linux-kernel - Re: [PATCH v1 1/3] mm/ksm: unmerge and clear VM_MERGEABLE when setting PR_SET_MEMORY

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Message-ID: <f809162e-4adc-cf9b-35f4-0f1b098ad283@redhat.com>
Date:   Fri, 21 Apr 2023 19:21:36 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Stefan Roesch <shr@...kernel.io>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-s390@...r.kernel.org, linux-kselftest@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...riel.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH v1 1/3] mm/ksm: unmerge and clear VM_MERGEABLE when
 setting PR_SET_MEMORY_MERGE=0

>> I understand we want to keep the name "symmetric" with
>> ksm_enable_merge_any, but it also unmerges the ksm pages. Do we want to
>> reflect that in the function name?
> 
> ksm_disable_merge_any_umerge() is suboptimal.
> 
> As ksm_disable_merge_any() now reverts what ksm_enable_merge_any() ended
> up doing, I think it's just fine.
> 
> (it would be a different story if we'd be using "set" / "clear"
> terminology instead of "enable" / "disable").
> 
> We can describe that in the comment.
> 
>>
>> Can we add a comment for the function?
> 
> Can do for symmetry with ksm_enable_merge_any().
> 

+/**
+ * ksm_disable_merge_any - Disable merging on all compatible VMA's of the mm,
+ *                        previously enabled via ksm_enable_merge_any().
+ *
+ * Disabling merging implies unmerging any merged pages, like setting
+ * MADV_UNMERGEABLE would. If unmerging fails, the whole operation fails and
+ * merging on all compatible VMA's remains enabled.
+ *
+ * @mm: Pointer to mm
+ *
+ * Returns 0 on success, otherwise error code
+ */


-- 
Thanks,

David / dhildenb