From d288db5dc0110c8e0732d099aaf7a05e2ea0e0c8 Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Wed, 2 Jul 2014 16:58:01 +0800 Subject: [PATCH] Btrfs: fix race of using total_bytes_pinned This percpu counter @total_bytes_pinned is introduced to skip unnecessary operations of 'commit transaction', it accounts for those space we may free but are stuck in delayed refs. And we zero out @space_info->total_bytes_pinned every transaction period so we have a better idea of how much space we'll actually free up by committing this transaction. However, we do the 'zero out' part a little earlier, before we actually unpin space, so we end up returning ENOSPC when we actually have free space that's just unpinned from committing transaction. xfstests/generic/074 complained then. This fixes it by actually accounting the percpu pinned number when 'unpin', and since it's protected by space_info->lock, the race is gone now. Signed-off-by: Liu Bo Reviewed-by: Miao Xie Signed-off-by: Chris Mason --- fs/btrfs/extent-tree.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 99c253918208..813537f362f9 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -5678,7 +5678,6 @@ void btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans, struct btrfs_caching_control *next; struct btrfs_caching_control *caching_ctl; struct btrfs_block_group_cache *cache; - struct btrfs_space_info *space_info; down_write(&fs_info->commit_root_sem); @@ -5701,9 +5700,6 @@ void btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans, up_write(&fs_info->commit_root_sem); - list_for_each_entry_rcu(space_info, &fs_info->space_info, list) - percpu_counter_set(&space_info->total_bytes_pinned, 0); - update_global_block_rsv(fs_info); } @@ -5741,6 +5737,7 @@ static int unpin_extent_range(struct btrfs_root *root, u64 start, u64 end) spin_lock(&cache->lock); cache->pinned -= len; space_info->bytes_pinned -= len; + percpu_counter_add(&space_info->total_bytes_pinned, -len); if (cache->ro) { space_info->bytes_readonly += len; readonly = true; -- 2.20.1