On 2018/11/13 8:34, Jaegeuk Kim wrote:
> On 11/12, Chao Yu wrote:
>> On 2018-11-12 20:01, Sheng Yong wrote:
>>> The following race could lead to inconsistent SIT bitmap:
>>>
>>> Task A Task B
>>> ====== ======
>>> f2fs_write_checkpoint
>>> block_operations
>>> f2fs_lock_all
>>> down_write(node_change)
>>> down_write(node_write)
>>> ... sync ...
>>> up_write(node_change)
>>> f2fs_file_write_iter
>>> set_inode_flag(FI_NO_PREALLOC)
>>> ......
>>> f2fs_write_begin(index=0, has inline data)
>>> prepare_write_begin
>>> __do_map_lock(AIO) =>
>>> down_read(node_change)
>>> f2fs_convert_inline_page => update SIT
>>> __do_map_lock(AIO) =>
>>> up_read(node_change)
>>> f2fs_flush_sit_entries <= inconsistent SIT
>>> finish write checkpoint
>>> sudden-power-off
>>>
>>> If SPO occurs after checkpoint is finished, SIT bitmap will be set
>>> incorrectly. This patch uses node_write to avoid the race condition.
>>
>> Good catch!
>>
>>>
>>> Signed-off-by: Sheng Yong <[email protected]>
>>> ---
>>> fs/f2fs/data.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>> index 106f116466bf..dc5b251aee86 100644
>>> --- a/fs/f2fs/data.c
>>> +++ b/fs/f2fs/data.c
>>> @@ -2355,7 +2355,9 @@ static int prepare_write_begin(struct f2fs_sb_info
>>> *sbi,
>>> if (inode->i_nlink)
>>> set_inline_node(ipage);
>>> } else {
>>> + down_read(&sbi->node_write);
>>
>> This makes lock dependence more complicated, how about calling f2fs_lock_op
>> for
>> inline data conversion case:
>>
>> struct extent_info ei = {0,0,0};
>> + int flag;
>> int err = 0;
>>
>> - if (f2fs_has_inline_data(inode) ||
>> - (pos & PAGE_MASK) >= i_size_read(inode)) {
>> - __do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO, true);
>> + if (f2fs_has_inline_data(inode)) {
>> + if (pos + len > MAX_INLINE_DATA(inode))
>> + flag = F2FS_GET_BLOCK_PRE_DIO;
>
> This is not DIO case. I think calling f2fs_lock_op() explicitly might be
> better.
Agreed.
>
>
>> + else if (pos & PAGE_MASK) >= i_size_read(inode))
>> + flag = F2FS_GET_BLOCK_PRE_AIO;
Sorry, there is a missing case that @flag doesn't be initialized, please
note that, Sheng Yong.
Thanks,
>> + __do_map_lock(sbi, flag, true);
>>
>> if (err || dn.data_blkaddr == NULL_ADDR) {
>> f2fs_put_dnode(&dn);
>> - __do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO,
>> - true);
>> + flag = F2FS_GET_BLOCK_PRE_AIO;
>> + __do_map_lock(sbi, flag, true);
>> locked = true;
>>
>> unlock_out:
>> if (locked)
>> - __do_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO, false);
>> + __do_map_lock(sbi, flag, false);
>>
>> Thanks,
>>
>>> err = f2fs_convert_inline_page(&dn, page);
>>> + up_read(&sbi->node_write);
>>> if (err)
>>> goto out;
>>> if (dn.data_blkaddr == NULL_ADDR)
>>>
>
> .
>
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