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, 7 insertions, 1 deletions

diff --git a/fs/bfs/inode.c b/fs/bfs/inode.c
index c4daf0f..d2e0936 100644
--- a/fs/bfs/inode.c
+++ b/fs/bfs/inode.c
@@ -322,9 +322,13 @@ static int bfs_fill_super(struct super_block *s, void *data, int silent)
 	int ret = -EINVAL;
 	unsigned long i_sblock, i_eblock, i_eoff, s_size;
 
+	lock_kernel();
+
 	info = kzalloc(sizeof(*info), GFP_KERNEL);
-	if (!info)
+	if (!info) {
+		unlock_kernel();
 		return -ENOMEM;
+	}
 	mutex_init(&info->bfs_lock);
 	s->s_fs_info = info;
 
@@ -439,6 +443,7 @@ static int bfs_fill_super(struct super_block *s, void *data, int silent)
 	brelse(bh);
 	brelse(sbh);
 	dump_imap("read_super", s);
+	unlock_kernel();
 	return 0;
 
 out3:
@@ -452,6 +457,7 @@ out:
 	mutex_destroy(&info->bfs_lock);
 	kfree(info);
 	s->s_fs_info = NULL;
+	unlock_kernel();
 	return ret;
 }