If nothing else, the simplification of this logic shows why I prefer
sg_ring over scatterlist chaining.
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
diff --git a/drivers/block/cciss_scsi.c b/drivers/block/cciss_scsi.c
--- a/drivers/block/cciss_scsi.c
+++ b/drivers/block/cciss_scsi.c
@@ -1191,28 +1191,28 @@ cciss_scatter_gather(struct pci_dev *pde
struct scsi_cmnd *cmd)
{
unsigned int len;
- struct scatterlist *sg;
+ struct sg_ring *sg;
__u64 addr64;
- int use_sg, i;
+ int count = 0, i;
- BUG_ON(scsi_sg_count(cmd) > MAXSGENTRIES);
-
- use_sg = scsi_dma_map(cmd);
- if (use_sg) { /* not too many addrs? */
- scsi_for_each_sg(cmd, sg, use_sg, i) {
- addr64 = (__u64) sg_dma_address(sg);
- len = sg_dma_len(sg);
+ if (scsi_dma_map(cmd) >= 0) { /* not too many addrs? */
+ sg_ring_for_each(scsi_sgring(cmd), sg, i) {
+ addr64 = (__u64) sg_dma_address(&sg->sg[i]);
+ len = sg_dma_len(&sg->sg[i]);
cp->SG[i].Addr.lower =
(__u32) (addr64 & (__u64) 0x00000000FFFFFFFF);
cp->SG[i].Addr.upper =
(__u32) ((addr64 >> 32) & (__u64) 0x00000000FFFFFFFF);
cp->SG[i].Len = len;
cp->SG[i].Ext = 0; // we are not chaining
+ count++;
}
}
- cp->Header.SGList = (__u8) use_sg; /* no. SGs contig in this cmd */
- cp->Header.SGTotal = (__u16) use_sg; /* total sgs in this cmd list */
+ cp->Header.SGList = (__u8) count; /* no. SGs contig in this cmd */
+ cp->Header.SGTotal = (__u16) count; /* total sgs in this cmd list */
+
+ BUG_ON(count > MAXSGENTRIES);
return;
}
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -619,18 +619,17 @@ void scsi_eh_prep_cmnd(struct scsi_cmnd
ses->data_direction = scmd->sc_data_direction;
ses->bufflen = scmd->request_bufflen;
ses->buffer = scmd->request_buffer;
- ses->use_sg = scmd->use_sg;
ses->resid = scmd->resid;
ses->result = scmd->result;
if (sense_bytes) {
scmd->request_bufflen = min_t(unsigned,
sizeof(scmd->sense_buffer), sense_bytes);
- sg_init_one(&ses->sense_sgl, scmd->sense_buffer,
- scmd->request_bufflen);
- scmd->request_buffer = &ses->sense_sgl;
+
+ sg_ring_single(&ses->sense_sg.ring, scmd->sense_buffer,
+ scmd->request_bufflen);
+ scmd->request_buffer = &ses->sense_sg;
scmd->sc_data_direction = DMA_FROM_DEVICE;
- scmd->use_sg = 1;
memset(scmd->cmnd, 0, sizeof(scmd->cmnd));
scmd->cmnd[0] = REQUEST_SENSE;
scmd->cmnd[4] = scmd->request_bufflen;
@@ -639,7 +638,6 @@ void scsi_eh_prep_cmnd(struct scsi_cmnd
scmd->request_buffer = NULL;
scmd->request_bufflen = 0;
scmd->sc_data_direction = DMA_NONE;
- scmd->use_sg = 0;
if (cmnd) {
memset(scmd->cmnd, 0, sizeof(scmd->cmnd));
memcpy(scmd->cmnd, cmnd, cmnd_size);
@@ -678,7 +676,6 @@ void scsi_eh_restore_cmnd(struct scsi_cm
scmd->sc_data_direction = ses->data_direction;
scmd->request_bufflen = ses->bufflen;
scmd->request_buffer = ses->buffer;
- scmd->use_sg = ses->use_sg;
scmd->resid = ses->resid;
scmd->result = ses->result;
}
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -17,7 +17,7 @@
#include <linux/pci.h>
#include <linux/delay.h>
#include <linux/hardirq.h>
-#include <linux/scatterlist.h>
+#include <linux/sg_ring.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
@@ -737,21 +737,31 @@ static inline unsigned int scsi_sgtable_
return index;
}
-struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
+static void free_sgring(struct sg_ring *sg)
{
struct scsi_host_sg_pool *sgp;
- struct scatterlist *sgl, *prev, *ret;
+
+ sgp = scsi_sg_pools + scsi_sgtable_index(sg->max);
+
+ mempool_free(sg, sgp->pool);
+}
+
+struct sg_ring *scsi_alloc_sgring(struct scsi_cmnd *cmd, unsigned int num,
+ gfp_t gfp_mask)
+{
+ struct scsi_host_sg_pool *sgp;
+ struct sg_ring *sg, *ret;
unsigned int index;
int this, left;
- BUG_ON(!cmd->use_sg);
+ BUG_ON(!num);
- left = cmd->use_sg;
- ret = prev = NULL;
+ left = num;
+ ret = NULL;
do {
this = left;
if (this > SCSI_MAX_SG_SEGMENTS) {
- this = SCSI_MAX_SG_SEGMENTS - 1;
+ this = SCSI_MAX_SG_SEGMENTS;
index = SG_MEMPOOL_NR - 1;
} else
index = scsi_sgtable_index(this);
@@ -760,32 +770,20 @@ struct scatterlist *scsi_alloc_sgtable(s
sgp = scsi_sg_pools + index;
- sgl = mempool_alloc(sgp->pool, gfp_mask);
- if (unlikely(!sgl))
+ sg = mempool_alloc(sgp->pool, gfp_mask);
+ if (unlikely(!sg))
goto enomem;
- sg_init_table(sgl, sgp->size);
+ sg_ring_init(sg, sgp->size);
/*
- * first loop through, set initial index and return value
+ * first loop through, set return value, otherwise
+ * attach this to the tail.
*/
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]);
+ ret = sg;
+ else
+ list_add_tail(&sg->list, &ret->list);
/*
* don't allow subsequent mempool allocs to sleep, it would
@@ -793,85 +791,28 @@ struct scatterlist *scsi_alloc_sgtable(s
*/
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];
- mempool_free(sgl, sgp->pool);
- }
-
- mempool_free(prev, sgp->pool);
+ while (!list_empty(&ret->list))
+ free_sgring(sg_ring_next(ret));
+ free_sgring(ret);
}
return NULL;
}
+EXPORT_SYMBOL(scsi_alloc_sgring);
-EXPORT_SYMBOL(scsi_alloc_sgtable);
+void scsi_free_sgring(struct scsi_cmnd *cmd)
+{
+ struct sg_ring *sg = cmd->request_buffer;
-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);
+ while (!list_empty(&sg->list))
+ free_sgring(sg_ring_next(sg));
+ free_sgring(sg);
}
-
-EXPORT_SYMBOL(scsi_free_sgtable);
+EXPORT_SYMBOL(scsi_free_sgring);
/*
* Function: scsi_release_buffers()
@@ -892,8 +833,8 @@ EXPORT_SYMBOL(scsi_free_sgtable);
*/
static void scsi_release_buffers(struct scsi_cmnd *cmd)
{
- if (cmd->use_sg)
- scsi_free_sgtable(cmd);
+ if (cmd->request_buffer)
+ scsi_free_sgring(cmd);
/*
* Zero these out. They now point to freed memory, and it is
@@ -1106,20 +1047,20 @@ static int scsi_init_io(struct scsi_cmnd
static int scsi_init_io(struct scsi_cmnd *cmd)
{
struct request *req = cmd->request;
- int count;
/*
* We used to not use scatter-gather for single segment request,
* but now we do (it makes highmem I/O easier to support without
* kmapping pages)
*/
- cmd->use_sg = req->nr_phys_segments;
/*
* If sg table allocation fails, requeue request later.
*/
- cmd->request_buffer = scsi_alloc_sgtable(cmd, GFP_ATOMIC);
+ cmd->request_buffer = scsi_alloc_sgring(cmd, req->nr_phys_segments,
+ GFP_ATOMIC);
if (unlikely(!cmd->request_buffer)) {
+ BUG();
scsi_unprep_request(req);
return BLKPREP_DEFER;
}
@@ -1134,9 +1075,7 @@ static int scsi_init_io(struct scsi_cmnd
* Next, walk the list, and fill in the addresses and sizes of
* each segment.
*/
- count = blk_rq_map_sg(req->q, req, cmd->request_buffer);
- BUG_ON(count > cmd->use_sg);
- cmd->use_sg = count;
+ blk_rq_map_sg_ring(req->q, req, cmd->request_buffer);
return BLKPREP_OK;
}
@@ -1193,7 +1132,6 @@ int scsi_setup_blk_pc_cmnd(struct scsi_d
cmd->request_bufflen = 0;
cmd->request_buffer = NULL;
- cmd->use_sg = 0;
req->buffer = NULL;
}
@@ -1751,7 +1689,7 @@ int __init scsi_init_queue(void)
for (i = 0; i < SG_MEMPOOL_NR; i++) {
struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
- int size = sgp->size * sizeof(struct scatterlist);
+ int size = sizeof(struct sg_ring) + sgp->size * sizeof(struct scatterlist);
sgp->slab = kmem_cache_create(sgp->name, size, 0,
SLAB_HWCACHE_ALIGN, NULL);
diff --git a/drivers/scsi/scsi_lib_dma.c b/drivers/scsi/scsi_lib_dma.c
--- a/drivers/scsi/scsi_lib_dma.c
+++ b/drivers/scsi/scsi_lib_dma.c
@@ -15,22 +15,17 @@
* scsi_dma_map - perform DMA mapping against command's sg lists
* @cmd: scsi command
*
- * Returns the number of sg lists actually used, zero if the sg lists
- * is NULL, or -ENOMEM if the mapping failed.
+ * Returns -ENOMEM if the mapping failed.
*/
int scsi_dma_map(struct scsi_cmnd *cmd)
{
- int nseg = 0;
-
- if (scsi_sg_count(cmd)) {
+ if (scsi_sgring(cmd)) {
struct device *dev = cmd->device->host->shost_gendev.parent;
- nseg = dma_map_sg(dev, scsi_sglist(cmd), scsi_sg_count(cmd),
- cmd->sc_data_direction);
- if (unlikely(!nseg))
- return -ENOMEM;
+ return dma_map_sg_ring(dev, scsi_sgring(cmd),
+ cmd->sc_data_direction);
}
- return nseg;
+ return 0;
}
EXPORT_SYMBOL(scsi_dma_map);
@@ -40,11 +35,10 @@ EXPORT_SYMBOL(scsi_dma_map);
*/
void scsi_dma_unmap(struct scsi_cmnd *cmd)
{
- if (scsi_sg_count(cmd)) {
+ if (scsi_sgring(cmd)) {
struct device *dev = cmd->device->host->shost_gendev.parent;
- dma_unmap_sg(dev, scsi_sglist(cmd), scsi_sg_count(cmd),
- cmd->sc_data_direction);
+ dma_unmap_sg_ring(dev, scsi_sgring(cmd),cmd->sc_data_direction);
}
}
EXPORT_SYMBOL(scsi_dma_unmap);
diff --git a/drivers/scsi/scsi_tgt_lib.c b/drivers/scsi/scsi_tgt_lib.c
--- a/drivers/scsi/scsi_tgt_lib.c
+++ b/drivers/scsi/scsi_tgt_lib.c
@@ -358,15 +358,15 @@ static int scsi_tgt_init_cmd(struct scsi
struct request *rq = cmd->request;
int count;
- cmd->use_sg = rq->nr_phys_segments;
- cmd->request_buffer = scsi_alloc_sgtable(cmd, gfp_mask);
+ cmd->request_buffer = scsi_alloc_sgring(cmd, rq->nr_phys_segments,
+ gfp_mask);
if (!cmd->request_buffer)
return -ENOMEM;
cmd->request_bufflen = rq->data_len;
dprintk("cmd %p cnt %d %lu\n", cmd, cmd->use_sg, rq_data_dir(rq));
- count = blk_rq_map_sg(rq->q, rq, cmd->request_buffer);
+ count = blk_rq_map_sg_ring(rq->q, rq, cmd->request_buffer);
BUG_ON(count > cmd->use_sg);
cmd->use_sg = count;
return 0;
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -66,10 +66,6 @@ struct scsi_cmnd {
struct timer_list eh_timeout; /* Used to time out the command. */
void *request_buffer; /* Actual requested buffer */
-
- /* These elements define the operation we ultimately want to perform */
- 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 +124,13 @@ extern void *scsi_kmap_atomic_sg(struct
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 void scsi_free_sgtable(struct scsi_cmnd *);
+extern struct sg_ring *scsi_alloc_sgring(struct scsi_cmnd *, unsigned, gfp_t);
+extern void scsi_free_sgring(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_sgring(cmd) ((struct sg_ring *)(cmd)->request_buffer)
#define scsi_bufflen(cmd) ((cmd)->request_bufflen)
static inline void scsi_set_resid(struct scsi_cmnd *cmd, int resid)
diff --git a/include/scsi/scsi_eh.h b/include/scsi/scsi_eh.h
--- a/include/scsi/scsi_eh.h
+++ b/include/scsi/scsi_eh.h
@@ -1,7 +1,7 @@
#ifndef _SCSI_SCSI_EH_H
#define _SCSI_SCSI_EH_H
-#include <linux/scatterlist.h>
+#include <linux/sg_ring.h>
#include <scsi/scsi_cmnd.h>
struct scsi_device;
@@ -75,10 +75,9 @@ struct scsi_eh_save {
void *buffer;
unsigned bufflen;
- unsigned short use_sg;
int resid;
- struct scatterlist sense_sgl;
+ DECLARE_SG_RING(sense_sg, 1);
};
extern void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd,
-
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