[PATCH] SQUASHME: Streamline pmem.c

[Boaz Harrosh <boaz@plexistor.com>]

Christoph why did you choose the fat and ugly version of
pmem.c beats me. Anyway, here are the cleanups you need on
top of your pmem patch.

Among other it does:
* Remove getgeo. It is not needed for modern fdisk and was never
  needed for libgparted and cfdisk.

* remove 89 lines of code to do a single memcpy. The reason
  this was so in brd (done badly BTW) is because destination
  memory is page-by-page based. With pmem we have the destination
  contiguous so we can do any size, in one go.

* Remove SECTOR_SHIFT. It is defined in 6 other places
  in the Kernel. I do not like a new one. 9 is used through
  out, including block core. I do not like pmem to blasphemy
  more than needed.

* More style stuff ...

Please squash into your initial submission

Signed-off-by: Boaz Harrosh <boaz@plexistor.com>
---
 drivers/block/pmem.c | 137 +++++++++++----------------------------------------
 1 file changed, 28 insertions(+), 109 deletions(-)

diff --git a/drivers/block/pmem.c b/drivers/block/pmem.c
index 545b13b..5a57a06 100644
--- a/drivers/block/pmem.c
+++ b/drivers/block/pmem.c
@@ -11,7 +11,7 @@
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  * more details.
  *
- * This driver is heavily based on drivers/block/brd.c.
+ * This driver's skeleton is based on drivers/block/brd.c.
  * Copyright (C) 2007 Nick Piggin
  * Copyright (C) 2007 Novell Inc.
  */
@@ -24,11 +24,6 @@
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/slab.h>
-
-#define SECTOR_SHIFT		9
-#define PAGE_SECTORS_SHIFT	(PAGE_SHIFT - SECTOR_SHIFT)
-#define PAGE_SECTORS		(1 << PAGE_SECTORS_SHIFT)
-
 #define PMEM_MINORS		16
 
 struct pmem_device {
@@ -44,100 +39,17 @@ struct pmem_device {
 static int pmem_major;
 static atomic_t pmem_index;
 
-static int pmem_getgeo(struct block_device *bd, struct hd_geometry *geo)
-{
-	/* some standard values */
-	geo->heads = 1 << 6;
-	geo->sectors = 1 << 5;
-	geo->cylinders = get_capacity(bd->bd_disk) >> 11;
-	return 0;
-}
-
-/*
- * 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 page_offset = sector >> PAGE_SECTORS_SHIFT;
-	size_t offset = page_offset << PAGE_SHIFT;
-
-	BUG_ON(offset >= pmem->size);
-	return pmem->virt_addr + offset;
-}
-
-/* sector must be page aligned */
-static unsigned long pmem_lookup_pfn(struct pmem_device *pmem, sector_t sector)
-{
-	size_t page_offset = sector >> PAGE_SECTORS_SHIFT;
-
-	BUG_ON(sector & (PAGE_SECTORS - 1));
-	return (pmem->phys_addr >> PAGE_SHIFT) + page_offset;
-}
-
-/*
- * 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);
-	}
-}
-
-/*
- * 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);
-	}
-}
-
 static void pmem_do_bvec(struct pmem_device *pmem, struct page *page,
 			unsigned int len, unsigned int off, int rw,
 			sector_t sector)
 {
 	void *mem = kmap_atomic(page);
+	size_t pmem_off = sector << 9;
+
+	BUG_ON(pmem_off >= pmem->size);
 
 	if (rw == READ) {
-		copy_from_pmem(mem + off, pmem, sector, len);
+		memcpy(mem + off, pmem->virt_addr + pmem_off, len);
 		flush_dcache_page(page);
 	} else {
 		/*
@@ -145,7 +57,7 @@ static void pmem_do_bvec(struct pmem_device *pmem, struct page *page,
 		 * NVDIMMs are actually durable before returning.
 		 */
 		flush_dcache_page(page);
-		copy_to_pmem(pmem, mem + off, sector, len);
+		memcpy(pmem->virt_addr + pmem_off, mem + off, len);
 	}
 
 	kunmap_atomic(mem);
@@ -161,25 +73,32 @@ static void pmem_make_request(struct request_queue *q, struct bio *bio)
 	struct bvec_iter iter;
 	int err = 0;
 
-	sector = bio->bi_iter.bi_sector;
-	if (bio_end_sector(bio) > get_capacity(bdev->bd_disk)) {
+	if (unlikely(bio_end_sector(bio) > get_capacity(bdev->bd_disk))) {
 		err = -EIO;
 		goto out;
 	}
 
-	BUG_ON(bio->bi_rw & REQ_DISCARD);
+	if (WARN_ON(bio->bi_rw & REQ_DISCARD)) {
+		err = -EINVAL;
+		goto out;
+	}
 
 	rw = bio_rw(bio);
 	if (rw == READA)
 		rw = READ;
 
+	sector = bio->bi_iter.bi_sector;
 	bio_for_each_segment(bvec, bio, iter) {
-		unsigned int len = bvec.bv_len;
-
-		BUG_ON(len > PAGE_SIZE);
-		pmem_do_bvec(pmem, bvec.bv_page, len,
-			    bvec.bv_offset, rw, sector);
-		sector += len >> SECTOR_SHIFT;
+		/* NOTE: There is a legend saying that bv_len might be
+		 * bigger than PAGE_SIZE in the case that bv_page points to
+		 * a physical contiguous PFN set. But for us it is fine because
+		 * it means the Kernel virtual mapping is also contiguous. And
+		 * on the pmem side we are always contiguous both virtual and
+		 * physical
+		 */
+		pmem_do_bvec(pmem, bvec.bv_page, bvec.bv_len, bvec.bv_offset,
+			     rw, sector);
+		sector += bvec.bv_len >> 9;
 	}
 
 out:
@@ -200,21 +119,21 @@ static long pmem_direct_access(struct block_device *bdev, sector_t sector,
 			      void **kaddr, unsigned long *pfn, long size)
 {
 	struct pmem_device *pmem = bdev->bd_disk->private_data;
+	size_t offset = sector << 9;
 
-	if (!pmem)
+	if (unlikely(!pmem))
 		return -ENODEV;
 
-	*kaddr = pmem_lookup_pg_addr(pmem, sector);
-	*pfn = pmem_lookup_pfn(pmem, sector);
+	*kaddr = pmem->virt_addr + offset;
+	*pfn = (pmem->phys_addr + offset) >> PAGE_SHIFT;
 
-	return pmem->size - (sector * 512);
+	return pmem->size - offset;
 }
 
 static const struct block_device_operations pmem_fops = {
 	.owner =		THIS_MODULE,
 	.rw_page =		pmem_rw_page,
 	.direct_access =	pmem_direct_access,
-	.getgeo =		pmem_getgeo,
 };
 
 /* pmem->phys_addr and pmem->size need to be set.
@@ -307,7 +226,7 @@ static int pmem_probe(struct platform_device *pdev)
 	disk->flags		= GENHD_FL_EXT_DEVT;
 	sprintf(disk->disk_name, "pmem%d", idx);
 	disk->driverfs_dev = &pdev->dev;
-	set_capacity(disk, pmem->size >> SECTOR_SHIFT);
+	set_capacity(disk, pmem->size >> 9);
 	pmem->pmem_disk = disk;
 
 	add_disk(disk);
-- 
1.9.3