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/qnx4/inode.c b/fs/qnx4/inode.c
index 16829722be93..86a7be1399a8 100644
--- a/fs/qnx4/inode.c
+++ b/fs/qnx4/inode.c
@@ -234,9 +234,13 @@ static int qnx4_fill_super(struct super_block *s, void *data, int silent)
         struct qnx4_sb_info *qs;
         int ret = -EINVAL;
 
+        lock_kernel();
+
         qs = kzalloc(sizeof(struct qnx4_sb_info), GFP_KERNEL);
-        if (!qs)
+        if (!qs) {
+                unlock_kernel();
                 return -ENOMEM;
+        }
         s->s_fs_info = qs;
 
         sb_set_blocksize(s, QNX4_BLOCK_SIZE);
@@ -284,6 +288,7 @@ static int qnx4_fill_super(struct super_block *s, void *data, int silent)
 
         brelse(bh);
 
+        unlock_kernel();
         return 0;
 
       outi:
@@ -293,6 +298,7 @@ static int qnx4_fill_super(struct super_block *s, void *data, int silent)
       outnobh:
         kfree(qs);
         s->s_fs_info = NULL;
+        unlock_kernel();
         return ret;
 }