compat: backport lib/scatterlist.c from 0db9299f

Backport the lib/scatterlist.c addition, this required
just removing the kmemleak stuff as that is not available
on older kernels.

mcgrof@frijol ~/linux-next (git::master)$ git describe --contains 0db9299f
v2.6.25-rc1~1173^2~2

commit 0db9299f48ebd4a860d6ad4e1d36ac50671d48e7
Author: Jens Axboe <jens.axboe@oracle.com>
Date:   Fri Nov 30 09:16:50 2007 +0100

    SG: Move functions to lib/scatterlist.c and add sg chaining allocator helpers

    Manually doing chained sg lists is not trivial, so add some helpers
    to make sure that drivers get it right.

    Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1   2.6.24              [  OK  ]
2   2.6.25              [  OK  ]
3   2.6.26              [  OK  ]
4   2.6.27              [  OK  ]
5   2.6.28              [  OK  ]
6   2.6.29              [  OK  ]
7   2.6.30              [  OK  ]
8   2.6.31              [  OK  ]
9   2.6.32              [  OK  ]
10  2.6.33              [  OK  ]
11  2.6.34              [  OK  ]
12  2.6.35              [  OK  ]
13  2.6.36              [  OK  ]
14  2.6.37              [  OK  ]
15  2.6.38              [  OK  ]
16  2.6.39              [  OK  ]
17  3.0.65              [  OK  ]
18  3.1.10              [  OK  ]
19  3.2.38              [  OK  ]
20  3.3.8               [  OK  ]
21  3.4.32              [  OK  ]
22  3.5.7               [  OK  ]
23  3.6.11              [  OK  ]
24  3.7.9               [  OK  ]
25  3.8.0               [  OK  ]
26  3.9-rc1             [  OK  ]

Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>

2 files changed, 224 insertions, 0 deletions

diff --git a/compat/compat-2.6.25.c b/compat/compat-2.6.25.c
index 15500249..20cc3dbd 100644
--- a/compat/compat-2.6.25.c
+++ b/compat/compat-2.6.25.c
@@ -12,6 +12,197 @@
 #include <linux/pci.h>
 
 /*
+ * 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
+	if (WARN_ON_ONCE(nents > max_ents))
+		return -EINVAL;
+#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)) {
+			/*
+			 * 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,
+			       gfp_mask, sg_kmalloc);
+	if (unlikely(ret))
+		__sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
+
+	return ret;
+}
+EXPORT_SYMBOL(sg_alloc_table);
+
+
+/*
  * To backport b718989d correctly pcibios_enable_device()
  * is required but we don't have access to it on modules
  * as its an architecture specific routine that is not
diff --git a/include/linux/compat-2.6.25.h b/include/linux/compat-2.6.25.h
index a08e0b26..dd986f5c 100644
--- a/include/linux/compat-2.6.25.h
+++ b/include/linux/compat-2.6.25.h
@@ -20,10 +20,43 @@
 #include <linux/errno.h>
 #include <linux/init.h>
 #include <linux/pci.h>
+#include <linux/scatterlist.h>
 #define __inet_lookup_established __inet_lookup_established_old
 #include <net/inet_hashtables.h>
 #undef __inet_lookup_established
 #include <linux/compat-3.9.h>
+
+struct sg_table {
+	struct scatterlist *sgl;        /* the list */
+	unsigned int nents;             /* number of mapped entries */
+	unsigned int orig_nents;        /* original size of list */
+};
+
+#define sg_alloc_fn LINUX_BACKPORT(sg_alloc_fn)
+typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
+
+#define sg_free_fn LINUX_BACKPORT(sg_free_fn)
+typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
+
+#define __sg_free_table LINUX_BACKPORT(__sg_free_table)
+void __sg_free_table(struct sg_table *table, unsigned int max_ents,
+		     sg_free_fn *free_fn);
+#define sg_free_table LINUX_BACKPORT(sg_free_table)
+void sg_free_table(struct sg_table *);
+#define __sg_alloc_table LINUX_BACKPORT(__sg_alloc_table)
+int __sg_alloc_table(struct sg_table *table, unsigned int nents,
+		     unsigned int max_ents, gfp_t gfp_mask,
+		     sg_alloc_fn *alloc_fn);
+#define sg_alloc_table LINUX_BACKPORT(sg_alloc_table)
+int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask);
+
+/*
+ * Maximum number of entries that will be allocated in one piece, if
+ * a list larger than this is required then chaining will be utilized.
+ */
+#define SG_MAX_SINGLE_ALLOC            (PAGE_SIZE / sizeof(struct scatterlist))
+
+
 /*
  * Sockets in TCP_CLOSE state are _always_ taken out of the hash, so we need
  * not check it for lookups anymore, thanks Alexey. -DaveM