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 4a3af7075c1d..d9803f73236f 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;
 }