linux-kernel - Re: [PATCH] mm,mremap: Bail out earlier in mremap

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Message-ID: <20190301152547.GA25732@rei>
Date:   Fri, 1 Mar 2019 16:25:48 +0100
From:   Cyril Hrubis <chrubis@...e.cz>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Oscar Salvador <osalvador@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        hughd@...gle.com, kirill@...temov.name, joel@...lfernandes.org,
        jglisse@...hat.com, yang.shi@...ux.alibaba.com,
        mgorman@...hsingularity.net
Subject: Re: [PATCH] mm,mremap: Bail out earlier in mremap_to under map
 pressure

Hi!
> Hopefully the only program that would start failing would be a LTP test
> testing the current behavior near the limit (if such test exists). And
> that can be adjusted.

There does not seem to be a mremap() test that would do such a thing, so
we should be safe :-).

BTW there was a similar fix for mmap() with MAP_FIXED that caused a LTP
test to fail and was fixed in:

commit e8420a8ece80b3fe810415ecf061d54ca7fab266
Author: Cyril Hrubis <chrubis@...e.cz>
Date:   Mon Apr 29 15:08:33 2013 -0700

    mm/mmap: check for RLIMIT_AS before unmapping

And I haven't heard of any breakages so far so I guess that this very
similar situation and that the possibility of breaking real world
applications here is really low.

-- 
Cyril Hrubis
chrubis@...e.cz