[PATCH 05/13] x86, dax: replace clear_pmem() with open coded memset + dax_ops->flush

[Dan Williams]

The clear_pmem() helper simply combines a memset() plus a cache flush.
Now that the flush routine is optionally provided by the dax device
driver we can avoid unnecessary cache management on dax devices fronting
volatile memory.

With clear_pmem() gone we can follow on with a patch to make pmem cache
management completely defined within the pmem driver.

Cc: <x86@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 arch/x86/include/asm/pmem.h |   13 -------------
 fs/dax.c                    |    5 ++++-
 include/linux/pmem.h        |   21 ---------------------
 3 files changed, 4 insertions(+), 35 deletions(-)

diff --git a/arch/x86/include/asm/pmem.h b/arch/x86/include/asm/pmem.h
index 0ca5e693f4a2..ab4983df7bff 100644
--- a/arch/x86/include/asm/pmem.h
+++ b/arch/x86/include/asm/pmem.h
@@ -64,19 +64,6 @@ static inline void arch_wb_cache_pmem(void *addr, size_t size)
 		clwb(p);
 }
 
-/**
- * arch_clear_pmem - zero a PMEM memory range
- * @addr:	virtual start address
- * @size:	number of bytes to zero
- *
- * Write zeros into the memory range starting at 'addr' for 'size' bytes.
- */
-static inline void arch_clear_pmem(void *addr, size_t size)
-{
-	memset(addr, 0, size);
-	arch_wb_cache_pmem(addr, size);
-}
-
 static inline void arch_invalidate_pmem(void *addr, size_t size)
 {
 	clflush_cache_range(addr, size);
diff --git a/fs/dax.c b/fs/dax.c
index 160024e403f6..8883ce4d391e 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -986,6 +986,7 @@ static bool dax_range_is_aligned(struct block_device *bdev,
 int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
 		unsigned int offset, unsigned int length)
 {
+	const struct dax_operations *dax_ops = to_dax_ops(bdev);
 	struct blk_dax_ctl dax = {
 		.sector		= sector,
 		.size		= PAGE_SIZE,
@@ -999,7 +1000,9 @@ int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
 	} else {
 		if (dax_map_atomic(bdev, &dax) < 0)
 			return PTR_ERR(dax.addr);
-		clear_pmem(dax.addr + offset, length);
+		memset(dax.addr + offset, 0, length);
+		if (dax_ops->flush)
+			dax_ops->flush(dax.addr + offset, length);
 		dax_unmap_atomic(bdev, &dax);
 	}
 	return 0;
diff --git a/include/linux/pmem.h b/include/linux/pmem.h
index 9d542a5600e4..772bd02a5b52 100644
--- a/include/linux/pmem.h
+++ b/include/linux/pmem.h
@@ -31,11 +31,6 @@ static inline void arch_memcpy_to_pmem(void *dst, const void *src, size_t n)
 	BUG();
 }
 
-static inline void arch_clear_pmem(void *addr, size_t size)
-{
-	BUG();
-}
-
 static inline void arch_wb_cache_pmem(void *addr, size_t size)
 {
 	BUG();
@@ -73,22 +68,6 @@ static inline void memcpy_to_pmem(void *dst, const void *src, size_t n)
 }
 
 /**
- * clear_pmem - zero a PMEM memory range
- * @addr:	virtual start address
- * @size:	number of bytes to zero
- *
- * Write zeros into the memory range starting at 'addr' for 'size' bytes.
- * See blkdev_issue_flush() note for memcpy_to_pmem().
- */
-static inline void clear_pmem(void *addr, size_t size)
-{
-	if (arch_has_pmem_api())
-		arch_clear_pmem(addr, size);
-	else
-		memset(addr, 0, size);
-}
-
-/**
  * invalidate_pmem - flush a pmem range from the cache hierarchy
  * @addr:	virtual start address
  * @size:	bytes to invalidate (internally aligned to cache line size)