--- /dev/null
+/*
+ * 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)
+{
+#ifdef CONFIG_DEBUG_SG
+ BUG_ON(sg->sg_magic != SG_MAGIC);
+#endif
+ 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_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)
+{
+#ifndef CONFIG_ARCH_HAS_SG_CHAIN
+ struct scatterlist *ret = &sgl[nents - 1];
+#else
+ struct scatterlist *sg, *ret = NULL;
+ unsigned int i;
+
+ for_each_sg(sgl, sg, nents, i)
+ ret = sg;
+
+#endif
+#ifdef CONFIG_DEBUG_SG
+ BUG_ON(sgl[0].sg_magic != SG_MAGIC);
+ BUG_ON(!sg_is_last(ret));
+#endif
+ 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);
+#ifdef CONFIG_DEBUG_SG
+ {
+ unsigned int i;
+ for (i = 0; i < nents; i++)
+ sgl[i].sg_magic = SG_MAGIC;
+ }
+#endif
+ sg_mark_end(&sgl[nents - 1]);
+}
+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(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)
+ * @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 long offset, unsigned long size,
+ gfp_t gfp_mask)
+{
+ unsigned int chunks;
+ unsigned int i;
+ unsigned int cur_page;
+ int ret;
+ struct scatterlist *s;
+
+ /* compute number of contiguous chunks */
+ chunks = 1;
+ for (i = 1; i < n_pages; ++i)
+ if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1)
+ ++chunks;
+
+ 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 long chunk_size;
+ unsigned int j;
+
+ /* look for the end of the current chunk */
+ for (j = cur_page + 1; j < n_pages; ++j)
+ if (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(size, chunk_size), offset);
+ size -= chunk_size;
+ offset = 0;
+ cur_page = j;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(sg_alloc_table_from_pages);
+
+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;
+ unsigned long pgoffset;
+
+ if (!__sg_page_iter_next(&miter->piter))
+ return false;
+
+ sg = miter->piter.sg;
+ pgoffset = miter->piter.sg_pgoffset;
+
+ miter->__offset = pgoffset ? 0 : sg->offset;
+ miter->__remaining = sg->offset + sg->length -
+ (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
+ * 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(!pagefault_disabled());
+ 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.
+ *
+ **/
+static 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 long flags;
+ 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;
+
+ local_irq_save_nort(flags);
+
+ while (sg_miter_next(&miter) && offset < buflen) {
+ 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);
+
+ local_irq_restore_nort(flags);
+ return offset;
+}
+
+/**
+ * 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,
+ void *buf, size_t buflen)
+{
+ return sg_copy_buffer(sgl, nents, 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
+ * @skip: Number of bytes to skip before copying
+ * @buflen: The number of bytes to copy
+ *
+ * Returns the number of copied bytes.
+ *
+ **/
+size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
+ void *buf, size_t buflen, off_t skip)
+{
+ return sg_copy_buffer(sgl, nents, 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
+ * @skip: Number of bytes to skip before copying
+ * @buflen: The number of bytes to copy
+ *
+ * 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);
Code Review / kvmfornfv.git / blobdiff