From f2d0f6765d6332f9be732965a0c6f3b8a55082b4 Mon Sep 17 00:00:00 2001 From: Alexandre Oliva Date: Mon, 28 Nov 2011 12:04:43 -0200 Subject: Btrfs: initialize new bitmaps' list We're failing to create clusters with bitmaps because setup_cluster_no_bitmap checks that the list is empty before inserting the bitmap entry in the list for setup_cluster_bitmap, but the list field is only initialized when it is restored from the on-disk free space cache, or when it is written out to disk. Besides a potential race condition due to the multiple use of the list field, filesystem performance severely degrades over time: as we use up all non-bitmap free extents, the try-to-set-up-cluster dance is done at every metadata block allocation. For every block group, we fail to set up a cluster, and after failing on them all up to twice, we fall back to the much slower unclustered allocation. To make matters worse, before the unclustered allocation, we try to create new block groups until we reach the 1% threshold, which introduces additional bitmaps and thus block groups that we'll iterate over at each metadata block request. --- fs/btrfs/free-space-cache.c | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/btrfs/free-space-cache.c') diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index 6e5b7e463698..ff179b1e7423 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -1470,6 +1470,7 @@ static void add_new_bitmap(struct btrfs_free_space_ctl *ctl, { info->offset = offset_to_bitmap(ctl, offset); info->bytes = 0; + INIT_LIST_HEAD(&info->list); link_free_space(ctl, info); ctl->total_bitmaps++; -- cgit From b78d09bceb524ee6481c21b77bda22d766b10e6a Mon Sep 17 00:00:00 2001 From: Alexandre Oliva Date: Wed, 30 Nov 2011 13:43:00 -0500 Subject: Btrfs: reset cluster's max_size when creating bitmap The field that indicates the size of the largest contiguous chunk of free space in the cluster is not initialized when setting up bitmaps, it's only increased when we find a larger contiguous chunk. We end up retaining a larger value than appropriate for highly-fragmented clusters, which may cause pointless searches for large contiguous groups, and even cause clusters that do not meet the density requirements to be set up. Signed-off-by: Alexandre Oliva Signed-off-by: Chris Mason --- fs/btrfs/free-space-cache.c | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/btrfs/free-space-cache.c') diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index ff179b1e7423..ec23d43d0c35 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -2320,6 +2320,7 @@ again: if (!found) { start = i; + cluster->max_size = 0; found = true; } -- cgit