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f82c458a2c
The fair reader/writer locks mean that btrfs_clear_path_blocking needs to strictly follow lock ordering rules even when we already have blocking locks on a given path. Before we can clear a blocking lock on the path, we need to make sure all of the locks have been converted to blocking. This will remove lock inversions against anyone spinning in write_lock() against the buffers we're trying to get read locks on. These inversions didn't exist before the fair read/writer locks, but now we need to be more careful. We papered over this deadlock in the past by changing btrfs_try_read_lock() to be a true trylock against both the spinlock and the blocking lock. This was slower, and not sufficient to fix all the deadlocks. This patch adds a btrfs_tree_read_lock_atomic(), which basically means get the spinlock but trylock on the blocking lock. Signed-off-by: Chris Mason <clm@fb.com> Signed-off-by: Josef Bacik <jbacik@fb.com> Reported-by: Patrick Schmid <schmid@phys.ethz.ch> cc: stable@vger.kernel.org #v3.15+
63 lines
2.1 KiB
C
63 lines
2.1 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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#ifndef __BTRFS_LOCKING_
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#define __BTRFS_LOCKING_
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#define BTRFS_WRITE_LOCK 1
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#define BTRFS_READ_LOCK 2
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#define BTRFS_WRITE_LOCK_BLOCKING 3
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#define BTRFS_READ_LOCK_BLOCKING 4
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void btrfs_tree_lock(struct extent_buffer *eb);
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void btrfs_tree_unlock(struct extent_buffer *eb);
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void btrfs_tree_read_lock(struct extent_buffer *eb);
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void btrfs_tree_read_unlock(struct extent_buffer *eb);
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void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb);
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void btrfs_set_lock_blocking_rw(struct extent_buffer *eb, int rw);
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void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw);
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void btrfs_assert_tree_locked(struct extent_buffer *eb);
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int btrfs_try_tree_read_lock(struct extent_buffer *eb);
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int btrfs_try_tree_write_lock(struct extent_buffer *eb);
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int btrfs_tree_read_lock_atomic(struct extent_buffer *eb);
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static inline void btrfs_tree_unlock_rw(struct extent_buffer *eb, int rw)
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{
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if (rw == BTRFS_WRITE_LOCK || rw == BTRFS_WRITE_LOCK_BLOCKING)
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btrfs_tree_unlock(eb);
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else if (rw == BTRFS_READ_LOCK_BLOCKING)
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btrfs_tree_read_unlock_blocking(eb);
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else if (rw == BTRFS_READ_LOCK)
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btrfs_tree_read_unlock(eb);
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else
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BUG();
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}
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static inline void btrfs_set_lock_blocking(struct extent_buffer *eb)
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{
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btrfs_set_lock_blocking_rw(eb, BTRFS_WRITE_LOCK);
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}
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static inline void btrfs_clear_lock_blocking(struct extent_buffer *eb)
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{
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btrfs_clear_lock_blocking_rw(eb, BTRFS_WRITE_LOCK_BLOCKING);
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}
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#endif
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