei.com> <20231221150558.2740823-9-libaokun1@huawei.com> <20240104105151.3c2yrg3f3efiajgv@quack3> From: Baokun Li In-Reply-To: <20240104105151.3c2yrg3f3efiajgv@quack3> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpeml500021.china.huawei.com (7.185.36.21) On 2024/1/4 18:51, Jan Kara wrote: > On Thu 21-12-23 23:05:58, Baokun Li wrote: >> Otherwise unlocking the group in ext4_grp_locked_error may allow other >> processes to modify the core block bitmap that is known to be corrupt. >> >> Signed-off-by: Baokun Li > I'm not opposed but I don't think this matters much. > ext4_grp_locked_error() unlocks the group only in errors=remount-ro case > these days and in that case we abort the journal so none of the changes > should make it to disk anyway. Anyway, in the name of defensive programming > feel free to add: > > Reviewed-by: Jan Kara > > :) > > Honza Thank you very much for your review! Yes, the unlock gap here does not cause corrupted data to be written to disk, which is why no issues have been reported here before. My concern is that core block bitmap corruption may cause kernel crash in some corners. That's why inode bitmap corruption is not a concern here, since there is no core inode bitmap. We encounter all sorts of hard-to-replicate kernel problems every day, and hopefully by fixing these trivial little issues, we can reduce the number of difficult problems that arise from all sorts of coincidental stacking. Cheers!😊 >> --- >> fs/ext4/mballoc.c | 23 +++++++++++------------ >> 1 file changed, 11 insertions(+), 12 deletions(-) >> >> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c >> index b862ca2750fd..c43eefebdaa3 100644 >> --- a/fs/ext4/mballoc.c >> +++ b/fs/ext4/mballoc.c >> @@ -564,14 +564,14 @@ static void mb_free_blocks_double(struct inode *inode, struct ext4_buddy *e4b, >> >> blocknr = ext4_group_first_block_no(sb, e4b->bd_group); >> blocknr += EXT4_C2B(EXT4_SB(sb), first + i); >> + ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group, >> + EXT4_GROUP_INFO_BBITMAP_CORRUPT); >> ext4_grp_locked_error(sb, e4b->bd_group, >> inode ? inode->i_ino : 0, >> blocknr, >> "freeing block already freed " >> "(bit %u)", >> first + i); >> - ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group, >> - EXT4_GROUP_INFO_BBITMAP_CORRUPT); >> } >> mb_clear_bit(first + i, e4b->bd_info->bb_bitmap); >> } >> @@ -1926,14 +1926,13 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b, >> blocknr = ext4_group_first_block_no(sb, e4b->bd_group); >> blocknr += EXT4_C2B(sbi, block); >> if (!(sbi->s_mount_state & EXT4_FC_REPLAY)) { >> + ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group, >> + EXT4_GROUP_INFO_BBITMAP_CORRUPT); >> ext4_grp_locked_error(sb, e4b->bd_group, >> inode ? inode->i_ino : 0, >> blocknr, >> "freeing already freed block (bit %u); block bitmap corrupt.", >> block); >> - ext4_mark_group_bitmap_corrupted( >> - sb, e4b->bd_group, >> - EXT4_GROUP_INFO_BBITMAP_CORRUPT); >> } else { >> mb_regenerate_buddy(e4b); >> goto check; >> @@ -2410,12 +2409,12 @@ void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac, >> >> k = mb_find_next_zero_bit(buddy, max, 0); >> if (k >= max) { >> + ext4_mark_group_bitmap_corrupted(ac->ac_sb, >> + e4b->bd_group, >> + EXT4_GROUP_INFO_BBITMAP_CORRUPT); >> ext4_grp_locked_error(ac->ac_sb, e4b->bd_group, 0, 0, >> "%d free clusters of order %d. But found 0", >> grp->bb_counters[i], i); >> - ext4_mark_group_bitmap_corrupted(ac->ac_sb, >> - e4b->bd_group, >> - EXT4_GROUP_INFO_BBITMAP_CORRUPT); >> break; >> } >> ac->ac_found++; >> @@ -2466,12 +2465,12 @@ void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac, >> * free blocks even though group info says we >> * have free blocks >> */ >> + ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group, >> + EXT4_GROUP_INFO_BBITMAP_CORRUPT); >> ext4_grp_locked_error(sb, e4b->bd_group, 0, 0, >> "%d free clusters as per " >> "group info. But bitmap says 0", >> free); >> - ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group, >> - EXT4_GROUP_INFO_BBITMAP_CORRUPT); >> break; >> } >> >> @@ -2497,12 +2496,12 @@ void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac, >> if (WARN_ON(ex.fe_len <= 0)) >> break; >> if (free < ex.fe_len) { >> + ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group, >> + EXT4_GROUP_INFO_BBITMAP_CORRUPT); >> ext4_grp_locked_error(sb, e4b->bd_group, 0, 0, >> "%d free clusters as per " >> "group info. But got %d blocks", >> free, ex.fe_len); >> - ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group, >> - EXT4_GROUP_INFO_BBITMAP_CORRUPT); >> /* >> * The number of free blocks differs. This mostly >> * indicate that the bitmap is corrupt. So exit >> -- >> 2.31.1 >> >> Thanks! -- With Best Regards, Baokun Li .