On 9/18/13 10:14 AM, David Sterba wrote: > On Mon, Sep 16, 2013 at 02:19:11PM -0400, Jeff Mahoney wrote: >> There are some feature bits that require no offline setup and can >> be enabled online. I've only reviewed extended irefs, but there will >> probably be more. > > Each feature bit being set online has to be treated separately regarding > safety of the data in flight. > > You can set extended irefs online, there's only one place where the bit > is checked (if the hadlink count overflows the leaf), it's ok to set the > bit anytime before or after and it will not break anything. > > Skinny metadata bit is checked all over the place and I'm not sure it's > ok to set it on after some portion of data has been processed in the > non-skinny mode. > > 'default_subvol', lzo are ok, the rest depends on mkfs and can't be > modified online at all. > > So, for skinny metadata it's most likely required to set the bit in a > delayed manner and schedule it eg. to post-commit time. Yep, that's why extended_iref is the only one I've enabled so far. Other features with harder requirements are going to need to be handled explicitly. > The sysfs and ioctl interface looks ok to me. Great, thanks. -Jeff -- Jeff Mahoney SUSE Labs
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