IB/uverbs: Add a simple allocator to uverbs_attr_bundle

This is similar in spirit to devm, it keeps track of any allocations
linked to this method call and ensures they are all freed when the method
exits. Further, if there is space in the internal/onstack buffer then the
allocator will hand out that memory and avoid an expensive call to
kalloc/kfree in the syscall path.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>

include/rdma/uverbs_ioctl.h

@@ -651,6 +651,20 @@ int uverbs_get_flags32(u32 *to, const struct uverbs_attr_bundle *attrs_bundle,
 		       size_t idx, u64 allowed_bits);
 int uverbs_copy_to(const struct uverbs_attr_bundle *attrs_bundle, size_t idx,
 		   const void *from, size_t size);
+__malloc void *_uverbs_alloc(struct uverbs_attr_bundle *bundle, size_t size,
+			     gfp_t flags);
+
+static inline __malloc void *uverbs_alloc(struct uverbs_attr_bundle *bundle,
+					  size_t size)
+{
+	return _uverbs_alloc(bundle, size, GFP_KERNEL);
+}
+
+static inline __malloc void *uverbs_zalloc(struct uverbs_attr_bundle *bundle,
+					   size_t size)
+{
+	return _uverbs_alloc(bundle, size, GFP_KERNEL | __GFP_ZERO);
+}
 #else
 static inline int
 uverbs_get_flags64(u64 *to, const struct uverbs_attr_bundle *attrs_bundle,
@@ -669,6 +683,16 @@ static inline int uverbs_copy_to(const struct uverbs_attr_bundle *attrs_bundle,
 {
 	return -EINVAL;
 }
+static inline __malloc void *uverbs_alloc(struct uverbs_attr_bundle *bundle,
+					  size_t size)
+{
+	return ERR_PTR(-EINVAL);
+}
+static inline __malloc void *uverbs_zalloc(struct uverbs_attr_bundle *bundle,
+					   size_t size)
+{
+	return ERR_PTR(-EINVAL);
+}
 #endif
 
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