The only difference between sg_pcopy_{from,to}_buffer() and
sg_copy_{from,to}_buffer() is an additional argument that specifies
the number of bytes to skip the SG list before copying.
Signed-off-by: Akinobu Mita <akinobu.m...@gmail.com>
Cc: Tejun Heo <t...@kernel.org>
Cc: Imre Deak <imre.d...@intel.com>
Cc: Herbert Xu <herb...@gondor.apana.org.au>
Cc: "David S. Miller" <da...@davemloft.net>
Cc: linux-cry...@vger.kernel.org
Cc: "James E.J. Bottomley" <jbottom...@parallels.com>
Cc: Douglas Gilbert <dgilb...@interlog.com>
Cc: linux-scsi@vger.kernel.org
---
* Change from v2
- Separate the change that factors out sg_miter_get_next_page()
- Add function comment for internal function sg_miter_seek()
include/linux/scatterlist.h | 5 +++
lib/scatterlist.c | 88 ++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 88 insertions(+), 5 deletions(-)
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 2680677..adae88f 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -244,6 +244,11 @@ size_t sg_copy_from_buffer(struct scatterlist *sgl,
unsigned int nents,
size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen);
+size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
+ 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);
+
/*
* 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 c35b929..f167392 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -476,6 +476,43 @@ static bool sg_miter_get_next_page(struct sg_mapping_iter
*miter)
}
/**
+ * sg_miter_seek - reposition mapping iterator
+ * @miter: sg mapping iter to be seeked
+ * @offset: number of bytes to plus the current location
+ *
+ * Description:
+ * Sets the offset of @miter to its current location plus @offset bytes.
+ *
+ * Notes:
+ * This function must be called just after sg_miter_start() or
sg_miter_stop()
+ *
+ * Context:
+ * Don't care.
+ *
+ * Returns:
+ * true if @miter contains the valid mapping. false if end of sg
+ * list is reached.
+ */
+static bool sg_miter_seek(struct sg_mapping_iter *miter, off_t offset)
+{
+ WARN_ON(miter->addr);
+
+ while (offset) {
+ off_t consumed;
+
+ if (!sg_miter_get_next_page(miter))
+ return false;
+
+ consumed = min_t(off_t, offset, miter->__remaining);
+ miter->__offset += consumed;
+ miter->__remaining -= consumed;
+ offset -= consumed;
+ }
+
+ return true;
+}
+
+/**
* sg_miter_next - proceed mapping iterator to the next mapping
* @miter: sg mapping iter to proceed
*
@@ -561,14 +598,16 @@ EXPORT_SYMBOL(sg_miter_stop);
* @nents: Number of SG entries
* @buf: Where to copy from
* @buflen: The number of bytes to copy
- * @to_buffer: transfer direction (non zero == from an sg
list to a
- * buffer, 0 == from a buffer to an sg list
+ * @skip: Number of bytes to skip before copying
+ * @to_buffer: transfer direction (true == from an sg list to a
+ * buffer, false == from a buffer to an sg list
*
* Returns the number of copied bytes.
*
**/
static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
- void *buf, size_t buflen, int to_buffer)
+ void *buf, size_t buflen, off_t skip,
+ bool to_buffer)
{
unsigned int offset = 0;
struct sg_mapping_iter miter;
@@ -582,6 +621,9 @@ static size_t sg_copy_buffer(struct scatterlist *sgl,
unsigned int nents,
sg_miter_start(&miter, sgl, nents, sg_flags);
+ if (!sg_miter_seek(&miter, skip))
+ return false;
+
local_irq_save(flags);
while (sg_miter_next(&miter) && offset < buflen) {
@@ -616,7 +658,7 @@ static size_t sg_copy_buffer(struct scatterlist *sgl,
unsigned int nents,
size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen)
{
- return sg_copy_buffer(sgl, nents, buf, buflen, 0);
+ return sg_copy_buffer(sgl, nents, buf, buflen, 0, false);
}
EXPORT_SYMBOL(sg_copy_from_buffer);
@@ -633,6 +675,42 @@ EXPORT_SYMBOL(sg_copy_from_buffer);
size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen)
{
- return sg_copy_buffer(sgl, nents, buf, buflen, 1);
+ return sg_copy_buffer(sgl, nents, buf, buflen, 0, true);
}
EXPORT_SYMBOL(sg_copy_to_buffer);
+
+/**
+ * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list
+ * @sgl: The SG list
+ * @nents: Number of SG entries
+ * @buf: Where to copy from
+ * @skip: Number of bytes to skip before copying
+ * @buflen: The number of bytes to copy
+ *
+ * Returns the number of copied bytes.
+ *
+ **/
+size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
+ void *buf, size_t buflen, off_t skip)
+{
+ return sg_copy_buffer(sgl, nents, buf, buflen, skip, false);
+}
+EXPORT_SYMBOL(sg_pcopy_from_buffer);
+
+/**
+ * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer
+ * @sgl: The SG list
+ * @nents: Number of SG entries
+ * @buf: Where to copy to
+ * @skip: Number of bytes to skip before copying
+ * @buflen: The number of bytes to copy
+ *
+ * Returns the number of copied bytes.
+ *
+ **/
+size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
+ void *buf, size_t buflen, off_t skip)
+{
+ return sg_copy_buffer(sgl, nents, buf, buflen, skip, true);
+}
+EXPORT_SYMBOL(sg_pcopy_to_buffer);
--
1.8.1.4
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
