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authorNikolay Borisov <nborisov@suse.com>2018-04-05 10:40:15 +0300
committerDavid Sterba <dsterba@suse.com>2018-04-05 19:22:35 +0200
commit1e1c50a929bc9e49bc3f9935b92450d9e69f8158 (patch)
tree1e950e1030b25534acc205832c6eae3b05aee1b4
parentb98def7ca6e152ee55e36863dddf6f41f12d1dc6 (diff)
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btrfs: Fix possible softlock on single core machines
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 <nborisov@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
-rw-r--r--fs/btrfs/extent-tree.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index f30548d7e0d2..2caf9958f3e1 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4643,6 +4643,7 @@ again:
if (wait_for_alloc) {
mutex_unlock(&fs_info->chunk_mutex);
wait_for_alloc = 0;
+ cond_resched();
goto again;
}