diff options
Diffstat (limited to 'lib/scatterlist.c')
| -rw-r--r-- | lib/scatterlist.c | 945 |
1 files changed, 945 insertions, 0 deletions
diff --git a/lib/scatterlist.c b/lib/scatterlist.c new file mode 100644 index 000000000..3b859201f --- /dev/null +++ b/lib/scatterlist.c @@ -0,0 +1,945 @@ +/* + * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com> + * + * Scatterlist handling helpers. + * + * This source code is licensed under the GNU General Public License, + * Version 2. See the file COPYING for more details. + */ +#include <linux/export.h> +#include <linux/slab.h> +#include <linux/scatterlist.h> +#include <linux/highmem.h> +#include <linux/kmemleak.h> + +/** + * sg_next - return the next scatterlist entry in a list + * @sg: The current sg entry + * + * Description: + * Usually the next entry will be @sg@ + 1, but if this sg element is part + * of a chained scatterlist, it could jump to the start of a new + * scatterlist array. + * + **/ +struct scatterlist *sg_next(struct scatterlist *sg) +{ + if (sg_is_last(sg)) + return NULL; + + sg++; + if (unlikely(sg_is_chain(sg))) + sg = sg_chain_ptr(sg); + + return sg; +} +EXPORT_SYMBOL(sg_next); + +/** + * sg_nents - return total count of entries in scatterlist + * @sg: The scatterlist + * + * Description: + * Allows to know how many entries are in sg, taking into acount + * chaining as well + * + **/ +int sg_nents(struct scatterlist *sg) +{ + int nents; + for (nents = 0; sg; sg = sg_next(sg)) + nents++; + return nents; +} +EXPORT_SYMBOL(sg_nents); + +/** + * sg_nents_for_len - return total count of entries in scatterlist + * needed to satisfy the supplied length + * @sg: The scatterlist + * @len: The total required length + * + * Description: + * Determines the number of entries in sg that are required to meet + * the supplied length, taking into acount chaining as well + * + * Returns: + * the number of sg entries needed, negative error on failure + * + **/ +int sg_nents_for_len(struct scatterlist *sg, u64 len) +{ + int nents; + u64 total; + + if (!len) + return 0; + + for (nents = 0, total = 0; sg; sg = sg_next(sg)) { + nents++; + total += sg->length; + if (total >= len) + return nents; + } + + return -EINVAL; +} +EXPORT_SYMBOL(sg_nents_for_len); + +/** + * sg_last - return the last scatterlist entry in a list + * @sgl: First entry in the scatterlist + * @nents: Number of entries in the scatterlist + * + * Description: + * Should only be used casually, it (currently) scans the entire list + * to get the last entry. + * + * Note that the @sgl@ pointer passed in need not be the first one, + * the important bit is that @nents@ denotes the number of entries that + * exist from @sgl@. + * + **/ +struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) +{ + struct scatterlist *sg, *ret = NULL; + unsigned int i; + + for_each_sg(sgl, sg, nents, i) + ret = sg; + + BUG_ON(!sg_is_last(ret)); + return ret; +} +EXPORT_SYMBOL(sg_last); + +/** + * sg_init_table - Initialize SG table + * @sgl: The SG table + * @nents: Number of entries in table + * + * Notes: + * If this is part of a chained sg table, sg_mark_end() should be + * used only on the last table part. + * + **/ +void sg_init_table(struct scatterlist *sgl, unsigned int nents) +{ + memset(sgl, 0, sizeof(*sgl) * nents); + sg_init_marker(sgl, nents); +} +EXPORT_SYMBOL(sg_init_table); + +/** + * sg_init_one - Initialize a single entry sg list + * @sg: SG entry + * @buf: Virtual address for IO + * @buflen: IO length + * + **/ +void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) +{ + sg_init_table(sg, 1); + sg_set_buf(sg, buf, buflen); +} +EXPORT_SYMBOL(sg_init_one); + +/* + * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree + * helpers. + */ +static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask) +{ + if (nents == SG_MAX_SINGLE_ALLOC) { + /* + * Kmemleak doesn't track page allocations as they are not + * commonly used (in a raw form) for kernel data structures. + * As we chain together a list of pages and then a normal + * kmalloc (tracked by kmemleak), in order to for that last + * allocation not to become decoupled (and thus a + * false-positive) we need to inform kmemleak of all the + * intermediate allocations. + */ + void *ptr = (void *) __get_free_page(gfp_mask); + kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask); + return ptr; + } else + return kmalloc_array(nents, sizeof(struct scatterlist), + gfp_mask); +} + +static void sg_kfree(struct scatterlist *sg, unsigned int nents) +{ + if (nents == SG_MAX_SINGLE_ALLOC) { + kmemleak_free(sg); + free_page((unsigned long) sg); + } else + kfree(sg); +} + +/** + * __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 + * @free_fn: Free function + * + * Description: + * Free an sg table previously allocated and setup with + * __sg_alloc_table(). The @max_ents value must be identical to + * that previously used with __sg_alloc_table(). + * + **/ +void __sg_free_table(struct sg_table *table, unsigned int max_ents, + bool skip_first_chunk, sg_free_fn *free_fn) +{ + struct scatterlist *sgl, *next; + + if (unlikely(!table->sgl)) + return; + + sgl = table->sgl; + while (table->orig_nents) { + unsigned int alloc_size = table->orig_nents; + unsigned int sg_size; + + /* + * If we have more than max_ents segments left, + * then assign 'next' to the sg table after the current one. + * 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; + 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; + else + free_fn(sgl, alloc_size); + sgl = next; + } + + table->sgl = NULL; +} +EXPORT_SYMBOL(__sg_free_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); +} +EXPORT_SYMBOL(sg_free_table); + +/** + * __sg_alloc_table - Allocate and initialize an sg table with given allocator + * @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 + * @gfp_mask: GFP allocation mask + * @alloc_fn: Allocator to use + * + * Description: + * This function returns a @table @nents long. The allocator is + * defined to return scatterlist chunks of maximum size @max_ents. + * Thus if @nents is bigger than @max_ents, the scatterlists will be + * chained in units of @max_ents. + * + * Notes: + * If this function returns non-0 (eg failure), the caller must call + * __sg_free_table() to cleanup any leftover allocations. + * + **/ +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) +{ + struct scatterlist *sg, *prv; + unsigned int left; + + memset(table, 0, sizeof(*table)); + + if (nents == 0) + return -EINVAL; +#ifndef CONFIG_ARCH_HAS_SG_CHAIN + if (WARN_ON_ONCE(nents > max_ents)) + return -EINVAL; +#endif + + left = nents; + prv = NULL; + do { + unsigned int sg_size, alloc_size = left; + + if (alloc_size > max_ents) { + alloc_size = max_ents; + sg_size = alloc_size - 1; + } else + sg_size = alloc_size; + + left -= sg_size; + + if (first_chunk) { + sg = first_chunk; + first_chunk = NULL; + } else { + sg = alloc_fn(alloc_size, gfp_mask); + } + if (unlikely(!sg)) { + /* + * Adjust entry count to reflect that the last + * entry of the previous table won't be used for + * linkage. Without this, sg_kfree() may get + * confused. + */ + if (prv) + table->nents = ++table->orig_nents; + + return -ENOMEM; + } + + sg_init_table(sg, alloc_size); + table->nents = table->orig_nents += sg_size; + + /* + * If this is the first mapping, assign the sg table header. + * If this is not the first mapping, chain previous part. + */ + if (prv) + sg_chain(prv, max_ents, sg); + else + table->sgl = sg; + + /* + * If no more entries after this one, mark the end + */ + if (!left) + sg_mark_end(&sg[sg_size - 1]); + + prv = sg; + } while (left); + + return 0; +} +EXPORT_SYMBOL(__sg_alloc_table); + +/** + * sg_alloc_table - Allocate and initialize an sg table + * @table: The sg table header to use + * @nents: Number of entries in sg list + * @gfp_mask: GFP allocation mask + * + * Description: + * Allocate and initialize an sg table. If @nents@ is larger than + * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. + * + **/ +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); + if (unlikely(ret)) + __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree); + + return ret; +} +EXPORT_SYMBOL(sg_alloc_table); + +/** + * __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 + * @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) + * @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. + * + * 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, unsigned int max_segment, + gfp_t gfp_mask) +{ + unsigned int chunks, cur_page, seg_len, i; + int ret; + struct scatterlist *s; + + if (WARN_ON(!max_segment || offset_in_page(max_segment))) + return -EINVAL; + + /* 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) { + 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) { + unsigned int j, chunk_size; + + /* look for the end of the current chunk */ + seg_len = 0; + 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) + break; + } + + chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset; + sg_set_page(s, pages[cur_page], + min_t(unsigned long, size, chunk_size), offset); + size -= chunk_size; + offset = 0; + cur_page = j; + } + + return 0; +} +EXPORT_SYMBOL(__sg_alloc_table_from_pages); + +/** + * 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 + * @offset: Offset from start of the first page to the start of a buffer + * @size: Number of valid bytes in the buffer (after offset) + * @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. + * + * 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) +{ + return __sg_alloc_table_from_pages(sgt, pages, n_pages, offset, size, + SCATTERLIST_MAX_SEGMENT, gfp_mask); +} +EXPORT_SYMBOL(sg_alloc_table_from_pages); + +#ifdef CONFIG_SGL_ALLOC + +/** + * sgl_alloc_order - allocate a scatterlist and its pages + * @length: Length in bytes of the scatterlist. Must be at least one + * @order: Second argument for alloc_pages() + * @chainable: Whether or not to allocate an extra element in the scatterlist + * for scatterlist chaining purposes + * @gfp: Memory allocation flags + * @nent_p: [out] Number of entries in the scatterlist that have pages + * + * Returns: A pointer to an initialized scatterlist or %NULL upon failure. + */ +struct scatterlist *sgl_alloc_order(unsigned long long length, + unsigned int order, bool chainable, + gfp_t gfp, unsigned int *nent_p) +{ + struct scatterlist *sgl, *sg; + struct page *page; + unsigned int nent, nalloc; + u32 elem_len; + + nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order); + /* Check for integer overflow */ + if (length > (nent << (PAGE_SHIFT + order))) + return NULL; + nalloc = nent; + if (chainable) { + /* Check for integer overflow */ + if (nalloc + 1 < nalloc) + return NULL; + nalloc++; + } + sgl = kmalloc_array(nalloc, sizeof(struct scatterlist), + (gfp & ~GFP_DMA) | __GFP_ZERO); + if (!sgl) + return NULL; + + sg_init_table(sgl, nalloc); + sg = sgl; + while (length) { + elem_len = min_t(u64, length, PAGE_SIZE << order); + page = alloc_pages(gfp, order); + if (!page) { + sgl_free_order(sgl, order); + return NULL; + } + + sg_set_page(sg, page, elem_len, 0); + length -= elem_len; + sg = sg_next(sg); + } + WARN_ONCE(length, "length = %lld\n", length); + if (nent_p) + *nent_p = nent; + return sgl; +} +EXPORT_SYMBOL(sgl_alloc_order); + +/** + * sgl_alloc - allocate a scatterlist and its pages + * @length: Length in bytes of the scatterlist + * @gfp: Memory allocation flags + * @nent_p: [out] Number of entries in the scatterlist + * + * Returns: A pointer to an initialized scatterlist or %NULL upon failure. + */ +struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp, + unsigned int *nent_p) +{ + return sgl_alloc_order(length, 0, false, gfp, nent_p); +} +EXPORT_SYMBOL(sgl_alloc); + +/** + * sgl_free_n_order - free a scatterlist and its pages + * @sgl: Scatterlist with one or more elements + * @nents: Maximum number of elements to free + * @order: Second argument for __free_pages() + * + * Notes: + * - If several scatterlists have been chained and each chain element is + * freed separately then it's essential to set nents correctly to avoid that a + * page would get freed twice. + * - All pages in a chained scatterlist can be freed at once by setting @nents + * to a high number. + */ +void sgl_free_n_order(struct scatterlist *sgl, int nents, int order) +{ + struct scatterlist *sg; + struct page *page; + int i; + + for_each_sg(sgl, sg, nents, i) { + if (!sg) + break; + page = sg_page(sg); + if (page) + __free_pages(page, order); + } + kfree(sgl); +} +EXPORT_SYMBOL(sgl_free_n_order); + +/** + * sgl_free_order - free a scatterlist and its pages + * @sgl: Scatterlist with one or more elements + * @order: Second argument for __free_pages() + */ +void sgl_free_order(struct scatterlist *sgl, int order) +{ + sgl_free_n_order(sgl, INT_MAX, order); +} +EXPORT_SYMBOL(sgl_free_order); + +/** + * sgl_free - free a scatterlist and its pages + * @sgl: Scatterlist with one or more elements + */ +void sgl_free(struct scatterlist *sgl) +{ + sgl_free_order(sgl, 0); +} +EXPORT_SYMBOL(sgl_free); + +#endif /* CONFIG_SGL_ALLOC */ + +void __sg_page_iter_start(struct sg_page_iter *piter, + struct scatterlist *sglist, unsigned int nents, + unsigned long pgoffset) +{ + piter->__pg_advance = 0; + piter->__nents = nents; + + piter->sg = sglist; + piter->sg_pgoffset = pgoffset; +} +EXPORT_SYMBOL(__sg_page_iter_start); + +static int sg_page_count(struct scatterlist *sg) +{ + return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT; +} + +bool __sg_page_iter_next(struct sg_page_iter *piter) +{ + if (!piter->__nents || !piter->sg) + return false; + + piter->sg_pgoffset += piter->__pg_advance; + piter->__pg_advance = 1; + + while (piter->sg_pgoffset >= sg_page_count(piter->sg)) { + piter->sg_pgoffset -= sg_page_count(piter->sg); + piter->sg = sg_next(piter->sg); + if (!--piter->__nents || !piter->sg) + return false; + } + + return true; +} +EXPORT_SYMBOL(__sg_page_iter_next); + +/** + * sg_miter_start - start mapping iteration over a sg list + * @miter: sg mapping iter to be started + * @sgl: sg list to iterate over + * @nents: number of sg entries + * + * Description: + * Starts mapping iterator @miter. + * + * Context: + * Don't care. + */ +void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, + unsigned int nents, unsigned int flags) +{ + memset(miter, 0, sizeof(struct sg_mapping_iter)); + + __sg_page_iter_start(&miter->piter, sgl, nents, 0); + WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); + miter->__flags = flags; +} +EXPORT_SYMBOL(sg_miter_start); + +static bool sg_miter_get_next_page(struct sg_mapping_iter *miter) +{ + if (!miter->__remaining) { + struct scatterlist *sg; + + if (!__sg_page_iter_next(&miter->piter)) + return false; + + sg = miter->piter.sg; + + miter->__offset = miter->piter.sg_pgoffset ? 0 : sg->offset; + miter->piter.sg_pgoffset += miter->__offset >> PAGE_SHIFT; + miter->__offset &= PAGE_SIZE - 1; + miter->__remaining = sg->offset + sg->length - + (miter->piter.sg_pgoffset << PAGE_SHIFT) - + miter->__offset; + miter->__remaining = min_t(unsigned long, miter->__remaining, + PAGE_SIZE - miter->__offset); + } + + return true; +} + +/** + * sg_miter_skip - reposition mapping iterator + * @miter: sg mapping iter to be skipped + * @offset: number of bytes to plus the current location + * + * Description: + * Sets the offset of @miter to its current location plus @offset bytes. + * If mapping iterator @miter has been proceeded by sg_miter_next(), this + * stops @miter. + * + * Context: + * Don't care if @miter is stopped, or not proceeded yet. + * Otherwise, preemption disabled if the SG_MITER_ATOMIC is set. + * + * Returns: + * true if @miter contains the valid mapping. false if end of sg + * list is reached. + */ +bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset) +{ + sg_miter_stop(miter); + + while (offset) { + off_t consumed; + + if (!sg_miter_get_next_page(miter)) + return false; + + consumed = min_t(off_t, offset, miter->__remaining); + miter->__offset += consumed; + miter->__remaining -= consumed; + offset -= consumed; + } + + return true; +} +EXPORT_SYMBOL(sg_miter_skip); + +/** + * sg_miter_next - proceed mapping iterator to the next mapping + * @miter: sg mapping iter to proceed + * + * Description: + * Proceeds @miter to the next mapping. @miter should have been started + * using sg_miter_start(). On successful return, @miter->page, + * @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. + * + * Returns: + * true if @miter contains the next mapping. false if end of sg + * list is reached. + */ +bool sg_miter_next(struct sg_mapping_iter *miter) +{ + sg_miter_stop(miter); + + /* + * Get to the next page if necessary. + * __remaining, __offset is adjusted by sg_miter_stop + */ + if (!sg_miter_get_next_page(miter)) + return false; + + miter->page = sg_page_iter_page(&miter->piter); + miter->consumed = miter->length = miter->__remaining; + + if (miter->__flags & SG_MITER_ATOMIC) + miter->addr = kmap_atomic(miter->page) + miter->__offset; + else + miter->addr = kmap(miter->page) + miter->__offset; + + return true; +} +EXPORT_SYMBOL(sg_miter_next); + +/** + * sg_miter_stop - stop mapping iteration + * @miter: sg mapping iter to be stopped + * + * Description: + * Stops mapping iterator @miter. @miter should have been started + * using sg_miter_start(). A stopped iteration can be resumed by + * calling sg_miter_next() on it. This is useful when resources (kmap) + * need to be released during iteration. + * + * Context: + * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care + * otherwise. + */ +void sg_miter_stop(struct sg_mapping_iter *miter) +{ + WARN_ON(miter->consumed > miter->length); + + /* drop resources from the last iteration */ + if (miter->addr) { + 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_ATOMIC) { + WARN_ON_ONCE(preemptible()); + kunmap_atomic(miter->addr); + } else + kunmap(miter->page); + + miter->page = NULL; + miter->addr = NULL; + miter->length = 0; + miter->consumed = 0; + } +} +EXPORT_SYMBOL(sg_miter_stop); + +/** + * sg_copy_buffer - Copy data between a linear buffer and an SG list + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy from + * @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 + * + * Returns the number of copied bytes. + * + **/ +size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, + size_t buflen, off_t skip, bool to_buffer) +{ + unsigned int offset = 0; + struct sg_mapping_iter miter; + unsigned int sg_flags = SG_MITER_ATOMIC; + + if (to_buffer) + sg_flags |= SG_MITER_FROM_SG; + else + sg_flags |= SG_MITER_TO_SG; + + sg_miter_start(&miter, sgl, nents, sg_flags); + + if (!sg_miter_skip(&miter, skip)) + return false; + + while ((offset < buflen) && sg_miter_next(&miter)) { + unsigned int len; + + len = min(miter.length, buflen - offset); + + if (to_buffer) + memcpy(buf + offset, miter.addr, len); + else + memcpy(miter.addr, buf + offset, len); + + offset += len; + } + + sg_miter_stop(&miter); + + return offset; +} +EXPORT_SYMBOL(sg_copy_buffer); + +/** + * sg_copy_from_buffer - Copy from a linear buffer to an SG list + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy from + * @buflen: The number of bytes to copy + * + * Returns the number of copied bytes. + * + **/ +size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, + const void *buf, size_t buflen) +{ + return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false); +} +EXPORT_SYMBOL(sg_copy_from_buffer); + +/** + * sg_copy_to_buffer - Copy from an SG list to a linear buffer + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy to + * @buflen: The number of bytes to copy + * + * Returns the number of copied bytes. + * + **/ +size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen) +{ + return sg_copy_buffer(sgl, nents, buf, buflen, 0, true); +} +EXPORT_SYMBOL(sg_copy_to_buffer); + +/** + * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy from + * @buflen: The number of bytes to copy + * @skip: Number of bytes to skip before copying + * + * Returns the number of copied bytes. + * + **/ +size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents, + const void *buf, size_t buflen, off_t skip) +{ + return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false); +} +EXPORT_SYMBOL(sg_pcopy_from_buffer); + +/** + * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy to + * @buflen: The number of bytes to copy + * @skip: Number of bytes to skip before copying + * + * Returns the number of copied bytes. + * + **/ +size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen, off_t skip) +{ + return sg_copy_buffer(sgl, nents, buf, buflen, skip, true); +} +EXPORT_SYMBOL(sg_pcopy_to_buffer); + +/** + * sg_zero_buffer - Zero-out a part of a SG list + * @sgl: The SG list + * @nents: Number of SG entries + * @buflen: The number of bytes to zero out + * @skip: Number of bytes to skip before zeroing + * + * Returns the number of bytes zeroed. + **/ +size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, + size_t buflen, off_t skip) +{ + unsigned int offset = 0; + struct sg_mapping_iter miter; + unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG; + + sg_miter_start(&miter, sgl, nents, sg_flags); + + if (!sg_miter_skip(&miter, skip)) + return false; + + while (offset < buflen && sg_miter_next(&miter)) { + unsigned int len; + + len = min(miter.length, buflen - offset); + memset(miter.addr, 0, len); + + offset += len; + } + + sg_miter_stop(&miter); + return offset; +} +EXPORT_SYMBOL(sg_zero_buffer); |