On Mon, 18 Jan 2021 20:04:20 -0500, Douglas Gilbert wrote:

quoted

quoted

+bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_skip,
+		     struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip,
+		     size_t n_bytes);
+
+bool sgl_compare_sgl_idx(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_skip,
+			 struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip,
+			 size_t n_bytes, size_t *miscompare_idx);  

This patch looks good and works fine as a replacement for
compare_and_write_do_cmp(). One minor suggestion would be to name it
sgl_equal() or similar, to perhaps better reflect the bool return and
avoid memcmp() confusion. Either way:
Reviewed-by: David Disseldorp <redacted>  

Thanks. NVMe calls the command that does this Compare and SCSI uses
COMPARE AND WRITE (and VERIFY(BYTCHK=1) ) but "equal" is fine with me.
There will be another patchset version (at least) so there is time
to change.

Do you want:
   - sgl_equal(...), or
   - sgl_equal_sgl(...) ?

I'd probably prefer the former as it's shorter, but I don't feel
strongly about it. The latter would make sense if you expect sgl compare
helpers for other buffer types.

Cheers, David