[SCSI] add support for per-host cmd pools

This allows drivers to specify the size of their per-command private
data in the host template and then get extra memory allocated for
each command instead of needing another allocation in ->queuecommand.

With the current SCSI code that already does multiple allocations for
each command this probably doesn't make a big performance impact, but
it allows to clean up the drivers, and prepare them for using the
blk-mq infrastructure where the common allocation will make a difference.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 77 insertions, 19 deletions

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 586c241c941e..c4d632c27a3e 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -331,46 +331,103 @@ void scsi_put_command(struct scsi_cmnd *cmd)
 }
 EXPORT_SYMBOL(scsi_put_command);
 
-static struct scsi_host_cmd_pool *scsi_get_host_cmd_pool(gfp_t gfp_mask)
+static struct scsi_host_cmd_pool *
+scsi_find_host_cmd_pool(struct Scsi_Host *shost)
 {
+        if (shost->hostt->cmd_size)
+                return shost->hostt->cmd_pool;
+        if (shost->unchecked_isa_dma)
+                return &scsi_cmd_dma_pool;
+        return &scsi_cmd_pool;
+}
+
+static void
+scsi_free_host_cmd_pool(struct scsi_host_cmd_pool *pool)
+{
+        kfree(pool->sense_name);
+        kfree(pool->cmd_name);
+        kfree(pool);
+}
+
+static struct scsi_host_cmd_pool *
+scsi_alloc_host_cmd_pool(struct Scsi_Host *shost)
+{
+        struct scsi_host_template *hostt = shost->hostt;
+        struct scsi_host_cmd_pool *pool;
+
+        pool = kzalloc(sizeof(*pool), GFP_KERNEL);
+        if (!pool)
+                return NULL;
+
+        pool->cmd_name = kasprintf(GFP_KERNEL, "%s_cmd", hostt->name);
+        pool->sense_name = kasprintf(GFP_KERNEL, "%s_sense", hostt->name);
+        if (!pool->cmd_name || !pool->sense_name) {
+                scsi_free_host_cmd_pool(pool);
+                return NULL;
+        }
+
+        pool->slab_flags = SLAB_HWCACHE_ALIGN;
+        if (shost->unchecked_isa_dma) {
+                pool->slab_flags |= SLAB_CACHE_DMA;
+                pool->gfp_mask = __GFP_DMA;
+        }
+        return pool;
+}
+
+static struct scsi_host_cmd_pool *
+scsi_get_host_cmd_pool(struct Scsi_Host *shost)
+{
+        struct scsi_host_template *hostt = shost->hostt;
         struct scsi_host_cmd_pool *retval = NULL, *pool;
+        size_t cmd_size = sizeof(struct scsi_cmnd) + hostt->cmd_size;
+
         /*
          * Select a command slab for this host and create it if not
          * yet existent.
          */
         mutex_lock(&host_cmd_pool_mutex);
-        pool = (gfp_mask & __GFP_DMA) ? &scsi_cmd_dma_pool :
-                &scsi_cmd_pool;
+        pool = scsi_find_host_cmd_pool(shost);
+        if (!pool) {
+                pool = scsi_alloc_host_cmd_pool(shost);
+                if (!pool)
+                        goto out;
+        }
+
         if (!pool->users) {
-                pool->cmd_slab = kmem_cache_create(pool->cmd_name,
-                                                   sizeof(struct scsi_cmnd), 0,
+                pool->cmd_slab = kmem_cache_create(pool->cmd_name, cmd_size, 0,
                                                    pool->slab_flags, NULL);
                 if (!pool->cmd_slab)
-                        goto fail;
+                        goto out_free_pool;
 
                 pool->sense_slab = kmem_cache_create(pool->sense_name,
                                                      SCSI_SENSE_BUFFERSIZE, 0,
                                                      pool->slab_flags, NULL);
-                if (!pool->sense_slab) {
-                        kmem_cache_destroy(pool->cmd_slab);
-                        goto fail;
-                }
+                if (!pool->sense_slab)
+                        goto out_free_slab;
         }
 
         pool->users++;
         retval = pool;
- fail:
+out:
         mutex_unlock(&host_cmd_pool_mutex);
         return retval;
+
+out_free_slab:
+        kmem_cache_destroy(pool->cmd_slab);
+out_free_pool:
+        if (hostt->cmd_size)
+                scsi_free_host_cmd_pool(pool);
+        goto out;
 }
 
-static void scsi_put_host_cmd_pool(gfp_t gfp_mask)
+static void scsi_put_host_cmd_pool(struct Scsi_Host *shost)
 {
+        struct scsi_host_template *hostt = shost->hostt;
         struct scsi_host_cmd_pool *pool;
 
         mutex_lock(&host_cmd_pool_mutex);
-        pool = (gfp_mask & __GFP_DMA) ? &scsi_cmd_dma_pool :
-                &scsi_cmd_pool;
+        pool = scsi_find_host_cmd_pool(shost);
+
         /*
          * This may happen if a driver has a mismatched get and put
          * of the command pool; the driver should be implicated in
@@ -381,6 +438,8 @@ static void scsi_put_host_cmd_pool(gfp_t gfp_mask)
         if (!--pool->users) {
                 kmem_cache_destroy(pool->cmd_slab);
                 kmem_cache_destroy(pool->sense_slab);
+                if (hostt->cmd_size)
+                        scsi_free_host_cmd_pool(pool);
         }
         mutex_unlock(&host_cmd_pool_mutex);
 }
@@ -397,14 +456,13 @@ static void scsi_put_host_cmd_pool(gfp_t gfp_mask)
  */
 int scsi_setup_command_freelist(struct Scsi_Host *shost)
 {
-        struct scsi_cmnd *cmd;
         const gfp_t gfp_mask = shost->unchecked_isa_dma ? GFP_DMA : GFP_KERNEL;
+        struct scsi_cmnd *cmd;
 
         spin_lock_init(&shost->free_list_lock);
         INIT_LIST_HEAD(&shost->free_list);
 
-        shost->cmd_pool = scsi_get_host_cmd_pool(gfp_mask);
-
+        shost->cmd_pool = scsi_get_host_cmd_pool(shost);
         if (!shost->cmd_pool)
                 return -ENOMEM;
 
@@ -413,7 +471,7 @@ int scsi_setup_command_freelist(struct Scsi_Host *shost)
          */
         cmd = scsi_host_alloc_command(shost, gfp_mask);
         if (!cmd) {
-                scsi_put_host_cmd_pool(gfp_mask);
+                scsi_put_host_cmd_pool(shost);
                 shost->cmd_pool = NULL;
                 return -ENOMEM;
         }
@@ -442,7 +500,7 @@ void scsi_destroy_command_freelist(struct Scsi_Host *shost)
                 scsi_host_free_command(shost, cmd);
         }
         shost->cmd_pool = NULL;
-        scsi_put_host_cmd_pool(shost->unchecked_isa_dma ? GFP_DMA : GFP_KERNEL);
+        scsi_put_host_cmd_pool(shost);
 }
 
 #ifdef CONFIG_SCSI_LOGGING