We have sg_miter_* APIs for accessing scsi sg buffer, so
use them to make code clean and bug free.
Cc: Matthew Dharm <mdharm-...@one-eyed-alien.net>
Cc: Alan Stern <st...@rowland.harvard.edu>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Signed-off-by: Ming Lei <ming....@canonical.com>
---
drivers/usb/storage/protocol.c | 82 ++++++++++++++--------------------------
1 file changed, 28 insertions(+), 54 deletions(-)
diff --git a/drivers/usb/storage/protocol.c b/drivers/usb/storage/protocol.c
index 5dfb4c3..01697e5 100644
--- a/drivers/usb/storage/protocol.c
+++ b/drivers/usb/storage/protocol.c
@@ -135,69 +135,43 @@ unsigned int usb_stor_access_xfer_buf(unsigned char
*buffer,
unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
unsigned int *offset, enum xfer_buf_dir dir)
{
- unsigned int cnt;
+ unsigned int cnt = 0;
struct scatterlist *sg = *sgptr;
+ struct sg_mapping_iter miter;
+ unsigned int nents = scsi_sg_count(srb);
- /* We have to go through the list one entry
- * at a time. Each s-g entry contains some number of pages, and
- * each page has to be kmap()'ed separately. If the page is already
- * in kernel-addressable memory then kmap() will return its address.
- * If the page is not directly accessible -- such as a user buffer
- * located in high memory -- then kmap() will map it to a temporary
- * position in the kernel's virtual address space.
- */
-
- if (!sg)
+ if (sg)
+ nents -= sg - scsi_sglist(srb);
+ else
sg = scsi_sglist(srb);
- /* This loop handles a single s-g list entry, which may
- * include multiple pages. Find the initial page structure
- * and the starting offset within the page, and update
- * the *offset and **sgptr values for the next loop.
- */
- cnt = 0;
- while (cnt < buflen && sg) {
- struct page *page = sg_page(sg) +
- ((sg->offset + *offset) >> PAGE_SHIFT);
- unsigned int poff = (sg->offset + *offset) & (PAGE_SIZE-1);
- unsigned int sglen = sg->length - *offset;
-
- if (sglen > buflen - cnt) {
-
- /* Transfer ends within this s-g entry */
- sglen = buflen - cnt;
- *offset += sglen;
- } else {
+ if (dir == FROM_XFER_BUF)
+ sg_miter_start(&miter, sg, nents, SG_MITER_FROM_SG);
+ else
+ sg_miter_start(&miter, sg, nents, SG_MITER_TO_SG);
- /* Transfer continues to next s-g entry */
- *offset = 0;
- sg = sg_next(sg);
- }
+ if (!sg_miter_skip(&miter, *offset))
+ return cnt;
+
+ while (sg_miter_next(&miter) && cnt < buflen) {
+ unsigned int len = min(miter.length, buflen - cnt);
+
+ if (dir == FROM_XFER_BUF)
+ memcpy(buffer + cnt, miter.addr, len);
+ else
+ memcpy(miter.addr, buffer + cnt, len);
- /* Transfer the data for all the pages in this
- * s-g entry. For each page: call kmap(), do the
- * transfer, and call kunmap() immediately after. */
- while (sglen > 0) {
- unsigned int plen = min(sglen, (unsigned int)
- PAGE_SIZE - poff);
- unsigned char *ptr = kmap(page);
-
- if (dir == TO_XFER_BUF)
- memcpy(ptr + poff, buffer + cnt, plen);
- else
- memcpy(buffer + cnt, ptr + poff, plen);
- kunmap(page);
-
- /* Start at the beginning of the next page */
- poff = 0;
- ++page;
- cnt += plen;
- sglen -= plen;
+ if (*offset + len < miter.piter.sg->length) {
+ *offset += len;
+ *sgptr = miter.piter.sg;
+ } else {
+ *offset = 0;
+ *sgptr = sg_next(miter.piter.sg);
}
+ cnt += len;
}
- *sgptr = sg;
+ sg_miter_stop(&miter);
- /* Return the amount actually transferred */
return cnt;
}
EXPORT_SYMBOL_GPL(usb_stor_access_xfer_buf);
--
1.7.9.5
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