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: Jens Axboe <jens.axboe@oracle.com>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 4cf902efbdbf14aa26422226491463aa05a2f7cc..3b5121c4c08110f6e3b2d601d6b94809fef7a87d 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -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);
@@ -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;
        }

diff --git a/drivers/scsi/scsi_tgt_lib.c b/drivers/scsi/scsi_tgt_lib.c
index 93ece8f4e5dea391c07c8a4241df9d180489c869..01e03f3f6ffa39ea7240dfe355ddd7edf5a5981c 100644 (file)
--- a/drivers/scsi/scsi_tgt_lib.c
+++ b/drivers/scsi/scsi_tgt_lib.c
@@ -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;

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index abd7479ff45298fbf25bd6d2fb9579531b29f652..a457fca66f6156c4b3629c06d10a71e4c453c5ee 100644 (file)
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -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)