In the ZBC and ZAC specifications, the requirement is that the write
granularity matches the physical block size.

However, in the ZNS specification, the requirement is simply that the
write granularity matches the logical block size.

See:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a805a4fa4fa376bbc145762bb8b09caa2fa8af48

In Linux, there is a zone_write_granularity sysfs property which abstracts
this away by providing, so let's make use of it.

Currently, it is theoretically possible that QEMU presents an inflated
write granularity for NVMe devices where the physical block size is larger
than the logical block size.

Fixes: a3c41f06d5a8 ("file-posix: add tracking of the zone write pointers")
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 block/file-posix.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 3c985da94f..63c52b1044 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1495,7 +1495,7 @@ static void raw_refresh_zoned_limits(BlockDriverState *bs, struct stat *st,
         bs->bl.max_append_sectors = ret >> BDRV_SECTOR_BITS;
     }
 
-    ret = get_sysfs_long_val(st, "physical_block_size");
+    ret = get_sysfs_long_val(st, "zone_write_granularity");
     if (ret >= 0) {
         bs->bl.write_granularity = ret;
     }
-- 
2.55.0

On Fri, Aug 07, 2026 at 08:02:57PM +0200, Niklas Cassel wrote:
> In the ZBC and ZAC specifications, the requirement is that the write
> granularity matches the physical block size.
> 
> However, in the ZNS specification, the requirement is simply that the
> write granularity matches the logical block size.
> 
> See:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a805a4fa4fa376bbc145762bb8b09caa2fa8af48
> 
> In Linux, there is a zone_write_granularity sysfs property which abstracts
> this away by providing, so let's make use of it.
> 
> Currently, it is theoretically possible that QEMU presents an inflated
> write granularity for NVMe devices where the physical block size is larger
> than the logical block size.
> 
> Fixes: a3c41f06d5a8 ("file-posix: add tracking of the zone write pointers")
> Signed-off-by: Niklas Cassel <cassel@kernel.org>
> ---
>  block/file-posix.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

On 2026/08/07 11:02, Niklas Cassel wrote:
> In the ZBC and ZAC specifications, the requirement is that the write
> granularity matches the physical block size.
> 
> However, in the ZNS specification, the requirement is simply that the
> write granularity matches the logical block size.
> 
> See:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a805a4fa4fa376bbc145762bb8b09caa2fa8af48
> 
> In Linux, there is a zone_write_granularity sysfs property which abstracts
> this away by providing, so let's make use of it.

s/by providing// ? Seems like the sentence is not complete otherwise...

> 
> Currently, it is theoretically possible that QEMU presents an inflated
> write granularity for NVMe devices where the physical block size is larger
> than the logical block size.
> 
> Fixes: a3c41f06d5a8 ("file-posix: add tracking of the zone write pointers")
> Signed-off-by: Niklas Cassel <cassel@kernel.org>

Other than that, looks OK to me.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>


-- 
Damien Le Moal
Western Digital Research

On Fri, Aug 07, 2026 at 08:02:57PM +0200, Niklas Cassel wrote:
> In the ZBC and ZAC specifications, the requirement is that the write
> granularity matches the physical block size.
> 
> However, in the ZNS specification, the requirement is simply that the
> write granularity matches the logical block size.
> 
> See:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a805a4fa4fa376bbc145762bb8b09caa2fa8af48
> 
> In Linux, there is a zone_write_granularity sysfs property which abstracts
> this away by providing, so let's make use of it.

nit:
this away, so let's make use of it.