For better code reuse use the newly added page iterator to iterate through the pages. The offset, length within the page is still calculated by the mapping iterator as well as the actual mapping. Idea from Tejun Heo tj@kernel.org.
Signed-off-by: Imre Deak imre.deak@intel.com --- include/linux/scatterlist.h | 6 +++--- lib/scatterlist.c | 46 ++++++++++++++++++++----------------------- 2 files changed, 24 insertions(+), 28 deletions(-)
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 788a853..a6cd692 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -295,9 +295,9 @@ struct sg_mapping_iter { size_t consumed; /* number of consumed bytes */
/* these are internal states, keep away */ - struct scatterlist *__sg; /* current entry */ - unsigned int __nents; /* nr of remaining entries */ - unsigned int __offset; /* offset within sg */ + unsigned int __offset; /* offset within page */ + struct sg_page_iter __piter; /* page iterator */ + unsigned int __remaining; /* remaining bytes on page */ unsigned int __flags; };
diff --git a/lib/scatterlist.c b/lib/scatterlist.c index a1d1564..4e4974a 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -449,9 +449,7 @@ void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, { memset(miter, 0, sizeof(struct sg_mapping_iter));
- miter->__sg = sgl; - miter->__nents = nents; - miter->__offset = 0; + __sg_page_iter_start(&miter->__piter, sgl, nents, 0); WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); miter->__flags = flags; } @@ -476,36 +474,33 @@ EXPORT_SYMBOL(sg_miter_start); */ bool sg_miter_next(struct sg_mapping_iter *miter) { - unsigned int off, len; - - /* check for end and drop resources from the last iteration */ - if (!miter->__nents) - return false; - sg_miter_stop(miter);
- /* get to the next sg if necessary. __offset is adjusted by stop */ - while (miter->__offset == miter->__sg->length) { - if (--miter->__nents) { - miter->__sg = sg_next(miter->__sg); - miter->__offset = 0; - } else + /* + * Get to the next page if necessary. + * __remaining, __offset is adjusted by sg_miter_stop + */ + if (!miter->__remaining) { + struct scatterlist *sg; + unsigned long pgoffset; + + if (!__sg_page_iter_next(&miter->__piter)) return false; - }
- /* map the next page */ - off = miter->__sg->offset + miter->__offset; - len = miter->__sg->length - miter->__offset; + sg = miter->__piter.sg; + pgoffset = miter->__piter.sg_pgoffset;
- miter->page = nth_page(sg_page(miter->__sg), off >> PAGE_SHIFT); - off &= ~PAGE_MASK; - miter->length = min_t(unsigned int, len, PAGE_SIZE - off); - miter->consumed = miter->length; + miter->__offset = pgoffset ? 0 : sg->offset; + miter->__remaining = sg->offset + sg->length - + (pgoffset << PAGE_SHIFT) - miter->__offset; + } + miter->page = miter->__piter.page; + miter->consumed = miter->length = miter->__remaining;
if (miter->__flags & SG_MITER_ATOMIC) - miter->addr = kmap_atomic(miter->page) + off; + miter->addr = kmap_atomic(miter->page) + miter->__offset; else - miter->addr = kmap(miter->page) + off; + miter->addr = kmap(miter->page) + miter->__offset;
return true; } @@ -532,6 +527,7 @@ void sg_miter_stop(struct sg_mapping_iter *miter) /* drop resources from the last iteration */ if (miter->addr) { miter->__offset += miter->consumed; + miter->__remaining -= miter->consumed;
if (miter->__flags & SG_MITER_TO_SG) flush_kernel_dcache_page(miter->page);