On Mon, 18 Jan 2021 11:30:05 -0500, Douglas Gilbert wrote: > After enabling copies between scatter gather lists (sgl_s), another > storage related operation is to compare two sgl_s. This new function > is modelled on NVMe's Compare command and the SCSI VERIFY(BYTCHK=1) > command. Like memcmp() this function returns false on the first > miscompare and stops comparing. > > A helper function called sgl_compare_sgl_idx() is added. It takes an > additional parameter (miscompare_idx) which is a pointer. If that > pointer is non-NULL and a miscompare is detected (i.e. the function > returns false) then the byte index of the first miscompare is written > to *miscomapre_idx. Knowing the location of the first miscompare is > needed to implement the SCSI COMPARE AND WRITE command properly. > > Reviewed-by: Bodo Stroesser <bostroesser@xxxxxxxxx> > Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx> > --- > include/linux/scatterlist.h | 8 +++ > lib/scatterlist.c | 109 ++++++++++++++++++++++++++++++++++++ > 2 files changed, 117 insertions(+) > > diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h > index 3f836a3246aa..71be65f9ebb5 100644 > --- a/include/linux/scatterlist.h > +++ b/include/linux/scatterlist.h > @@ -325,6 +325,14 @@ size_t sgl_copy_sgl(struct scatterlist *d_sgl, unsigned int d_nents, off_t d_ski > struct scatterlist *s_sgl, unsigned int s_nents, off_t s_skip, > size_t n_bytes); > > +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 <ddiss@xxxxxxx> Cheers, David
