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SubjectRe: [f2fs-dev] [PATCH] f2fs: fix data corruption issue with hardware encryption
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On 2018/10/11 11:05, Jaegeuk Kim wrote:
> On 10/10, Jaegeuk Kim wrote:
>> On 10/11, Sahitya Tummala wrote:
>>> On Wed, Oct 10, 2018 at 02:34:02PM -0700, Jaegeuk Kim wrote:
>>>> On 10/10, Sahitya Tummala wrote:
>>>>> Direct IO can be used in case of hardware encryption. The following
>>>>> scenario results into data corruption issue in this path -
>>>>>
>>>>> Thread A - Thread B-
>>>>> -> write file#1 in direct IO
>>>>> -> GC gets kicked in
>>>>> -> GC submitted bio on meta mapping
>>>>> for file#1, but pending completion
>>>>> -> write file#1 again with new data
>>>>> in direct IO
>>>>> -> GC bio gets completed now
>>>>> -> GC writes old data to the new
>>>>> location and thus file#1 is
>>>>> corrupted.
>>>>>
>>>>> Fix this by submitting and waiting for pending io on meta mapping
>>>>> for direct IO case in f2fs_map_blocks().
>>>>>
>>>>> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
>>>>> ---
>>>>> fs/f2fs/data.c | 12 ++++++++++++
>>>>> 1 file changed, 12 insertions(+)
>>>>>
>>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>>>> index 9ef6f1f..7b2fef0 100644
>>>>> --- a/fs/f2fs/data.c
>>>>> +++ b/fs/f2fs/data.c
>>>>> @@ -1028,6 +1028,12 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
>>>>> map->m_pblk = ei.blk + pgofs - ei.fofs;
>>>>> map->m_len = min((pgoff_t)maxblocks, ei.fofs + ei.len - pgofs);
>>>>> map->m_flags = F2FS_MAP_MAPPED;
>>>>> + /* for HW encryption, but to avoid potential issue in future */
>>>>> + if (flag == F2FS_GET_BLOCK_DIO) {
>>>>> + blkaddr = map->m_pblk;
>>>>> + for (; blkaddr < map->m_pblk + map->m_len; blkaddr++)
>>>>> + f2fs_wait_on_block_writeback(sbi, blkaddr);
>>>>
>>>> Do we need this? IIRC, DIO would give create=1.
>>>
>>> Yes, we need it. When we are overwriting an existing file, DIO calls
>>> f2fs_map_blocks() with create=0. From the DIO code, I see that this happens
>>> because blockdev_direct_IO() passes this dio flag DIO_SKIP_HOLES. And then
>>> in get_more_blocks(), below code updates create=0, when we are overwriting
>>> an existing file.
>>>
>>> create = dio->op == REQ_OP_WRITE;
>>> if (dio->flags & DIO_SKIP_HOLES) {
>>> if (fs_startblk <= ((i_size_read(dio->inode) - 1) >>
>>> i_blkbits))
>>> create = 0;
>>> }
>>>
>>> ret = (*sdio->get_block)(dio->inode, fs_startblk,
>>> map_bh, create);
>>>
>>
>> Got it.
>> How about this?
>>
>
> Sorry, this is v2.
>
>>From b78dd7b2e0317be18716b9496269e9792829f63e Mon Sep 17 00:00:00 2001
> From: Sahitya Tummala <stummala@codeaurora.org>
> Date: Wed, 10 Oct 2018 10:56:22 +0530
> Subject: [PATCH] f2fs: fix data corruption issue with hardware encryption
>
> Direct IO can be used in case of hardware encryption. The following
> scenario results into data corruption issue in this path -
>
> Thread A - Thread B-
> -> write file#1 in direct IO
> -> GC gets kicked in
> -> GC submitted bio on meta mapping
> for file#1, but pending completion
> -> write file#1 again with new data
> in direct IO
> -> GC bio gets completed now
> -> GC writes old data to the new
> location and thus file#1 is
> corrupted.
>
> Fix this by submitting and waiting for pending io on meta mapping
> for direct IO case in f2fs_map_blocks().
>
> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Nice catch!

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

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