| 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 | /* |
| 29 | * locks the per buffer mutex in an extent buffer. This uses adaptive locks |
| 30 | * and the spin is not tuned very extensively. The spinning does make a big |
| 31 | * difference in almost every workload, but spinning for the right amount of |
| 32 | * time needs some help. |
| 33 | * |
| 34 | * In general, we want to spin as long as the lock holder is doing btree |
| 35 | * searches, and we should give up if they are in more expensive code. |
| 36 | */ |
| 37 | |
| 38 | int btrfs_tree_lock(struct extent_buffer *eb) |
| 39 | { |
| 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 | /* |
| 61 | * btrfs_search_slot uses this to decide if it should drop its locks |
| 62 | * before doing something expensive like allocating free blocks for cow. |
| 63 | */ |
| 64 | int btrfs_path_lock_waiting(struct btrfs_path *path, int level) |
| 65 | { |
| 66 | int i; |
| 67 | struct extent_buffer *eb; |
| 68 | for (i = level; i <= level + 1 && i < BTRFS_MAX_LEVEL; i++) { |
| 69 | eb = path->nodes[i]; |
| 70 | if (!eb) |
| 71 | break; |
| 72 | smp_mb(); |
| 73 | if (!list_empty(&eb->mutex.wait_list)) |
| 74 | return 1; |
| 75 | } |
| 76 | return 0; |
| 77 | } |
| 78 | |