BKL: Explicitly add BKL around get_sb/fill_super

This patch is a preparation necessary to remove the BKL from do_new_mount().
It explicitly adds calls to lock_kernel()/unlock_kernel() around
get_sb/fill_super operations for filesystems that still uses the BKL.

I've read through all the code formerly covered by the BKL inside
do_kern_mount() and have satisfied myself that it doesn't need the BKL
any more.

do_kern_mount() is already called without the BKL when mounting the rootfs
and in nfsctl. do_kern_mount() calls vfs_kern_mount(), which is called
from various places without BKL: simple_pin_fs(), nfs_do_clone_mount()
through nfs_follow_mountpoint(), afs_mntpt_do_automount() through
afs_mntpt_follow_link(). Both later functions are actually the filesystems
follow_link inode operation. vfs_kern_mount() is calling the specified
get_sb function and lets the filesystem do its job by calling the given
fill_super function.

Therefore I think it is safe to push down the BKL from the VFS to the
low-level filesystems get_sb/fill_super operation.

[arnd: do not add the BKL to those file systems that already
       don't use it elsewhere]

Signed-off-by: Jan Blunck <jblunck@infradead.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Christoph Hellwig <hch@infradead.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index d510c1b9181..6b9be90dae7 100644
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -696,6 +696,8 @@ static int ufs_fill_super(struct super_block *sb, void *data, int silent)
 	unsigned maxsymlen;
 	int ret = -EINVAL;
 
+	lock_kernel();
+
 	uspi = NULL;
 	ubh = NULL;
 	flags = 0;
@@ -1163,6 +1165,7 @@ magic_found:
 			goto failed;
 
 	UFSD("EXIT\n");
+	unlock_kernel();
 	return 0;
 
 dalloc_failed:
@@ -1174,10 +1177,12 @@ failed:
 	kfree(sbi);
 	sb->s_fs_info = NULL;
 	UFSD("EXIT (FAILED)\n");
+	unlock_kernel();
 	return ret;
 
 failed_nomem:
 	UFSD("EXIT (NOMEM)\n");
+	unlock_kernel();
 	return -ENOMEM;
 }