diff options
| author | Jens Axboe <axboe@kernel.dk> | 2022-08-05 16:44:34 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-08-22 10:07:56 -0600 |
| commit | e88811bc43b971e06fa82d4e421e21b3c999c1a7 (patch) | |
| tree | 63b3e0072fbd45bd78ec3b04c0973db6e61c6347 | |
| parent | 8af870aa5b84729d7a39f84226be6f84e4943d8f (diff) | |
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 <kch@nvidia.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/blk-map.c | 14 |
1 files changed, 11 insertions, 3 deletions
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); |