Commit 793955bc authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: Limit btree writeback to prevent seeks 



Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 015a739c

fs/btrfs/disk-io.c

+9 −0
Original line number Diff line number Diff line
@@ -210,6 +210,15 @@ static int btree_writepages(struct address_space *mapping, 
{

	struct extent_map_tree *tree;

	tree = &BTRFS_I(mapping->host)->extent_tree;

	if (wbc->sync_mode == WB_SYNC_NONE) {

		u64 num_dirty;

		u64 start = 0;

		unsigned long thresh = 96 * 1024 * 1024;

		num_dirty = count_range_bits(tree, &start, thresh, EXTENT_DIRTY);

		if (num_dirty < thresh) {

			return 0;

		}

	}

	return extent_writepages(tree, mapping, btree_get_extent, wbc);

}

fs/btrfs/extent_map.c

+39 −0
Original line number Diff line number Diff line
@@ -1106,6 +1106,45 @@ u64 find_lock_delalloc_range(struct extent_map_tree *tree, 
	return found;

}



u64 count_range_bits(struct extent_map_tree *tree,

		     u64 *start, u64 max_bytes, unsigned long bits)

{

	struct rb_node *node;

	struct extent_state *state;

	u64 cur_start = *start;

	u64 total_bytes = 0;

	int found = 0;



	write_lock_irq(&tree->lock);

	/*

	 * this search will find all the extents that end after

	 * our range starts.

	 */

	node = tree_search(&tree->state, cur_start);

	if (!node || IS_ERR(node)) {

		goto out;

	}



	while(1) {

		state = rb_entry(node, struct extent_state, rb_node);

		if ((state->state & bits)) {

			total_bytes += state->end - state->start + 1;

			if (total_bytes >= max_bytes)

				break;

			if (!found) {

				*start = state->start;

				found = 1;

			}

		}

		node = rb_next(node);

		if (!node)

			break;

	}

out:

	write_unlock_irq(&tree->lock);

	return total_bytes;

}



/*

 * helper function to lock both pages and extents in the tree.

 * pages must be locked first.

fs/btrfs/extent_map.h

+3 −0
Original line number Diff line number Diff line
@@ -113,6 +113,9 @@ int extent_read_full_page(struct extent_map_tree *tree, struct page *page, 
int __init extent_map_init(void);

void __exit extent_map_exit(void);



u64 count_range_bits(struct extent_map_tree *tree,

		     u64 *start, u64 max_bytes, unsigned long bits);



int test_range_bit(struct extent_map_tree *tree, u64 start, u64 end,

		   int bits, int filled);

int clear_extent_bits(struct extent_map_tree *tree, u64 start, u64 end,