NVMe: Implement Flush

Linux implements Flush as a bit in the bio.  That means there may also be
data associated with the flush; if so the flush should be sent before the
data.  To avoid completing the bio twice, I add CMD_CTX_FLUSH to indicate
the completion routine should do nothing.

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/drivers/block/nvme.c b/drivers/block/nvme.c
index ce919b49b30d..d99b400ccd79 100644
--- a/drivers/block/nvme.c
+++ b/drivers/block/nvme.c
@@ -191,10 +191,12 @@ enum {
         bio_completion_id,
 };
 
+/* Special values must be a multiple of 4, and less than 0x1000 */
 #define CMD_CTX_BASE            (POISON_POINTER_DELTA + sync_completion_id)
 #define CMD_CTX_CANCELLED       (0x30C + CMD_CTX_BASE)
 #define CMD_CTX_COMPLETED       (0x310 + CMD_CTX_BASE)
 #define CMD_CTX_INVALID         (0x314 + CMD_CTX_BASE)
+#define CMD_CTX_FLUSH           (0x318 + CMD_CTX_BASE)
 
 static unsigned long free_cmdid(struct nvme_queue *nvmeq, int cmdid)
 {
@@ -416,6 +418,33 @@ static int nvme_map_bio(struct device *dev, struct nvme_bio *nbio,
         return dma_map_sg(dev, nbio->sg, nbio->nents, dma_dir);
 }
 
+static int nvme_submit_flush(struct nvme_queue *nvmeq, struct nvme_ns *ns,
+                                                                int cmdid)
+{
+        struct nvme_command *cmnd = &nvmeq->sq_cmds[nvmeq->sq_tail];
+
+        memset(cmnd, 0, sizeof(*cmnd));
+        cmnd->common.opcode = nvme_cmd_flush;
+        cmnd->common.command_id = cmdid;
+        cmnd->common.nsid = cpu_to_le32(ns->ns_id);
+
+        if (++nvmeq->sq_tail == nvmeq->q_depth)
+                nvmeq->sq_tail = 0;
+        writel(nvmeq->sq_tail, nvmeq->q_db);
+
+        return 0;
+}
+
+static int nvme_submit_flush_data(struct nvme_queue *nvmeq, struct nvme_ns *ns)
+{
+        int cmdid = alloc_cmdid(nvmeq, (void *)CMD_CTX_FLUSH,
+                                                sync_completion_id, IO_TIMEOUT);
+        if (unlikely(cmdid < 0))
+                return cmdid;
+
+        return nvme_submit_flush(nvmeq, ns, cmdid);
+}
+
 static int nvme_submit_bio_queue(struct nvme_queue *nvmeq, struct nvme_ns *ns,
                                                                 struct bio *bio)
 {
@@ -427,6 +456,12 @@ static int nvme_submit_bio_queue(struct nvme_queue *nvmeq, struct nvme_ns *ns,
         u32 dsmgmt;
         int psegs = bio_phys_segments(ns->queue, bio);
 
+        if ((bio->bi_rw & REQ_FLUSH) && psegs) {
+                result = nvme_submit_flush_data(nvmeq, ns);
+                if (result)
+                        return result;
+        }
+
         nbio = alloc_nbio(psegs, GFP_ATOMIC);
         if (!nbio)
                 goto nomem;
@@ -437,6 +472,9 @@ static int nvme_submit_bio_queue(struct nvme_queue *nvmeq, struct nvme_ns *ns,
         if (unlikely(cmdid < 0))
                 goto free_nbio;
 
+        if ((bio->bi_rw & REQ_FLUSH) && !psegs)
+                return nvme_submit_flush(nvmeq, ns, cmdid);
+
         control = 0;
         if (bio->bi_rw & REQ_FUA)
                 control |= NVME_RW_FUA;
@@ -520,6 +558,8 @@ static void sync_completion(struct nvme_queue *nvmeq, void *ctx,
         struct sync_cmd_info *cmdinfo = ctx;
         if (unlikely((unsigned long)cmdinfo == CMD_CTX_CANCELLED))
                 return;
+        if ((unsigned long)cmdinfo == CMD_CTX_FLUSH)
+                return;
         if (unlikely((unsigned long)cmdinfo == CMD_CTX_COMPLETED)) {
                 dev_warn(nvmeq->q_dmadev,
                                 "completed id %d twice on queue %d\n",