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/smbfs/inode.c b/fs/smbfs/inode.c
index 450c919..8fc5e50 100644
--- a/fs/smbfs/inode.c
+++ b/fs/smbfs/inode.c
@@ -501,6 +501,8 @@ static int smb_fill_super(struct super_block *sb, void *raw_data, int silent)
 	void *mem;
 	static int warn_count;
 
+	lock_kernel();
+
 	if (warn_count < 5) {
 		warn_count++;
 		printk(KERN_EMERG "smbfs is deprecated and will be removed"
@@ -621,6 +623,7 @@ static int smb_fill_super(struct super_block *sb, void *raw_data, int silent)
 
 	smb_new_dentry(sb->s_root);
 
+	unlock_kernel();
 	return 0;
 
 out_no_root:
@@ -643,9 +646,11 @@ out_wrong_data:
 out_no_data:
 	printk(KERN_ERR "smb_fill_super: missing data argument\n");
 out_fail:
+	unlock_kernel();
 	return -EINVAL;
 out_no_server:
 	printk(KERN_ERR "smb_fill_super: cannot allocate struct smb_sb_info\n");
+	unlock_kernel();
 	return -ENOMEM;
 }