EXPORT_SYMBOL(sg_alloc_table);
/**
+ * sg_miter_start - start mapping iteration over a sg list
+ * @miter: sg mapping iter to be started
+ * @sgl: sg list to iterate over
+ * @nents: number of sg entries
+ *
+ * Description:
+ * Starts mapping iterator @miter.
+ *
+ * Context:
+ * Don't care.
+ */
+void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
+ unsigned int nents, unsigned int flags)
+{
+ memset(miter, 0, sizeof(struct sg_mapping_iter));
+
+ miter->__sg = sgl;
+ miter->__nents = nents;
+ miter->__offset = 0;
+ WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
+ miter->__flags = flags;
+}
+EXPORT_SYMBOL(sg_miter_start);
+
+/**
+ * sg_miter_next - proceed mapping iterator to the next mapping
+ * @miter: sg mapping iter to proceed
+ *
+ * Description:
+ * Proceeds @miter@ to the next mapping. @miter@ should have been
+ * started using sg_miter_start(). On successful return,
+ * @miter@->page, @miter@->addr and @miter@->length point to the
+ * current mapping.
+ *
+ * Context:
+ * IRQ disabled if SG_MITER_ATOMIC. IRQ must stay disabled till
+ * @miter@ is stopped. May sleep if !SG_MITER_ATOMIC.
+ *
+ * Returns:
+ * true if @miter contains the next mapping. false if end of sg
+ * list is reached.
+ */
+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
+ return false;
+ }
+
+ /* map the next page */
+ off = miter->__sg->offset + miter->__offset;
+ len = miter->__sg->length - miter->__offset;
+
+ 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;
+
+ if (miter->__flags & SG_MITER_ATOMIC)
+ miter->addr = kmap_atomic(miter->page, KM_BIO_SRC_IRQ) + off;
+ else
+ miter->addr = kmap(miter->page) + off;
+
+ return true;
+}
+EXPORT_SYMBOL(sg_miter_next);
+
+/**
+ * sg_miter_stop - stop mapping iteration
+ * @miter: sg mapping iter to be stopped
+ *
+ * Description:
+ * Stops mapping iterator @miter. @miter should have been started
+ * started using sg_miter_start(). A stopped iteration can be
+ * resumed by calling sg_miter_next() on it. This is useful when
+ * resources (kmap) need to be released during iteration.
+ *
+ * Context:
+ * IRQ disabled if the SG_MITER_ATOMIC is set. Don't care otherwise.
+ */
+void sg_miter_stop(struct sg_mapping_iter *miter)
+{
+ WARN_ON(miter->consumed > miter->length);
+
+ /* drop resources from the last iteration */
+ if (miter->addr) {
+ miter->__offset += miter->consumed;
+
+ if (miter->__flags & SG_MITER_TO_SG)
+ flush_kernel_dcache_page(miter->page);
+
+ if (miter->__flags & SG_MITER_ATOMIC) {
+ WARN_ON(!irqs_disabled());
+ kunmap_atomic(miter->addr, KM_BIO_SRC_IRQ);
+ } else
+ kunmap(miter->page);
+
+ miter->page = NULL;
+ miter->addr = NULL;
+ miter->length = 0;
+ miter->consumed = 0;
+ }
+}
+EXPORT_SYMBOL(sg_miter_stop);
+
+/**
* sg_copy_buffer - Copy data between a linear buffer and an SG list
* @sgl: The SG list
* @nents: Number of SG entries
static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen, int to_buffer)
{
- struct scatterlist *sg;
- size_t buf_off = 0;
- int i;
-
- WARN_ON(!irqs_disabled());
-
- for_each_sg(sgl, sg, nents, i) {
- struct page *page;
- int n = 0;
- unsigned int sg_off = sg->offset;
- unsigned int sg_copy = sg->length;
-
- if (sg_copy > buflen)
- sg_copy = buflen;
- buflen -= sg_copy;
-
- while (sg_copy > 0) {
- unsigned int page_copy;
- void *p;
-
- page_copy = PAGE_SIZE - sg_off;
- if (page_copy > sg_copy)
- page_copy = sg_copy;
-
- page = nth_page(sg_page(sg), n);
- p = kmap_atomic(page, KM_BIO_SRC_IRQ);
-
- if (to_buffer)
- memcpy(buf + buf_off, p + sg_off, page_copy);
- else {
- memcpy(p + sg_off, buf + buf_off, page_copy);
- flush_kernel_dcache_page(page);
- }
-
- kunmap_atomic(p, KM_BIO_SRC_IRQ);
-
- buf_off += page_copy;
- sg_off += page_copy;
- if (sg_off == PAGE_SIZE) {
- sg_off = 0;
- n++;
- }
- sg_copy -= page_copy;
- }
+ unsigned int offset = 0;
+ struct sg_mapping_iter miter;
+ unsigned long flags;
+ unsigned int sg_flags = SG_MITER_ATOMIC;
+
+ if (to_buffer)
+ sg_flags |= SG_MITER_FROM_SG;
+ else
+ sg_flags |= SG_MITER_TO_SG;
+
+ sg_miter_start(&miter, sgl, nents, sg_flags);
- if (!buflen)
- break;
+ local_irq_save(flags);
+
+ while (sg_miter_next(&miter) && offset < buflen) {
+ unsigned int len;
+
+ len = min(miter.length, buflen - offset);
+
+ if (to_buffer)
+ memcpy(buf + offset, miter.addr, len);
+ else
+ memcpy(miter.addr, buf + offset, len);
+
+ offset += len;
}
- return buf_off;
+ sg_miter_stop(&miter);
+
+ local_irq_restore(flags);
+ return offset;
}
/**
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff