Commit 1bdc76ae authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

iov_iter: use bvec iterator to implement iterate_bvec() 



bvec has one native/mature iterator for long time, so not
necessary to use the reinvented wheel for iterating bvecs
in lib/iov_iter.c.

Two ITER_BVEC test cases are run:
	- xfstest(-g auto) on loop dio/aio, no regression found
	- swap file works well under extreme stress(stress-ng --all 64 -t
	  800 -v), and lots of OOMs are triggerd, and the whole
	system still survives

Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMing Lei <ming.lei@canonical.com>
Tested-by: default avatarHannes Reinecke <hare@suse.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 80f162ff

lib/iov_iter.c

+15 −30
Original line number Diff line number Diff line
@@ -56,37 +56,24 @@ 
	n = wanted;					\

}



#define iterate_bvec(i, n, __v, __p, skip, STEP) {	\

	size_t wanted = n;				\

	__p = i->bvec;					\

	__v.bv_len = min_t(size_t, n, __p->bv_len - skip);	\

	if (likely(__v.bv_len)) {			\

		__v.bv_page = __p->bv_page;		\

		__v.bv_offset = __p->bv_offset + skip; 	\

		(void)(STEP);				\

		skip += __v.bv_len;			\

		n -= __v.bv_len;			\

	}						\

	while (unlikely(n)) {				\

		__p++;					\

		__v.bv_len = min_t(size_t, n, __p->bv_len);	\

		if (unlikely(!__v.bv_len))		\

#define iterate_bvec(i, n, __v, __bi, skip, STEP) {	\

	struct bvec_iter __start;			\

	__start.bi_size = n;				\

	__start.bi_bvec_done = skip;			\

	__start.bi_idx = 0;				\

	for_each_bvec(__v, i->bvec, __bi, __start) {	\

		if (!__v.bv_len)			\

			continue;			\

		__v.bv_page = __p->bv_page;		\

		__v.bv_offset = __p->bv_offset;		\

		(void)(STEP);				\

		skip = __v.bv_len;			\

		n -= __v.bv_len;			\

	}						\

	n = wanted;					\

}



#define iterate_all_kinds(i, n, v, I, B, K) {			\

	size_t skip = i->iov_offset;				\

	if (unlikely(i->type & ITER_BVEC)) {			\

		const struct bio_vec *bvec;			\

		struct bio_vec v;				\

		iterate_bvec(i, n, v, bvec, skip, (B))		\

		struct bvec_iter __bi;				\

		iterate_bvec(i, n, v, __bi, skip, (B))		\

	} else if (unlikely(i->type & ITER_KVEC)) {		\

		const struct kvec *kvec;			\

		struct kvec v;					\
@@ -104,15 +91,13 @@ 
	if (i->count) {						\

		size_t skip = i->iov_offset;			\

		if (unlikely(i->type & ITER_BVEC)) {		\

			const struct bio_vec *bvec;		\

			const struct bio_vec *bvec = i->bvec;	\

			struct bio_vec v;			\

			iterate_bvec(i, n, v, bvec, skip, (B))	\

			if (skip == bvec->bv_len) {		\

				bvec++;				\

				skip = 0;			\

			}					\

			i->nr_segs -= bvec - i->bvec;		\

			i->bvec = bvec;				\

			struct bvec_iter __bi;			\

			iterate_bvec(i, n, v, __bi, skip, (B))	\

			i->bvec = __bvec_iter_bvec(i->bvec, __bi);	\

			i->nr_segs -= i->bvec - bvec;		\

			skip = __bi.bi_bvec_done;		\

		} else if (unlikely(i->type & ITER_KVEC)) {	\

			const struct kvec *kvec;		\

			struct kvec v;				\

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