65b51a009e
A btree block cow has two parts, the first is to allocate a destination block and the second is to copy the old bock over. The first part needs locks in the extent allocation tree, and may need to do IO. This changeset splits that into a separate function that can be called without any tree locks held. btrfs_search_slot is changed to drop its path and start over if it has to COW a contended block. This often means that many writers will pre-alloc a new destination for a the same contended block, but they cache their prealloc for later use on lower levels in the tree. Signed-off-by: Chris Mason <chris.mason@oracle.com>
74 lines
1.7 KiB
C
74 lines
1.7 KiB
C
/*
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* Copyright (C) 2008 Oracle. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*/
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#include <linux/sched.h>
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#include <linux/gfp.h>
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#include <linux/pagemap.h>
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#include <linux/spinlock.h>
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#include <linux/page-flags.h>
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#include <asm/bug.h>
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#include "ctree.h"
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#include "extent_io.h"
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#include "locking.h"
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int btrfs_tree_lock(struct extent_buffer *eb)
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{
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int i;
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if (mutex_trylock(&eb->mutex))
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return 0;
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for (i = 0; i < 512; i++) {
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cpu_relax();
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if (mutex_trylock(&eb->mutex))
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return 0;
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}
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cpu_relax();
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mutex_lock_nested(&eb->mutex, BTRFS_MAX_LEVEL - btrfs_header_level(eb));
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return 0;
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}
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int btrfs_try_tree_lock(struct extent_buffer *eb)
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{
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return mutex_trylock(&eb->mutex);
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}
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int btrfs_tree_unlock(struct extent_buffer *eb)
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{
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mutex_unlock(&eb->mutex);
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return 0;
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}
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int btrfs_tree_locked(struct extent_buffer *eb)
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{
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return mutex_is_locked(&eb->mutex);
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}
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int btrfs_path_lock_waiting(struct btrfs_path *path, int level)
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{
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int i;
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struct extent_buffer *eb;
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for (i = level; i <= level + 1 && i < BTRFS_MAX_LEVEL; i++) {
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eb = path->nodes[i];
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if (!eb)
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break;
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smp_mb();
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if (!list_empty(&eb->mutex.wait_list))
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return 1;
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}
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return 0;
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}
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