[PATCH v2 16/16] nvme: Ensure atomic writes will be executed atomically

[John Garry]

From: Alan Adamson <alan.adamson@xxxxxxxxxx>

There is no dedicated NVMe atomic write command (which may error for a
command which exceeds the controller atomic write limits).

As an insurance policy against the block layer sending requests which
cannot be executed atomically, add a check in the queue path.

Signed-off-by: Alan Adamson <alan.adamson@xxxxxxxxxx>
Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
---
 drivers/nvme/host/core.c | 23 +++++++++++++++++++++++
 drivers/nvme/host/nvme.h |  2 ++
 2 files changed, 25 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index fd4f09f9dbe8..6b89ee7e9921 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -905,6 +905,26 @@ static inline blk_status_t nvme_setup_rw(struct nvme_ns *ns,
 	if (req->cmd_flags & REQ_RAHEAD)
 		dsmgmt |= NVME_RW_DSM_FREQ_PREFETCH;
 
+	/*
+	 * Ensure that nothing has been sent which cannot be executed
+	 * atomically.
+	 */
+	if (req->cmd_flags & REQ_ATOMIC) {
+		if (blk_rq_bytes(req) > ns->atomic_max)
+			return BLK_STS_IOERR;
+
+		if (ns->atomic_boundary) {
+			u32 boundary = ns->atomic_boundary >> ns->lba_shift;
+			u32 imask = ~(boundary - 1);
+			u32 lba = nvme_sect_to_lba(ns, blk_rq_pos(req));
+			u32 end = lba + (blk_rq_bytes(req) >> ns->lba_shift)
+					- 1;
+
+			if ((lba & imask) != (end & imask))
+				return BLK_STS_IOERR;
+		}
+	}
+
 	cmnd->rw.opcode = op;
 	cmnd->rw.flags = 0;
 	cmnd->rw.nsid = cpu_to_le32(ns->head->ns_id);
@@ -1937,6 +1957,9 @@ static void nvme_update_atomic_write_disk_info(struct gendisk *disk,
 				id->nabo);
 	}
 
+	ns->atomic_max = atomic_bs;
+	ns->atomic_boundary = boundary;
+
 	blk_queue_atomic_write_max_bytes(disk->queue, atomic_bs);
 	blk_queue_atomic_write_unit_min_sectors(disk->queue, bs >> SECTOR_SHIFT);
 	blk_queue_atomic_write_unit_max_sectors(disk->queue,
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index e7411dac00f7..5a3d76bc816f 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -520,6 +520,8 @@ struct nvme_ns {
 
 	struct nvme_fault_inject fault_inject;
 
+	u32 atomic_max;
+	u32 atomic_boundary;
 };
 
 /* NVMe ns supports metadata actions by the controller (generate/strip) */
-- 
2.35.3