Messages in this thread | | | Date | Tue, 18 Nov 2014 13:41:10 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm: frontswap: invalidate expired data on a dup-store failure |
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On Tue, 18 Nov 2014 16:51:36 +0800 Weijie Yang <weijie.yang@samsung.com> wrote:
> If a frontswap dup-store failed, it should invalidate the expired page > in the backend, or it could trigger some data corruption issue. > Such as: > 1. use zswap as the frontswap backend with writeback feature > 2. store a swap page(version_1) to entry A, success > 3. dup-store a newer page(version_2) to the same entry A, fail > 4. use __swap_writepage() write version_2 page to swapfile, success > 5. zswap do shrink, writeback version_1 page to swapfile > 6. version_2 page is overwrited by version_1, data corrupt. > > This patch fixes this issue by invalidating expired data immediately > when meet a dup-store failure. > > ... > > --- a/mm/frontswap.c > +++ b/mm/frontswap.c > @@ -244,8 +244,10 @@ int __frontswap_store(struct page *page) > the (older) page from frontswap > */ > inc_frontswap_failed_stores(); > - if (dup) > + if (dup) { > __frontswap_clear(sis, offset); > + frontswap_ops->invalidate_page(type, offset); > + } > } > if (frontswap_writethrough_enabled) > /* report failure so swap also writes to swap device */
I tagged this for backporting into -stable kernels. Please shout at me if you think that was inappropriate.
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