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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>
This commit is contained in:
James Bottomley 2008-01-13 14:15:28 -06:00 committed by Jens Axboe
parent 5ed7959ede
commit 7cedb1f17f
3 changed files with 35 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/scsi/scsi_lib.c
View File

@ -761,9 +761,11 @@ int scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
BUG_ON(!cmd->use_sg);
ret = __sg_alloc_table(&cmd->sg_table, cmd->use_sg, gfp_mask, scsi_sg_alloc);
ret = __sg_alloc_table(&cmd->sg_table, cmd->use_sg,
SCSI_MAX_SG_SEGMENTS, gfp_mask, scsi_sg_alloc);
if (unlikely(ret))
__sg_free_table(&cmd->sg_table, scsi_sg_free);
__sg_free_table(&cmd->sg_table, SCSI_MAX_SG_SEGMENTS,
scsi_sg_free);
cmd->request_buffer = cmd->sg_table.sgl;
return ret;
@ -773,7 +775,7 @@ EXPORT_SYMBOL(scsi_alloc_sgtable);
void scsi_free_sgtable(struct scsi_cmnd *cmd)
{
__sg_free_table(&cmd->sg_table, scsi_sg_free);
__sg_free_table(&cmd->sg_table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
}
EXPORT_SYMBOL(scsi_free_sgtable);

5
include/linux/scatterlist.h
View File

@ -207,9 +207,10 @@ void sg_init_one(struct scatterlist *, const void *, unsigned int);
typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t);
typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
void __sg_free_table(struct sg_table *, sg_free_fn *);
void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *);
void sg_free_table(struct sg_table *);
int __sg_alloc_table(struct sg_table *, unsigned int, gfp_t, sg_alloc_fn *);
int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t,
sg_alloc_fn *);
int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
/*

41
lib/scatterlist.c
View File

@ -130,13 +130,17 @@ static void sg_kfree(struct scatterlist *sg, unsigned int nents)
/**
* __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 @@ void __sg_free_table(struct sg_table *table, sg_free_fn *free_fn)
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 @@ EXPORT_SYMBOL(__sg_free_table);
**/
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 @@ 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, 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 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask,
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 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask,
* 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 sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
{
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;
}