[PATCH v7 3/9] pmem: add wb_cache_pmem() to the PMEM API

[Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>]

The function __arch_wb_cache_pmem() was already an internal implementation
detail of the x86 PMEM API, but this functionality needs to be exported as
part of the general PMEM API to handle the fsync/msync case for DAX mmaps.

One thing worth noting is that we really do want this to be part of the
PMEM API as opposed to a stand-alone function like clflush_cache_range()
because of ordering restrictions.  By having wb_cache_pmem() as part of the
PMEM API we can leave it unordered, call it multiple times to write back
large amounts of memory, and then order the multiple calls with a single
wmb_pmem().

Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/pmem.h | 11 ++++++-----
 include/linux/pmem.h        | 22 +++++++++++++++++++++-
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/pmem.h b/arch/x86/include/asm/pmem.h
index 1544fab..c57fd1e 100644
--- a/arch/x86/include/asm/pmem.h
+++ b/arch/x86/include/asm/pmem.h
@@ -67,18 +67,19 @@ static inline void arch_wmb_pmem(void)
 }
 
 /**
- * __arch_wb_cache_pmem - write back a cache range with CLWB
+ * arch_wb_cache_pmem - write back a cache range with CLWB
  * @vaddr:     virtual start address
  * @size:      number of bytes to write back
  *
  * Write back a cache range using the CLWB (cache line write back)
  * instruction.  This function requires explicit ordering with an
- * arch_wmb_pmem() call.  This API is internal to the x86 PMEM implementation.
+ * arch_wmb_pmem() call.
  */
-static inline void __arch_wb_cache_pmem(void *vaddr, size_t size)
+static inline void arch_wb_cache_pmem(void __pmem *addr, size_t size)
 {
        u16 x86_clflush_size = boot_cpu_data.x86_clflush_size;
        unsigned long clflush_mask = x86_clflush_size - 1;
+       void *vaddr = (void __force *)addr;
        void *vend = vaddr + size;
        void *p;
 
@@ -115,7 +116,7 @@ static inline size_t arch_copy_from_iter_pmem(void __pmem 
*addr, size_t bytes,
        len = copy_from_iter_nocache(vaddr, bytes, i);
 
        if (__iter_needs_pmem_wb(i))
-               __arch_wb_cache_pmem(vaddr, bytes);
+               arch_wb_cache_pmem(addr, bytes);
 
        return len;
 }
@@ -133,7 +134,7 @@ static inline void arch_clear_pmem(void __pmem *addr, 
size_t size)
        void *vaddr = (void __force *)addr;
 
        memset(vaddr, 0, size);
-       __arch_wb_cache_pmem(vaddr, size);
+       arch_wb_cache_pmem(addr, size);
 }
 
 static inline bool __arch_has_wmb_pmem(void)
diff --git a/include/linux/pmem.h b/include/linux/pmem.h
index acfea8c..7c3d11a 100644
--- a/include/linux/pmem.h
+++ b/include/linux/pmem.h
@@ -53,12 +53,18 @@ static inline void arch_clear_pmem(void __pmem *addr, 
size_t size)
 {
        BUG();
 }
+
+static inline void arch_wb_cache_pmem(void __pmem *addr, size_t size)
+{
+       BUG();
+}
 #endif
 
 /*
  * Architectures that define ARCH_HAS_PMEM_API must provide
  * implementations for arch_memcpy_to_pmem(), arch_wmb_pmem(),
- * arch_copy_from_iter_pmem(), arch_clear_pmem() and arch_has_wmb_pmem().
+ * arch_copy_from_iter_pmem(), arch_clear_pmem(), arch_wb_cache_pmem()
+ * and arch_has_wmb_pmem().
  */
 static inline void memcpy_from_pmem(void *dst, void __pmem const *src, size_t 
size)
 {
@@ -178,4 +184,18 @@ static inline void clear_pmem(void __pmem *addr, size_t 
size)
        else
                default_clear_pmem(addr, size);
 }
+
+/**
+ * wb_cache_pmem - write back processor cache for PMEM memory range
+ * @addr:      virtual start address
+ * @size:      number of bytes to write back
+ *
+ * Write back the processor cache range starting at 'addr' for 'size' bytes.
+ * This function requires explicit ordering with a wmb_pmem() call.
+ */
+static inline void wb_cache_pmem(void __pmem *addr, size_t size)
+{
+       if (arch_has_pmem_api())
+               arch_wb_cache_pmem(addr, size);
+}
 #endif /* __PMEM_H__ */
-- 
2.5.0