| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 144/210] raid1: include bio_end_io_list in nr_queued to prevent freeze_array hang | Date | Sun, 10 Apr 2016 11:36:05 -0700 |
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4.4-stable review patch. If anyone has any objections, please let me know.
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From: Nate Dailey <nate.dailey@stratus.com>
commit ccfc7bf1f09d6190ef86693ddc761d5fe3fa47cb upstream.
If raid1d is handling a mix of read and write errors, handle_read_error's call to freeze_array can get stuck.
This can happen because, though the bio_end_io_list is initially drained, writes can be added to it via handle_write_finished as the retry_list is processed. These writes contribute to nr_pending but are not included in nr_queued.
If a later entry on the retry_list triggers a call to handle_read_error, freeze array hangs waiting for nr_pending == nr_queued+extra. The writes on the bio_end_io_list aren't included in nr_queued so the condition will never be satisfied.
To prevent the hang, include bio_end_io_list writes in nr_queued.
There's probably a better way to handle decrementing nr_queued, but this seemed like the safest way to avoid breaking surrounding code.
I'm happy to supply the script I used to repro this hang.
Fixes: 55ce74d4bfe1b(md/raid1: ensure device failure recorded before write request returns.) Signed-off-by: Nate Dailey <nate.dailey@stratus.com> Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/md/raid1.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -2274,6 +2274,7 @@ static void handle_write_finished(struct if (fail) { spin_lock_irq(&conf->device_lock); list_add(&r1_bio->retry_list, &conf->bio_end_io_list); + conf->nr_queued++; spin_unlock_irq(&conf->device_lock); md_wakeup_thread(conf->mddev->thread); } else { @@ -2391,8 +2392,10 @@ static void raid1d(struct md_thread *thr LIST_HEAD(tmp); spin_lock_irqsave(&conf->device_lock, flags); if (!test_bit(MD_CHANGE_PENDING, &mddev->flags)) { - list_add(&tmp, &conf->bio_end_io_list); - list_del_init(&conf->bio_end_io_list); + while (!list_empty(&conf->bio_end_io_list)) { + list_move(conf->bio_end_io_list.prev, &tmp); + conf->nr_queued--; + } } spin_unlock_irqrestore(&conf->device_lock, flags); while (!list_empty(&tmp)) {
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