[SCSI] mpt2sas: Create a pool of chain buffer instead of dedicated per IOs

Create a pool of chain buffers, instead of dedicated per IO:
This enahancment is to address memory allocation failure when asking
for more than 2300 IOs per host.   There is just not enough contiquious
DMA physical memory to make one single allocation to hold both message
frames and chain buffers when asking for more than 2300 request. In order
to address this problem we will have to allocate memory for each chain
buffer in a seperate individual memory allocation, placing each chain
element of 128 bytes onto a pool of available chains, which can be
shared amoung all request.
Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 32 insertions, 24 deletions

diff --git a/drivers/scsi/mpt2sas/mpt2sas_scsih.c b/drivers/scsi/mpt2sas/mpt2sas_scsih.c
index 5af5781d9464..3e9c78aa4ccb 100644
--- a/drivers/scsi/mpt2sas/mpt2sas_scsih.c
+++ b/drivers/scsi/mpt2sas/mpt2sas_scsih.c
@@ -931,31 +931,32 @@ _scsih_scsi_lookup_find_by_lun(struct MPT2SAS_ADAPTER *ioc, int id,
 }
 
 /**
- * _scsih_get_chain_buffer_dma - obtain block of chains (dma address)
+ * _scsih_get_chain_buffer_tracker - obtain chain tracker
  * @ioc: per adapter object
- * @smid: system request message index
+ * @smid: smid associated to an IO request
  *
- * Returns phys pointer to chain buffer.
+ * Returns chain tracker(from ioc->free_chain_list)
  */
-static dma_addr_t
-_scsih_get_chain_buffer_dma(struct MPT2SAS_ADAPTER *ioc, u16 smid)
+static struct chain_tracker *
+_scsih_get_chain_buffer_tracker(struct MPT2SAS_ADAPTER *ioc, u16 smid)
 {
-	return ioc->chain_dma + ((smid - 1) * (ioc->request_sz *
-	    ioc->chains_needed_per_io));
-}
+	struct chain_tracker *chain_req;
+	unsigned long flags;
 
-/**
- * _scsih_get_chain_buffer - obtain block of chains assigned to a mf request
- * @ioc: per adapter object
- * @smid: system request message index
- *
- * Returns virt pointer to chain buffer.
- */
-static void *
-_scsih_get_chain_buffer(struct MPT2SAS_ADAPTER *ioc, u16 smid)
-{
-	return (void *)(ioc->chain + ((smid - 1) * (ioc->request_sz *
-	    ioc->chains_needed_per_io)));
+	spin_lock_irqsave(&ioc->scsi_lookup_lock, flags);
+	if (list_empty(&ioc->free_chain_list)) {
+		spin_unlock_irqrestore(&ioc->scsi_lookup_lock, flags);
+		printk(MPT2SAS_WARN_FMT "chain buffers not available\n",
+		    ioc->name);
+		return NULL;
+	}
+	chain_req = list_entry(ioc->free_chain_list.next,
+	    struct chain_tracker, tracker_list);
+	list_del_init(&chain_req->tracker_list);
+	list_add_tail(&chain_req->tracker_list,
+	    &ioc->scsi_lookup[smid - 1].chain_list);
+	spin_unlock_irqrestore(&ioc->scsi_lookup_lock, flags);
+	return chain_req;
 }
 
 /**
@@ -986,6 +987,7 @@ _scsih_build_scatter_gather(struct MPT2SAS_ADAPTER *ioc,
 	u32 sgl_flags;
 	u32 sgl_flags_last_element;
 	u32 sgl_flags_end_buffer;
+	struct chain_tracker *chain_req;
 
 	mpi_request = mpt2sas_base_get_msg_frame(ioc, smid);
 
@@ -1033,8 +1035,11 @@ _scsih_build_scatter_gather(struct MPT2SAS_ADAPTER *ioc,
 
 	/* initializing the chain flags and pointers */
 	chain_flags = MPI2_SGE_FLAGS_CHAIN_ELEMENT << MPI2_SGE_FLAGS_SHIFT;
-	chain = _scsih_get_chain_buffer(ioc, smid);
-	chain_dma = _scsih_get_chain_buffer_dma(ioc, smid);
+	chain_req = _scsih_get_chain_buffer_tracker(ioc, smid);
+	if (!chain_req)
+		return -1;
+	chain = chain_req->chain_buffer;
+	chain_dma = chain_req->chain_buffer_dma;
 	do {
 		sges_in_segment = (sges_left <=
 		    ioc->max_sges_in_chain_message) ? sges_left :
@@ -1070,8 +1075,11 @@ _scsih_build_scatter_gather(struct MPT2SAS_ADAPTER *ioc,
 			sges_in_segment--;
 		}
 
-		chain_dma += ioc->request_sz;
-		chain += ioc->request_sz;
+		chain_req = _scsih_get_chain_buffer_tracker(ioc, smid);
+		if (!chain_req)
+			return -1;
+		chain = chain_req->chain_buffer;
+		chain_dma = chain_req->chain_buffer_dma;
 	} while (1);