NVMe: Create discard zero quirk white list

The NVMe specification does not require discarded blocks return zeroes on
read, but provides that behavior as a possibility. Some applications more
efficiently use an SSD if reads on discarded blocks were deterministically
zero, based on the "discard_zeroes_data" queue attribute.

There is no specification defined way to determine device behavior on
discarded blocks, so the driver always left the queue setting disabled. We
can only know behavior based on individual device models, so this patch
adds a flag to the NVMe "quirk" list that vendors may set if they know
their controller works that way. The patch also sets the new flag for one
such known device.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Suggested-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
(cherry picked from commit 08095e70783f1d8296f858d37a9e1878f5da0623)

Orabug: 25130845

Signed-off-by: Ashok Vairavan <ashok.vairavan@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index ad275f2f660f0e6569a6864f1211f2c7df05ab7e..58573ffa2ae213612062ed8fc6c5546b564d583e 100644 (file)
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -731,8 +731,14 @@ static void nvme_init_integrity(struct nvme_ns *ns)
 
 static void nvme_config_discard(struct nvme_ns *ns)
 {
+       struct nvme_ctrl *ctrl = ns->ctrl;
        u32 logical_block_size = queue_logical_block_size(ns->queue);
-       ns->queue->limits.discard_zeroes_data = 0;
+
+       if (ctrl->quirks & NVME_QUIRK_DISCARD_ZEROES)
+               ns->queue->limits.discard_zeroes_data = 1;
+       else
+               ns->queue->limits.discard_zeroes_data = 0;
+
        ns->queue->limits.discard_alignment = logical_block_size;
        ns->queue->limits.discard_granularity = logical_block_size;
        blk_queue_max_discard_sectors(ns->queue, UINT_MAX);

diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 1a449283c858a9599496d2fee221118b4fae0de1..5e88b21b99d62b27479445720322ff8163992c44 100644 (file)
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -53,6 +53,17 @@ enum nvme_quirks {
         * specific Identify field.
         */
        NVME_QUIRK_STRIPE_SIZE                  = (1 << 0),
+       /*
+        * The controller doesn't handle Identify value others than 0 or 1
+        * correctly.
+        */
+       NVME_QUIRK_IDENTIFY_CNS                 = (1 << 1),
+
+       /*
+        * The controller deterministically returns O's on reads to discarded
+        * logical blocks.
+        */
+       NVME_QUIRK_DISCARD_ZEROES               = (1 << 2),
 };
 
 enum nvme_ctrl_state {