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/adfs/super.c b/fs/adfs/super.c
index 4a3af70..d9803f7 100644
--- a/fs/adfs/super.c
+++ b/fs/adfs/super.c
@@ -352,11 +352,15 @@ static int adfs_fill_super(struct super_block *sb, void *data, int silent)
 	struct adfs_sb_info *asb;
 	struct inode *root;
 
+	lock_kernel();
+
 	sb->s_flags |= MS_NODIRATIME;
 
 	asb = kzalloc(sizeof(*asb), GFP_KERNEL);
-	if (!asb)
+	if (!asb) {
+		unlock_kernel();
 		return -ENOMEM;
+	}
 	sb->s_fs_info = asb;
 
 	/* set default options */
@@ -474,6 +478,7 @@ static int adfs_fill_super(struct super_block *sb, void *data, int silent)
 		goto error;
 	} else
 		sb->s_root->d_op = &adfs_dentry_operations;
+	unlock_kernel();
 	return 0;
 
 error_free_bh:
@@ -481,6 +486,7 @@ error_free_bh:
 error:
 	sb->s_fs_info = NULL;
 	kfree(asb);
+	unlock_kernel();
 	return -EINVAL;
 }