mm/slub: Move krealloc() and related code to slub.c

This is a preparation for the following refactoring of krealloc(),
for more efficient function calling as it will call some internal
functions defined in slub.c.

Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

1 files changed, 84 insertions, 0 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 83579b637578..2ccb016c7f99 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4711,6 +4711,90 @@ void kfree(const void *object)
 }
 EXPORT_SYMBOL(kfree);
 
+static __always_inline __realloc_size(2) void *
+__do_krealloc(const void *p, size_t new_size, gfp_t flags)
+{
+	void *ret;
+	size_t ks;
+
+	/* Check for double-free before calling ksize. */
+	if (likely(!ZERO_OR_NULL_PTR(p))) {
+		if (!kasan_check_byte(p))
+			return NULL;
+		ks = ksize(p);
+	} else
+		ks = 0;
+
+	/* If the object still fits, repoison it precisely. */
+	if (ks >= new_size) {
+		/* Zero out spare memory. */
+		if (want_init_on_alloc(flags)) {
+			kasan_disable_current();
+			memset(kasan_reset_tag(p) + new_size, 0, ks - new_size);
+			kasan_enable_current();
+		}
+
+		p = kasan_krealloc((void *)p, new_size, flags);
+		return (void *)p;
+	}
+
+	ret = kmalloc_node_track_caller_noprof(new_size, flags, NUMA_NO_NODE, _RET_IP_);
+	if (ret && p) {
+		/* Disable KASAN checks as the object's redzone is accessed. */
+		kasan_disable_current();
+		memcpy(ret, kasan_reset_tag(p), ks);
+		kasan_enable_current();
+	}
+
+	return ret;
+}
+
+/**
+ * krealloc - reallocate memory. The contents will remain unchanged.
+ * @p: object to reallocate memory for.
+ * @new_size: how many bytes of memory are required.
+ * @flags: the type of memory to allocate.
+ *
+ * If @p is %NULL, krealloc() behaves exactly like kmalloc().  If @new_size
+ * is 0 and @p is not a %NULL pointer, the object pointed to is freed.
+ *
+ * If __GFP_ZERO logic is requested, callers must ensure that, starting with the
+ * initial memory allocation, every subsequent call to this API for the same
+ * memory allocation is flagged with __GFP_ZERO. Otherwise, it is possible that
+ * __GFP_ZERO is not fully honored by this API.
+ *
+ * This is the case, since krealloc() only knows about the bucket size of an
+ * allocation (but not the exact size it was allocated with) and hence
+ * implements the following semantics for shrinking and growing buffers with
+ * __GFP_ZERO.
+ *
+ *         new             bucket
+ * 0       size             size
+ * |--------|----------------|
+ * |  keep  |      zero      |
+ *
+ * In any case, the contents of the object pointed to are preserved up to the
+ * lesser of the new and old sizes.
+ *
+ * Return: pointer to the allocated memory or %NULL in case of error
+ */
+void *krealloc_noprof(const void *p, size_t new_size, gfp_t flags)
+{
+	void *ret;
+
+	if (unlikely(!new_size)) {
+		kfree(p);
+		return ZERO_SIZE_PTR;
+	}
+
+	ret = __do_krealloc(p, new_size, flags);
+	if (ret && kasan_reset_tag(p) != kasan_reset_tag(ret))
+		kfree(p);
+
+	return ret;
+}
+EXPORT_SYMBOL(krealloc_noprof);
+
 struct detached_freelist {
 	struct slab *slab;
 	void *tail;