From 56ccc1125bc141cf63927eda7febff4216dea2d3 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 28 May 2015 17:53:29 +1000 Subject: [PATCH] md: fix race when unfreezing sync_action A recent change removed the need for locking around writing to "sync_action" (and various other places), but introduced a subtle race. When e.g. setting 'reshape' on a 'frozen' array, the 'frozen' flag is cleared before 'reshape' is set, so the md thread can get in and start trying recovery - which isn't wanted. So instead of clearing MD_RECOVERY_FROZEN for any command except 'frozen', only clear it when each specific command is parsed. This allows the handling of 'reshape' to clear the bit while a lock is held. Also remove some places where we set MD_RECOVERY_NEEDED, as it is always set on non-error exit of the function. Signed-off-by: NeilBrown Fixes: 6791875e2e53 ("md: make reconfig_mutex optional for writes to md sysfs files.") --- drivers/md/md.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index d4f31e195e26..8f10f4ea70ea 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -4211,12 +4211,12 @@ action_store(struct mddev *mddev, const char *page, size_t len) if (!mddev->pers || !mddev->pers->sync_request) return -EINVAL; - if (cmd_match(page, "frozen")) - set_bit(MD_RECOVERY_FROZEN, &mddev->recovery); - else - clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); if (cmd_match(page, "idle") || cmd_match(page, "frozen")) { + if (cmd_match(page, "frozen")) + set_bit(MD_RECOVERY_FROZEN, &mddev->recovery); + else + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); flush_workqueue(md_misc_wq); if (mddev->sync_thread) { set_bit(MD_RECOVERY_INTR, &mddev->recovery); @@ -4229,16 +4229,17 @@ action_store(struct mddev *mddev, const char *page, size_t len) test_bit(MD_RECOVERY_NEEDED, &mddev->recovery)) return -EBUSY; else if (cmd_match(page, "resync")) - set_bit(MD_RECOVERY_NEEDED, &mddev->recovery); + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); else if (cmd_match(page, "recover")) { + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); set_bit(MD_RECOVERY_RECOVER, &mddev->recovery); - set_bit(MD_RECOVERY_NEEDED, &mddev->recovery); } else if (cmd_match(page, "reshape")) { int err; if (mddev->pers->start_reshape == NULL) return -EINVAL; err = mddev_lock(mddev); if (!err) { + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); err = mddev->pers->start_reshape(mddev); mddev_unlock(mddev); } @@ -4250,6 +4251,7 @@ action_store(struct mddev *mddev, const char *page, size_t len) set_bit(MD_RECOVERY_CHECK, &mddev->recovery); else if (!cmd_match(page, "repair")) return -EINVAL; + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); set_bit(MD_RECOVERY_REQUESTED, &mddev->recovery); set_bit(MD_RECOVERY_SYNC, &mddev->recovery); }