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![Zhou Wang](/assets/img/avatar_default.png)
In function sg_split, the second sg_calculate_split will return -EINVAL when in_mapped_nents is 0. Indeed there is no need to do second sg_calculate_split and sg_split_mapped when in_mapped_nents is 0, as in_mapped_nents indicates no mapped entry in original sgl. Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com> Acked-by: Robert Jarzmik <robert.jarzmik@free.fr> Signed-off-by: Jens Axboe <axboe@kernel.dk>
202 lines
5 KiB
C
202 lines
5 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2015 Robert Jarzmik <robert.jarzmik@free.fr>
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*
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* Scatterlist splitting helpers.
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*/
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#include <linux/scatterlist.h>
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#include <linux/slab.h>
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struct sg_splitter {
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struct scatterlist *in_sg0;
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int nents;
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off_t skip_sg0;
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unsigned int length_last_sg;
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struct scatterlist *out_sg;
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};
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static int sg_calculate_split(struct scatterlist *in, int nents, int nb_splits,
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off_t skip, const size_t *sizes,
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struct sg_splitter *splitters, bool mapped)
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{
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int i;
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unsigned int sglen;
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size_t size = sizes[0], len;
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struct sg_splitter *curr = splitters;
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struct scatterlist *sg;
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for (i = 0; i < nb_splits; i++) {
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splitters[i].in_sg0 = NULL;
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splitters[i].nents = 0;
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}
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for_each_sg(in, sg, nents, i) {
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sglen = mapped ? sg_dma_len(sg) : sg->length;
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if (skip > sglen) {
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skip -= sglen;
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continue;
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}
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len = min_t(size_t, size, sglen - skip);
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if (!curr->in_sg0) {
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curr->in_sg0 = sg;
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curr->skip_sg0 = skip;
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}
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size -= len;
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curr->nents++;
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curr->length_last_sg = len;
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while (!size && (skip + len < sglen) && (--nb_splits > 0)) {
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curr++;
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size = *(++sizes);
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skip += len;
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len = min_t(size_t, size, sglen - skip);
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curr->in_sg0 = sg;
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curr->skip_sg0 = skip;
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curr->nents = 1;
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curr->length_last_sg = len;
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size -= len;
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}
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skip = 0;
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if (!size && --nb_splits > 0) {
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curr++;
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size = *(++sizes);
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}
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if (!nb_splits)
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break;
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}
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return (size || !splitters[0].in_sg0) ? -EINVAL : 0;
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}
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static void sg_split_phys(struct sg_splitter *splitters, const int nb_splits)
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{
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int i, j;
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struct scatterlist *in_sg, *out_sg;
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struct sg_splitter *split;
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for (i = 0, split = splitters; i < nb_splits; i++, split++) {
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in_sg = split->in_sg0;
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out_sg = split->out_sg;
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for (j = 0; j < split->nents; j++, out_sg++) {
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*out_sg = *in_sg;
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if (!j) {
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out_sg->offset += split->skip_sg0;
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out_sg->length -= split->skip_sg0;
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} else {
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out_sg->offset = 0;
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}
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sg_dma_address(out_sg) = 0;
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sg_dma_len(out_sg) = 0;
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in_sg = sg_next(in_sg);
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}
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out_sg[-1].length = split->length_last_sg;
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sg_mark_end(out_sg - 1);
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}
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}
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static void sg_split_mapped(struct sg_splitter *splitters, const int nb_splits)
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{
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int i, j;
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struct scatterlist *in_sg, *out_sg;
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struct sg_splitter *split;
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for (i = 0, split = splitters; i < nb_splits; i++, split++) {
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in_sg = split->in_sg0;
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out_sg = split->out_sg;
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for (j = 0; j < split->nents; j++, out_sg++) {
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sg_dma_address(out_sg) = sg_dma_address(in_sg);
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sg_dma_len(out_sg) = sg_dma_len(in_sg);
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if (!j) {
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sg_dma_address(out_sg) += split->skip_sg0;
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sg_dma_len(out_sg) -= split->skip_sg0;
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}
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in_sg = sg_next(in_sg);
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}
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sg_dma_len(--out_sg) = split->length_last_sg;
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}
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}
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/**
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* sg_split - split a scatterlist into several scatterlists
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* @in: the input sg list
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* @in_mapped_nents: the result of a dma_map_sg(in, ...), or 0 if not mapped.
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* @skip: the number of bytes to skip in the input sg list
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* @nb_splits: the number of desired sg outputs
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* @split_sizes: the respective size of each output sg list in bytes
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* @out: an array where to store the allocated output sg lists
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* @out_mapped_nents: the resulting sg lists mapped number of sg entries. Might
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* be NULL if sglist not already mapped (in_mapped_nents = 0)
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* @gfp_mask: the allocation flag
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*
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* This function splits the input sg list into nb_splits sg lists, which are
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* allocated and stored into out.
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* The @in is split into :
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* - @out[0], which covers bytes [@skip .. @skip + @split_sizes[0] - 1] of @in
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* - @out[1], which covers bytes [@skip + split_sizes[0] ..
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* @skip + @split_sizes[0] + @split_sizes[1] -1]
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* etc ...
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* It will be the caller's duty to kfree() out array members.
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*
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* Returns 0 upon success, or error code
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*/
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int sg_split(struct scatterlist *in, const int in_mapped_nents,
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const off_t skip, const int nb_splits,
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const size_t *split_sizes,
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struct scatterlist **out, int *out_mapped_nents,
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gfp_t gfp_mask)
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{
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int i, ret;
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struct sg_splitter *splitters;
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splitters = kcalloc(nb_splits, sizeof(*splitters), gfp_mask);
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if (!splitters)
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return -ENOMEM;
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ret = sg_calculate_split(in, sg_nents(in), nb_splits, skip, split_sizes,
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splitters, false);
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if (ret < 0)
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goto err;
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ret = -ENOMEM;
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for (i = 0; i < nb_splits; i++) {
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splitters[i].out_sg = kmalloc_array(splitters[i].nents,
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sizeof(struct scatterlist),
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gfp_mask);
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if (!splitters[i].out_sg)
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goto err;
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}
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/*
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* The order of these 3 calls is important and should be kept.
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*/
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sg_split_phys(splitters, nb_splits);
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if (in_mapped_nents) {
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ret = sg_calculate_split(in, in_mapped_nents, nb_splits, skip,
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split_sizes, splitters, true);
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if (ret < 0)
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goto err;
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sg_split_mapped(splitters, nb_splits);
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}
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for (i = 0; i < nb_splits; i++) {
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out[i] = splitters[i].out_sg;
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if (out_mapped_nents)
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out_mapped_nents[i] = splitters[i].nents;
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}
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kfree(splitters);
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return 0;
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err:
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for (i = 0; i < nb_splits; i++)
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kfree(splitters[i].out_sg);
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kfree(splitters);
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return ret;
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}
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EXPORT_SYMBOL(sg_split);
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