Commit 240d5d48 authored Nov 10, 2008 by Chris Mason

Btrfs: tune btrfs unplug functions for a small number of devices



When btrfs unplugs, it tries to find the correct device to unplug
via search through the extent_map tree.  This avoids unplugging
a device that doesn't need it, but is a waste of time for filesystems
with a small number of devices.

This patch checks the total number of devices before doing the
search.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

parent b47eda86

fs/btrfs/disk-io.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -1201,6 +1201,16 @@ void btrfs_unplug_io_fn(struct backing_dev_info bdi, struct page page)
		return;

		inode = mapping->host;

		/*
		* don't do the expensive searching for a small number of
		* devices
		*/
		if (BTRFS_I(inode)->root->fs_info->fs_devices->open_devices <= 2) {
		__unplug_io_fn(bdi, page);
		return;
		}

		offset = page_offset(page);

		em_tree = &BTRFS_I(inode)->extent_tree;