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md: remove check for MD_RECOVERY_NEEDED in action_store.

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md currently doesn't allow a 'sync_action' such as 'reshape' to be set
while MD_RECOVERY_NEEDED is set.

This s a problem, particularly since commit 738a273806 as that can
cause ->check_shape to call mddev_resume() which sets
MD_RECOVERY_NEEDED.  So by the time we come to start 'reshape' it is
very likely that MD_RECOVERY_NEEDED is still set.

Testing for this flag is not really needed and is in any case very
racy as it can be set at any moment - asynchronously.  Any race
between setting a sync_action and setting MD_RECOVERY_NEEDED must
already be handled properly in some locked code, probably
md_check_recovery(), so remove the test here.

The test on MD_RECOVERY_RUNNING is also racy in the 'reshape' case
so we should test it again after getting mddev_lock().

As this fixes a race and a regression which can cause 'reshape' to
fail, it is suitable for -stable kernels since 4.1

Reported-by: Xiao Ni <xni@redhat.com>
Fixes: 738a273806 ("md/raid5: fix allocation of 'scribble' array.")
Cc: stable@vger.kernel.org (v4.1+)
Signed-off-by: NeilBrown <neilb@suse.com>
This commit is contained in:
NeilBrown 2015-12-21 11:01:21 +11:00
parent 9f7e432786
commit 312045eef9
1 changed files with 7 additions and 4 deletions
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11
drivers/md/md.c
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@ -4326,8 +4326,7 @@ action_store(struct mddev *mddev, const char *page, size_t len)
}
mddev_unlock(mddev);
}
} else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))
} else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
return -EBUSY;
else if (cmd_match(page, "resync"))
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
@ -4340,8 +4339,12 @@ action_store(struct mddev *mddev, const char *page, size_t len)
return -EINVAL;
err = mddev_lock(mddev);
if (!err) {
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
err = mddev->pers->start_reshape(mddev);
if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
err = -EBUSY;
else {
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
err = mddev->pers->start_reshape(mddev);
}
mddev_unlock(mddev);
}
if (err)