Hi,
在 2023/07/17 22:39, Sergei Shtepa 写道:
On 7/11/23 04:02, Yu Kuai wrote:
bdev_disk_changed() is not handled, where delete_partition() and
add_partition() will be called, this means blkfilter for partiton will
be removed after partition rescan. Am I missing something?
Yes, when the bdev_disk_changed() is called, all disk block devices
are deleted and new ones are re-created. Therefore, the information
about the attached filters will be lost. This is equivalent to
removing the disk and adding it back.
For the blksnap module, partition rescan will mean the loss of the
change trackers data. If a snapshot was created, then such
a partition rescan will cause the snapshot to be corrupted.
I haven't review blksnap code yet, but this sounds like a problem.
possible solutions I have in mind:
1. Store blkfilter for each partition from bdev_disk_changed() before
delete_partition(), and add blkfilter back after add_partition().
2. Store blkfilter from gendisk as a xarray, and protect it by
'open_mutex' like 'part_tbl', block_device can keep the pointer to
reference blkfilter so that performance from fast path is ok, and the
lifetime of blkfiter can be managed separately.
There was an idea to do filtering at the disk level,
but I abandoned it.
.
I think it's better to do filtering at the partition level as well.
Thanks,
Kuai
