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/udf/super.c b/fs/udf/super.c
index 65412d84a45d..76f3d6d97b40 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -1880,6 +1880,8 @@ static int udf_fill_super(struct super_block *sb, void *options, int silent)
         struct kernel_lb_addr rootdir, fileset;
         struct udf_sb_info *sbi;
 
+        lock_kernel();
+
         uopt.flags = (1 << UDF_FLAG_USE_AD_IN_ICB) | (1 << UDF_FLAG_STRICT);
         uopt.uid = -1;
         uopt.gid = -1;
@@ -1888,8 +1890,10 @@ static int udf_fill_super(struct super_block *sb, void *options, int silent)
         uopt.dmode = UDF_INVALID_MODE;
 
         sbi = kzalloc(sizeof(struct udf_sb_info), GFP_KERNEL);
-        if (!sbi)
+        if (!sbi) {
+                unlock_kernel();
                 return -ENOMEM;
+        }
 
         sb->s_fs_info = sbi;
 
@@ -2035,6 +2039,7 @@ static int udf_fill_super(struct super_block *sb, void *options, int silent)
                 goto error_out;
         }
         sb->s_maxbytes = MAX_LFS_FILESIZE;
+        unlock_kernel();
         return 0;
 
 error_out:
@@ -2055,6 +2060,7 @@ error_out:
         kfree(sbi);
         sb->s_fs_info = NULL;
 
+        unlock_kernel();
         return -EINVAL;
 }