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NVMe: Create discard zero quirk white list

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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 <[email protected]>
Suggested-by: Artur Paszkiewicz <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Reviewed-by: Johannes Thumshirn <[email protected]>
Reviewed-by: Sagi Grimberg <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Keith Busch 2016-03-04 13:15:17 -07:00 • committed by Jens Axboe
commit 08095e7078
3 changed files with 15 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

8
drivers/nvme/host/core.c
View file

@ -582,8 +582,14 @@ 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, 0xffffffff);

6
drivers/nvme/host/nvme.h
View file

@ -59,6 +59,12 @@ enum nvme_quirks {
* 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),
};
struct nvme_ctrl {

3
drivers/nvme/host/pci.c
View file

@ -2130,7 +2130,8 @@ static const struct pci_error_handlers nvme_err_handler = {
static const struct pci_device_id nvme_id_table[] = {
{ PCI_VDEVICE(INTEL, 0x0953),
.driver_data = NVME_QUIRK_STRIPE_SIZE, },
.driver_data = NVME_QUIRK_STRIPE_SIZE |
NVME_QUIRK_DISCARD_ZEROES, },
{ PCI_VDEVICE(INTEL, 0x5845), /* Qemu emulated controller */
.driver_data = NVME_QUIRK_IDENTIFY_CNS, },
{ PCI_DEVICE_CLASS(PCI_CLASS_STORAGE_EXPRESS, 0xffffff) },