ufs: remove the BKL

This introduces a new per-superblock mutex in UFS to replace
the big kernel lock. I have been careful to avoid nested
calls to lock_ufs and to get the lock order right with
respect to other mutexes, in particular lock_super.

I did not make any attempt to prove that the big kernel
lock is not needed in a particular place in the code,
which is very possible.

The mutex has a significant performance impact, so it is only
used on SMP or PREEMPT configurations.

As Nick Piggin noticed, any allocation inside of the lock
may end up deadlocking when we get to ufs_getfrag_block
in the reclaim task, so we now use GFP_NOFS.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Nick Bowler <nbowler@elliptictech.com>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Cc: Nick Piggin <npiggin@gmail.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/ufs/util.c b/fs/ufs/util.c
index d2c36d53fe66..95425b59ce0a 100644
--- a/fs/ufs/util.c
+++ b/fs/ufs/util.c
@@ -27,7 +27,7 @@ struct ufs_buffer_head * _ubh_bread_ (struct ufs_sb_private_info * uspi,
         if (count > UFS_MAXFRAG)
                 return NULL;
         ubh = (struct ufs_buffer_head *)
-                kmalloc (sizeof (struct ufs_buffer_head), GFP_KERNEL);
+                kmalloc (sizeof (struct ufs_buffer_head), GFP_NOFS);
         if (!ubh)
                 return NULL;
         ubh->fragment = fragment;