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SG: Convert SCSI to use scatterlist helpers for sg chaining
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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: Jens Axboe <[email protected]>
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Jens Axboe committed Jan 28, 2008
1 parent 0db9299 commit 5ed7959
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Showing 3 changed files with 24 additions and 124 deletions.
138 changes: 20 additions & 118 deletions drivers/scsi/scsi_lib.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
sgp = scsi_sg_pools + scsi_sgtable_index(nents);
mempool_free(sgl, sgp->pool);
}

sgl = mempool_alloc(sgp->pool, gfp_mask);
if (unlikely(!sgl))
goto enomem;
static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
{
struct scsi_host_sg_pool *sgp;

sg_init_table(sgl, sgp->size);
sgp = scsi_sg_pools + scsi_sgtable_index(nents);
return mempool_alloc(sgp->pool, gfp_mask);
}

/*
* first loop through, set initial index and return value
*/
if (!ret)
ret = sgl;
int scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
{
int ret;

/*
* 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);
BUG_ON(!cmd->use_sg);

/*
* if we have nothing left, mark the last segment as
* end-of-list
*/
if (!left)
sg_mark_end(&sgl[this - 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);

/*
* 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;
cmd->request_buffer = cmd->sg_table.sgl;
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];
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)
{
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);

left -= this;

sgp = scsi_sg_pools + index;

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

mempool_free(sgl, sgp->pool);
}

/*
* 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);

mempool_free(sgl, sgp->pool);
__sg_free_table(&cmd->sg_table, scsi_sg_free);
}

EXPORT_SYMBOL(scsi_free_sgtable);
Expand Down Expand Up @@ -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;
}
Expand Down
3 changes: 1 addition & 2 deletions drivers/scsi/scsi_tgt_lib.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down
7 changes: 3 additions & 4 deletions include/scsi/scsi_cmnd.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,6 @@
#include <linux/scatterlist.h>

struct request;
struct scatterlist;
struct Scsi_Host;
struct scsi_device;

Expand Down Expand Up @@ -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 */
Expand Down Expand Up @@ -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)
Expand Down

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