On Tue, Apr 5, 2022 at 5:55 PM Jane Chu <jane.chu@xxxxxxxxxx> wrote: > > On 3/30/2022 9:18 AM, Darrick J. Wong wrote: > > On Wed, Mar 30, 2022 at 08:49:29AM -0700, Christoph Hellwig wrote: > >> On Wed, Mar 30, 2022 at 06:58:21PM +0800, Shiyang Ruan wrote: > >>> As the code I pasted before, pmem driver will subtract its ->data_offset, > >>> which is byte-based. And the filesystem who implements ->notify_failure() > >>> will calculate the offset in unit of byte again. > >>> > >>> So, leave its function signature byte-based, to avoid repeated conversions. > >> > >> I'm actually fine either way, so I'll wait for Dan to comment. > > > > FWIW I'd convinced myself that the reason for using byte units is to > > make it possible to reduce the pmem failure blast radius to subpage > > units... but then I've also been distracted for months. :/ > > > > Yes, thanks Darrick! I recall that. > Maybe just add a comment about why byte unit is used? I think we start with page failure notification and then figure out how to get finer grained through the dax interface in follow-on changes. Otherwise, for finer grained error handling support, memory_failure() would also need to be converted to stop upcasting cache-line granularity to page granularity failures. The native MCE notification communicates a 'struct mce' that can be in terms of sub-page bytes, but the memory management implications are all page based. I assume the FS implications are all FS-block-size based?
