Thank you very much for taking the time to review this patch. Due to poor thinking, there are some
problems with this patch. I think this patch can be ignored. Thank you again for your time.
thanks
Andreas Dilger wrote on 2020/8/13 16:44:
> On Aug 7, 2020, at 5:32 AM, brookxu <brookxu.cn@xxxxxxxxx> wrote:
>>
>> Delete invalid ac_b_extent backup inside ext4_mb_use_best_found(),
>> we have done this operation in ext4_mb_new_group_pa() and
>> ext4_mb_new_inode_pa().
>
> I'm not sure I understand this patch completely.
>
> The calls to ext4_mb_new_group_pa() and ext4_mb_new_inode_pa() are
> done from ext4_mb_new_preallocation(), which is called at the *end*
> of ext4_mb_use_best_found() (i.e. after the lines that are being
> deleted).
>
> Maybe I'm confused by the description "we *have done* this operation"
> makes it seem like it was already done, but really it should be
> "we *will do* this operation in ..."?
>
> That said, it would make more sense to keep the one line here in
> ext4_mb_use_best_found() and remove the two duplicate lines in
> ext4_mb_new_group_pa() and ext4_mb_new_inode_pa()? In that case,
> the patch description would be more correct, like:
>
> Delete duplicate ac_b_extent backup in ext4_mb_new_group_pa()
> and ext4_mb_new_inode_pa(), since we have done this operation
> in ext4_mb_use_best_found() already.
>
> Cheers, Andreas
>
> PS: thank you for taking the time to look at this code and improve it.
> I know it is complex and hard to understand, but going through it like
> this and trimming off the bad bits makes it a bit easier to understand
> and maintain with each small patch.
>
>> Signed-off-by: Chunguang Xu <brookxu@xxxxxxxxxxx>
>>
>> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
>> index 9b1c3ad..fb63e9f 100644
>> --- a/fs/ext4/mballoc.c
>> +++ b/fs/ext4/mballoc.c
>> @@ -1704,10 +1704,6 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac,
>> ac->ac_b_ex.fe_logical = ac->ac_g_ex.fe_logical;
>> ret = mb_mark_used(e4b, &ac->ac_b_ex);
>>
>> - /* preallocation can change ac_b_ex, thus we store actually
>> - * allocated blocks for history */
>> - ac->ac_f_ex = ac->ac_b_ex;
>> -
>> ac->ac_status = AC_STATUS_FOUND;
>> ac->ac_tail = ret & 0xffff;
>> ac->ac_buddy = ret >> 16;
>> @@ -1726,8 +1722,8 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac,
>> /* store last allocated for subsequent stream allocation */
>> if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) {
>> spin_lock(&sbi->s_md_lock);
>> - sbi->s_mb_last_group = ac->ac_f_ex.fe_group;
>> - sbi->s_mb_last_start = ac->ac_f_ex.fe_start;
>> + sbi->s_mb_last_group = ac->ac_b_ex.fe_group;
>> + sbi->s_mb_last_start = ac->ac_b_ex.fe_start;
>> spin_unlock(&sbi->s_md_lock);
>> }
>> /*
>> --
>> 1.8.3.1
>
>
> Cheers, Andreas
>
>
>
>
>
