Re: [PATCH 03/21] fs/bdev: Add atomic write support info to statx

[Martin K. Petersen]

Bart,

> Neither the SCSI SBC standard nor the NVMe standard defines a "minimum
> atomic write unit". So why to introduce something in the Linux kernel
> that is not defined in common storage standards?

>From SBC-5:

"The ATOMIC TRANSFER LENGTH GRANULARITY field indicates the minimum
transfer length for an atomic write command."

> I propose to leave out stx_atomic_write_unit_min from
> struct statx and also to leave out atomic_write_unit_min_sectors from
> struct queue_limits. My opinion is that we should not support block
> devices in the Linux kernel that do not write logical blocks atomically.

The statx values exist to describe the limits for I/Os sent using
RWF_ATOMIC and IOCB_ATOMIC. These limits may be different from other
reported values such as the filesystem block size and the logical block
size of the underlying device.

-- 
Martin K. Petersen	Oracle Linux Engineering