From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D0A2944BC94; Fri, 11 Sep 2026 19:45:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789155950; cv=none; b=X8+eUzA7rbVtTAD0MOWfdxjPEexbwqaSAf+vM8IOUmEqPq2T2ZtAgFGyRLLns9P1YLtXMAblBQrB666s8Ep9XnWKXcfXS03t66gf3Jwe6n47qERmIKJAGBlNML+I6rmS7I+/Unnq+VXb4D8pIcGjM5NYYsS4nBhEcNI7a0g6t+U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789155950; c=relaxed/simple; bh=YNJ9YeSxPjoByAaDIVZsmZrOztcEH6WnAs2id4cpoSc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bqgaBwjINcgu45U6BuYY5sGlqq2JM12e83Txv7Y1HSQLgdqD4CxlU0pHjkLDpnZfkIluwkkHRh5CMhEzOyZjL479qvaO9iU3JflYcGCNdD43eb6K5tn+rIX3wKczZ6x2LpS6ktS+1f3u8BXL8Z3P2nywogZ/ZszJNZWXrSFAVoE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=i64kGb/3; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="i64kGb/3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9EC71F00898; Fri, 11 Sep 2026 19:45:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789155925; bh=fK4p93/u6AanIHtu5vXzEzaRXDt40DQgX7Ravxuqpxw=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=i64kGb/3X9BQVjACRQTmztK6UN9vfAAH0CDAv2AoWhz2hBGqmDrBgVd3MhMcWzXNO 1ctBcxLoO6M9eaVjGcglS+1j6O97tmY2YcHWzkHZDPcEu7r6Y8h604/6HNvNd7InFA bRAtyHJ36NibHuSvj9NC2CeNsn3mDxPZTkAgEAwY/baM1XygvBqU4jWnV+4kWZFiKn UhnfZgglAgptZjfXFwyoojUDhs9WKgwBsVhvuhWJsrFQ9C04ew4ZUCHEesEgIq+SvN uOvRQbnj7fd65dbi5C+7gavgD16qrtTA9Ge0gMxyAh5un2EXZSnXzk/2AmXm/6Eh+2 kgp4njV5imiZQ== Date: Fri, 11 Sep 2026 20:45:20 +0100 From: "Lorenzo Stoakes (ARM)" To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, liam@infradead.org, vbabka@kernel.org, david@kernel.org, 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 v4 4/7] proc/task_mmu: remove special-casing of smap_gather_stats() start parameter Message-ID: References: <20260911194145.1781926-1-surenb@google.com> <20260911194145.1781926-5-surenb@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260911194145.1781926-5-surenb@google.com> On Fri, Sep 11, 2026 at 12:41:42PM -0700, Suren Baghdasaryan wrote: > smap_gather_stats() interprets its start parameter to mean vma->vm_start > when it's set to 0. Eliminate this special interpretation and provide two > separate functions for a partial and complete VMA walk. > > Since smap_gather_stats() operates within a single VMA, we can replace > walk_page_vma()/walk_page_range() calls with walk_page_range_vma() > which is simpler and also can be called while holding per-VMA lock. > > No functional change intended. > > Suggested by: Lorenzo Stoakes > Signed-off-by: Suren Baghdasaryan LGTM so: Reviewed-by: Lorenzo Stoakes (ARM) > --- > fs/proc/task_mmu.c | 52 +++++++++++++++++++++++++++++++--------------- > 1 file changed, 35 insertions(+), 17 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 0e53eb065a3e..a6026ffd07f1 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -1246,20 +1246,26 @@ get_smaps_shmem_walk_ops(struct proc_maps_private *priv) > return &smaps_shmem_walk_vma_lock_ops; > } > > -/* > - * Gather mem stats from @vma with the indicated beginning > - * address @start, and keep them in @mss. > +/** > + * smap_gather_stats_range() - Gather mem stats from a portion of the @vma. > + * @priv: proc maps private state. > + * @vma: The VMA to gather stats for. > + * @mss: The accumulated stats. > + * @start: The address from which to start. > * > - * Use vm_start of @vma as the beginning address if @start is 0. > + * This gathers stats for the portion of the VMA starting at the @start > + * address. > */ > -static void smap_gather_stats(struct proc_maps_private *priv, > - struct vm_area_struct *vma, > - struct mem_size_stats *mss, unsigned long start) > +static void smap_gather_stats_range(struct proc_maps_private *priv, > + struct vm_area_struct *vma, > + struct mem_size_stats *mss, > + unsigned long start) > { > const struct mm_walk_ops *ops = get_smaps_walk_ops(priv); > + const bool is_partial = start > vma->vm_start; > > /* Invalid start */ > - if (start >= vma->vm_end) > + if (start < vma->vm_start || start >= vma->vm_end) > return; > > if (vma == get_gate_vma(priv->lock_ctx.mm)) > @@ -1278,20 +1284,31 @@ static void smap_gather_stats(struct proc_maps_private *priv, > const unsigned long shmem_swapped = shmem_swap_usage(vma); > const bool is_cow = vma_is_cow_mapping(vma); > > - if (start || (shmem_swapped && is_cow)) > + if (is_partial || (shmem_swapped && is_cow)) > ops = get_smaps_shmem_walk_ops(priv); > else > mss->swap += shmem_swapped; > } > > - if (!start) > - walk_page_vma(vma, ops, mss); > - else > - walk_page_range(vma->vm_mm, start, vma->vm_end, ops, mss); > + walk_page_range_vma(vma, start, vma->vm_end, ops, mss); > > reacquire_rcu(priv); > } > > +/** > + * smap_gather_stats() - Gather mem stats from the entire @vma. > + * @priv: proc maps private state. > + * @vma: The VMA to gather stats for. > + * @mss: The accumulated stats. > + * > + * This gathers stats for the whole of the VMA. > + */ > +static void smap_gather_stats(struct proc_maps_private *priv, > + struct vm_area_struct *vma, struct mem_size_stats *mss) > +{ > + smap_gather_stats_range(priv, vma, mss, vma->vm_start); > +} > + > #define SEQ_PUT_DEC(str, val) \ > seq_put_decimal_ull_width(m, str, (val) >> 10, 8) > > @@ -1342,7 +1359,7 @@ static int show_smap(struct seq_file *m, void *v) > struct vm_area_struct *vma = v; > struct mem_size_stats mss = {}; > > - smap_gather_stats(priv, vma, &mss, 0); > + smap_gather_stats(priv, vma, &mss); > > show_map_vma(m, vma); > > @@ -1395,7 +1412,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v) > > vma_start = vma->vm_start; > do { > - smap_gather_stats(priv, vma, &mss, 0); > + smap_gather_stats(priv, vma, &mss); > last_vma_end = vma->vm_end; > > /* > @@ -1454,14 +1471,15 @@ static int show_smaps_rollup(struct seq_file *m, void *v) > > /* Case 1 and 2 above */ > if (vma->vm_start >= last_vma_end) { > - smap_gather_stats(priv, vma, &mss, 0); > + smap_gather_stats(priv, vma, &mss); > last_vma_end = vma->vm_end; > continue; > } > > /* Case 4 above */ > if (vma->vm_end > last_vma_end) { > - smap_gather_stats(priv, vma, &mss, last_vma_end); > + smap_gather_stats_range(priv, vma, &mss, > + last_vma_end); > last_vma_end = vma->vm_end; > } > } > -- > 2.55.0.1007.g17ff1f9808-goog > -- Cheers, Lorenzo