lib/sg_split.c

Source file repositories/reference/linux-study-clean/lib/sg_split.c

File Facts

System
Linux kernel
Corpus path
lib/sg_split.c
Extension
.c
Size
5102 bytes
Lines
200
Domain
Kernel Services
Bucket
lib
Inferred role
Kernel Services: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Shared kernel service surface used by multiple subsystems, including helpers, cryptography, virtualization support, and async I/O infrastructure.

Dependency Surface

Detected Declarations

Annotated Snippet

struct sg_splitter {
	struct scatterlist *in_sg0;
	int nents;
	off_t skip_sg0;
	unsigned int length_last_sg;

	struct scatterlist *out_sg;
};

static int sg_calculate_split(struct scatterlist *in, int nents, int nb_splits,
			      off_t skip, const size_t *sizes,
			      struct sg_splitter *splitters, bool mapped)
{
	int i;
	unsigned int sglen;
	size_t size = sizes[0], len;
	struct sg_splitter *curr = splitters;
	struct scatterlist *sg;

	for (i = 0; i < nb_splits; i++) {
		splitters[i].in_sg0 = NULL;
		splitters[i].nents = 0;
	}

	for_each_sg(in, sg, nents, i) {
		sglen = mapped ? sg_dma_len(sg) : sg->length;
		if (skip > sglen) {
			skip -= sglen;
			continue;
		}

		len = min_t(size_t, size, sglen - skip);
		if (!curr->in_sg0) {
			curr->in_sg0 = sg;
			curr->skip_sg0 = skip;
		}
		size -= len;
		curr->nents++;
		curr->length_last_sg = len;

		while (!size && (skip + len < sglen) && (--nb_splits > 0)) {
			curr++;
			size = *(++sizes);
			skip += len;
			len = min_t(size_t, size, sglen - skip);

			curr->in_sg0 = sg;
			curr->skip_sg0 = skip;
			curr->nents = 1;
			curr->length_last_sg = len;
			size -= len;
		}
		skip = 0;

		if (!size && --nb_splits > 0) {
			curr++;
			size = *(++sizes);
		}

		if (!nb_splits)
			break;
	}

	return (size || !splitters[0].in_sg0) ? -EINVAL : 0;
}

static void sg_split_phys(struct sg_splitter *splitters, const int nb_splits)
{
	int i, j;
	struct scatterlist *in_sg, *out_sg;
	struct sg_splitter *split;

	for (i = 0, split = splitters; i < nb_splits; i++, split++) {
		in_sg = split->in_sg0;
		out_sg = split->out_sg;
		for (j = 0; j < split->nents; j++, out_sg++) {
			*out_sg = *in_sg;
			if (!j) {
				out_sg->offset += split->skip_sg0;
				out_sg->length -= split->skip_sg0;
			}
			sg_dma_address(out_sg) = 0;
			sg_dma_len(out_sg) = 0;
			in_sg = sg_next(in_sg);
		}
		out_sg[-1].length = split->length_last_sg;
		sg_mark_end(out_sg - 1);
	}
}

Annotation

Implementation Notes