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/ntfs/super.c b/fs/ntfs/super.c
index 512806171bfa..1f31e77fc41f 100644
--- a/fs/ntfs/super.c
+++ b/fs/ntfs/super.c
@@ -2732,6 +2732,8 @@ static int ntfs_fill_super(struct super_block *sb, void *opt, const int silent)
 	struct inode *tmp_ino;
 	int blocksize, result;
 
+	lock_kernel();
+
 	/*
 	 * We do a pretty difficult piece of bootstrap by reading the
 	 * MFT (and other metadata) from disk into memory. We'll only
@@ -2755,6 +2757,7 @@ static int ntfs_fill_super(struct super_block *sb, void *opt, const int silent)
 			ntfs_error(sb, "Allocation of NTFS volume structure "
 					"failed. Aborting mount...");
 		lockdep_on();
+		unlock_kernel();
 		return -ENOMEM;
 	}
 	/* Initialize ntfs_volume structure. */
@@ -2942,6 +2945,7 @@ static int ntfs_fill_super(struct super_block *sb, void *opt, const int silent)
 		sb->s_export_op = &ntfs_export_ops;
 		lock_kernel();
 		lockdep_on();
+		unlock_kernel();
 		return 0;
 	}
 	ntfs_error(sb, "Failed to allocate root directory.");
@@ -3062,6 +3066,7 @@ err_out_now:
 	kfree(vol);
 	ntfs_debug("Failed, returning -EINVAL.");
 	lockdep_on();
+	unlock_kernel();
 	return -EINVAL;
 }