reiserfs: fix dependency inversion between inode and reiserfs mutexes

The reiserfs mutex already depends on the inode mutex, so we can't lock
the inode mutex in reiserfs_unpack() without using the safe locking API,
because reiserfs_unpack() is always called with the reiserfs mutex locked.

This fixes:

  =======================================================
  [ INFO: possible circular locking dependency detected ]
  2.6.35c torvalds#13
  -------------------------------------------------------
  lilo/1606 is trying to acquire lock:
   (&sb->s_type->i_mutex_key#8){+.+.+.}, at: [<d0329450>] reiserfs_unpack+0x60/0x110 [reiserfs]

  but task is already holding lock:
   (&REISERFS_SB(s)->lock){+.+.+.}, at: [<d032a268>] reiserfs_write_lock+0x28/0x40 [reiserfs]

  which lock already depends on the new lock.

  the existing dependency chain (in reverse order) is:

  -> #1 (&REISERFS_SB(s)->lock){+.+.+.}:
         [<c1056347>] lock_acquire+0x67/0x80
         [<c12f083d>] __mutex_lock_common+0x4d/0x410
         [<c12f0c58>] mutex_lock_nested+0x18/0x20
         [<d032a268>] reiserfs_write_lock+0x28/0x40 [reiserfs]
         [<d0329e9a>] reiserfs_lookup_privroot+0x2a/0x90 [reiserfs]
         [<d0316b81>] reiserfs_fill_super+0x941/0xe60 [reiserfs]
         [<c10b7d17>] get_sb_bdev+0x117/0x170
         [<d0313e21>] get_super_block+0x21/0x30 [reiserfs]
         [<c10b74ba>] vfs_kern_mount+0x6a/0x1b0
         [<c10b7659>] do_kern_mount+0x39/0xe0
         [<c10cebe0>] do_mount+0x340/0x790
         [<c10cf0b4>] sys_mount+0x84/0xb0
         [<c12f25cd>] syscall_call+0x7/0xb

  -> #0 (&sb->s_type->i_mutex_key#8){+.+.+.}:
         [<c1056186>] __lock_acquire+0x1026/0x1180
         [<c1056347>] lock_acquire+0x67/0x80
         [<c12f083d>] __mutex_lock_common+0x4d/0x410
         [<c12f0c58>] mutex_lock_nested+0x18/0x20
         [<d0329450>] reiserfs_unpack+0x60/0x110 [reiserfs]
         [<d0329772>] reiserfs_ioctl+0x272/0x320 [reiserfs]
         [<c10c3228>] vfs_ioctl+0x28/0xa0
         [<c10c3c5d>] do_vfs_ioctl+0x32d/0x5c0
         [<c10c3f53>] sys_ioctl+0x63/0x70
         [<c12f25cd>] syscall_call+0x7/0xb

  other info that might help us debug this:

  1 lock held by lilo/1606:
   #0:  (&REISERFS_SB(s)->lock){+.+.+.}, at: [<d032a268>] reiserfs_write_lock+0x28/0x40 [reiserfs]

  stack backtrace:
  Pid: 1606, comm: lilo Not tainted 2.6.35c torvalds#13
  Call Trace:
   [<c1056186>] __lock_acquire+0x1026/0x1180
   [<c1056347>] lock_acquire+0x67/0x80
   [<c12f083d>] __mutex_lock_common+0x4d/0x410
   [<c12f0c58>] mutex_lock_nested+0x18/0x20
   [<d0329450>] reiserfs_unpack+0x60/0x110 [reiserfs]
   [<d0329772>] reiserfs_ioctl+0x272/0x320 [reiserfs]
   [<c10c3228>] vfs_ioctl+0x28/0xa0
   [<c10c3c5d>] do_vfs_ioctl+0x32d/0x5c0
   [<c10c3f53>] sys_ioctl+0x63/0x70
   [<c12f25cd>] syscall_call+0x7/0xb

Reported-by: Jarek Poplawski <jarkao2@gmail.com>
Tested-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: <stable@kernel.org>		[2.6.32 and later]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/reiserfs/ioctl.c

@@ -188,7 +188,7 @@ int reiserfs_unpack(struct inode *inode, struct file *filp)
 	/* we need to make sure nobody is changing the file size beneath
 	 ** us
 	 */
-	mutex_lock(&inode->i_mutex);
+	reiserfs_mutex_lock_safe(&inode->i_mutex, inode->i_sb);
 	reiserfs_write_lock(inode->i_sb);
 
 	write_from = inode->i_size & (blocksize - 1);