From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: UBIFS and page migration (take 2) To: Richard Weinberger , linux-fsdevel@vger.kernel.org References: <1459461513-31765-1-git-send-email-richard@nod.at> Cc: linux-mtd@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, boris.brezillon@free-electrons.com, maxime.ripard@free-electrons.com, david@sigma-star.at, david@fromorbit.com, dedekind1@gmail.com, alex@nextthing.co, akpm@linux-foundation.org, sasha.levin@oracle.com, iamjoonsoo.kim@lge.com, rvaswani@codeaurora.org, tony.luck@intel.com, shailendra.capricorn@gmail.com, kirill.shutemov@linux.intel.com, hch@infradead.org, hughd@google.com, mgorman@techsingularity.net From: Vlastimil Babka Message-ID: <56FE49CD.1000302@suse.cz> Date: Fri, 1 Apr 2016 12:13:33 +0200 MIME-Version: 1.0 In-Reply-To: <1459461513-31765-1-git-send-email-richard@nod.at> Content-Type: text/plain; charset=iso-8859-2; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: 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() > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org