pmem: add copy_from_iter_pmem() and clear_pmem()

Add support for two new PMEM APIs, copy_from_iter_pmem() and
clear_pmem().  copy_from_iter_pmem() is used to copy data from an
iterator into a PMEM buffer.  clear_pmem() zeros a PMEM memory range.

Both of these new APIs must be explicitly ordered using a wmb_pmem()
function call and are implemented in such a way that the wmb_pmem()
will make the stores to PMEM durable.  Because both APIs are unordered
they can be called as needed without introducing any unwanted memory
barriers.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 62 insertions, 2 deletions

diff --git a/include/linux/pmem.h b/include/linux/pmem.h
index a0706ea04efd..a9d84bf335ee 100644
--- a/include/linux/pmem.h
+++ b/include/linux/pmem.h
@@ -14,6 +14,7 @@
 #define __PMEM_H__
 
 #include <linux/io.h>
+#include <linux/uio.h>
 
 #ifdef CONFIG_ARCH_HAS_PMEM_API
 #include <asm/pmem.h>
@@ -33,12 +34,24 @@ static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src,
 {
         BUG();
 }
+
+static inline size_t arch_copy_from_iter_pmem(void __pmem *addr, size_t bytes,
+                struct iov_iter *i)
+{
+        BUG();
+        return 0;
+}
+
+static inline void arch_clear_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(), and
- * arch_has_wmb_pmem().
+ * implementations for arch_memcpy_to_pmem(), arch_wmb_pmem(),
+ * arch_copy_from_iter_pmem(), arch_clear_pmem() and arch_has_wmb_pmem().
  */
 
 static inline void memcpy_from_pmem(void *dst, void __pmem const *src, size_t size)
@@ -78,6 +91,20 @@ static inline void default_memcpy_to_pmem(void __pmem *dst, const void *src,
         memcpy((void __force *) dst, src, size);
 }
 
+static inline size_t default_copy_from_iter_pmem(void __pmem *addr,
+                size_t bytes, struct iov_iter *i)
+{
+        return copy_from_iter_nocache((void __force *)addr, bytes, i);
+}
+
+static inline void default_clear_pmem(void __pmem *addr, size_t size)
+{
+        if (size == PAGE_SIZE && ((unsigned long)addr & ~PAGE_MASK) == 0)
+                clear_page((void __force *)addr);
+        else
+                memset((void __force *)addr, 0, size);
+}
+
 /**
  * memremap_pmem - map physical persistent memory for pmem api
  * @offset: physical address of persistent memory
@@ -134,4 +161,37 @@ static inline void wmb_pmem(void)
         if (arch_has_pmem_api())
                 arch_wmb_pmem();
 }
+
+/**
+ * copy_from_iter_pmem - copy data from an iterator to PMEM
+ * @addr:       PMEM destination address
+ * @bytes:      number of bytes to copy
+ * @i:          iterator with source data
+ *
+ * Copy data from the iterator 'i' to the PMEM buffer starting at 'addr'.
+ * This function requires explicit ordering with a wmb_pmem() call.
+ */
+static inline size_t copy_from_iter_pmem(void __pmem *addr, size_t bytes,
+                struct iov_iter *i)
+{
+        if (arch_has_pmem_api())
+                return arch_copy_from_iter_pmem(addr, bytes, i);
+        return default_copy_from_iter_pmem(addr, bytes, i);
+}
+
+/**
+ * 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.
+ * This function requires explicit ordering with a wmb_pmem() call.
+ */
+static inline void clear_pmem(void __pmem *addr, size_t size)
+{
+        if (arch_has_pmem_api())
+                arch_clear_pmem(addr, size);
+        else
+                default_clear_pmem(addr, size);
+}
 #endif /* __PMEM_H__ */