Commit 7cedb1f1 authored by James Bottomley's avatar James Bottomley Committed by Jens Axboe
Browse files

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: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 5ed7959e

drivers/scsi/scsi_lib.c

+5 −3
Original line number Diff line number Diff line
@@ -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);

include/linux/scatterlist.h

+3 −2
Original line number Diff line number Diff line
@@ -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);



/*

lib/scatterlist.c

+27 −14
Original line number Diff line number Diff line
@@ -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;

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE