Re: [PATCH 4/4] io_uring/rsrc: send exact nr_segs for fixed buffer

[Nitesh Shetty <nj.shetty@samsung.com>]

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On 17/04/25 10:34AM, Pavel Begunkov wrote:
>On 4/17/25 10:32, Pavel Begunkov wrote:
>>From: Nitesh Shetty <nj.shetty@samsung.com>
>...
>>diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
>>index 5cf854318b1d..4099b8225670 100644
>>--- a/io_uring/rsrc.c
>>+++ b/io_uring/rsrc.c
>>@@ -1037,6 +1037,7 @@ static int io_import_fixed(int ddir, struct iov_iter *iter,
>>  			   u64 buf_addr, size_t len)
>>  {
>>  	const struct bio_vec *bvec;
>>+	size_t folio_mask;
>>  	unsigned nr_segs;
>>  	size_t offset;
>>  	int ret;
>>@@ -1067,6 +1068,7 @@ static int io_import_fixed(int ddir, struct iov_iter *iter,
>>  	 * 2) all bvecs are the same in size, except potentially the
>>  	 *    first and last bvec
>>  	 */
>>+	folio_mask = (1UL << imu->folio_shift) - 1;
>>  	bvec = imu->bvec;
>>  	if (offset >= bvec->bv_len) {
>>  		unsigned long seg_skip;
>>@@ -1075,10 +1077,10 @@ static int io_import_fixed(int ddir, struct iov_iter *iter,
>>  		offset -= bvec->bv_len;
>>  		seg_skip = 1 + (offset >> imu->folio_shift);
>>  		bvec += seg_skip;
>>-		offset &= (1UL << imu->folio_shift) - 1;
>>+		offset &= folio_mask;
>>  	}
>>-	nr_segs = imu->nr_bvecs - (bvec - imu->bvec);
>>+	nr_segs = (offset + len + folio_mask) >> imu->folio_shift;
>
>Nitesh, let me know if you're happy with this version.
>
This looks great to me, I tested this series and see the
improvement in IOPS from 7.15 to 7.65M here.

Thanks,
Nitesh Shetty

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