Re: [PATCH blktests v4] block/053: add a torn atomic write test for block devices

[John Garry <john.garry@linux.dev>]

On 10/30/26 23:26, Tal Zussman wrote:
> A block device atomic write is a hardware atomic write, submitted as a
> single bio, so when its buffer can't be fully pinned, the direct I/O
> path has to fail the write rather than submit the pinned part.
> Otherwise, it submits what was pinned with REQ_ATOMIC set and leaves
> the rest to the buffered fallback, tearing the write at the pin
> boundary.
> 
> This is a regression test for that issue, fixed by commit 73a0ff6030af
> ("block: fail a short atomic pin in bio_iov_iter_get_pages()").
> 
> Issue a two-page pwritev2() with RWF_ATOMIC to a scsi_debug device with
> atomic_wr=1 from a buffer whose last page is PROT_NONE, so that pinning
> the buffer stops one page short. Check with statx() that the device
> supports an atomic write of that size, then check that the write fails
> with EINVAL and that the range still reads back as the old data.
> 
> Two pages is the smallest write that leaves one page unpinnable, and
> atomic_wr_max_length=256 raises the atomic write unit max to 128K so
> that two pages fit for any page size up to 64K.
> 
> Signed-off-by: Tal Zussman<tz2294@columbia.edu>

This generally looks ok, thanks.

Reviewed-by: John Garry <john.garry@linux.dev>