[PATCH] nvme: implement the DEAC bit for the Write Zeroes command

Christoph Hellwig
2022-10-30T16:29:12Z

While the specification allows devices to either deallocate data
or to actually write zeroes on any Write Zeroes command, many SSDs
only do the sensible thing and deallocate data when the DEAC bit
is specific. Set it when it is suppored and the caller doesn't
explicitly opt out of deallocation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---

BTW, I'm tempted to slap a

Fixes: 6e02318eaea5 ("nvme: add support for the Write Zeroes command")

onto this. While it doesn't fix the Write Zeroes support per se,
it should help us with a lot of the devices timing out on Write Zeroes.

drivers/nvme/host/core.c | 6 +++++-
drivers/nvme/host/nvme.h | 1 +
include/linux/nvme.h | 1 +
3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 0090dc0b3ae6f..14568ae308fba 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -850,8 +850,11 @@ static inline blk_status_t nvme_setup_write_zeroes(struct nvme_ns *ns,
cmnd->write_zeroes.length =
cpu_to_le16((blk_rq_bytes(req) >> ns->lba_shift) - 1);

+ if (!(req->cmd_flags & REQ_NOUNMAP) && ns->dlfeat & (1 << 3))
+ cmnd->write_zeroes.control |= cpu_to_le16(NVME_WZ_DEAC);
+
if (nvme_ns_has_pi(ns)) {
- cmnd->write_zeroes.control = cpu_to_le16(NVME_RW_PRINFO_PRACT);
+ cmnd->write_zeroes.control |= cpu_to_le16(NVME_RW_PRINFO_PRACT);

switch (ns->pi_type) {
case NVME_NS_DPS_PI_TYPE1:
@@ -2004,6 +2007,7 @@ static int nvme_update_ns_info_block(struct nvme_ns *ns,
}
}

+ ns->dlfeat = id->dlfeat;
set_disk_ro(ns->disk, nvme_ns_is_readonly(ns, info));
set_bit(NVME_NS_READY, &ns->flags);
blk_mq_unfreeze_queue(ns->disk->queue);
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index a29877217ee65..00d3b438efe3f 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -477,6 +477,7 @@ struct nvme_ns {
u32 sws;
u8 pi_type;
u8 guard_type;
+ u8 dlfeat;
#ifdef CONFIG_BLK_DEV_ZONED
u64 zsze;
#endif
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index 050d7d0cd81b0..c96930b2c28fe 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -963,6 +963,7 @@ enum {
NVME_RW_PRINFO_PRCHK_GUARD = 1 << 12,
NVME_RW_PRINFO_PRACT = 1 << 13,
NVME_RW_DTYPE_STREAMS = 1 << 4,
+ NVME_WZ_DEAC = 1 << 9,
};

struct nvme_dsm_cmd {
--
2.30.2