[Devel] [RFC][PATCH 3/4] create fill_if_new_sb() helper

[Dave Hansen]

As I was migrating /proc away from get_sb_single() use, I
noticed I was duplicating a lot of functionality in the /proc
code from get_sb_single().  I then noticed that get_sb_nodev()
does basically the same thing.

So, I created a fill_if_new_sb() helper to work on the superblock
after sget() to fill it only when necessary and handle the work
with sb->s_flags and the s->s_umount semaphore.

I'll use this in a moment in /proc as well.

---

 lxc-dave/fs/super.c         |   43 +++++++++++++++++++++++--------------------
 lxc-dave/include/linux/fs.h |    2 ++
 2 files changed, 25 insertions(+), 20 deletions(-)

diff -puN fs/super.c~A2-fill_if_new_sb fs/super.c
--- lxc/fs/super.c~A2-fill_if_new_sb	2007-01-26 14:29:17.000000000 -0800
+++ lxc-dave/fs/super.c	2007-01-26 14:29:17.000000000 -0800
@@ -810,6 +810,23 @@ void kill_block_super(struct super_block
 EXPORT_SYMBOL(kill_block_super);
 #endif
 
+int fill_if_new_sb(struct super_block *s, void *data, int flags,
+		int (*fill_super)(struct super_block *, void *, int))
+{
+	int error;
+	if (s->s_root)
+		return 0;
+	s->s_flags = flags;
+	error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
+	if (error) {
+		up_write(&s->s_umount);
+		deactivate_super(s);
+		return error;
+	}
+	s->s_flags |= MS_ACTIVE;
+	return error;
+}
+
 int get_sb_nodev(struct file_system_type *fs_type,
 	int flags, void *data,
 	int (*fill_super)(struct super_block *, void *, int),
@@ -820,16 +837,9 @@ int get_sb_nodev(struct file_system_type
 
 	if (IS_ERR(s))
 		return PTR_ERR(s);
-
-	s->s_flags = flags;
-
-	error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
-	if (error) {
-		up_write(&s->s_umount);
-		deactivate_super(s);
+	error = fill_if_new_sb(s, data, flags, fill_super);
+	if (error)
 		return error;
-	}
-	s->s_flags |= MS_ACTIVE;
 	return simple_set_mnt(mnt, s);
 }
 
@@ -845,22 +855,15 @@ int get_sb_single(struct file_system_typ
 	int (*fill_super)(struct super_block *, void *, int),
 	struct vfsmount *mnt)
 {
-	struct super_block *s;
 	int error;
+	struct super_block *s;
 
 	s = sget(fs_type, compare_single, set_anon_super, NULL);
 	if (IS_ERR(s))
 		return PTR_ERR(s);
-	if (!s->s_root) {
-		s->s_flags = flags;
-		error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
-		if (error) {
-			up_write(&s->s_umount);
-			deactivate_super(s);
-			return error;
-		}
-		s->s_flags |= MS_ACTIVE;
-	}
+	error = fill_if_new_sb(s, data, flags, fill_super);
+	if (error)
+		return error;
 	do_remount_sb(s, flags, data, 0);
 	return simple_set_mnt(mnt, s);
 }
diff -puN include/linux/fs.h~A2-fill_if_new_sb include/linux/fs.h
--- lxc/include/linux/fs.h~A2-fill_if_new_sb	2007-01-26 14:29:17.000000000 -0800
+++ lxc-dave/include/linux/fs.h	2007-01-26 14:29:17.000000000 -0800
@@ -1416,6 +1416,8 @@ extern int get_sb_nodev(struct file_syst
 	int flags, void *data,
 	int (*fill_super)(struct super_block *, void *, int),
 	struct vfsmount *mnt);
+extern int fill_if_new_sb(struct super_block *s, void *data, int flags,
+	int (*fill_super)(struct super_block *, void *, int));
 void generic_shutdown_super(struct super_block *sb);
 void kill_block_super(struct super_block *sb);
 void kill_anon_super(struct super_block *sb);
_
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