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/nilfs2/super.c b/fs/nilfs2/super.c
index 922263393c76..0d573c2a6860 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -1113,9 +1113,12 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
 	if (!(flags & MS_RDONLY))
 		mode |= FMODE_WRITE;
 
+	lock_kernel();
 	sd.bdev = open_bdev_exclusive(dev_name, mode, fs_type);
-	if (IS_ERR(sd.bdev))
+	if (IS_ERR(sd.bdev)) {
+		unlock_kernel();
 		return PTR_ERR(sd.bdev);
+	}
 
 	/*
 	 * To get mount instance using sget() vfs-routine, NILFS needs
@@ -1198,6 +1201,7 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
 	if (need_to_close)
 		close_bdev_exclusive(sd.bdev, mode);
 	simple_set_mnt(mnt, s);
+	unlock_kernel();
 	return 0;
 
  failed_unlock:
@@ -1206,6 +1210,7 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
  failed:
 	close_bdev_exclusive(sd.bdev, mode);
 
+	unlock_kernel();
 	return err;
 
  cancel_new:
@@ -1218,6 +1223,7 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
 	 * We must finish all post-cleaning before this call;
 	 * put_nilfs() needs the block device.
 	 */
+	unlock_kernel();
 	return err;
 }