fs/btrfs/locking.c

   1 /*
   2  * Copyright (C) 2008 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18 #include <linux/sched.h>
  19 #include <linux/gfp.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/spinlock.h>
  22 #include <linux/page-flags.h>
  23 #include <asm/bug.h>
  24 #include "ctree.h"
  25 #include "extent_io.h"
  26 #include "locking.h"
  27
  28 int btrfs_tree_lock(struct extent_buffer *eb)
  29 {
  30         int i;
  31
  32         if (mutex_trylock(&eb->mutex))
  33                 return 0;
  34         for (i = 0; i < 512; i++) {
  35                 cpu_relax();
  36                 if (mutex_trylock(&eb->mutex))
  37                         return 0;
  38         }
  39         cpu_relax();
  40         mutex_lock_nested(&eb->mutex, BTRFS_MAX_LEVEL - btrfs_header_level(eb));
  41         return 0;
  42 }
  43
  44 int btrfs_try_tree_lock(struct extent_buffer *eb)
  45 {
  46         return mutex_trylock(&eb->mutex);
  47 }
  48
  49 int btrfs_tree_unlock(struct extent_buffer *eb)
  50 {
  51         mutex_unlock(&eb->mutex);
  52         return 0;
  53 }
  54
  55 int btrfs_tree_locked(struct extent_buffer *eb)
  56 {
  57         return mutex_is_locked(&eb->mutex);
  58 }
  59
  60 int btrfs_path_lock_waiting(struct btrfs_path *path, int level)
  61 {
  62         int i;
  63         struct extent_buffer *eb;
  64         for (i = level; i <= level + 1 && i < BTRFS_MAX_LEVEL; i++) {
  65                 eb = path->nodes[i];
  66                 if (!eb)
  67                         break;
  68                 smp_mb();
  69                 if (!list_empty(&eb->mutex.wait_list))
  70                         return 1;
  71         }
  72         return 0;
  73 }
  74