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, 9 insertions, 2 deletions

diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c
index 662bba099501..58dd9cf06206 100644
--- a/fs/jffs2/super.c
+++ b/fs/jffs2/super.c
@@ -146,14 +146,19 @@ static const struct super_operations jffs2_super_operations =
 static int jffs2_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct jffs2_sb_info *c;
+	int ret;
+
+	lock_kernel();
 
 	D1(printk(KERN_DEBUG "jffs2_get_sb_mtd():"
 		  " New superblock for device %d (\"%s\")\n",
 		  sb->s_mtd->index, sb->s_mtd->name));
 
 	c = kzalloc(sizeof(*c), GFP_KERNEL);
-	if (!c)
+	if (!c) {
+		unlock_kernel();
 		return -ENOMEM;
+	}
 
 	c->mtd = sb->s_mtd;
 	c->os_priv = sb;
@@ -175,7 +180,9 @@ static int jffs2_fill_super(struct super_block *sb, void *data, int silent)
 #ifdef CONFIG_JFFS2_FS_POSIX_ACL
 	sb->s_flags |= MS_POSIXACL;
 #endif
-	return jffs2_do_fill_super(sb, data, silent);
+	ret = jffs2_do_fill_super(sb, data, silent);
+	unlock_kernel();
+	return ret;
 }
 
 static int jffs2_get_sb(struct file_system_type *fs_type,