[PATCH] SQUASHME: pmem: no need to copy a page at a time

[Boaz Harrosh <boaz@plexistor.com>]

With current code structure a single pmem device always spans
a single contiguous memory range both in the physical as well
as the Kernel virtual space. So this means a contiguous block's
sectors means contiguous virtual addressing.

So we do not need to memcpy a page boundary at a time we can
memcpy any arbitrary memory range.

TODO: Further optimization can be done at callers of
	copy_to/from_pmem

Signed-off-by: Boaz Harrosh <boaz@plexistor.com>
---
 drivers/block/pmem.c | 37 +++----------------------------------
 1 file changed, 3 insertions(+), 34 deletions(-)

diff --git a/drivers/block/pmem.c b/drivers/block/pmem.c
index 8e15c19..780ed94 100644
--- a/drivers/block/pmem.c
+++ b/drivers/block/pmem.c
@@ -56,12 +56,10 @@ static int pmem_getgeo(struct block_device *bd, struct hd_geometry *geo)
 /*
  * direct translation from (pmem,sector) => void*
  * We do not require that sector be page aligned.
- * The return value will point to the beginning of the page containing the
- * given sector, not to the sector itself.
  */
 static void *pmem_lookup_pg_addr(struct pmem_device *pmem, sector_t sector)
 {
-	size_t offset = round_down(sector << SECTOR_SHIFT, PAGE_SIZE);
+	size_t offset = sector << SECTOR_SHIFT;
 
 	BUG_ON(offset >= pmem->size);
 	return pmem->virt_addr + offset;
@@ -69,55 +67,26 @@ static void *pmem_lookup_pg_addr(struct pmem_device *pmem, sector_t sector)
 
 /*
  * sector is not required to be page aligned.
- * n is at most a single page, but could be less.
  */
 static void copy_to_pmem(struct pmem_device *pmem, const void *src,
 			sector_t sector, size_t n)
 {
 	void *dst;
-	unsigned int offset = (sector & (PAGE_SECTORS - 1)) << SECTOR_SHIFT;
-	size_t copy;
-
-	BUG_ON(n > PAGE_SIZE);
 
-	copy = min_t(size_t, n, PAGE_SIZE - offset);
 	dst = pmem_lookup_pg_addr(pmem, sector);
-	memcpy(dst + offset, src, copy);
-
-	if (copy < n) {
-		src += copy;
-		sector += copy >> SECTOR_SHIFT;
-		copy = n - copy;
-		dst = pmem_lookup_pg_addr(pmem, sector);
-		memcpy(dst, src, copy);
-	}
+	memcpy(dst, src, n);
 }
 
 /*
  * sector is not required to be page aligned.
- * n is at most a single page, but could be less.
  */
 static void copy_from_pmem(void *dst, struct pmem_device *pmem,
 			  sector_t sector, size_t n)
 {
 	void *src;
-	unsigned int offset = (sector & (PAGE_SECTORS - 1)) << SECTOR_SHIFT;
-	size_t copy;
-
-	BUG_ON(n > PAGE_SIZE);
 
-	copy = min_t(size_t, n, PAGE_SIZE - offset);
 	src = pmem_lookup_pg_addr(pmem, sector);
-
-	memcpy(dst, src + offset, copy);
-
-	if (copy < n) {
-		dst += copy;
-		sector += copy >> SECTOR_SHIFT;
-		copy = n - copy;
-		src = pmem_lookup_pg_addr(pmem, sector);
-		memcpy(dst, src, copy);
-	}
+	memcpy(dst, src, n);
 }
 
 static void pmem_do_bvec(struct pmem_device *pmem, struct page *page,
-- 
1.9.3