block: optimize bvec iteration in bvec_iter_advance
There is no need to only iterate in chunks of PAGE_SIZE or less in bvec_iter_advance, given that the callers pass in the chunk length that they are operating on - either that already is less than PAGE_SIZE because they do classic page-based iteration, or it is larger because the caller operates on multi-page bvecs. This should help shaving off a few cycles of the I/O hot path. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -112,14 +112,15 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
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}
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while (bytes) {
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unsigned iter_len = bvec_iter_len(bv, *iter);
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unsigned len = min(bytes, iter_len);
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const struct bio_vec *cur = bv + iter->bi_idx;
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unsigned len = min3(bytes, iter->bi_size,
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cur->bv_len - iter->bi_bvec_done);
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bytes -= len;
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iter->bi_size -= len;
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iter->bi_bvec_done += len;
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if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
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if (iter->bi_bvec_done == cur->bv_len) {
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iter->bi_bvec_done = 0;
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iter->bi_idx++;
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}
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