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Date: Tue, 24 May 2022 06:44:16 +0000 From: HORIGUCHI NAOYA(堀口 直也) <naoya.horiguchi@....com> To: Miaohe Lin <linmiaohe@...wei.com> CC: "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "hughd@...gle.com" <hughd@...gle.com>, "willy@...radead.org" <willy@...radead.org>, "vbabka@...e.cz" <vbabka@...e.cz>, "dhowells@...hat.com" <dhowells@...hat.com>, "neilb@...e.de" <neilb@...e.de>, "apopple@...dia.com" <apopple@...dia.com>, "david@...hat.com" <david@...hat.com>, "surenb@...gle.com" <surenb@...gle.com>, "peterx@...hat.com" <peterx@...hat.com>, "rcampbell@...dia.com" <rcampbell@...dia.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v4 4/5] mm/shmem: fix infinite loop when swap in shmem error at swapoff time On Mon, May 23, 2022 at 07:23:53PM +0800, Miaohe Lin wrote: ... > > > > I reproduced the deadloop issues when swapin error occurs at swapoff time in my linux-next-next-20220520 env, > > and I found this patch could solve the issue now with the fix in my another email. > > > > BTW: When I use dm-dust to inject the swapin IO error, I don't see non-uptodate folio when shmem_swapin_folio > > and swapoff succeeds. There might be some issues around that module (so I resort to the another way to inject > > the swapin error), but the patch itself works anyway. ;) > > Sorry, the reason I don't see non-uptodate folio when shmem_swapin_folio is that all the shmem pages are still > in the swapcache. They're not read from disk so there is no really IO error. :) When they're indeed freed, the > deadloop issue occurs. > > I am thinking about extending the function of MADV_PAGEOUT to free the swapcache page. The page resides in the > swapcache does not save the system memory anyway. And this could help test the swapin behavior. But I'm not > sure whether it's needed. The extension make MADV_PAGEOUT free swapcaches makes sense to me, so I'll support it if the original implementer agrees the change. Thanks, Naoya Horiguchi
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