diff options
Diffstat (limited to 'lib/scatterlist.c')
| -rw-r--r-- | lib/scatterlist.c | 86 |
1 files changed, 61 insertions, 25 deletions
diff --git a/lib/scatterlist.c b/lib/scatterlist.c index 7874b01e816..b83c144d731 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -394,6 +394,44 @@ int sg_alloc_table_from_pages(struct sg_table *sgt, } EXPORT_SYMBOL(sg_alloc_table_from_pages); +void __sg_page_iter_start(struct sg_page_iter *piter, + struct scatterlist *sglist, unsigned int nents, + unsigned long pgoffset) +{ + piter->__pg_advance = 0; + piter->__nents = nents; + + piter->page = NULL; + piter->sg = sglist; + piter->sg_pgoffset = pgoffset; +} +EXPORT_SYMBOL(__sg_page_iter_start); + +static int sg_page_count(struct scatterlist *sg) +{ + return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT; +} + +bool __sg_page_iter_next(struct sg_page_iter *piter) +{ + if (!piter->__nents || !piter->sg) + return false; + + piter->sg_pgoffset += piter->__pg_advance; + piter->__pg_advance = 1; + + while (piter->sg_pgoffset >= sg_page_count(piter->sg)) { + piter->sg_pgoffset -= sg_page_count(piter->sg); + piter->sg = sg_next(piter->sg); + if (!--piter->__nents || !piter->sg) + return false; + } + piter->page = nth_page(sg_page(piter->sg), piter->sg_pgoffset); + + return true; +} +EXPORT_SYMBOL(__sg_page_iter_next); + /** * sg_miter_start - start mapping iteration over a sg list * @miter: sg mapping iter to be started @@ -411,9 +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; } @@ -438,36 +474,35 @@ 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->__remaining = min_t(unsigned long, miter->__remaining, + PAGE_SIZE - 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; } @@ -494,6 +529,7 @@ 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); |