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, 10 insertions, 2 deletions

diff --git a/fs/jfs/super.c b/fs/jfs/super.c
index ec8c3e4..eb31f67 100644
--- a/fs/jfs/super.c
+++ b/fs/jfs/super.c
@@ -438,14 +438,20 @@ static int jfs_fill_super(struct super_block *sb, void *data, int silent)
 	s64 newLVSize = 0;
 	int flag, ret = -EINVAL;
 
+	lock_kernel();
+
 	jfs_info("In jfs_read_super: s_flags=0x%lx", sb->s_flags);
 
-	if (!new_valid_dev(sb->s_bdev->bd_dev))
+	if (!new_valid_dev(sb->s_bdev->bd_dev)) {
+		unlock_kernel();
 		return -EOVERFLOW;
+	}
 
 	sbi = kzalloc(sizeof (struct jfs_sb_info), GFP_KERNEL);
-	if (!sbi)
+	if (!sbi) {
+		unlock_kernel();
 		return -ENOMEM;
+	}
 	sb->s_fs_info = sbi;
 	sbi->sb = sb;
 	sbi->uid = sbi->gid = sbi->umask = -1;
@@ -542,6 +548,7 @@ static int jfs_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_maxbytes = min(((u64) PAGE_CACHE_SIZE << 32) - 1, (u64)sb->s_maxbytes);
 #endif
 	sb->s_time_gran = 1;
+	unlock_kernel();
 	return 0;
 
 out_no_root:
@@ -564,6 +571,7 @@ out_unload:
 		unload_nls(sbi->nls_tab);
 out_kfree:
 	kfree(sbi);
+	unlock_kernel();
 	return ret;
 }