writeback: Fix wakeup and logging timeouts for !DETECT_HUNG_TASK

[ Upstream commit 9eed043d10f17301c1b5141e16bb98a85a8fd07e ]

Recent changes of fs-writeback cause such warnings if DETECT_HUNG_TASK
is not enabled:

INFO: The task sync:1342 has been waiting for writeback completion for more than 1 seconds.

The reason is sysctl_hung_task_timeout_secs is 0 when DETECT_HUNG_TASK
is not enabled, then it causes the warning message even if the writeback
lasts for only one second.

Guard the wakeup and logging with "#ifdef CONFIG_DETECT_HUNG_TASK" can
eliminate the warning messages. But on the other hand, it is possible
that sysctl_hung_task_timeout_secs be also 0 when DETECT_HUNG_TASK is
enabled. So let's just check the value of sysctl_hung_task_timeout_secs
to decide whether do wakeup and logging.

Fixes: 1888635532fb ("writeback: Wake up waiting tasks when finishing the writeback of a chunk.")
Fixes: d6e621590764 ("writeback: Add logging for slow writeback (exceeds sysctl_hung_task_timeout_secs)")
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Link: https://patch.msgid.link/20260203094014.2273240-1-chenhuacai@loongson.cn
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5444fc706ac7d697c64f293054aab808ceafbd48..79b02ac66ac6d8b6a230e12aaee103d6edd90866 100644 (file)
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -198,10 +198,11 @@ static void wb_queue_work(struct bdi_writeback *wb,
 
 static bool wb_wait_for_completion_cb(struct wb_completion *done)
 {
+       unsigned long timeout = sysctl_hung_task_timeout_secs;
        unsigned long waited_secs = (jiffies - done->wait_start) / HZ;
 
        done->progress_stamp = jiffies;
-       if (waited_secs > sysctl_hung_task_timeout_secs)
+       if (timeout && (waited_secs > timeout))
                pr_info("INFO: The task %s:%d has been waiting for writeback "
                        "completion for more than %lu seconds.",
                        current->comm, current->pid, waited_secs);
@@ -1944,6 +1945,7 @@ static long writeback_sb_inodes(struct super_block *sb,
                .range_end              = LLONG_MAX,
        };
        unsigned long start_time = jiffies;
+       unsigned long timeout = sysctl_hung_task_timeout_secs;
        long write_chunk;
        long total_wrote = 0;  /* count both pages and inodes */
        unsigned long dirtied_before = jiffies;
@@ -2030,9 +2032,8 @@ static long writeback_sb_inodes(struct super_block *sb,
                __writeback_single_inode(inode, &wbc);
 
                /* Report progress to inform the hung task detector of the progress. */
-               if (work->done && work->done->progress_stamp &&
-                  (jiffies - work->done->progress_stamp) > HZ *
-                  sysctl_hung_task_timeout_secs / 2)
+               if (work->done && work->done->progress_stamp && timeout &&
+                  (jiffies - work->done->progress_stamp) > HZ * timeout / 2)
                        wake_up_all(work->done->waitq);
 
                wbc_detach_inode(&wbc);