From e88811bc43b971e06fa82d4e421e21b3c999c1a7 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 5 Aug 2022 16:44:34 -0600 Subject: block: use on-stack page vec for <= UIO_FASTIOV Avoid a kmalloc+kfree for each page array, if we only have a few pages that are mapped. An alloc+free for each IO is quite expensive, and it's pretty pointless if we're only dealing with 1 or a few vecs. Use UIO_FASTIOV like we do in other spots to set a sane limit for how big of an IO we want to avoid allocations for. Reviewed-by: Chaitanya Kulkarni Signed-off-by: Jens Axboe --- block/blk-map.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'block/blk-map.c') diff --git a/block/blk-map.c b/block/blk-map.c index 16153fdc478f..f3768876d618 100644 --- a/block/blk-map.c +++ b/block/blk-map.c @@ -268,12 +268,19 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter, } while (iov_iter_count(iter)) { - struct page **pages; + struct page **pages, *stack_pages[UIO_FASTIOV]; ssize_t bytes; size_t offs, added = 0; int npages; - bytes = iov_iter_get_pages_alloc2(iter, &pages, LONG_MAX, &offs); + if (nr_vecs <= ARRAY_SIZE(stack_pages)) { + pages = stack_pages; + bytes = iov_iter_get_pages2(iter, pages, LONG_MAX, + nr_vecs, &offs); + } else { + bytes = iov_iter_get_pages_alloc2(iter, &pages, + LONG_MAX, &offs); + } if (unlikely(bytes <= 0)) { ret = bytes ? bytes : -EFAULT; goto out_unmap; @@ -309,7 +316,8 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter, */ while (j < npages) put_page(pages[j++]); - kvfree(pages); + if (pages != stack_pages) + kvfree(pages); /* couldn't stuff something into bio? */ if (bytes) { iov_iter_revert(iter, bytes); -- cgit v1.2.3