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, 4 insertions, 0 deletions

diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index cbd4e18adb20..c4af92fa12c3 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -36,6 +36,7 @@
 #include <linux/parser.h>
 #include <linux/fs_stack.h>
 #include <linux/slab.h>
+#include <linux/smp_lock.h>     /* For lock_kernel() */
 #include "ecryptfs_kernel.h"
 
 /**
@@ -550,6 +551,7 @@ static int ecryptfs_get_sb(struct file_system_type *fs_type, int flags,
         const char *err = "Getting sb failed";
         int rc;
 
+        lock_kernel();
         sbi = kmem_cache_zalloc(ecryptfs_sb_info_cache, GFP_KERNEL);
         if (!sbi) {
                 rc = -ENOMEM;
@@ -608,6 +610,7 @@ static int ecryptfs_get_sb(struct file_system_type *fs_type, int flags,
                 goto out;
         }
         simple_set_mnt(mnt, s);
+        unlock_kernel();
         return 0;
 
 out:
@@ -616,6 +619,7 @@ out:
                 kmem_cache_free(ecryptfs_sb_info_cache, sbi);
         }
         printk(KERN_ERR "%s; rc = [%d]\n", err, rc);
+        unlock_kernel();
         return rc;
 }