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b=IhUCYUY30J8Exyx9w/d0UNOfjomlG50EDn07gvcqRDTwSvFJnY2gF+bowzT8FxMEF 5cPILEaSujtn/AV3/SVhu98XX1YSQQVY7VlUku+xoBRFFnZwDrYrotgfuUpizi+KAQ I9mD4wTN3v3aiMrZOf6yhOSJhu0pE1ZtACsC1OaQX6YLrCiHMMqRyvc4sT6nnb1PDt fy65LGPzykioDTDOzSSrkjjnBOyaE56dXLR+RTwxxImiQrQ0VE+NenXqkHuBxx4NcQ AWRjI1I4zzW0mdkIz+XV5xeFptSAP35ASzhsBiVAIb7s/J1LQb6NhUwceAU5F2qq8L lKQ8fAukXOL+A== Date: Fri, 11 Sep 2026 20:03:00 +0100 From: "Lorenzo Stoakes (ARM)" To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, liam@infradead.org, vbabka@kernel.org, david@redhat.com, willy@infradead.org, jannh@google.com, paulmck@kernel.org, pfalcato@suse.de, xueyuan.chen21@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v3 5/7] proc/task_mmu: change proc_get_vma() to stop returning gate VMA at the end Message-ID: References: <20260910234737.1340642-1-surenb@google.com> <20260910234737.1340642-6-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C2F04160017 X-Stat-Signature: 3xnmkc8t5cdg1qfi3ktzsr5us4h363ii X-HE-Tag: 1789153387-182681 X-HE-Meta: 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 f/YElEhO huFIeeocaB8k8OwQkKkjrzS8V8sR3jkj2DfpP8NX3i5oG0Pl5ozEN3z6Mz3ok2GrAT3s0SDrWMKOKV9HmrVb18lOsriZ5OmLFzkj+LjFPiL46QEvzt7mJQaRCtrmCAYDD3QAwCrWdjR/sTISS60w2WNQLbbgu1lIUxF/WW0pNadyADu+iJTKraIo0cSvfzzaypootOBHfujO5ivtF8unLKN7h5gt/eKC+2oa6IfTePM77zTkDE/AbN+YjNrP3A6sMqt1HZxUqS4Ip7eG0m+GqArWj/qsKTqUBzWuX3TGBS3W7ax7DjiDEGvtZ7kxEWfDgI6atugD2ka4GlmnasoqrcpjySYtAPRCnk9/yjiwfyO+D/XaLK32QZ0SyCYvgMP8rnF4O4rUBRX+dc2ooGOHWlwucl6k7dlxRk9ruL6jzcphBWvw= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Sep 11, 2026 at 07:26:49PM +0100, Lorenzo Stoakes (ARM) wrote: > On Thu, Sep 10, 2026 at 04:47:35PM -0700, Suren Baghdasaryan wrote: > > proc_get_vma() returning gate VMA at the end is desirable for the its > > current m_start/m_next callers, as they need to report a gate VMA at the > > end of the address space. This behavior is very specific to these callers > > and makes proc_get_vma() hard to use for other purposes. > > > > Move this usage-specific behavior into the callers themselves so that > > proc_get_vma() returns either a valid VMA, an error or a NULL when no > > more VMAs are available. This makes it more generic, simpler and usable > > in the later patches. > > > > Signed-off-by: Suren Baghdasaryan > > Yes, very good change, thanks! > > Reviewed-by: Lorenzo Stoakes (ARM) > > > --- > > fs/proc/task_mmu.c | 23 ++++++++++++++++++----- > > 1 file changed, 18 insertions(+), 5 deletions(-) > > > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > > index ecce7ce116cb..9a3c996c1d61 100644 > > --- a/fs/proc/task_mmu.c > > +++ b/fs/proc/task_mmu.c > > @@ -236,9 +236,6 @@ static struct vm_area_struct *proc_get_vma(struct seq_file *m, loff_t *ppos) > > * found the extended vma with the same vm_start. > > */ > > *ppos = vma->vm_end; > > - } else { > > - *ppos = SENTINEL_VMA_GATE; > > - vma = get_gate_vma(priv->lock_ctx.mm); > > Yeah this is just so confusing as-was. > > > } > > > > return vma; > > @@ -248,6 +245,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos) > > { > > struct proc_maps_private *priv = m->private; > > struct proc_maps_locking_ctx *lock_ctx; > > + struct vm_area_struct *vma; > > loff_t last_addr = *ppos; > > struct mm_struct *mm; > > > > @@ -280,16 +278,31 @@ static void *m_start(struct seq_file *m, loff_t *ppos) > > if (last_addr == SENTINEL_VMA_GATE) > > return get_gate_vma(mm); > > > > - return proc_get_vma(m, ppos); > > + vma = proc_get_vma(m, ppos); > > + if (vma) > > + return vma; > > + > > + /* Return gate VMA at the end */ > > + *ppos = SENTINEL_VMA_GATE; > > + return get_gate_vma(mm); > > } > > > > static void *m_next(struct seq_file *m, void *v, loff_t *ppos) > > { > > + struct proc_maps_private *priv = m->private; > > + struct vm_area_struct *vma; > > + > > if (*ppos == SENTINEL_VMA_GATE) { > > *ppos = SENTINEL_VMA_END; > > return NULL; > > } > > - return proc_get_vma(m, ppos); > > + vma = proc_get_vma(m, ppos); > > + if (vma) > > + return vma; > > OK so I guess the logic is, iterate through every VMA, then once you run out, > report the gate VMA. Makes sense. Hmm one thing on this though - m_start() still has: if (last_addr == SENTINEL_VMA_GATE) return get_gate_vma(mm); As well as: vma = proc_get_vma(m, ppos); if (vma) return vma; /* Return gate VMA at the end */ *ppos = SENTINEL_VMA_GATE; return get_gate_vma(mm); Now at the end. Is this correct? Is it maybe duplicated now? > > > + > > + /* Return gate VMA at the end */ > > + *ppos = SENTINEL_VMA_GATE; > > + return get_gate_vma(priv->lock_ctx.mm); > > } > > > > static void m_stop(struct seq_file *m, void *v) > > -- > > 2.55.0.1007.g17ff1f9808-goog > > > > -- > Cheers, Lorenzo -- Cheers, Lorenzo