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Btrfs: Use mutex_lock_nested for tree locking

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Lockdep has the notion of locking subclasses so that you can identify
locks you expect to be taken after other locks of the same class.  This
changes the per-extent buffer btree locking routines to use a subclass based
on the level in the tree.

Unfortunately, lockdep can only handle 8 total subclasses, and the btrfs
max level is also 8.  So when lockdep is on, use a lower max level.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason 2008-07-22 11:18:09 -04:00
parent f421950f86
commit 6dddcbeb28
2 changed files with 6 additions and 2 deletions
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6
fs/btrfs/ctree.h
View File

@ -42,7 +42,11 @@ struct btrfs_ordered_sum;
#define BTRFS_MAGIC "_B5RfS_M"
#define BTRFS_MAX_LEVEL 8
#ifdef CONFIG_LOCKDEP
# define BTRFS_MAX_LEVEL 7
#else
# define BTRFS_MAX_LEVEL 8
#endif
/* holds pointers to all of the tree roots */
#define BTRFS_ROOT_TREE_OBJECTID 1ULL

2
fs/btrfs/locking.c
View File

@ -37,7 +37,7 @@ int btrfs_tree_lock(struct extent_buffer *eb)
return 0;
}
cpu_relax();
mutex_lock(&eb->mutex);
mutex_lock_nested(&eb->mutex, BTRFS_MAX_LEVEL - btrfs_header_level(eb));
return 0;
}