[PATCH v2] nvmet: fix mismatched serial

[PATCH v2] nvmet: fix mismatched serial

[zhenwei pi]

Target side uses 'bin2hex' to convert u64 serial number to a hex
string, saving serial number as be64 to keep the right byte order.
Also use format '%016llx' to show the full serial string to avoid
to drop prefixed zero.

Test on x86 server, config '0123456789abcdef' to 'attr_serial' on
target side, and run 'nvme id-ctrl /dev/nvme0' on initiator side,
then we can get the same SN string.

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Reported-by: kernel test robot <lkp@intel.com>
---
 drivers/nvme/target/configfs.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 37e1d7784e17..6404b9ce09eb 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -996,8 +996,9 @@ static ssize_t nvmet_subsys_attr_serial_show(struct config_item *item,
 					     char *page)
 {
 	struct nvmet_subsys *subsys = to_subsys(item);
+	u64 serial = be64_to_cpu((__force __be64)subsys->serial);
 
-	return snprintf(page, PAGE_SIZE, "%llx\n", subsys->serial);
+	return snprintf(page, PAGE_SIZE, "%016llx\n", serial);
 }
 
 static ssize_t nvmet_subsys_attr_serial_store(struct config_item *item,
@@ -1009,7 +1010,7 @@ static ssize_t nvmet_subsys_attr_serial_store(struct config_item *item,
 		return -EINVAL;
 
 	down_write(&nvmet_config_sem);
-	to_subsys(item)->serial = serial;
+	to_subsys(item)->serial = (__force u64)cpu_to_be64(serial);
 	up_write(&nvmet_config_sem);
 
 	return count;
-- 
2.25.1

Re: [PATCH v2] nvmet: fix mismatched serial

[Christoph Hellwig]

On Sat, Dec 12, 2020 at 03:58:01PM +0800, zhenwei pi wrote:
> Target side uses 'bin2hex' to convert u64 serial number to a hex
> string, saving serial number as be64 to keep the right byte order.
> Also use format '%016llx' to show the full serial string to avoid
> to drop prefixed zero.
> 
> Test on x86 server, config '0123456789abcdef' to 'attr_serial' on
> target side, and run 'nvme id-ctrl /dev/nvme0' on initiator side,
> then we can get the same SN string.

We can't change this interface any more, as it can break tons of user
space.