[PATCH v6 4/4] scatterlist: add sgl_memset()

Douglas Gilbert
2021-01-18T16:33:44Z

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 | 20 +++++++++-
lib/scatterlist.c | 79 +++++++++++++++++++++----------------
2 files changed, 62 insertions(+), 37 deletions(-)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 71be65f9ebb5..69e87280b44d 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -318,8 +318,6 @@ size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
const void *buf, size_t buflen, off_t skip);
size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen, off_t skip);
-size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
- size_t buflen, off_t skip);

size_t sgl_copy_sgl(struct scatterlist *d_sgl, unsigned int d_nents, off_t d_skip,
struct scatterlist *s_sgl, unsigned int s_nents, off_t s_skip,
@@ -333,6 +331,24 @@ 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);
+
+/**
+ * sg_zero_buffer - Zero-out a part of a SG list
+ * @sgl: The SG list
+ * @nents: Number of SG entries
+ * @buflen: The number of bytes to zero out
+ * @skip: Number of bytes to skip before zeroing
+ *
+ * Returns the number of bytes zeroed.
+ **/
+static inline size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
+ size_t buflen, off_t skip)
+{
+ return sgl_memset(sgl, nents, skip, 0, buflen);
+}
+
/*
* 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 e3182de753d0..7e6acc67e9f6 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -1023,41 +1023,6 @@ size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
}
EXPORT_SYMBOL(sg_pcopy_to_buffer);

-/**
- * sg_zero_buffer - Zero-out a part of a SG list
- * @sgl: The SG list
- * @nents: Number of SG entries
- * @buflen: The number of bytes to zero out
- * @skip: Number of bytes to skip before zeroing
- *
- * Returns the number of bytes zeroed.
- **/
-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;
-}
-EXPORT_SYMBOL(sg_zero_buffer);
-
/**
* sgl_copy_sgl - Copy over a destination sgl from a source sgl
* @d_sgl: Destination sgl
@@ -1240,3 +1205,47 @@ bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_sk
return sgl_compare_sgl_idx(x_sgl, x_nents, x_skip, y_sgl, y_nents, y_skip, n_bytes, NULL);
}
EXPORT_SYMBOL(sgl_compare_sgl);
+
+/**
+ * sgl_memset - set byte 'val' up to n_bytes times on SG list
+ * @sgl: The SG list
+ * @nents: Number of SG entries in sgl
+ * @skip: Number of bytes to skip before starting
+ * @val: byte value to write to sgl
+ * @n_bytes: The (maximum) number of bytes to modify
+ *
+ * Returns:
+ * The number of bytes written.
+ *
+ * Notes:
+ * Stops writing if either sgl or n_bytes is exhausted. If n_bytes is
+ * set SIZE_MAX then val will be written to each byte until the end
+ * of sgl.
+ *
+ * The notes in sgl_copy_sgl() about large sgl_s _applies here as well.
+ *
+ **/
+size_t sgl_memset(struct scatterlist *sgl, unsigned int nents, off_t skip,
+ u8 val, size_t n_bytes)
+{
+ size_t offset = 0;
+ size_t len;
+ struct sg_mapping_iter miter;
+
+ if (n_bytes == 0)
+ return 0;
+ sg_miter_start(&miter, sgl, nents, SG_MITER_ATOMIC | SG_MITER_TO_SG);
+ if (!sg_miter_skip(&miter, skip))
+ goto fini;
+
+ while ((offset < n_bytes) && sg_miter_next(&miter)) {
+ len = min(miter.length, n_bytes - offset);
+ memset(miter.addr, val, len);
+ offset += len;
+ }
+fini:
+ sg_miter_stop(&miter);
+ return offset;
+}
+EXPORT_SYMBOL(sgl_memset);
+
--
2.25.1