Re: [PATCH] UBIFS: kill BKL

[Artem Bityutskiy <dedekind1@gmail.com>]

On Mon, 2009-07-20 at 09:16 +0300, Adrian Hunter wrote:
> Artem Bityutskiy wrote:
> > From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
> > 
> > The BKL was pushed down from VFS to the file-systems. It used
> > to serialize mount/unmount/remount. UBIFS must be safe if several
> > file-systems are mounted/unmounted/re-mounted at the same time,
> > so kill kick the BKL out of UBIFS.
> > 
> > Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
> > ---
> 
> Looks like protection is always provided by sb->s_umount

Not for 2 or more instances of fs mounted/umounted/remounted at
the same time, which I meant in my comment. But I've fixed the
comment.

> Missing {} below, btw.

New version is below.

>From 347a38db88429400f0f479dc4d7de2b673999433 Mon Sep 17 00:00:00 2001
From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Date: Sun, 19 Jul 2009 13:51:04 +0300
Subject: [PATCH] UBIFS: kill BKL

The BKL was pushed down from VFS to the file-systems. It used
to serialize mount/unmount/remount and prevented more than one
instance of the same file-system from doing
mount/umount/remount at the same time. But it is OK for UBIFS
and it does not need any additional locking for these cases.
Thus, kick the BKL out of UBIFS.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
---
Changelog: fixed parentheses
           remove #include <linux/smp_lock.h>

 fs/ubifs/super.c |   13 +------------
 1 files changed, 1 insertions(+), 12 deletions(-)

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 26d2e0d..13e7ed4 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -36,7 +36,6 @@
 #include <linux/mount.h>
 #include <linux/math64.h>
 #include <linux/writeback.h>
-#include <linux/smp_lock.h>
 #include "ubifs.h"
 
 /*
@@ -1726,8 +1725,6 @@ static void ubifs_put_super(struct super_block *sb)
 	ubifs_msg("un-mount UBI device %d, volume %d", c->vi.ubi_num,
 		  c->vi.vol_id);
 
-	lock_kernel();
-
 	/*
 	 * The following asserts are only valid if there has not been a failure
 	 * of the media. For example, there will be dirty inodes if we failed
@@ -1792,8 +1789,6 @@ static void ubifs_put_super(struct super_block *sb)
 	ubi_close_volume(c->ubi);
 	mutex_unlock(&c->umount_mutex);
 	kfree(c);
-
-	unlock_kernel();
 }
 
 static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
@@ -1809,22 +1804,17 @@ static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
 		return err;
 	}
 
-	lock_kernel();
 	if ((sb->s_flags & MS_RDONLY) && !(*flags & MS_RDONLY)) {
 		if (c->ro_media) {
 			ubifs_msg("cannot re-mount due to prior errors");
-			unlock_kernel();
 			return -EROFS;
 		}
 		err = ubifs_remount_rw(c);
-		if (err) {
-			unlock_kernel();
+		if (err)
 			return err;
-		}
 	} else if (!(sb->s_flags & MS_RDONLY) && (*flags & MS_RDONLY)) {
 		if (c->ro_media) {
 			ubifs_msg("cannot re-mount due to prior errors");
-			unlock_kernel();
 			return -EROFS;
 		}
 		ubifs_remount_ro(c);
@@ -1839,7 +1829,6 @@ static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
 	}
 
 	ubifs_assert(c->lst.taken_empty_lebs > 0);
-	unlock_kernel();
 	return 0;
 }
 
-- 
1.6.0.6