[PATCH 9/9] scsi: add support for per-host cmd pools

Christoph Hellwig
2014-02-20T22:23:59Z

[-- Attachment #1: 0009-scsi-add-support-for-per-host-cmd-pools.patch --]
[-- Type: text/plain, Size: 5945 bytes --]

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>
---
drivers/scsi/scsi.c | 96 +++++++++++++++++++++++++++++++++++++---------
include/scsi/scsi_host.h | 7 ++++
2 files changed, 84 insertions(+), 19 deletions(-)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index a94a486..a45f01c 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -332,46 +332,103 @@ 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
@@ -382,6 +439,8 @@ 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);
}
@@ -398,14 +457,13 @@ 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;

@@ -414,7 +472,7 @@ 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;
}
@@ -443,7 +501,7 @@ 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
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 53075e5..94844fc 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -15,6 +15,7 @@ struct completion;
struct module;
struct scsi_cmnd;
struct scsi_device;
+struct scsi_host_cmd_pool;
struct scsi_target;
struct Scsi_Host;
struct scsi_host_cmd_pool;
@@ -524,6 +525,12 @@ struct scsi_host_template {
* scsi_netlink.h
*/
u64 vendor_id;
+
+ /*
+ * Additional per-command data allocated for the driver.
+ */
+ unsigned int cmd_size;
+ struct scsi_host_cmd_pool *cmd_pool;
};

/*
--
1.7.10.4