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Subject[PATCH 3/4] mm: Add free()
Date
From: Matthew Wilcox <mawilcox@microsoft.com>

free() can free many different kinds of memory.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
include/linux/kernel.h | 2 ++
mm/util.c | 39 +++++++++++++++++++++++++++++++++++++++
2 files changed, 41 insertions(+)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 3fd291503576..8bb578938e65 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -933,6 +933,8 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
"pointer type mismatch in container_of()"); \
((type *)(__mptr - offsetof(type, member))); })

+void free(const void *);
+
/* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */
#ifdef CONFIG_FTRACE_MCOUNT_RECORD
# define REBUILD_DUE_TO_FTRACE_MCOUNT_RECORD
diff --git a/mm/util.c b/mm/util.c
index dc4c7b551aaf..8aa2071059b0 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -26,6 +26,45 @@ static inline int is_kernel_rodata(unsigned long addr)
addr < (unsigned long)__end_rodata;
}

+/**
+ * free() - Free memory
+ * @ptr: Pointer to memory
+ *
+ * This function can free almost any type of memory. It can safely be
+ * called on:
+ * * NULL pointers.
+ * * Pointers to read-only data (will do nothing).
+ * * Pointers to memory allocated from kmalloc().
+ * * Pointers to memory allocated from kmem_cache_alloc().
+ * * Pointers to memory allocated from vmalloc().
+ * * Pointers to memory allocated from alloc_percpu().
+ * * Pointers to memory allocated from __get_free_pages().
+ * * Pointers to memory allocated from page_frag_alloc().
+ *
+ * It cannot free memory allocated by dma_pool_alloc() or dma_alloc_coherent().
+ */
+void free(const void *ptr)
+{
+ struct page *page;
+
+ if (unlikely(ZERO_OR_NULL_PTR(ptr)))
+ return;
+ if (is_kernel_rodata((unsigned long)ptr))
+ return;
+
+ page = virt_to_head_page(ptr);
+ if (likely(PageSlab(page)))
+ return kmem_cache_free(page->slab_cache, (void *)ptr);
+
+ if (is_vmalloc_addr(ptr))
+ return vfree(ptr);
+ if (is_kernel_percpu_address((unsigned long)ptr))
+ free_percpu((void __percpu *)ptr);
+ if (put_page_testzero(page))
+ __put_page(page);
+}
+EXPORT_SYMBOL(free);
+
/**
* kfree_const - conditionally free memory
* @x: pointer to the memory
--
2.16.2
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