SG: work with the SCSI fixed maximum allocations.
SCSI sg table allocation has a maximum size (of SCSI_MAX_SG_SEGMENTS,
currently 128) and this will cause a BUG_ON() in SCSI if something
tries an allocation over it. This patch adds a size limit to the
chaining allocator to allow the specification of the maximum
allocation size for chaining, so we always chain in units of the
maximum SCSI allocation size.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 02aaa27..acca4901 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -130,13 +130,17 @@
/**
* __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().
+ * 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, sg_free_fn *free_fn)
+void __sg_free_table(struct sg_table *table, unsigned int max_ents,
+ sg_free_fn *free_fn)
{
struct scatterlist *sgl, *next;
@@ -149,14 +153,14 @@
unsigned int sg_size;
/*
- * If we have more than SG_MAX_SINGLE_ALLOC segments left,
+ * 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 > SG_MAX_SINGLE_ALLOC) {
- next = sg_chain_ptr(&sgl[SG_MAX_SINGLE_ALLOC - 1]);
- alloc_size = SG_MAX_SINGLE_ALLOC;
+ 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;
@@ -179,7 +183,7 @@
**/
void sg_free_table(struct sg_table *table)
{
- __sg_free_table(table, sg_kfree);
+ __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
}
EXPORT_SYMBOL(sg_free_table);
@@ -187,22 +191,30 @@
* __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, gfp_t gfp_mask,
+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 > SG_MAX_SINGLE_ALLOC);
+ BUG_ON(nents > max_ents);
#endif
memset(table, 0, sizeof(*table));
@@ -212,8 +224,8 @@
do {
unsigned int sg_size, alloc_size = left;
- if (alloc_size > SG_MAX_SINGLE_ALLOC) {
- alloc_size = SG_MAX_SINGLE_ALLOC;
+ if (alloc_size > max_ents) {
+ alloc_size = max_ents;
sg_size = alloc_size - 1;
} else
sg_size = alloc_size;
@@ -232,7 +244,7 @@
* If this is not the first mapping, chain previous part.
*/
if (prv)
- sg_chain(prv, SG_MAX_SINGLE_ALLOC, sg);
+ sg_chain(prv, max_ents, sg);
else
table->sgl = sg;
@@ -272,9 +284,10 @@
{
int ret;
- ret = __sg_alloc_table(table, nents, gfp_mask, sg_kmalloc);
+ ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
+ gfp_mask, sg_kmalloc);
if (unlikely(ret))
- __sg_free_table(table, sg_kfree);
+ __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
return ret;
}
