diff options
Diffstat (limited to 'lib/scatterlist.c')
-rw-r--r-- | lib/scatterlist.c | 555 |
1 files changed, 477 insertions, 78 deletions
diff --git a/lib/scatterlist.c b/lib/scatterlist.c index eacb82468437..68b45c82c37a 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -9,6 +9,8 @@ #include <linux/scatterlist.h> #include <linux/highmem.h> #include <linux/kmemleak.h> +#include <linux/bvec.h> +#include <linux/uio.h> /** * sg_next - return the next scatterlist entry in a list @@ -38,7 +40,7 @@ EXPORT_SYMBOL(sg_next); * @sg: The scatterlist * * Description: - * Allows to know how many entries are in sg, taking into acount + * Allows to know how many entries are in sg, taking into account * chaining as well * **/ @@ -59,7 +61,7 @@ EXPORT_SYMBOL(sg_nents); * * Description: * Determines the number of entries in sg that are required to meet - * the supplied length, taking into acount chaining as well + * the supplied length, taking into account chaining as well * * Returns: * the number of sg entries needed, negative error on failure @@ -179,8 +181,10 @@ static void sg_kfree(struct scatterlist *sg, unsigned int nents) * __sg_free_table - Free a previously mapped sg table * @table: The sg table header to use * @max_ents: The maximum number of entries per single scatterlist - * @skip_first_chunk: don't free the (preallocated) first scatterlist chunk + * @nents_first_chunk: Number of entries int the (preallocated) first + * scatterlist chunk, 0 means no such preallocated first chunk * @free_fn: Free function + * @num_ents: Number of entries in the table * * Description: * Free an sg table previously allocated and setup with @@ -189,16 +193,18 @@ static void sg_kfree(struct scatterlist *sg, unsigned int nents) * **/ void __sg_free_table(struct sg_table *table, unsigned int max_ents, - bool skip_first_chunk, sg_free_fn *free_fn) + unsigned int nents_first_chunk, sg_free_fn *free_fn, + unsigned int num_ents) { struct scatterlist *sgl, *next; + unsigned curr_max_ents = nents_first_chunk ?: max_ents; if (unlikely(!table->sgl)) return; sgl = table->sgl; - while (table->orig_nents) { - unsigned int alloc_size = table->orig_nents; + while (num_ents) { + unsigned int alloc_size = num_ents; unsigned int sg_size; /* @@ -207,21 +213,22 @@ void __sg_free_table(struct sg_table *table, unsigned int max_ents, * sg_size is then one less than alloc size, since the last * element is the chain pointer. */ - if (alloc_size > max_ents) { - next = sg_chain_ptr(&sgl[max_ents - 1]); - alloc_size = max_ents; + if (alloc_size > curr_max_ents) { + next = sg_chain_ptr(&sgl[curr_max_ents - 1]); + alloc_size = curr_max_ents; sg_size = alloc_size - 1; } else { sg_size = alloc_size; next = NULL; } - table->orig_nents -= sg_size; - if (skip_first_chunk) - skip_first_chunk = false; + num_ents -= sg_size; + if (nents_first_chunk) + nents_first_chunk = 0; else free_fn(sgl, alloc_size); sgl = next; + curr_max_ents = max_ents; } table->sgl = NULL; @@ -229,13 +236,27 @@ void __sg_free_table(struct sg_table *table, unsigned int max_ents, EXPORT_SYMBOL(__sg_free_table); /** + * sg_free_append_table - Free a previously allocated append sg table. + * @table: The mapped sg append table header + * + **/ +void sg_free_append_table(struct sg_append_table *table) +{ + __sg_free_table(&table->sgt, SG_MAX_SINGLE_ALLOC, 0, sg_kfree, + table->total_nents); +} +EXPORT_SYMBOL(sg_free_append_table); + + +/** * sg_free_table - Free a previously allocated sg table * @table: The mapped sg table header * **/ void sg_free_table(struct sg_table *table) { - __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree); + __sg_free_table(table, SG_MAX_SINGLE_ALLOC, 0, sg_kfree, + table->orig_nents); } EXPORT_SYMBOL(sg_free_table); @@ -244,6 +265,9 @@ EXPORT_SYMBOL(sg_free_table); * @table: The sg table header to use * @nents: Number of entries in sg list * @max_ents: The maximum number of entries the allocator returns per call + * @first_chunk: first SGL if preallocated (may be %NULL) + * @nents_first_chunk: Number of entries in the (preallocated) first + * scatterlist chunk, 0 means no such preallocated chunk provided by user * @gfp_mask: GFP allocation mask * @alloc_fn: Allocator to use * @@ -260,10 +284,13 @@ EXPORT_SYMBOL(sg_free_table); **/ int __sg_alloc_table(struct sg_table *table, unsigned int nents, unsigned int max_ents, struct scatterlist *first_chunk, - gfp_t gfp_mask, sg_alloc_fn *alloc_fn) + unsigned int nents_first_chunk, gfp_t gfp_mask, + sg_alloc_fn *alloc_fn) { struct scatterlist *sg, *prv; unsigned int left; + unsigned curr_max_ents = nents_first_chunk ?: max_ents; + unsigned prv_max_ents; memset(table, 0, sizeof(*table)); @@ -279,8 +306,8 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents, do { unsigned int sg_size, alloc_size = left; - if (alloc_size > max_ents) { - alloc_size = max_ents; + if (alloc_size > curr_max_ents) { + alloc_size = curr_max_ents; sg_size = alloc_size - 1; } else sg_size = alloc_size; @@ -303,7 +330,7 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents, if (prv) table->nents = ++table->orig_nents; - return -ENOMEM; + return -ENOMEM; } sg_init_table(sg, alloc_size); @@ -314,7 +341,7 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents, * If this is not the first mapping, chain previous part. */ if (prv) - sg_chain(prv, max_ents, sg); + sg_chain(prv, prv_max_ents, sg); else table->sgl = sg; @@ -325,6 +352,8 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents, sg_mark_end(&sg[sg_size - 1]); prv = sg; + prv_max_ents = curr_max_ents; + curr_max_ents = max_ents; } while (left); return 0; @@ -347,66 +376,141 @@ int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) int ret; ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, - NULL, gfp_mask, sg_kmalloc); + NULL, 0, gfp_mask, sg_kmalloc); if (unlikely(ret)) - __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree); - + sg_free_table(table); return ret; } EXPORT_SYMBOL(sg_alloc_table); +static struct scatterlist *get_next_sg(struct sg_append_table *table, + struct scatterlist *cur, + unsigned long needed_sges, + gfp_t gfp_mask) +{ + struct scatterlist *new_sg, *next_sg; + unsigned int alloc_size; + + if (cur) { + next_sg = sg_next(cur); + /* Check if last entry should be keeped for chainning */ + if (!sg_is_last(next_sg) || needed_sges == 1) + return next_sg; + } + + alloc_size = min_t(unsigned long, needed_sges, SG_MAX_SINGLE_ALLOC); + new_sg = sg_kmalloc(alloc_size, gfp_mask); + if (!new_sg) + return ERR_PTR(-ENOMEM); + sg_init_table(new_sg, alloc_size); + if (cur) { + table->total_nents += alloc_size - 1; + __sg_chain(next_sg, new_sg); + } else { + table->sgt.sgl = new_sg; + table->total_nents = alloc_size; + } + return new_sg; +} + +static bool pages_are_mergeable(struct page *a, struct page *b) +{ + if (page_to_pfn(a) != page_to_pfn(b) + 1) + return false; + if (!zone_device_pages_have_same_pgmap(a, b)) + return false; + return true; +} + /** - * __sg_alloc_table_from_pages - Allocate and initialize an sg table from - * an array of pages - * @sgt: The sg table header to use - * @pages: Pointer to an array of page pointers - * @n_pages: Number of pages in the pages array + * sg_alloc_append_table_from_pages - Allocate and initialize an append sg + * table from an array of pages + * @sgt_append: The sg append table to use + * @pages: Pointer to an array of page pointers + * @n_pages: Number of pages in the pages array * @offset: Offset from start of the first page to the start of a buffer * @size: Number of valid bytes in the buffer (after offset) - * @max_segment: Maximum size of a scatterlist node in bytes (page aligned) + * @max_segment: Maximum size of a scatterlist element in bytes + * @left_pages: Left pages caller have to set after this call * @gfp_mask: GFP allocation mask * - * Description: - * Allocate and initialize an sg table from a list of pages. Contiguous - * ranges of the pages are squashed into a single scatterlist node up to the - * maximum size specified in @max_segment. An user may provide an offset at a - * start and a size of valid data in a buffer specified by the page array. - * The returned sg table is released by sg_free_table. + * Description: + * In the first call it allocate and initialize an sg table from a list of + * pages, else reuse the scatterlist from sgt_append. Contiguous ranges of + * the pages are squashed into a single scatterlist entry up to the maximum + * size specified in @max_segment. A user may provide an offset at a start + * and a size of valid data in a buffer specified by the page array. The + * returned sg table is released by sg_free_append_table * * Returns: * 0 on success, negative error on failure + * + * Notes: + * If this function returns non-0 (eg failure), the caller must call + * sg_free_append_table() to cleanup any leftover allocations. + * + * In the fist call, sgt_append must by initialized. */ -int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages, - unsigned int n_pages, unsigned int offset, - unsigned long size, unsigned int max_segment, - gfp_t gfp_mask) +int sg_alloc_append_table_from_pages(struct sg_append_table *sgt_append, + struct page **pages, unsigned int n_pages, unsigned int offset, + unsigned long size, unsigned int max_segment, + unsigned int left_pages, gfp_t gfp_mask) { - unsigned int chunks, cur_page, seg_len, i; - int ret; - struct scatterlist *s; + unsigned int chunks, cur_page, seg_len, i, prv_len = 0; + unsigned int added_nents = 0; + struct scatterlist *s = sgt_append->prv; + struct page *last_pg; - if (WARN_ON(!max_segment || offset_in_page(max_segment))) + /* + * The algorithm below requires max_segment to be aligned to PAGE_SIZE + * otherwise it can overshoot. + */ + max_segment = ALIGN_DOWN(max_segment, PAGE_SIZE); + if (WARN_ON(max_segment < PAGE_SIZE)) return -EINVAL; + if (IS_ENABLED(CONFIG_ARCH_NO_SG_CHAIN) && sgt_append->prv) + return -EOPNOTSUPP; + + if (sgt_append->prv) { + unsigned long next_pfn = (page_to_phys(sg_page(sgt_append->prv)) + + sgt_append->prv->offset + sgt_append->prv->length) / PAGE_SIZE; + + if (WARN_ON(offset)) + return -EINVAL; + + /* Merge contiguous pages into the last SG */ + prv_len = sgt_append->prv->length; + if (page_to_pfn(pages[0]) == next_pfn) { + last_pg = pfn_to_page(next_pfn - 1); + while (n_pages && pages_are_mergeable(pages[0], last_pg)) { + if (sgt_append->prv->length + PAGE_SIZE > max_segment) + break; + sgt_append->prv->length += PAGE_SIZE; + last_pg = pages[0]; + pages++; + n_pages--; + } + if (!n_pages) + goto out; + } + } + /* compute number of contiguous chunks */ chunks = 1; seg_len = 0; for (i = 1; i < n_pages; i++) { seg_len += PAGE_SIZE; if (seg_len >= max_segment || - page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) { + !pages_are_mergeable(pages[i], pages[i - 1])) { chunks++; seg_len = 0; } } - ret = sg_alloc_table(sgt, chunks, gfp_mask); - if (unlikely(ret)) - return ret; - /* merging chunks and putting them into the scatterlist */ cur_page = 0; - for_each_sg(sgt->sgl, s, sgt->orig_nents, i) { + for (i = 0; i < chunks; i++) { unsigned int j, chunk_size; /* look for the end of the current chunk */ @@ -414,51 +518,82 @@ int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages, for (j = cur_page + 1; j < n_pages; j++) { seg_len += PAGE_SIZE; if (seg_len >= max_segment || - page_to_pfn(pages[j]) != - page_to_pfn(pages[j - 1]) + 1) + !pages_are_mergeable(pages[j], pages[j - 1])) break; } + /* Pass how many chunks might be left */ + s = get_next_sg(sgt_append, s, chunks - i + left_pages, + gfp_mask); + if (IS_ERR(s)) { + /* + * Adjust entry length to be as before function was + * called. + */ + if (sgt_append->prv) + sgt_append->prv->length = prv_len; + return PTR_ERR(s); + } chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset; sg_set_page(s, pages[cur_page], min_t(unsigned long, size, chunk_size), offset); + added_nents++; size -= chunk_size; offset = 0; cur_page = j; } - + sgt_append->sgt.nents += added_nents; + sgt_append->sgt.orig_nents = sgt_append->sgt.nents; + sgt_append->prv = s; +out: + if (!left_pages) + sg_mark_end(s); return 0; } -EXPORT_SYMBOL(__sg_alloc_table_from_pages); +EXPORT_SYMBOL(sg_alloc_append_table_from_pages); /** - * sg_alloc_table_from_pages - Allocate and initialize an sg table from - * an array of pages + * sg_alloc_table_from_pages_segment - Allocate and initialize an sg table from + * an array of pages and given maximum + * segment. * @sgt: The sg table header to use * @pages: Pointer to an array of page pointers * @n_pages: Number of pages in the pages array * @offset: Offset from start of the first page to the start of a buffer * @size: Number of valid bytes in the buffer (after offset) + * @max_segment: Maximum size of a scatterlist element in bytes * @gfp_mask: GFP allocation mask * * Description: * Allocate and initialize an sg table from a list of pages. Contiguous - * ranges of the pages are squashed into a single scatterlist node. A user - * may provide an offset at a start and a size of valid data in a buffer - * specified by the page array. The returned sg table is released by - * sg_free_table. + * ranges of the pages are squashed into a single scatterlist node up to the + * maximum size specified in @max_segment. A user may provide an offset at a + * start and a size of valid data in a buffer specified by the page array. * - * Returns: + * The returned sg table is released by sg_free_table. + * + * Returns: * 0 on success, negative error on failure */ -int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages, - unsigned int n_pages, unsigned int offset, - unsigned long size, gfp_t gfp_mask) +int sg_alloc_table_from_pages_segment(struct sg_table *sgt, struct page **pages, + unsigned int n_pages, unsigned int offset, + unsigned long size, unsigned int max_segment, + gfp_t gfp_mask) { - return __sg_alloc_table_from_pages(sgt, pages, n_pages, offset, size, - SCATTERLIST_MAX_SEGMENT, gfp_mask); + struct sg_append_table append = {}; + int err; + + err = sg_alloc_append_table_from_pages(&append, pages, n_pages, offset, + size, max_segment, 0, gfp_mask); + if (err) { + sg_free_append_table(&append); + return err; + } + memcpy(sgt, &append.sgt, sizeof(*sgt)); + WARN_ON(append.total_nents != sgt->orig_nents); + return 0; } -EXPORT_SYMBOL(sg_alloc_table_from_pages); +EXPORT_SYMBOL(sg_alloc_table_from_pages_segment); #ifdef CONFIG_SGL_ALLOC @@ -494,7 +629,7 @@ struct scatterlist *sgl_alloc_order(unsigned long long length, nalloc++; } sgl = kmalloc_array(nalloc, sizeof(struct scatterlist), - (gfp & ~GFP_DMA) | __GFP_ZERO); + gfp & ~GFP_DMA); if (!sgl) return NULL; @@ -504,7 +639,7 @@ struct scatterlist *sgl_alloc_order(unsigned long long length, elem_len = min_t(u64, length, PAGE_SIZE << order); page = alloc_pages(gfp, order); if (!page) { - sgl_free(sgl); + sgl_free_order(sgl, order); return NULL; } @@ -654,6 +789,7 @@ EXPORT_SYMBOL(__sg_page_iter_dma_next); * @miter: sg mapping iter to be started * @sgl: sg list to iterate over * @nents: number of sg entries + * @flags: sg iterator flags * * Description: * Starts mapping iterator @miter. @@ -706,8 +842,7 @@ static bool sg_miter_get_next_page(struct sg_mapping_iter *miter) * stops @miter. * * Context: - * Don't care if @miter is stopped, or not proceeded yet. - * Otherwise, preemption disabled if the SG_MITER_ATOMIC is set. + * Don't care. * * Returns: * true if @miter contains the valid mapping. false if end of sg @@ -743,8 +878,7 @@ EXPORT_SYMBOL(sg_miter_skip); * @miter->addr and @miter->length point to the current mapping. * * Context: - * Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled - * till @miter is stopped. May sleep if !SG_MITER_ATOMIC. + * May sleep if !SG_MITER_ATOMIC. * * Returns: * true if @miter contains the next mapping. false if end of sg @@ -784,8 +918,7 @@ EXPORT_SYMBOL(sg_miter_next); * need to be released during iteration. * * Context: - * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care - * otherwise. + * Don't care otherwise. */ void sg_miter_stop(struct sg_mapping_iter *miter) { @@ -796,12 +929,11 @@ void sg_miter_stop(struct sg_mapping_iter *miter) miter->__offset += miter->consumed; miter->__remaining -= miter->consumed; - if ((miter->__flags & SG_MITER_TO_SG) && - !PageSlab(miter->page)) - flush_kernel_dcache_page(miter->page); + if (miter->__flags & SG_MITER_TO_SG) + flush_dcache_page(miter->page); if (miter->__flags & SG_MITER_ATOMIC) { - WARN_ON_ONCE(preemptible()); + WARN_ON_ONCE(!pagefault_disabled()); kunmap_atomic(miter->addr); } else kunmap(miter->page); @@ -822,7 +954,7 @@ EXPORT_SYMBOL(sg_miter_stop); * @buflen: The number of bytes to copy * @skip: Number of bytes to skip before copying * @to_buffer: transfer direction (true == from an sg list to a - * buffer, false == from a buffer to an sg list + * buffer, false == from a buffer to an sg list) * * Returns the number of copied bytes. * @@ -842,7 +974,7 @@ size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, sg_miter_start(&miter, sgl, nents, sg_flags); if (!sg_miter_skip(&miter, skip)) - return false; + return 0; while ((offset < buflen) && sg_miter_next(&miter)) { unsigned int len; @@ -967,3 +1099,270 @@ size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, return offset; } EXPORT_SYMBOL(sg_zero_buffer); + +/* + * Extract and pin a list of up to sg_max pages from UBUF- or IOVEC-class + * iterators, and add them to the scatterlist. + */ +static ssize_t extract_user_to_sg(struct iov_iter *iter, + ssize_t maxsize, + struct sg_table *sgtable, + unsigned int sg_max, + iov_iter_extraction_t extraction_flags) +{ + struct scatterlist *sg = sgtable->sgl + sgtable->nents; + struct page **pages; + unsigned int npages; + ssize_t ret = 0, res; + size_t len, off; + + /* We decant the page list into the tail of the scatterlist */ + pages = (void *)sgtable->sgl + + array_size(sg_max, sizeof(struct scatterlist)); + pages -= sg_max; + + do { + res = iov_iter_extract_pages(iter, &pages, maxsize, sg_max, + extraction_flags, &off); + if (res < 0) + goto failed; + + len = res; + maxsize -= len; + ret += len; + npages = DIV_ROUND_UP(off + len, PAGE_SIZE); + sg_max -= npages; + + for (; npages > 0; npages--) { + struct page *page = *pages; + size_t seg = min_t(size_t, PAGE_SIZE - off, len); + + *pages++ = NULL; + sg_set_page(sg, page, seg, off); + sgtable->nents++; + sg++; + len -= seg; + off = 0; + } + } while (maxsize > 0 && sg_max > 0); + + return ret; + +failed: + while (sgtable->nents > sgtable->orig_nents) + unpin_user_page(sg_page(&sgtable->sgl[--sgtable->nents])); + return res; +} + +/* + * Extract up to sg_max pages from a BVEC-type iterator and add them to the + * scatterlist. The pages are not pinned. + */ +static ssize_t extract_bvec_to_sg(struct iov_iter *iter, + ssize_t maxsize, + struct sg_table *sgtable, + unsigned int sg_max, + iov_iter_extraction_t extraction_flags) +{ + const struct bio_vec *bv = iter->bvec; + struct scatterlist *sg = sgtable->sgl + sgtable->nents; + unsigned long start = iter->iov_offset; + unsigned int i; + ssize_t ret = 0; + + for (i = 0; i < iter->nr_segs; i++) { + size_t off, len; + + len = bv[i].bv_len; + if (start >= len) { + start -= len; + continue; + } + + len = min_t(size_t, maxsize, len - start); + off = bv[i].bv_offset + start; + + sg_set_page(sg, bv[i].bv_page, len, off); + sgtable->nents++; + sg++; + sg_max--; + + ret += len; + maxsize -= len; + if (maxsize <= 0 || sg_max == 0) + break; + start = 0; + } + + if (ret > 0) + iov_iter_advance(iter, ret); + return ret; +} + +/* + * Extract up to sg_max pages from a KVEC-type iterator and add them to the + * scatterlist. This can deal with vmalloc'd buffers as well as kmalloc'd or + * static buffers. The pages are not pinned. + */ +static ssize_t extract_kvec_to_sg(struct iov_iter *iter, + ssize_t maxsize, + struct sg_table *sgtable, + unsigned int sg_max, + iov_iter_extraction_t extraction_flags) +{ + const struct kvec *kv = iter->kvec; + struct scatterlist *sg = sgtable->sgl + sgtable->nents; + unsigned long start = iter->iov_offset; + unsigned int i; + ssize_t ret = 0; + + for (i = 0; i < iter->nr_segs; i++) { + struct page *page; + unsigned long kaddr; + size_t off, len, seg; + + len = kv[i].iov_len; + if (start >= len) { + start -= len; + continue; + } + + kaddr = (unsigned long)kv[i].iov_base + start; + off = kaddr & ~PAGE_MASK; + len = min_t(size_t, maxsize, len - start); + kaddr &= PAGE_MASK; + + maxsize -= len; + ret += len; + do { + seg = min_t(size_t, len, PAGE_SIZE - off); + if (is_vmalloc_or_module_addr((void *)kaddr)) + page = vmalloc_to_page((void *)kaddr); + else + page = virt_to_page((void *)kaddr); + + sg_set_page(sg, page, len, off); + sgtable->nents++; + sg++; + sg_max--; + + len -= seg; + kaddr += PAGE_SIZE; + off = 0; + } while (len > 0 && sg_max > 0); + + if (maxsize <= 0 || sg_max == 0) + break; + start = 0; + } + + if (ret > 0) + iov_iter_advance(iter, ret); + return ret; +} + +/* + * Extract up to sg_max folios from an XARRAY-type iterator and add them to + * the scatterlist. The pages are not pinned. + */ +static ssize_t extract_xarray_to_sg(struct iov_iter *iter, + ssize_t maxsize, + struct sg_table *sgtable, + unsigned int sg_max, + iov_iter_extraction_t extraction_flags) +{ + struct scatterlist *sg = sgtable->sgl + sgtable->nents; + struct xarray *xa = iter->xarray; + struct folio *folio; + loff_t start = iter->xarray_start + iter->iov_offset; + pgoff_t index = start / PAGE_SIZE; + ssize_t ret = 0; + size_t offset, len; + XA_STATE(xas, xa, index); + + rcu_read_lock(); + + xas_for_each(&xas, folio, ULONG_MAX) { + if (xas_retry(&xas, folio)) + continue; + if (WARN_ON(xa_is_value(folio))) + break; + if (WARN_ON(folio_test_hugetlb(folio))) + break; + + offset = offset_in_folio(folio, start); + len = min_t(size_t, maxsize, folio_size(folio) - offset); + + sg_set_page(sg, folio_page(folio, 0), len, offset); + sgtable->nents++; + sg++; + sg_max--; + + maxsize -= len; + ret += len; + if (maxsize <= 0 || sg_max == 0) + break; + } + + rcu_read_unlock(); + if (ret > 0) + iov_iter_advance(iter, ret); + return ret; +} + +/** + * extract_iter_to_sg - Extract pages from an iterator and add to an sglist + * @iter: The iterator to extract from + * @maxsize: The amount of iterator to copy + * @sgtable: The scatterlist table to fill in + * @sg_max: Maximum number of elements in @sgtable that may be filled + * @extraction_flags: Flags to qualify the request + * + * Extract the page fragments from the given amount of the source iterator and + * add them to a scatterlist that refers to all of those bits, to a maximum + * addition of @sg_max elements. + * + * The pages referred to by UBUF- and IOVEC-type iterators are extracted and + * pinned; BVEC-, KVEC- and XARRAY-type are extracted but aren't pinned; PIPE- + * and DISCARD-type are not supported. + * + * No end mark is placed on the scatterlist; that's left to the caller. + * + * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA + * be allowed on the pages extracted. + * + * If successful, @sgtable->nents is updated to include the number of elements + * added and the number of bytes added is returned. @sgtable->orig_nents is + * left unaltered. + * + * The iov_iter_extract_mode() function should be used to query how cleanup + * should be performed. + */ +ssize_t extract_iter_to_sg(struct iov_iter *iter, size_t maxsize, + struct sg_table *sgtable, unsigned int sg_max, + iov_iter_extraction_t extraction_flags) +{ + if (maxsize == 0) + return 0; + + switch (iov_iter_type(iter)) { + case ITER_UBUF: + case ITER_IOVEC: + return extract_user_to_sg(iter, maxsize, sgtable, sg_max, + extraction_flags); + case ITER_BVEC: + return extract_bvec_to_sg(iter, maxsize, sgtable, sg_max, + extraction_flags); + case ITER_KVEC: + return extract_kvec_to_sg(iter, maxsize, sgtable, sg_max, + extraction_flags); + case ITER_XARRAY: + return extract_xarray_to_sg(iter, maxsize, sgtable, sg_max, + extraction_flags); + default: + pr_err("%s(%u) unsupported\n", __func__, iov_iter_type(iter)); + WARN_ON_ONCE(1); + return -EIO; + } +} +EXPORT_SYMBOL_GPL(extract_iter_to_sg); |