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Subject[PATCH 2/5] dax: increase granularity of dax_clear_blocks() operations
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dax_clear_blocks is currently performing a cond_resched() after every
PAGE_SIZE memset. We need not check so frequently, for example md-raid
only calls cond_resched() at stripe granularity. Also, in preparation
for introducing a dax_map_atomic() operation that temporarily pins a dax
mapping move the call to cond_resched() to the outer loop.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
fs/dax.c | 27 ++++++++++++---------------
1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 5dc33d788d50..f8e543839e5c 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -28,6 +28,7 @@
#include <linux/sched.h>
#include <linux/uio.h>
#include <linux/vmstat.h>
+#include <linux/sizes.h>

int dax_clear_blocks(struct inode *inode, sector_t block, long size)
{
@@ -38,24 +39,20 @@ int dax_clear_blocks(struct inode *inode, sector_t block, long size)
do {
void __pmem *addr;
unsigned long pfn;
- long count;
+ long count, sz;

- count = bdev_direct_access(bdev, sector, &addr, &pfn, size);
+ sz = min_t(long, size, SZ_1M);
+ count = bdev_direct_access(bdev, sector, &addr, &pfn, sz);
if (count < 0)
return count;
- BUG_ON(size < count);
- while (count > 0) {
- unsigned pgsz = PAGE_SIZE - offset_in_page(addr);
- if (pgsz > count)
- pgsz = count;
- clear_pmem(addr, pgsz);
- addr += pgsz;
- size -= pgsz;
- count -= pgsz;
- BUG_ON(pgsz & 511);
- sector += pgsz / 512;
- cond_resched();
- }
+ if (count < sz)
+ sz = count;
+ clear_pmem(addr, sz);
+ addr += sz;
+ size -= sz;
+ BUG_ON(sz & 511);
+ sector += sz / 512;
+ cond_resched();
} while (size);

wmb_pmem();


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