Re: [PATCH v5 4/4] scatterlist: add sgl_memset()

[Douglas Gilbert]

On 2021-01-07 12:46 p.m., Jason Gunthorpe wrote:
> On Mon, Dec 28, 2020 at 06:49:55PM -0500, Douglas Gilbert wrote:
> > The existing sg_zero_buffer() function is a bit restrictive. For
> > example protection information (PI) blocks are usually initialized
> > to 0xff bytes. As its name suggests sgl_memset() is modelled on
> > memset(). One difference is the type of the val argument which is
> > u8 rather than int. Plus it returns the number of bytes (over)written.
> >
> > Change implementation of sg_zero_buffer() to call this new function.
> >
> > Reviewed-by: Bodo Stroesser <bostroesser@xxxxxxxxx>
> > Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
> >   include/linux/scatterlist.h |  3 ++
> >   lib/scatterlist.c           | 65 +++++++++++++++++++++++++------------
> >   2 files changed, 48 insertions(+), 20 deletions(-)
> >
> > diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
> > index 71be65f9ebb5..70d3f1f73df1 100644
> > +++ b/include/linux/scatterlist.h
> > @@ -333,6 +333,9 @@ bool sgl_compare_sgl_idx(struct scatterlist *x_sgl, unsigned int x_nents, off_t
> >   			 struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip,
> >   			 size_t n_bytes, size_t *miscompare_idx);
> >   
> > +size_t sgl_memset(struct scatterlist *sgl, unsigned int nents, off_t skip,
> > +		  u8 val, size_t n_bytes);
> > +
> >   /*
> >    * Maximum number of entries that will be allocated in one piece, if
> >    * a list larger than this is required then chaining will be utilized.
> > diff --git a/lib/scatterlist.c b/lib/scatterlist.c
> > index 9332365e7eb6..f06614a880c8 100644
> > +++ b/lib/scatterlist.c
> > @@ -1038,26 +1038,7 @@ EXPORT_SYMBOL(sg_pcopy_to_buffer);
> >   size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
> >   		       size_t buflen, off_t skip)
> >   {
> > -	unsigned int offset = 0;
> > -	struct sg_mapping_iter miter;
> > -	unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG;
> > -
> > -	sg_miter_start(&miter, sgl, nents, sg_flags);
> > -
> > -	if (!sg_miter_skip(&miter, skip))
> > -		return false;
> > -
> > -	while (offset < buflen && sg_miter_next(&miter)) {
> > -		unsigned int len;
> > -
> > -		len = min(miter.length, buflen - offset);
> > -		memset(miter.addr, 0, len);
> > -
> > -		offset += len;
> > -	}
> > -
> > -	sg_miter_stop(&miter);
> > -	return offset;
> > +	return sgl_memset(sgl, nents, skip, 0, buflen);
> >   }
> >   EXPORT_SYMBOL(sg_zero_buffer);
>
> May as well make this one liner a static inline in the header. Just
> rename this function to sgl_memset so the diff is clearer

Yes, fine. I can roll a new version.

Doug Gilbert