diff options
authorNeilBrown <>2015-05-28 17:53:29 +1000
committerGreg Kroah-Hartman <>2015-06-06 08:21:09 -0700
commitc368845702b75c0febc8d54a0489d1e9505cc81d (patch)
parent9ac144beb909307828a779745d8189bfa52a45f9 (diff)
md: fix race when unfreezing sync_action
commit 56ccc1125bc141cf63927eda7febff4216dea2d3 upstream. 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.") Signed-off-by: Greg Kroah-Hartman <>
1 files changed, 8 insertions, 6 deletions
diff --git a/drivers/md/md.c b/drivers/md/md.c
index e47d1dd..907534b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4138,12 +4138,12 @@ 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);
if (mddev->sync_thread) {
set_bit(MD_RECOVERY_INTR, &mddev->recovery);
@@ -4156,16 +4156,17 @@ 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);
@@ -4177,6 +4178,7 @@ 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);