[SCSI] use dynamically allocated sense buffer

This removes static array sense_buffer in scsi_cmnd and uses
dynamically allocated sense_buffer (with GFP_DMA).

The reason for doing this is that some architectures need cacheline
aligned buffer for DMA:

http://lkml.org/lkml/2007/11/19/2

The problems are that scsi_eh_prep_cmnd puts scsi_cmnd::sense_buffer
to sglist and some LLDs directly DMA to scsi_cmnd::sense_buffer. It's
necessary to DMA to scsi_cmnd::sense_buffer safely. This patch solves
these issues.

__scsi_get_command allocates sense_buffer via kmem_cache_alloc and
attaches it to a scsi_cmnd so everything just work as before.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

3 files changed, 69 insertions, 3 deletions

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 9a10b4335e76..f5d3fbb55717 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -268,6 +268,7 @@ static void scsi_host_dev_release(struct device *dev)
         }
 
         scsi_destroy_command_freelist(shost);
+        scsi_destroy_command_sense_buffer(shost);
         if (shost->bqt)
                 blk_free_tags(shost->bqt);
 
@@ -372,10 +373,14 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
         else
                 shost->dma_boundary = 0xffffffff;
 
-        rval = scsi_setup_command_freelist(shost);
+        rval = scsi_setup_command_sense_buffer(shost);
         if (rval)
                 goto fail_kfree;
 
+        rval = scsi_setup_command_freelist(shost);
+        if (rval)
+                goto fail_destroy_sense;
+
         device_initialize(&shost->shost_gendev);
         snprintf(shost->shost_gendev.bus_id, BUS_ID_SIZE, "host%d",
                 shost->host_no);
@@ -399,6 +404,8 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 
  fail_destroy_freelist:
         scsi_destroy_command_freelist(shost);
+ fail_destroy_sense:
+        scsi_destroy_command_sense_buffer(shost);
  fail_kfree:
         kfree(shost);
         return NULL;
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 54ff611b8677..0a4a5b8b87c6 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -161,6 +161,9 @@ static struct scsi_host_cmd_pool scsi_cmd_dma_pool = {
 
 static DEFINE_MUTEX(host_cmd_pool_mutex);
 
+static struct kmem_cache *sense_buffer_slab;
+static int sense_buffer_slab_users;
+
 /**
  * __scsi_get_command - Allocate a struct scsi_cmnd
  * @shost: host to transmit command
@@ -172,6 +175,7 @@ static DEFINE_MUTEX(host_cmd_pool_mutex);
 struct scsi_cmnd *__scsi_get_command(struct Scsi_Host *shost, gfp_t gfp_mask)
 {
         struct scsi_cmnd *cmd;
+        unsigned char *buf;
 
         cmd = kmem_cache_alloc(shost->cmd_pool->slab,
                         gfp_mask | shost->cmd_pool->gfp_mask);
@@ -186,6 +190,21 @@ struct scsi_cmnd *__scsi_get_command(struct Scsi_Host *shost, gfp_t gfp_mask)
                         list_del_init(&cmd->list);
                 }
                 spin_unlock_irqrestore(&shost->free_list_lock, flags);
+
+                if (cmd) {
+                        buf = cmd->sense_buffer;
+                        memset(cmd, 0, sizeof(*cmd));
+                        cmd->sense_buffer = buf;
+                }
+        } else {
+                buf = kmem_cache_alloc(sense_buffer_slab, __GFP_DMA|gfp_mask);
+                if (likely(buf)) {
+                        memset(cmd, 0, sizeof(*cmd));
+                        cmd->sense_buffer = buf;
+                } else {
+                        kmem_cache_free(shost->cmd_pool->slab, cmd);
+                        cmd = NULL;
+                }
         }
 
         return cmd;
@@ -212,7 +231,6 @@ struct scsi_cmnd *scsi_get_command(struct scsi_device *dev, gfp_t gfp_mask)
         if (likely(cmd != NULL)) {
                 unsigned long flags;
 
-                memset(cmd, 0, sizeof(*cmd));
                 cmd->device = dev;
                 init_timer(&cmd->eh_timeout);
                 INIT_LIST_HEAD(&cmd->list);
@@ -246,8 +264,10 @@ void __scsi_put_command(struct Scsi_Host *shost, struct scsi_cmnd *cmd,
         }
         spin_unlock_irqrestore(&shost->free_list_lock, flags);
 
-        if (likely(cmd != NULL))
+        if (likely(cmd != NULL)) {
+                kmem_cache_free(sense_buffer_slab, cmd->sense_buffer);
                 kmem_cache_free(shost->cmd_pool->slab, cmd);
+        }
 
         put_device(dev);
 }
@@ -290,6 +310,7 @@ int scsi_setup_command_freelist(struct Scsi_Host *shost)
 {
         struct scsi_host_cmd_pool *pool;
         struct scsi_cmnd *cmd;
+        unsigned char *sense_buffer;
 
         spin_lock_init(&shost->free_list_lock);
         INIT_LIST_HEAD(&shost->free_list);
@@ -319,9 +340,18 @@ int scsi_setup_command_freelist(struct Scsi_Host *shost)
                         GFP_KERNEL | shost->cmd_pool->gfp_mask);
         if (!cmd)
                 goto fail2;
+
+        sense_buffer = kmem_cache_alloc(sense_buffer_slab,
+                                        GFP_KERNEL | __GFP_DMA);
+        if (!sense_buffer)
+                goto destroy_backup;
+
+        cmd->sense_buffer = sense_buffer;
         list_add(&cmd->list, &shost->free_list);
         return 0;
 
+destroy_backup:
+        kmem_cache_free(shost->cmd_pool->slab, cmd);
  fail2:
         mutex_lock(&host_cmd_pool_mutex);
         if (!--pool->users)
@@ -342,6 +372,7 @@ void scsi_destroy_command_freelist(struct Scsi_Host *shost)
 
                 cmd = list_entry(shost->free_list.next, struct scsi_cmnd, list);
                 list_del_init(&cmd->list);
+                kmem_cache_free(sense_buffer_slab, cmd->sense_buffer);
                 kmem_cache_free(shost->cmd_pool->slab, cmd);
         }
 
@@ -351,6 +382,32 @@ void scsi_destroy_command_freelist(struct Scsi_Host *shost)
         mutex_unlock(&host_cmd_pool_mutex);
 }
 
+int scsi_setup_command_sense_buffer(struct Scsi_Host *shost)
+{
+        mutex_lock(&host_cmd_pool_mutex);
+        if (!sense_buffer_slab_users) {
+                sense_buffer_slab = kmem_cache_create("scsi_sense_buffer",
+                                                      SCSI_SENSE_BUFFERSIZE,
+                                                      0, SLAB_CACHE_DMA, NULL);
+                if (!sense_buffer_slab) {
+                        mutex_unlock(&host_cmd_pool_mutex);
+                        return -ENOMEM;
+                }
+        }
+        sense_buffer_slab_users++;
+        mutex_unlock(&host_cmd_pool_mutex);
+
+        return 0;
+}
+
+void scsi_destroy_command_sense_buffer(struct Scsi_Host *shost)
+{
+        mutex_lock(&host_cmd_pool_mutex);
+        if (!--sense_buffer_slab_users)
+                kmem_cache_destroy(sense_buffer_slab);
+        mutex_unlock(&host_cmd_pool_mutex);
+}
+
 #ifdef CONFIG_SCSI_LOGGING
 void scsi_log_send(struct scsi_cmnd *cmd)
 {
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index 3f34e9376b0a..55c6f71a9aee 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -27,6 +27,8 @@ extern void scsi_exit_hosts(void);
 extern int scsi_dispatch_cmd(struct scsi_cmnd *cmd);
 extern int scsi_setup_command_freelist(struct Scsi_Host *shost);
 extern void scsi_destroy_command_freelist(struct Scsi_Host *shost);
+extern int scsi_setup_command_sense_buffer(struct Scsi_Host *shost);
+extern void scsi_destroy_command_sense_buffer(struct Scsi_Host *shost);
 extern void __scsi_done(struct scsi_cmnd *cmd);
 #ifdef CONFIG_SCSI_LOGGING
 void scsi_log_send(struct scsi_cmnd *cmd);