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, 8 insertions, 2 deletions

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 1ec602673ea8..f98c390caf1d 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -747,15 +747,18 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 	__le32 features;
 	int err;
 
+	lock_kernel();
+
+	err = -ENOMEM;
 	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
 	if (!sbi)
-		return -ENOMEM;
+		goto failed_unlock;
 
 	sbi->s_blockgroup_lock =
 		kzalloc(sizeof(struct blockgroup_lock), GFP_KERNEL);
 	if (!sbi->s_blockgroup_lock) {
 		kfree(sbi);
-		return -ENOMEM;
+		goto failed_unlock;
 	}
 	sb->s_fs_info = sbi;
 	sbi->s_sb_block = sb_block;
@@ -1083,6 +1086,7 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 	if (ext2_setup_super (sb, es, sb->s_flags & MS_RDONLY))
 		sb->s_flags |= MS_RDONLY;
 	ext2_write_super(sb);
+	unlock_kernel();
 	return 0;
 
 cantfind_ext2:
@@ -1107,6 +1111,8 @@ failed_sbi:
 	sb->s_fs_info = NULL;
 	kfree(sbi->s_blockgroup_lock);
 	kfree(sbi);
+failed_unlock:
+	unlock_kernel();
 	return ret;
 }