Forwarded: Re: [syzbot] [xfs?] INFO: task hung in xlog_force_lsn (2)

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Subject: Re: [syzbot] [xfs?] INFO: task hung in xlog_force_lsn (2)
Author: ytohnuki@amazon.com

#syz test

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index f807f8f4f705..2645052042bf 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -426,6 +426,23 @@ xlog_state_shutdown_callbacks(
 	struct xlog_in_core	*iclog;
 	LIST_HEAD(cb_list);
 
+	/*
+	 * Shutdown waiters on ic_force_wait do not require callback completion.
+	 * Once log shutdown has been established, they only need to wake,
+	 * observe xlog_is_shutdown(), and abort with -EIO.
+	 *
+	 * Wake them before processing callbacks to avoid deadlock if callback
+	 * processing blocks on a buffer lock and prevents the wakeup from being
+	 * reached.
+	 *
+	 * Keep ic_write_wait wakeups ordered after callback processing so
+	 * shutdown callback side effects still complete before teardown progresses.
+	 */
+	iclog = log->l_iclog;
+	do {
+		wake_up_all(&iclog->ic_force_wait);
+	} while ((iclog = iclog->ic_next) != log->l_iclog);
+
 	iclog = log->l_iclog;
 	do {
 		if (atomic_read(&iclog->ic_refcnt)) {
@@ -439,7 +456,6 @@ xlog_state_shutdown_callbacks(
 
 		spin_lock(&log->l_icloglock);
 		wake_up_all(&iclog->ic_write_wait);
-		wake_up_all(&iclog->ic_force_wait);
 	} while ((iclog = iclog->ic_next) != log->l_iclog);
 
 	wake_up_all(&log->l_flush_wait);
-- 
2.50.1




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