On 11/17/2017 01:36 PM, Anand Jain wrote:
> If the device is not present at the time of (-o degrade) mount,
> the mount context will create a dummy missing struct btrfs_device.
> Later this device may reappear after the FS is mounted and
> then device is included in the device list but it missed the
> open_device part. So this patch handles that case by going
> through the open_device steps which this device missed and finally
> adds to the device alloc list.
What happens if the first devices got writes before the "last device" is joined
?
Supposing to have a raid1 pair of devices: sda, sdb
- sda is dissappeared (usb detached ?)
- the filesystem is mounted as
mount -o degraded /dev/sdb
- some writes happens on /dev/sdb
- the user reattach /dev/sda
- udev run "btrfs dev scan"
- the system joins /dev/sda to the filesystem disks pool
Because the filesystem is a raid1, btrfs may read from /dev/sdb (updated data)
or /dev/sda (old data), or worse read something from the former and something
from the later (metadata from sda and data from sdb ) ???
Am I missing something ?
BR
G.Baroncelli
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