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Commit a61e6f29 authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: Use a mutex in the extent buffer for tree block locking 



This replaces the use of the page cache lock bit for locking, which wasn't
suitable for block size < page size and couldn't be used recursively.

The mutexes alone don't fix either problem, but they are the first step.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 6af118ce

fs/btrfs/extent-tree.c

+1 −6
Original line number Diff line number Diff line
@@ -1451,7 +1451,7 @@ static int pin_down_bytes(struct btrfs_root *root, u64 bytenr, u32 num_bytes, 
		struct extent_buffer *buf;

		buf = btrfs_find_tree_block(root, bytenr, num_bytes);

		if (buf) {

			if (!btrfs_try_tree_lock(buf) &&

			if (btrfs_try_tree_lock(buf) &&

			    btrfs_buffer_uptodate(buf, 0)) {

				u64 transid =

				    root->fs_info->running_transaction->transid;
@@ -3345,11 +3345,6 @@ int btrfs_read_block_groups(struct btrfs_root *root) 
		set_state_private(block_group_cache, found_key.objectid,

				  (unsigned long)cache);



		/* hack for now */

		if (cache->flags & BTRFS_BLOCK_GROUP_METADATA) {

			cache_block_group(root->fs_info->extent_root,

					  cache);

		}

		if (key.objectid >=

		    btrfs_super_total_bytes(&info->super_copy))

			break;

fs/btrfs/extent_io.c

+9 −0
Original line number Diff line number Diff line
@@ -2690,6 +2690,7 @@ static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree, 
	eb = kmem_cache_zalloc(extent_buffer_cache, mask);

	eb->start = start;

	eb->len = len;

	mutex_init(&eb->mutex);

	spin_lock_irqsave(&leak_lock, flags);

	list_add(&eb->leak_list, &buffers);

	spin_unlock_irqrestore(&leak_lock, flags);
@@ -2837,6 +2838,7 @@ int clear_extent_buffer_dirty(struct extent_io_tree *tree, 


	for (i = 0; i < num_pages; i++) {

		page = extent_buffer_page(eb, i);

		lock_page(page);

		if (i == 0)

			set_page_extent_head(page, eb->len);

		else
@@ -2854,6 +2856,7 @@ int clear_extent_buffer_dirty(struct extent_io_tree *tree, 
			end  = start + PAGE_CACHE_SIZE - 1;

			if (test_range_bit(tree, start, end,

					   EXTENT_DIRTY, 0)) {

				unlock_page(page);

				continue;

			}

		}
@@ -2865,6 +2868,7 @@ int clear_extent_buffer_dirty(struct extent_io_tree *tree, 
						PAGECACHE_TAG_DIRTY);

		}

		read_unlock_irq(&page->mapping->tree_lock);

		unlock_page(page);

	}

	return 0;

}
@@ -2893,12 +2897,17 @@ int set_extent_buffer_dirty(struct extent_io_tree *tree, 
		 * on us if the page isn't already dirty.

		 */

		if (i == 0) {

			lock_page(page);

			set_page_extent_head(page, eb->len);

		} else if (PagePrivate(page) &&

			   page->private != EXTENT_PAGE_PRIVATE) {

			lock_page(page);

			set_page_extent_mapped(page);

			unlock_page(page);

		}

		__set_page_dirty_nobuffers(extent_buffer_page(eb, i));

		if (i == 0)

			unlock_page(page);

	}

	return set_extent_dirty(tree, eb->start,

				eb->start + eb->len - 1, GFP_NOFS);

fs/btrfs/extent_io.h

+1 −0
Original line number Diff line number Diff line
@@ -90,6 +90,7 @@ struct extent_buffer { 
	int flags;

	struct list_head leak_list;

	struct rb_node rb_node;

	struct mutex mutex;

};



struct extent_map_tree;

fs/btrfs/locking.c

+6 −7
Original line number Diff line number Diff line
@@ -29,32 +29,31 @@ int btrfs_tree_lock(struct extent_buffer *eb) 
{

	int i;



	if (!TestSetPageLocked(eb->first_page))

	if (mutex_trylock(&eb->mutex))

		return 0;

	for (i = 0; i < 512; i++) {

		cpu_relax();

		if (!TestSetPageLocked(eb->first_page))

		if (mutex_trylock(&eb->mutex))

			return 0;

	}

	cpu_relax();

	lock_page(eb->first_page);

	mutex_lock(&eb->mutex);

	return 0;

}



int btrfs_try_tree_lock(struct extent_buffer *eb)

{

	return TestSetPageLocked(eb->first_page);

	return mutex_trylock(&eb->mutex);

}



int btrfs_tree_unlock(struct extent_buffer *eb)

{

	WARN_ON(!PageLocked(eb->first_page));

	unlock_page(eb->first_page);

	mutex_unlock(&eb->mutex);

	return 0;

}



int btrfs_tree_locked(struct extent_buffer *eb)

{

	return PageLocked(eb->first_page);

	return mutex_is_locked(&eb->mutex);

}