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a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789026279; bh=KeY2ecBYXILjnJfvlD+aKbn3Fj7q03e1zhdxzP3owm4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=K/1yX6wYqGx3DlHOpx6z/zg5BRMRmre61T0TfyWVd7E6qvYnkkqKgkjYP8bl+8p4K Fz/WMtRF+bz6n4RmOcAd4SRb1SS9EBF+Wam8pC4EKJqKfHOiVbxbwC1pQW5e72ATWn BTulP01ah/PWT1SKdtfCFZ835ua++8yjbDQgpnWcCbcMaIF7w9F+GCauHPtwyuWqXJ lijRSdW/evnZOnPtk6oD+LlfebWXweMNXh80ckD2iODwAySofHwKwFOi8WKGtUrLXT g84/ydHeHETnkXPU5XSl13qkllkRGo7e+SjUzrHEza8LSKroR1KzNDTpgmyaJ/K89y XOETAU5f/2JTA== Message-ID: Date: Thu, 10 Sep 2026 09:44:33 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/5] proc/task_mmu: read proc/pid/smaps_rollup under per-vma lock To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, liam@infradead.org, ljs@kernel.org, vbabka@kernel.org, willy@infradead.org, jannh@google.com, paulmck@kernel.org, pfalcato@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20260907063918.3432401-1-surenb@google.com> <20260907063918.3432401-5-surenb@google.com> <19e428e5-d8bc-4abb-b052-e23442464cba@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 76C0C40006 X-Stat-Signature: 5aca31if93ocp57bjqdw3m8fktac1t7p X-HE-Tag: 1789026280-254974 X-HE-Meta: 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 h1r24r+l j8ICtbkbfo3cq4T2sD0737ZS/xxsZx6F5ptYrMrmjiYWLED+tSesSjgi6cs57tJl1X8wZJTjjlYDJQhNuDSSDjdiu+wntQpcUfmdQn/98sX1a4C2Qi1coad2R+/b68nEQkASGkuZMJfx6kKvWenIeaQ129zcCEbBIrLcxv+89MEa9TVaSTpqD7oUZGvypXwAXxTkQ3iC5vo5j6KIIn1MFw1Sf7Z+7RL/wDXhueaKPraN6dq/N6k6T3mQv7y8A24VuSMIXq2HIRqoGS/dvpLjfbLG1KA5dhfkUd6m51jj4wIVIBZg4JhZXmVivpNHvP2pDi0eRV5hgU0e3UO3cWxLJwLmzdx/jq2AHyqGB Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/9/26 19:58, Suren Baghdasaryan wrote: > On Wed, Sep 9, 2026 at 10:23 AM David Hildenbrand (Arm) > wrote: >> >> >>> - vma_start = vma->vm_start; >>> - do { >>> - smap_gather_stats(priv, vma, &mss, vma->vm_start); >>> - last_vma_end = vma->vm_end; >>> + if (!IS_ERR(vma) && vma != get_gate_vma(lock_ctx->mm)) >>> + vma_start = vma->vm_start; >>> + >>> + while (vma) { >>> + if (IS_ERR(vma)) { >>> + ret = PTR_ERR(vma); >>> + goto out_unlock; >>> + } >>> + >> >> Can we add a comment whey we break (and not e.g., continue) whenw e hit the gate >> VMA? >> >> (I seriously don't kmow ... should I know? :) ) > > The way m_next() is implemented, the gate VMA always placed at the end > of the address space, so the next VMA will be NULL and we can break > once we see the gate. But now that I'm looking closer into this code, > reading smaps_rollup file does not invoke m_next(), so we should never > encounter a gate VMA (it's not in the maple tree, so for_each_vma() > should never return it). I think I can remove the special handling for > that case. > > Thanks for the question, David! It made me realize we can simplify this further. good! :) -- Cheers, David