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Date:   Thu, 13 Jan 2022 16:46:52 +0100
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Subject: Re: [PATCH v4 09/66] mm/mmap: Use the maple tree in find_vma()
 instead of the rbtree.
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To:     Liam Howlett <liam.howlett@oracle.com>
Cc:     "maple-tree@lists.infradead.org" <maple-tree@lists.infradead.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Song Liu <songliubraving@fb.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        Laurent Dufour <ldufour@linux.ibm.com>,
        David Rientjes <rientjes@google.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Rik van Riel <riel@surriel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Michel Lespinasse <walken.cr@gmail.com>,
        Jerome Glisse <jglisse@redhat.com>,
        Minchan Kim <minchan@google.com>,
        Joel Fernandes <joelaf@google.com>,
        Rom Lemarchand <romlem@google.com>
References: <20211201142918.921493-1-Liam.Howlett@oracle.com>
 <20211201142918.921493-10-Liam.Howlett@oracle.com>
 <4207b5a3-efac-40f3-6b42-6713c9283cdd@suse.cz>
 <20211215180903.huv74nff62lgepsa@revolver>
From:   Vlastimil Babka <vbabka@suse.cz>
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On 12/15/21 19:09, Liam Howlett wrote:
>> - the future lookup of address vma->vm_end will return this vma, although
>> the address doesn't belong to it. Wouldn't be surprised if this caused
>> infrequent mysterious bugs?
>>
>> Both will resolve with vmacache removal later, but better still fix this.
> This is certainly worth fixing.  I am surprised that I did not hit a
> random bug as you said above, I would expect it to occur as well.
> Although, I didn't run each patch individually for long unless I was
> tracking down an issue on a rebase.

Ah, it doesn't cause a bug because vmacache_find() checks the boundaries of
vmas in the vmacache.