Re: Fwd: [suggestion] Add verbose notification about inode-cache rebuild to kernel log

[Goffredo Baroncelli <kreijack@inwind.it>]

Hi David,

On 05/12/2014 04:39 PM, David Sterba wrote:
>> Because most modern hardware is 64 bit (with the exception of ARM ?),
>> > could be make sense to allow btrfs to work without inode_cache only on
>> > 64bit, loosing the possibility to be used on 32 bit system.
>> > 
>> > Instead when the inode_cache is used, btrfs still be compatible with
>> > both 32bit and 64bit systems.
> There are 32bit machines in use and inode_cache brings some
> compatibility assurance. Just that I would not recommend it to use by
> default.
> 
>> > How often a filesystem is moved between a 64bit and 32bit systems ?
> Not so often I'd say, but for example the block device on a 32bit
> machine can be exported via iscsi to a 64bit machine temporarily, then
> the changes made on the 64bit host can make it unusable.


To be clear, I would like to avoid inode_cache on 64bit machine.

In order to avoid the risk to exhaust the inode on 32bit and to be backward compatible with what already exists, we could add a flag to mkfs.btrfs to be only 64bit compatible and avoid inode_cache.

It it would be faster, I am sure that there are uses cases for that.

The major drawback that I see, is that it would be a code path less tested: I think that the 32bit system[*] would disappear soon

Finally I have a question: it is possible to disable inode_cache ? what means the flag "noinode_cache" ? It means disable the inode cache at all, or only avoid to store on disk the inode cache ?


[*] I means 32bit system were it is reasonable that btrfs would run.

BR
G.Baroncelli
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