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.
Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
---
include/linux/scatterlist.h | 3 +++
lib/scatterlist.c | 54 ++++++++++++++++++++++++++++++++++---
2 files changed, 54 insertions(+), 3 deletions(-)
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index ae260dc5fedb..a40012c8a4e6 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -329,6 +329,9 @@ bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_sk
struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip,
size_t n_bytes);
+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 d910776a4c96..a704039ab54d 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -985,7 +985,8 @@ EXPORT_SYMBOL(sg_zero_buffer);
* @s_skip: Number of bytes to skip in source before starting
* @n_bytes: The (maximum) number of bytes to copy
*
- * Returns the number of copied bytes.
+ * Returns:
+ * The number of copied bytes.
*
* Notes:
* Destination arguments appear before the source arguments, as with memcpy().
@@ -1058,8 +1059,9 @@ EXPORT_SYMBOL(sgl_copy_sgl);
* @y_skip: Number of bytes to skip in y (right) before starting
* @n_bytes: The (maximum) number of bytes to compare
*
- * Returns true if x and y compare equal before x, y or n_bytes is exhausted.
- * Otherwise on a miscompare, returns false (and stops comparing).
+ * Returns:
+ * true if x and y compare equal before x, y or n_bytes is exhausted.
+ * Otherwise on a miscompare, returns false (and stops comparing).
*
* Notes:
* x and y are symmetrical: they can be swapped and the result is the same.
@@ -1108,3 +1110,49 @@ bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_sk
return equ;
}
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;
+ miter.consumed = len;
+ sg_miter_stop(&miter);
+ }
+fini:
+ sg_miter_stop(&miter);
+ return offset;
+}
+EXPORT_SYMBOL(sgl_memset);
+
--
2.25.1
