[RFC v2 1/3] file: Introduce iterate_fd_locked

[aloktiagi <aloktiagi@xxxxxxxxx>]

Callers holding the files->file_lock lock can call iterate_fd_locked instead of
iterate_fd

Signed-off-by: aloktiagi <aloktiagi@xxxxxxxxx>
Reviewed-by: Tycho Andersen <tycho@tycho.pizza>
---
 fs/file.c               | 21 +++++++++++++++------
 include/linux/fdtable.h |  3 +++
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index c942c89ca4cd..4b2346b8a5ee 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -1295,15 +1295,12 @@ int f_dupfd(unsigned int from, struct file *file, unsigned flags)
 	return err;
 }
 
-int iterate_fd(struct files_struct *files, unsigned n,
-		int (*f)(const void *, struct file *, unsigned),
-		const void *p)
+int iterate_fd_locked(struct files_struct *files, unsigned n,
+                int (*f)(const void *, struct file *, unsigned),
+                const void *p)
 {
 	struct fdtable *fdt;
 	int res = 0;
-	if (!files)
-		return 0;
-	spin_lock(&files->file_lock);
 	for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
 		struct file *file;
 		file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
@@ -1313,6 +1310,18 @@ int iterate_fd(struct files_struct *files, unsigned n,
 		if (res)
 			break;
 	}
+	return res;
+}
+
+int iterate_fd(struct files_struct *files, unsigned n,
+		int (*f)(const void *, struct file *, unsigned),
+		const void *p)
+{
+	int res = 0;
+	if (!files)
+		return 0;
+	spin_lock(&files->file_lock);
+	res = iterate_fd_locked(files, n, f, p);
 	spin_unlock(&files->file_lock);
 	return res;
 }
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index e066816f3519..14882520d1fe 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -122,6 +122,9 @@ void do_close_on_exec(struct files_struct *);
 int iterate_fd(struct files_struct *, unsigned,
 		int (*)(const void *, struct file *, unsigned),
 		const void *);
+int iterate_fd_locked(struct files_struct *, unsigned,
+			int (*)(const void *, struct file *, unsigned),
+			const void *);
 
 extern int close_fd(unsigned int fd);
 extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags);
-- 
2.34.1