On 2021-01-07 12:46 p.m., Jason Gunthorpe wrote:

On Mon, Dec 28, 2020 at 06:49:55PM -0500, Douglas Gilbert wrote:

quoted

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@gmail.com>
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
  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