[PATCH v2 bpf-next 1/6] bpf: add a __btf_get_by_fd helper

[Anton Protopopov <aspsk@xxxxxxxxxxxxx>]

Add a new helper to get a pointer to a struct btf from a file
descriptor which doesn't increase a refcount.

Signed-off-by: Anton Protopopov <aspsk@xxxxxxxxxxxxx>
---
 include/linux/btf.h | 13 +++++++++++++
 kernel/bpf/btf.c    | 13 ++++---------
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 4214e76c9168..050051a578a8 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -4,6 +4,7 @@
 #ifndef _LINUX_BTF_H
 #define _LINUX_BTF_H 1
 
+#include <linux/file.h>
 #include <linux/types.h>
 #include <linux/bpfptr.h>
 #include <linux/bsearch.h>
@@ -143,6 +144,18 @@ void btf_get(struct btf *btf);
 void btf_put(struct btf *btf);
 const struct btf_header *btf_header(const struct btf *btf);
 int btf_new_fd(const union bpf_attr *attr, bpfptr_t uattr, u32 uattr_sz);
+
+static inline struct btf *__btf_get_by_fd(struct fd f)
+{
+	if (fd_empty(f))
+		return ERR_PTR(-EBADF);
+
+	if (unlikely(fd_file(f)->f_op != &btf_fops))
+		return ERR_PTR(-EINVAL);
+
+	return fd_file(f)->private_data;
+}
+
 struct btf *btf_get_by_fd(int fd);
 int btf_get_info_by_fd(const struct btf *btf,
 		       const union bpf_attr *attr,
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index e7a59e6462a9..ad5310fa1d3b 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -7743,17 +7743,12 @@ int btf_new_fd(const union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 
 struct btf *btf_get_by_fd(int fd)
 {
-	struct btf *btf;
 	CLASS(fd, f)(fd);
+	struct btf *btf;
 
-	if (fd_empty(f))
-		return ERR_PTR(-EBADF);
-
-	if (fd_file(f)->f_op != &btf_fops)
-		return ERR_PTR(-EINVAL);
-
-	btf = fd_file(f)->private_data;
-	refcount_inc(&btf->refcnt);
+	btf = __btf_get_by_fd(f);
+	if (!IS_ERR(btf))
+		refcount_inc(&btf->refcnt);
 
 	return btf;
 }
-- 
2.34.1