The .zfs control directory implementation currently relies on
the fact that there is a direct 1:1 mapping from an object id
to its inode number. This works well as long as the system
uses a 64-bit value to store the inode number.
Unfortunately, the Linux kernel defines the inode number as
an 'unsigned long' type. This means that for 32-bit systems
will only have 32-bit inode numbers but we still have 64-bit
object ids.
This problem is particularly acute for the .zfs directories
which leverage those upper 32-bits. This is done to avoid
conflicting with object ids which are allocated monotonically
starting from 0. This is likely to also be a problem for
datasets on 32-bit systems with more than ~2 billion files.
The right long term fix must remove the simple 1:1 mapping.
Until that's done the only safe thing to do is to disable the
.zfs directory on 32-bit systems.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Brian Behlendorf
fc173c8589