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@@ -1751,6 +1751,7 @@ static int cleaner_kthread(void *arg)
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{
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struct btrfs_root *root = arg;
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int again;
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+ struct btrfs_trans_handle *trans;
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do {
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again = 0;
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@@ -1798,6 +1799,34 @@ sleep:
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__set_current_state(TASK_RUNNING);
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}
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} while (!kthread_should_stop());
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+
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+ /*
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+ * Transaction kthread is stopped before us and wakes us up.
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+ * However we might have started a new transaction and COWed some
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+ * tree blocks when deleting unused block groups for example. So
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+ * make sure we commit the transaction we started to have a clean
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+ * shutdown when evicting the btree inode - if it has dirty pages
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+ * when we do the final iput() on it, eviction will trigger a
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+ * writeback for it which will fail with null pointer dereferences
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+ * since work queues and other resources were already released and
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+ * destroyed by the time the iput/eviction/writeback is made.
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+ */
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+ trans = btrfs_attach_transaction(root);
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+ if (IS_ERR(trans)) {
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+ if (PTR_ERR(trans) != -ENOENT)
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+ btrfs_err(root->fs_info,
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+ "cleaner transaction attach returned %ld",
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+ PTR_ERR(trans));
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+ } else {
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+ int ret;
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+
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+ ret = btrfs_commit_transaction(trans, root);
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+ if (ret)
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+ btrfs_err(root->fs_info,
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+ "cleaner open transaction commit returned %d",
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+ ret);
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+ }
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+
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return 0;
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}
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Filipe Manana