Btrfs: [PATCH] extent_map: fix locking for bio completion

The bio completion handlers can be run in any context, e.g. when using
the old ide driver they run in hardirq context with irqs disabled so
lockdep rightfully warns about using write_lock_irq useage in these
handlers.

This patch switches clear_extent_bit and set_extent_bit to
write_lock_irqsave to fix this problem.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/extent_map.c

@@ -456,6 +456,7 @@ int clear_extent_bit(struct extent_map_tree *tree, u64 start, u64 end,
 	struct extent_state *state;
 	struct extent_state *prealloc = NULL;
 	struct rb_node *node;
+	unsigned long flags;
 	int err;
 	int set = 0;
 
@@ -466,7 +467,7 @@ again:
 			return -ENOMEM;
 	}
 
-	write_lock_irq(&tree->lock);
+	write_lock_irqsave(&tree->lock, flags);
 	/*
 	 * this search will find the extents that end after
 	 * our range starts
@@ -533,7 +534,7 @@ again:
 	goto search_again;
 
 out:
-	write_unlock_irq(&tree->lock);
+	write_unlock_irqrestore(&tree->lock, flags);
 	if (prealloc)
 		free_extent_state(prealloc);
 
@@ -542,7 +543,7 @@ out:
 search_again:
 	if (start >= end)
 		goto out;
-	write_unlock_irq(&tree->lock);
+	write_unlock_irqrestore(&tree->lock, flags);
 	if (mask & __GFP_WAIT)
 		cond_resched();
 	goto again;
@@ -628,6 +629,7 @@ int set_extent_bit(struct extent_map_tree *tree, u64 start, u64 end, int bits,
 	struct extent_state *state;
 	struct extent_state *prealloc = NULL;
 	struct rb_node *node;
+	unsigned long flags;
 	int err = 0;
 	int set;
 	u64 last_start;
@@ -639,7 +641,7 @@ again:
 			return -ENOMEM;
 	}
 
-	write_lock_irq(&tree->lock);
+	write_lock_irqsave(&tree->lock, flags);
 	/*
 	 * this search will find all the extents that end after
 	 * our range starts.
@@ -759,7 +761,7 @@ again:
 	goto search_again;
 
 out:
-	write_unlock_irq(&tree->lock);
+	write_unlock_irqrestore(&tree->lock, flags);
 	if (prealloc)
 		free_extent_state(prealloc);
 
@@ -768,7 +770,7 @@ out:
 search_again:
 	if (start > end)
 		goto out;
-	write_unlock_irq(&tree->lock);
+	write_unlock_irqrestore(&tree->lock, flags);
 	if (mask & __GFP_WAIT)
 		cond_resched();
 	goto again;