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, 1 deletions

diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
index c2903b84bb7a..667d7ceba8c9 100644
--- a/fs/ocfs2/dlmfs/dlmfs.c
+++ b/fs/ocfs2/dlmfs/dlmfs.c
@@ -44,6 +44,7 @@
 #include <linux/string.h>
 #include <linux/backing-dev.h>
 #include <linux/poll.h>
+#include <linux/smp_lock.h>
 
 #include <asm/uaccess.h>
 
@@ -588,21 +589,27 @@ static int dlmfs_fill_super(struct super_block * sb,
         struct inode * inode;
         struct dentry * root;
 
+        lock_kernel();
+
         sb->s_maxbytes = MAX_LFS_FILESIZE;
         sb->s_blocksize = PAGE_CACHE_SIZE;
         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
         sb->s_magic = DLMFS_MAGIC;
         sb->s_op = &dlmfs_ops;
         inode = dlmfs_get_root_inode(sb);
-        if (!inode)
+        if (!inode) {
+                unlock_kernel();
                 return -ENOMEM;
+        }
 
         root = d_alloc_root(inode);
         if (!root) {
                 iput(inode);
+                unlock_kernel();
                 return -ENOMEM;
         }
         sb->s_root = root;
+        unlock_kernel();
         return 0;
 }