This is a note to let you know that I've just added the patch titled
md: fix race when unfreezing sync_action
to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
md-fix-race-when-unfreezing-sync_action.patch
and it can be found in the queue-4.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 56ccc1125bc141cf63927eda7febff4216dea2d3 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@xxxxxxx>
Date: Thu, 28 May 2015 17:53:29 +1000
Subject: md: fix race when unfreezing sync_action
From: NeilBrown <neilb@xxxxxxx>
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 <neilb@xxxxxxx>
Fixes: 6791875e2e53 ("md: make reconfig_mutex optional for writes to md sysfs files.")
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/md.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4138,12 +4138,12 @@ action_store(struct mddev *mddev, const
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);
@@ -4156,16 +4156,17 @@ action_store(struct mddev *mddev, const
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);
}
@@ -4177,6 +4178,7 @@ action_store(struct mddev *mddev, const
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);
}
Patches currently in stable-queue which might be from neilb@xxxxxxx are
queue-4.0/md-raid5-don-t-record-new-size-if-resize_stripes-fails.patch
queue-4.0/md-raid0-fix-restore-to-sector-variable-in-raid0_make_request.patch
queue-4.0/md-fix-race-when-unfreezing-sync_action.patch
queue-4.0/sched-always-use-blk_schedule_flush_plug-in-io_schedule_out.patch
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