[SCSI] add kmemcache for scsi_io_context

Add kmemcache of scsi io contexts.

In the future when we finalize on where these functions will live
we can add a mempool for it and do a bioset for out REQ_BLOCK_PC
bios. This is needed becuase the dm-multipath handlers will
want to use the scsi_exectute* functions for failover and we cannot
have them and the bio device allocating from the same mempool.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 3e136bfe4219..54a72f197487 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -306,6 +306,8 @@ struct scsi_io_context {
         char sense[SCSI_SENSE_BUFFERSIZE];
 };
 
+static kmem_cache_t *scsi_io_context_cache;
+
 static void scsi_end_async(struct request *req)
 {
         struct scsi_io_context *sioc = req->end_io_data;
@@ -313,7 +315,7 @@ static void scsi_end_async(struct request *req)
         if (sioc->done)
                 sioc->done(sioc->data, sioc->sense, req->errors, req->data_len);
 
-        kfree(sioc);
+        kmem_cache_free(scsi_io_context_cache, sioc);
         __blk_put_request(req->q, req);
 }
 
@@ -452,9 +454,10 @@ int scsi_execute_async(struct scsi_device *sdev, const unsigned char *cmd,
         int err = 0;
         int write = (data_direction == DMA_TO_DEVICE);
 
-        sioc = kzalloc(sizeof(*sioc), gfp);
+        sioc = kmem_cache_alloc(scsi_io_context_cache, gfp);
         if (!sioc)
                 return DRIVER_ERROR << 24;
+        memset(sioc, 0, sizeof(*sioc));
 
         req = blk_get_request(sdev->request_queue, write, gfp);
         if (!req)
@@ -1765,6 +1768,14 @@ int __init scsi_init_queue(void)
 {
         int i;
 
+        scsi_io_context_cache = kmem_cache_create("scsi_io_context",
+                                        sizeof(struct scsi_io_context),
+                                        0, 0, NULL, NULL);
+        if (!scsi_io_context_cache) {
+                printk(KERN_ERR "SCSI: can't init scsi io context cache\n");
+                return -ENOMEM;
+        }
+
         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);
@@ -1792,6 +1803,8 @@ void scsi_exit_queue(void)
 {
         int i;
 
+        kmem_cache_destroy(scsi_io_context_cache);
+
         for (i = 0; i < SG_MEMPOOL_NR; i++) {
                 struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
                 mempool_destroy(sgp->pool);