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H A D | raid1.c | ccfc7bf1 Mon Feb 29 09:43:58 CST 2016 Nate Dailey <nate.dailey@stratus.com> 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: 55ce74d4bfe1b(md/raid1: ensure device failure recorded before write request returns.) Cc: stable@vger.kernel.org (v4.3+) Signed-off-by: Nate Dailey <nate.dailey@stratus.com> Signed-off-by: Shaohua Li <shli@fb.com> ccfc7bf1 Mon Feb 29 09:43:58 CST 2016 Nate Dailey <nate.dailey@stratus.com> 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: 55ce74d4bfe1b(md/raid1: ensure device failure recorded before write request returns.) Cc: stable@vger.kernel.org (v4.3+) Signed-off-by: Nate Dailey <nate.dailey@stratus.com> Signed-off-by: Shaohua Li <shli@fb.com>
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