From ac05f256691fe427a3e84c19261adb0b67dd73c0 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Tue, 30 Sep 2014 08:10:42 +1000 Subject: [PATCH] md: don't start resync thread directly from md thread. The main 'md' thread is needed for processing writes, so if it blocks write requests could be delayed. Starting a new thread requires some GFP_KERNEL allocations and so can wait for writes to complete. This can deadlock. So instead, ask a workqueue to start the sync thread. There is no particular rush for this to happen, so any work queue will do. MD_RECOVERY_RUNNING is used to ensure only one thread is started. Reported-by: BillStuff Signed-off-by: NeilBrown --- drivers/md/md.c | 59 ++++++++++++++++++++++++++++++------------------- 1 file changed, 36 insertions(+), 23 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index a7e9fae6c639..19171c58d790 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -7767,6 +7767,33 @@ no_add: return spares; } +static void md_start_sync(struct work_struct *ws) +{ + struct mddev *mddev = container_of(ws, struct mddev, del_work); + + mddev->sync_thread = md_register_thread(md_do_sync, + mddev, + "resync"); + if (!mddev->sync_thread) { + printk(KERN_ERR "%s: could not start resync" + " thread...\n", + mdname(mddev)); + /* leave the spares where they are, it shouldn't hurt */ + clear_bit(MD_RECOVERY_SYNC, &mddev->recovery); + clear_bit(MD_RECOVERY_RESHAPE, &mddev->recovery); + clear_bit(MD_RECOVERY_REQUESTED, &mddev->recovery); + clear_bit(MD_RECOVERY_CHECK, &mddev->recovery); + clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery); + if (test_and_clear_bit(MD_RECOVERY_RECOVER, + &mddev->recovery)) + if (mddev->sysfs_action) + sysfs_notify_dirent_safe(mddev->sysfs_action); + } else + md_wakeup_thread(mddev->sync_thread); + sysfs_notify_dirent_safe(mddev->sysfs_action); + md_new_event(mddev); +} + /* * This routine is regularly called by all per-raid-array threads to * deal with generic issues like resync and super-block update. @@ -7883,7 +7910,7 @@ void md_check_recovery(struct mddev *mddev) if (!test_and_clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery) || test_bit(MD_RECOVERY_FROZEN, &mddev->recovery)) - goto unlock; + goto not_running; /* no recovery is running. * remove any failed drives, then * add spares if possible. @@ -7895,7 +7922,7 @@ void md_check_recovery(struct mddev *mddev) if (mddev->pers->check_reshape == NULL || mddev->pers->check_reshape(mddev) != 0) /* Cannot proceed */ - goto unlock; + goto not_running; set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery); clear_bit(MD_RECOVERY_RECOVER, &mddev->recovery); } else if ((spares = remove_and_add_spares(mddev, NULL))) { @@ -7908,7 +7935,7 @@ void md_check_recovery(struct mddev *mddev) clear_bit(MD_RECOVERY_RECOVER, &mddev->recovery); } else if (!test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) /* nothing to be done ... */ - goto unlock; + goto not_running; if (mddev->pers->sync_request) { if (spares) { @@ -7918,27 +7945,11 @@ void md_check_recovery(struct mddev *mddev) */ bitmap_write_all(mddev->bitmap); } - mddev->sync_thread = md_register_thread(md_do_sync, - mddev, - "resync"); - if (!mddev->sync_thread) { - printk(KERN_ERR "%s: could not start resync" - " thread...\n", - mdname(mddev)); - /* leave the spares where they are, it shouldn't hurt */ - clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery); - clear_bit(MD_RECOVERY_SYNC, &mddev->recovery); - clear_bit(MD_RECOVERY_RESHAPE, &mddev->recovery); - clear_bit(MD_RECOVERY_REQUESTED, &mddev->recovery); - clear_bit(MD_RECOVERY_CHECK, &mddev->recovery); - } else - md_wakeup_thread(mddev->sync_thread); - sysfs_notify_dirent_safe(mddev->sysfs_action); - md_new_event(mddev); + INIT_WORK(&mddev->del_work, md_start_sync); + queue_work(md_misc_wq, &mddev->del_work); + goto unlock; } - unlock: - wake_up(&mddev->sb_wait); - + not_running: if (!mddev->sync_thread) { clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery); if (test_and_clear_bit(MD_RECOVERY_RECOVER, @@ -7946,6 +7957,8 @@ void md_check_recovery(struct mddev *mddev) if (mddev->sysfs_action) sysfs_notify_dirent_safe(mddev->sysfs_action); } + unlock: + wake_up(&mddev->sb_wait); mddev_unlock(mddev); } } -- 2.20.1