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lib/scatterlist: use page iterator in the mapping iterator

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.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Cc: Maxim Levitsky <maximlevitsky@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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commit 4225fc8555a992c7f91d174ef424384d6781e144 1 parent a321e91
Imre Deak authored committed
4 drivers/mmc/host/dw_mmc.c
View
@@ -1453,7 +1453,7 @@ static void dw_mci_read_data_pio(struct dw_mci *host)
if (!sg_miter_next(sg_miter))
goto done;
- host->sg = sg_miter->__sg;
+ host->sg = sg_miter->piter.sg;
buf = sg_miter->addr;
remain = sg_miter->length;
offset = 0;
@@ -1508,7 +1508,7 @@ static void dw_mci_write_data_pio(struct dw_mci *host)
if (!sg_miter_next(sg_miter))
goto done;
- host->sg = sg_miter->__sg;
+ host->sg = sg_miter->piter.sg;
buf = sg_miter->addr;
remain = sg_miter->length;
offset = 0;
6 include/linux/scatterlist.h
View
@@ -293,11 +293,11 @@ struct sg_mapping_iter {
void *addr; /* pointer to the mapped area */
size_t length; /* length of the mapped area */
size_t consumed; /* number of consumed bytes */
+ struct sg_page_iter piter; /* page iterator */
/* 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 */
+ unsigned int __remaining; /* remaining bytes on page */
unsigned int __flags;
};
48 lib/scatterlist.c
View
@@ -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 +474,35 @@ 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;
}
@@ -532,6 +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);
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