linux-ext4 - Re: [PATCH] ext4: limit the number of blocks in one ADD

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Date:   Tue, 7 Sep 2021 19:21:31 +0800
From:   Hou Tao <houtao1@...wei.com>
To:     <tytso@....edu>, <adilger.kernel@...ger.ca>,
        <harshadshirwadkar@...il.com>
CC:     <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: limit the number of blocks in one ADD_RANGE TLV

ping ?

On 8/30/2021 3:52 PM, Hou Tao wrote:
> ping ?
>
> On 8/20/2021 12:45 PM, Hou Tao wrote:
>> Now EXT4_FC_TAG_ADD_RANGE uses ext4_extent to track the
>> newly-added blocks, but the limit on the max value of
>> ee_len field is ignored, and it can lead to BUG_ON as
>> shown below when running command "fallocate -l 128M file"
>> on a fast_commit-enabled fs:
>>
>>   kernel BUG at fs/ext4/ext4_extents.h:199!
>>   invalid opcode: 0000 [#1] SMP PTI
>>   CPU: 3 PID: 624 Comm: fallocate Not tainted 5.14.0-rc6+ #1
>>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
>>   RIP: 0010:ext4_fc_write_inode_data+0x1f3/0x200
>>   Call Trace:
>>    ? ext4_fc_write_inode+0xf2/0x150
>>    ext4_fc_commit+0x93b/0xa00
>>    ? ext4_fallocate+0x1ad/0x10d0
>>    ext4_sync_file+0x157/0x340
>>    ? ext4_sync_file+0x157/0x340
>>    vfs_fsync_range+0x49/0x80
>>    do_fsync+0x3d/0x70
>>    __x64_sys_fsync+0x14/0x20
>>    do_syscall_64+0x3b/0xc0
>>    entry_SYSCALL_64_after_hwframe+0x44/0xae
>>
>> Simply fixing it by limiting the number of blocks
>> in one EXT4_FC_TAG_ADD_RANGE TLV.
>>
>> Fixes: aa75f4d3daae ("ext4: main fast-commit commit path")
>> Signed-off-by: Hou Tao <houtao1@...wei.com>
>> ---
>>  fs/ext4/fast_commit.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
>> index e8195229c252..782d05a3f97a 100644
>> --- a/fs/ext4/fast_commit.c
>> +++ b/fs/ext4/fast_commit.c
>> @@ -893,6 +893,12 @@ static int ext4_fc_write_inode_data(struct inode *inode, u32 *crc)
>>  					    sizeof(lrange), (u8 *)&lrange, crc))
>>  				return -ENOSPC;
>>  		} else {
>> +			unsigned int max = (map.m_flags & EXT4_MAP_UNWRITTEN) ?
>> +				EXT_UNWRITTEN_MAX_LEN : EXT_INIT_MAX_LEN;
>> +
>> +			/* Limit the number of blocks in one extent */
>> +			map.m_len = min(max, map.m_len);
>> +
>>  			fc_ext.fc_ino = cpu_to_le32(inode->i_ino);
>>  			ex = (struct ext4_extent *)&fc_ext.fc_ex;
>>  			ex->ee_block = cpu_to_le32(map.m_lblk);
> .