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/coda/inode.c b/fs/coda/inode.c
index 6526e6f21ecf..bfe8179b1295 100644
--- a/fs/coda/inode.c
+++ b/fs/coda/inode.c
@@ -148,6 +148,8 @@ static int coda_fill_super(struct super_block *sb, void *data, int silent)
         int error;
         int idx;
 
+        lock_kernel();
+
         idx = get_device_index((struct coda_mount_data *) data);
 
         /* Ignore errors in data, for backward compatibility */
@@ -159,11 +161,13 @@ static int coda_fill_super(struct super_block *sb, void *data, int silent)
         vc = &coda_comms[idx];
         if (!vc->vc_inuse) {
                 printk("coda_read_super: No pseudo device\n");
+                unlock_kernel();
                 return -EINVAL;
         }
 
         if ( vc->vc_sb ) {
                 printk("coda_read_super: Device already mounted\n");
+                unlock_kernel();
                 return -EBUSY;
         }
 
@@ -202,7 +206,8 @@ static int coda_fill_super(struct super_block *sb, void *data, int silent)
         sb->s_root = d_alloc_root(root);
         if (!sb->s_root)
                 goto error;
-        return 0;
+        unlock_kernel();
+        return 0;
 
  error:
         bdi_destroy(&vc->bdi);
@@ -212,6 +217,7 @@ static int coda_fill_super(struct super_block *sb, void *data, int silent)
         if (vc)
                 vc->vc_sb = NULL;
 
+        unlock_kernel();
         return -EINVAL;
 }