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md: Prevent IO hold during accessing to faulty raid5 array
After array enters in faulty state (e.g. number of failed drives becomes more then accepted for raid5 level) it sets error flags (one of this flags is MD_CHANGE_PENDING). For internal metadata arrays MD_CHANGE_PENDING cleared into md_update_sb, but not for external metadata arrays. MD_CHANGE_PENDING flag set prevents to finish all new or non-finished IOs to array and hold them in pending state. In some cases this can leads to deadlock situation. For example, we have faulty array (2 of 4 drives failed) and udev handle array state changes and blkid started (or other userspace application that used array to read/write) but unable to finish reads due to IO hold. At the same time we unable to get exclusive access to array (to stop array in our case) because another external application still use this array. Fix makes possible to return IO with errors immediately. So external application can finish working with array and give exclusive access to other applications to perform required management actions with array. Signed-off-by: Alexey Obitotskiy <aleksey.obitotskiy@intel.com> Signed-off-by: Shaohua Li <shli@fb.com>
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@ -4640,7 +4640,9 @@ finish:
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}
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if (!bio_list_empty(&s.return_bi)) {
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if (test_bit(MD_CHANGE_PENDING, &conf->mddev->flags)) {
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if (test_bit(MD_CHANGE_PENDING, &conf->mddev->flags) &&
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(s.failed <= conf->max_degraded ||
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conf->mddev->external == 0)) {
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spin_lock_irq(&conf->device_lock);
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bio_list_merge(&conf->return_bi, &s.return_bi);
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spin_unlock_irq(&conf->device_lock);
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