From a0270cd17b01d1c66a6815cd8e5121161bd161ce Mon Sep 17 00:00:00 2001 From: Nikolay Borisov Date: Thu, 5 Apr 2018 10:40:15 +0300 Subject: [PATCH] btrfs: Fix possible softlock on single core machines [ Upstream commit 1e1c50a929bc9e49bc3f9935b92450d9e69f8158 ] do_chunk_alloc implements a loop checking whether there is a pending chunk allocation and if so causes the caller do loop. Generally this loop is executed only once, however testing with btrfs/072 on a single core vm machines uncovered an extreme case where the system could loop indefinitely. This is due to a missing cond_resched when loop which doesn't give a chance to the previous chunk allocator finish its job. The fix is to simply add the missing cond_resched. Fixes: 6d74119f1a3e ("Btrfs: avoid taking the chunk_mutex in do_chunk_alloc") Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/extent-tree.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 131fe194f9e9a..3f5fc150c2b7c 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3946,6 +3946,7 @@ again: if (wait_for_alloc) { mutex_unlock(&fs_info->chunk_mutex); wait_for_alloc = 0; + cond_resched(); goto again; } -- 2.47.3