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SubjectRe: [f2fs-dev] [PATCH v4] f2fs: introduce fragment allocation mode mount option
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On 2021/9/4 12:40, Daeho Jeong wrote:
>> As a per curseg field.
>>
>>> Maybe, we run into the same race condition issue you told before for
>>> fragment_remained_chunk.
>>> Could you clarify this more?
>>
>> e.g.
>>
>> F2FS_OPTION(sbi).fs_mode = FS_MODE_FRAGMENT_FIXED_BLK
>> fragment_chunk_size = 384
>> fragment_hole_size = 384
>>
>> When creating hole:
>>
>> - f2fs_allocate_data_block
>> - __refresh_next_blkoff
>> chunk locates in [0, 383] of current segment
>> seg->next_blkoff = 384
>> sbi->fragment_remained_chunk = 0
>> then we will reset sbi->fragment_remained_chunk to 384
>> and move seg->next_blkoff forward to 768 (384 + 384)
>> - __has_curseg_space() returns false
>> - allocate_segment() allocates new current segment
>>
>> So, for such case that hole may cross two segments, hole size may be truncated
>> to left size of previous segment.
>
> First, sbi->fragment_remained_chunk should be seg->fragment_remained_chunk.

Oh, correct.

> I understand what you mean, so you mean we need to take the leftover
> "hole" size over to the next segment?
> In the example, the leftover hole size will be (384 - (512-384)). Do
> you want to take this over to the next segment?

Yes, the left 256 block-sized hole should be created before next chunk
in next opened segment.

Thanks,

>

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