Commit ccfc7bf1 authored by Nate Dailey's avatar Nate Dailey Committed by Shaohua Li

raid1: include bio_end_io_list in nr_queued to prevent freeze_array hang

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: 55ce74d4(md/raid1: ensure device failure recorded before write request returns.)
Cc: (v4.3+)
Signed-off-by: default avatarNate Dailey <>
Signed-off-by: default avatarShaohua Li <>
parent d85326cf
......@@ -2274,6 +2274,7 @@ static void handle_write_finished(struct r1conf *conf, struct r1bio *r1_bio)
if (fail) {
list_add(&r1_bio->retry_list, &conf->bio_end_io_list);
} else {
......@@ -2391,8 +2392,10 @@ static void raid1d(struct md_thread *thread)
spin_lock_irqsave(&conf->device_lock, flags);
if (!test_bit(MD_CHANGE_PENDING, &mddev->flags)) {
list_add(&tmp, &conf->bio_end_io_list);
while (!list_empty(&conf->bio_end_io_list)) {
list_move(conf->bio_end_io_list.prev, &tmp);
spin_unlock_irqrestore(&conf->device_lock, flags);
while (!list_empty(&tmp)) {
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