md/raid1: skip recovery of already synced areas #248
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When a new disk is added during running recovery, the kernel may restart recovery from the beginning of the device and submit write io to ranges that have already been synchronized. Reproduce: mdadm -CR /dev/md0 -l1 -n3 /dev/sda missing missing mdadm --add /dev/md0 /dev/sdb sleep 10 cat /proc/mdstat # partially synchronized mdadm --add /dev/md0 /dev/sdc cat /proc/mdstat # start from 0 iostat 1 sdb sdc # sdb has io, too If 'rdev->recovery_offset' is ahead of the current recovery sector, read from that device instead of issuing a write. It prevents unnecessary writes while still preserving the chance to back up data if it is the last copy. Signed-off-by: Li Nan <linan122@huawei.com>
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Upstream branch: c17fb54 |
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Pull request for series with
subject: md/raid1: skip recovery of already synced areas
version: 1
url: https://patchwork.kernel.org/project/linux-raid/list/?series=1000853