From e5fc70d5ccc3d005bb038c0275ffdf57a34b1496 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Tue, 26 Nov 2013 12:44:13 +0800 Subject: USB: storage: use sg_miter_* APIs to access scsi buffer We have sg_miter_* APIs for accessing scsi sg buffer, so use them to make code clean and bug free. Cc: Matthew Dharm Cc: Alan Stern Cc: Greg Kroah-Hartman Signed-off-by: Ming Lei Signed-off-by: Greg Kroah-Hartman --- drivers/usb/storage/protocol.c | 80 ++++++++++++++---------------------------- 1 file changed, 26 insertions(+), 54 deletions(-) diff --git a/drivers/usb/storage/protocol.c b/drivers/usb/storage/protocol.c index 5dfb4c36a1b0..f54e5fea9230 100644 --- a/drivers/usb/storage/protocol.c +++ b/drivers/usb/storage/protocol.c @@ -135,69 +135,41 @@ 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_nents(sg); + 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 { + sg_miter_start(&miter, sg, nents, dir == FROM_XFER_BUF ? + SG_MITER_FROM_SG: 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); -- cgit v1.2.3-55-g7522