Re: [PATCH] io_uring/rsrc: fix incorrect assignment of iter->nr_segs in io_import_fixed

[Chenliang Li <lcljoric@gmail.com>]

在 2024/6/19 22:27, Pavel Begunkov 写道:
> On 6/19/24 07:38, Chenliang Li wrote:
>> In io_import_fixed when advancing the iter within the first bvec, the
>> iter->nr_segs is set to bvec->bv_len. nr_segs should be the number of
>> bvecs, plus we don't need to adjust it here, so just remove it.
>
> Good catch, quite old. It's our luck that bvec iteration
> honours the length and doesn't step outside of the first entry.
>
>> Fixes: b000ae0ec2d7 ("io_uring/rsrc: optimise single entry advance")
>> Signed-off-by: Chenliang Li <cliang01.li@samsung.com>
>> ---
>>   io_uring/rsrc.c | 1 -
>>   1 file changed, 1 deletion(-)
>>
>> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
>> index 60c00144471a..a860516bf448 100644
>> --- a/io_uring/rsrc.c
>> +++ b/io_uring/rsrc.c
>> @@ -1049,7 +1049,6 @@ int io_import_fixed(int ddir, struct iov_iter 
>> *iter,
>>                * branch doesn't expect non PAGE_SIZE'd chunks.
>>                */
>>               iter->bvec = bvec;
>> -            iter->nr_segs = bvec->bv_len;
>
> iter->nr_segs = 1, please
Why 1? There could be multiple bvecs.
>
>
>>               iter->count -= offset;
>>               iter->iov_offset = offset;
>>           } else {
>>
>> base-commit: 3b87184f7eff27fef7d7ee18b65f173152e1bb81
>