On 2021/6/26 下午2:14, Andrei Borzenkov wrote:
On 26.06.2021 08:17, NeilBrown wrote:
On Sat, 26 Jun 2021, Bart Van Assche wrote:
On 6/25/21 5:54 PM, NeilBrown wrote:
On Sat, 26 Jun 2021, Martin Steigerwald wrote:
And that Baloo needs an "invariant" for
a file. See comment #11 of that bug report:
That is really hard to provide in general. Possibly the best approach
is to use the statfs() systemcall to get the "f_fsid" field. This is
64bits. It is not supported uniformly well by all filesystems, but I
think it is at least not worse than using the device number. For a lot
of older filesystems it is just an encoding of the device number.
For btrfs, xfs, ext4 it is much much better.
How about combining the UUID of the partition with the file path? An
example from one of the VMs on my workstation:
A btrfs filesystem can span multiple partitions, and those partitions
can be added and removed dynamically. So you could migrated from one to
another.
I suspect it was intended to be "filesytemm UUID". At least that is the
field in lsblk output that was referenced.
Filesystem UUID is not enough.
In btrfs, all subvolumes share the same fsid.
While for statfs() call, we do extra XOR with subvolume id to generate
unique f_fsid for each subvolume.
Thanks,
Qu
f_fsid really is best for any modern filesystem.
NeilBrown
