linux-kernel - Re: [PATCH] mm: mempolicy: make mbind() return -EIO when MPOL_MF

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Message-ID: <alpine.DEB.2.21.1903191748090.18028@chino.kir.corp.google.com>
Date:   Tue, 19 Mar 2019 17:49:14 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
cc:     chrubis@...e.cz, vbabka@...e.cz, kirill@...temov.name,
        osalvador@...e.de, akpm@...ux-foundation.org,
        stable@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT
 is specified

On Wed, 20 Mar 2019, Yang Shi wrote:

> When MPOL_MF_STRICT was specified and an existing page was already
> on a node that does not follow the policy, mbind() should return -EIO.
> But commit 6f4576e3687b ("mempolicy: apply page table walker on
> queue_pages_range()") broke the rule.
> 
> And, commit c8633798497c ("mm: mempolicy: mbind and migrate_pages
> support thp migration") didn't return the correct value for THP mbind()
> too.
> 
> If MPOL_MF_STRICT is set, ignore vma_migratable() to make sure it reaches
> queue_pages_to_pte_range() or queue_pages_pmd() to check if an existing
> page was already on a node that does not follow the policy.  And,
> non-migratable vma may be used, return -EIO too if MPOL_MF_MOVE or
> MPOL_MF_MOVE_ALL was specified.
> 
> Tested with https://github.com/metan-ucw/ltp/blob/master/testcases/kernel/syscalls/mbind/mbind02.c
> 
> Fixes: 6f4576e3687b ("mempolicy: apply page table walker on queue_pages_range()")
> Reported-by: Cyril Hrubis <chrubis@...e.cz>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: stable@...r.kernel.org
> Suggested-by: Kirill A. Shutemov <kirill@...temov.name>
> Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>
> Signed-off-by: Oscar Salvador <osalvador@...e.de>

Acked-by: David Rientjes <rientjes@...gle.com>

Thanks.  I think this needs stable for 4.0+, can you confirm?