Messages in this thread | | | Subject | Re: UBIFS and page migration (take 2) | From | Vlastimil Babka <> | Date | Fri, 1 Apr 2016 12:13:33 +0200 |
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On 03/31/2016 11:58 PM, Richard Weinberger wrote: > During page migrations UBIFS gets confused. We triggered this by using CMA > on two different targets. > It turned out that fallback_migrate_page() is not suitable for UBIFS as it > does not copy the PagePrivate flag. > UBIFS is using this flag among with PageChecked to account free space. > One possible solution is implementing a ->migratepage() function in UBIFS > which does more or less the same as fallback_migrate_page() but also > copies PagePrivate. I'm not at all sure whether this is they way to go. > IMHO either page migration should not happen if ->migratepage() is not implement > or fallback_migrate_page() has to work for all filesystems.
Yes, we could document more thoroughly the expectations of fallback_migrate_page() and audit the existing users, but still relying on every new address_space_operations instance to verify them isn't without risk. And I doubt there can be a default fallback that's guaranteed safe for all filesystems.
> Comments? Flames? :-) > > Thanks, > //richard > > [PATCH 1/2] mm: Export migrate_page_move_mapping and > [PATCH 2/2] UBIFS: Implement ->migratepage() >
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