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, 6 insertions, 0 deletions

diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index 88b4f860665..ab1a401a0e1 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -87,11 +87,14 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
 	u64 lookup_table_start, xattr_id_table_start;
 	int err;
 
+	lock_kernel();
+
 	TRACE("Entered squashfs_fill_superblock\n");
 
 	sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
 	if (sb->s_fs_info == NULL) {
 		ERROR("Failed to allocate squashfs_sb_info\n");
+		unlock_kernel();
 		return -ENOMEM;
 	}
 	msblk = sb->s_fs_info;
@@ -301,6 +304,7 @@ allocate_root:
 
 	TRACE("Leaving squashfs_fill_super\n");
 	kfree(sblk);
+	unlock_kernel();
 	return 0;
 
 failed_mount:
@@ -315,11 +319,13 @@ failed_mount:
 	kfree(sb->s_fs_info);
 	sb->s_fs_info = NULL;
 	kfree(sblk);
+	unlock_kernel();
 	return err;
 
 failure:
 	kfree(sb->s_fs_info);
 	sb->s_fs_info = NULL;
+	unlock_kernel();
 	return -ENOMEM;
 }