2.6.25-rc7

 lib

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
new file mode 100644
index 0000000..acca490
--- /dev/null
+++ b/lib/scatterlist.c
@@ -0,0 +1,294 @@
+/*
+ * 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/module.h>
+#include <linux/scatterlist.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_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 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)
+      return (struct scatterlist *) __get_free_page(gfp_mask);
+   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)
+      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
+ * @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,
+           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;
+      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, 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, gfp_t gfp_mask,
+           sg_alloc_fn *alloc_fn)
+{
+   struct scatterlist *sg, *prv;
+   unsigned int left;
+
+#ifndef ARCH_HAS_SG_CHAIN
+   BUG_ON(nents > max_ents);
+#endif
+
+   memset(table, 0, sizeof(*table));
+
+   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;
+
+      sg = alloc_fn(alloc_size, gfp_mask);
+      if (unlikely(!sg))
+         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]);
+
+      /*
+       * only really needed for mempool backed sg allocations (like
+       * SCSI), a possible improvement here would be to pass the
+       * table pointer into the allocator and let that clear these
+       * flags
+       */
+      gfp_mask &= ~__GFP_WAIT;
+      gfp_mask |= __GFP_HIGH;
+      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,
+                gfp_mask, sg_kmalloc);
+   if (unlikely(ret))
+      __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
+
+   return ret;
+}
+EXPORT_SYMBOL(sg_alloc_table);