vfs: Abstract rcu_dereference_check for files-fdtable use

Create an rcu_dereference_check_fdtable() that encapsulates the
rcu_dereference_check() condition for fcheck_files() use.  This
has the beneficial side-effect of getting rid of a very long
line.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1266887105-1528-9-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index 144412f..013dc52 100644 (file)
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -57,11 +57,14 @@ struct files_struct {
        struct file * fd_array[NR_OPEN_DEFAULT];
 };
 
-#define files_fdtable(files) \
-       (rcu_dereference_check((files)->fdt, \
+#define rcu_dereference_check_fdtable(files, fdtfd) \
+       (rcu_dereference_check((fdtfd), \
                               rcu_read_lock_held() || \
                               lockdep_is_held(&(files)->file_lock) || \
-                              atomic_read(&files->count) == 1))
+                              atomic_read(&(files)->count) == 1))
+
+#define files_fdtable(files) \
+               (rcu_dereference_check_fdtable((files), (files)->fdt))
 
 struct file_operations;
 struct vfsmount;
@@ -82,7 +85,7 @@ static inline struct file * fcheck_files(struct files_struct *files, unsigned in
        struct fdtable *fdt = files_fdtable(files);
 
        if (fd < fdt->max_fds)
-               file = rcu_dereference_check(fdt->fd[fd], rcu_read_lock_held() || lockdep_is_held(&files->file_lock) || atomic_read(&files->count) == 1);
+               file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
        return file;
 }