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, 2 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 26147746c272..0f0021f4990c 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2568,6 +2568,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
         int err;
         unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
 
+        lock_kernel();
+
         sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
         if (!sbi)
                 goto out_free_orig;
@@ -3166,7 +3168,6 @@ no_journal:
         if (es->s_error_count)
                 mod_timer(&sbi->s_err_report, jiffies + 300*HZ); /* 5 minutes */
 
-        lock_kernel();
         kfree(orig_data);
         return 0;
 
@@ -3213,8 +3214,11 @@ out_fail:
         sb->s_fs_info = NULL;
         kfree(sbi->s_blockgroup_lock);
         kfree(sbi);
-        lock_kernel();
+        kfree(orig_data);
+        return ret;
+
 out_free_orig:
+        unlock_kernel();
         kfree(orig_data);
         return ret;
 }