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io_uring: do not always copy iovec in io_req_map_rw()

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In io_read_prep() or io_write_prep(), io_req_map_rw() takes
struct io_async_rw's fast_iov as argument to call io_import_iovec(),
and if io_import_iovec() uses struct io_async_rw's fast_iov as
valid iovec array, later indeed io_req_map_rw() does not need
to do the memcpy operation, because they are same pointers.

Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Xiaoguang Wang 2020-04-08 22:29:58 +08:00 committed by Jens Axboe
parent 08a1d26eb8
commit 45097daea2
1 changed files with 3 additions and 2 deletions
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5
fs/io_uring.c
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@ -2493,8 +2493,9 @@ static void io_req_map_rw(struct io_kiocb *req, ssize_t io_size,
req->io->rw.iov = iovec;
if (!req->io->rw.iov) {
req->io->rw.iov = req->io->rw.fast_iov;
memcpy(req->io->rw.iov, fast_iov,
sizeof(struct iovec) * iter->nr_segs);
if (req->io->rw.iov != fast_iov)
memcpy(req->io->rw.iov, fast_iov,
sizeof(struct iovec) * iter->nr_segs);
} else {
req->flags |= REQ_F_NEED_CLEANUP;
}