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Commit 5ed7959e authored by Jens Axboe's avatar Jens Axboe
Browse files

SG: Convert SCSI to use scatterlist helpers for sg chaining 



Also change scsi_alloc_sgtable() to just return 0/failure, since it
maps to the command passed in. ->request_buffer is now no longer needed,
once drivers are adapted to use scsi_sglist() it can be killed.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 0db9299f

drivers/scsi/scsi_lib.c

+20 −118
Original line number Diff line number Diff line
@@ -739,138 +739,41 @@ static inline unsigned int scsi_sgtable_index(unsigned short nents) 
	return index;

}



struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)

static void scsi_sg_free(struct scatterlist *sgl, unsigned int nents)

{

	struct scsi_host_sg_pool *sgp;

	struct scatterlist *sgl, *prev, *ret;

	unsigned int index;

	int this, left;



	BUG_ON(!cmd->use_sg);



	left = cmd->use_sg;

	ret = prev = NULL;

	do {

		this = left;

		if (this > SCSI_MAX_SG_SEGMENTS) {

			this = SCSI_MAX_SG_SEGMENTS - 1;

			index = SG_MEMPOOL_NR - 1;

		} else

			index = scsi_sgtable_index(this);



		left -= this;



		sgp = scsi_sg_pools + index;



		sgl = mempool_alloc(sgp->pool, gfp_mask);

		if (unlikely(!sgl))

			goto enomem;



		sg_init_table(sgl, sgp->size);



		/*

		 * first loop through, set initial index and return value

		 */

		if (!ret)

			ret = sgl;



		/*

		 * chain previous sglist, if any. we know the previous

		 * sglist must be the biggest one, or we would not have

		 * ended up doing another loop.

		 */

		if (prev)

			sg_chain(prev, SCSI_MAX_SG_SEGMENTS, sgl);



		/*

		 * if we have nothing left, mark the last segment as

		 * end-of-list

		 */

		if (!left)

			sg_mark_end(&sgl[this - 1]);



		/*

		 * don't allow subsequent mempool allocs to sleep, it would

		 * violate the mempool principle.

		 */

		gfp_mask &= ~__GFP_WAIT;

		gfp_mask |= __GFP_HIGH;

		prev = sgl;

	} while (left);



	/*

	 * ->use_sg may get modified after dma mapping has potentially

	 * shrunk the number of segments, so keep a copy of it for free.

	 */

	cmd->__use_sg = cmd->use_sg;

	return ret;

enomem:

	if (ret) {

		/*

		 * Free entries chained off ret. Since we were trying to

		 * allocate another sglist, we know that all entries are of

		 * the max size.

		 */

		sgp = scsi_sg_pools + SG_MEMPOOL_NR - 1;

		prev = ret;

		ret = &ret[SCSI_MAX_SG_SEGMENTS - 1];



		while ((sgl = sg_chain_ptr(ret)) != NULL) {

			ret = &sgl[SCSI_MAX_SG_SEGMENTS - 1];

	sgp = scsi_sg_pools + scsi_sgtable_index(nents);

	mempool_free(sgl, sgp->pool);

}



		mempool_free(prev, sgp->pool);

	}

	return NULL;

}



EXPORT_SYMBOL(scsi_alloc_sgtable);



void scsi_free_sgtable(struct scsi_cmnd *cmd)

static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)

{

	struct scatterlist *sgl = cmd->request_buffer;

	struct scsi_host_sg_pool *sgp;



	/*

	 * if this is the biggest size sglist, check if we have

	 * chained parts we need to free

	 */

	if (cmd->__use_sg > SCSI_MAX_SG_SEGMENTS) {

		unsigned short this, left;

		struct scatterlist *next;

		unsigned int index;



		left = cmd->__use_sg - (SCSI_MAX_SG_SEGMENTS - 1);

		next = sg_chain_ptr(&sgl[SCSI_MAX_SG_SEGMENTS - 1]);

		while (left && next) {

			sgl = next;

			this = left;

			if (this > SCSI_MAX_SG_SEGMENTS) {

				this = SCSI_MAX_SG_SEGMENTS - 1;

				index = SG_MEMPOOL_NR - 1;

			} else

				index = scsi_sgtable_index(this);

	sgp = scsi_sg_pools + scsi_sgtable_index(nents);

	return mempool_alloc(sgp->pool, gfp_mask);

}



			left -= this;

int scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)

{

	int ret;



			sgp = scsi_sg_pools + index;

	BUG_ON(!cmd->use_sg);



			if (left)

				next = sg_chain_ptr(&sgl[sgp->size - 1]);

	ret = __sg_alloc_table(&cmd->sg_table, cmd->use_sg, gfp_mask, scsi_sg_alloc);

	if (unlikely(ret))

		__sg_free_table(&cmd->sg_table, scsi_sg_free);



			mempool_free(sgl, sgp->pool);

	cmd->request_buffer = cmd->sg_table.sgl;

	return ret;

}



		/*

		 * Restore original, will be freed below

		 */

		sgl = cmd->request_buffer;

		sgp = scsi_sg_pools + SG_MEMPOOL_NR - 1;

	} else

		sgp = scsi_sg_pools + scsi_sgtable_index(cmd->__use_sg);

EXPORT_SYMBOL(scsi_alloc_sgtable);



	mempool_free(sgl, sgp->pool);

void scsi_free_sgtable(struct scsi_cmnd *cmd)

{

	__sg_free_table(&cmd->sg_table, scsi_sg_free);

}



EXPORT_SYMBOL(scsi_free_sgtable);
@@ -1120,8 +1023,7 @@ static int scsi_init_io(struct scsi_cmnd *cmd) 
	/*

	 * If sg table allocation fails, requeue request later.

	 */

	cmd->request_buffer = scsi_alloc_sgtable(cmd, GFP_ATOMIC);

	if (unlikely(!cmd->request_buffer)) {

	if (unlikely(scsi_alloc_sgtable(cmd, GFP_ATOMIC))) {

		scsi_unprep_request(req);

		return BLKPREP_DEFER;

	}

drivers/scsi/scsi_tgt_lib.c

+1 −2
Original line number Diff line number Diff line
@@ -359,8 +359,7 @@ static int scsi_tgt_init_cmd(struct scsi_cmnd *cmd, gfp_t gfp_mask) 
	int count;



	cmd->use_sg = rq->nr_phys_segments;

	cmd->request_buffer = scsi_alloc_sgtable(cmd, gfp_mask);

	if (!cmd->request_buffer)

	if (scsi_alloc_sgtable(cmd, gfp_mask))

		return -ENOMEM;



	cmd->request_bufflen = rq->data_len;

include/scsi/scsi_cmnd.h

+3 −4
Original line number Diff line number Diff line
@@ -8,7 +8,6 @@ 
#include <linux/scatterlist.h>



struct request;

struct scatterlist;

struct Scsi_Host;

struct scsi_device;
@@ -68,8 +67,8 @@ struct scsi_cmnd { 
	void *request_buffer;		/* Actual requested buffer */



	/* These elements define the operation we ultimately want to perform */

	struct sg_table sg_table;

	unsigned short use_sg;	/* Number of pieces of scatter-gather */

	unsigned short __use_sg;



	unsigned underflow;	/* Return error if less than

				   this amount is transferred */
@@ -128,14 +127,14 @@ extern void *scsi_kmap_atomic_sg(struct scatterlist *sg, int sg_count, 
				 size_t *offset, size_t *len);

extern void scsi_kunmap_atomic_sg(void *virt);



extern struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *, gfp_t);

extern int scsi_alloc_sgtable(struct scsi_cmnd *, gfp_t);

extern void scsi_free_sgtable(struct scsi_cmnd *);



extern int scsi_dma_map(struct scsi_cmnd *cmd);

extern void scsi_dma_unmap(struct scsi_cmnd *cmd);



#define scsi_sg_count(cmd) ((cmd)->use_sg)

#define scsi_sglist(cmd) ((struct scatterlist *)(cmd)->request_buffer)

#define scsi_sglist(cmd) ((cmd)->sg_table.sgl)

#define scsi_bufflen(cmd) ((cmd)->request_bufflen)



static inline void scsi_set_resid(struct scsi_cmnd *cmd, int resid)