We can race with the unmount of an fs and the stopping of a kthread where we will free the block group before we're done using it. The reason for this is because we do not hold a reference on the block group while its caching, since the allocator drops its reference once it exits or moves on to the next block group. This patch fixes the problem by taking a reference to the block group before we start caching and dropping it when we're done to make sure all accesses to the block group are safe. Thanks, Signed-off-by: Josef Bacik <josef@xxxxxxxxxx> --- fs/btrfs/extent-tree.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 2a4cdce..197bc1b 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -399,6 +399,8 @@ err: put_caching_control(caching_ctl); atomic_dec(&block_group->space_info->caching_threads); + btrfs_put_block_group(block_group); + return 0; } @@ -439,6 +441,7 @@ static int cache_block_group(struct btrfs_block_group_cache *cache) up_write(&fs_info->extent_commit_sem); atomic_inc(&cache->space_info->caching_threads); + atomic_inc(&cache->count); tsk = kthread_run(caching_kthread, cache, "btrfs-cache-%llu\n", cache->key.objectid); -- 1.5.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
