[PATCH] fdtable: Provide free_fdtable() wrapper

Christoph Hellwig has expressed concerns that the recent fdtable changes
expose the details of the RCU methodology used to release no-longer-used
fdtable structures to the rest of the kernel.  The trivial patch below
addresses these concerns by introducing the appropriate free_fdtable()
calls, which simply wrap the release RCU usage.  Since free_fdtable() is a
one-liner, it makes sense to promote it to an inline helper.

Signed-off-by: Vadim Lobanov <vlobanov@speakeasy.net>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/file.c

@@ -206,7 +206,7 @@ static int expand_fdtable(struct files_struct *files, int nr)
 		copy_fdtable(new_fdt, cur_fdt);
 		rcu_assign_pointer(files->fdt, new_fdt);
 		if (cur_fdt->max_fds > NR_OPEN_DEFAULT)
-			call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
+			free_fdtable(cur_fdt);
 	} else {
 		/* Somebody else expanded, so undo our attempt */
 		free_fdarr(new_fdt);

include/linux/file.h

@@ -80,6 +80,11 @@ extern int expand_files(struct files_struct *, int nr);
 extern void free_fdtable_rcu(struct rcu_head *rcu);
 extern void __init files_defer_init(void);
 
+static inline void free_fdtable(struct fdtable *fdt)
+{
+	call_rcu(&fdt->rcu, free_fdtable_rcu);
+}
+
 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
 {
 	struct file * file = NULL;

kernel/exit.c

@@ -468,7 +468,7 @@ void fastcall put_files_struct(struct files_struct *files)
 		fdt = files_fdtable(files);
 		if (fdt != &files->fdtab)
 			kmem_cache_free(files_cachep, files);
-		call_rcu(&fdt->rcu, free_fdtable_rcu);
+		free_fdtable(fdt);
 	}
 }