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Mon, 12 Sep 2022 00:13:25 -0700 (PDT) Date: Mon, 12 Sep 2022 01:13:21 -0600 From: Yu Zhao To: Liam Howlett Cc: "maple-tree@lists.infradead.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Morton Subject: Re: [PATCH v14 67/70] mm/vmscan: Use vma iterator instead of vm_next Message-ID: References: <20220906194824.2110408-1-Liam.Howlett@oracle.com> <20220906194824.2110408-68-Liam.Howlett@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662966806; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=5PBnObJ86DaSFv/Dn+kEE30YGOmbqTKM2FIWKrmzEvs=; b=SRQzgUlH1rplevtGQizvtDmopLLQyQVqlMyTc1WswyKlZmq+XNCjVtgdRh/dPUgbQfySwF abZpfj5cho+8MQTkzJxWM8VHNc6BLYyN5YZ02FmkHEJvufn0hAHX+LAQ8nh4HUfXPziTr2 pE9dARSfHrOIF0hGcWfS24rEBfhCHYg= ARC-Authentication-Results: i=1; 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> > unsigned long end = (start | ~mask) + 1; > > + VMA_ITERATOR(vmi, args->mm, start); > > > > VM_WARN_ON_ONCE(mask & size); > > VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask)); > > > > - while (args->vma) { > > - if (start >= args->vma->vm_end) { > > - args->vma = args->vma->vm_next; > > + for_each_vma_range(vmi, args->vma, end) { > > + if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args)) > > continue; > > - } > > - > > - if (end && end <= args->vma->vm_start) > > - return false; > > Here the original code leaves args->vma pointing the first vma out of > the range [start, end). This allows the caller (page table walker) to > resume at that vma, if it chooses to. ^^^^^^ continue (without releasing mmap_lock) > With for_each_vma_range(), under the same condition, args->vma is set to > NULL. And the page table walker may terminate prematurely. Apparently I > overlooked until I was told MGLRU in mm-unstable is slower than itself > on 6.0-rc4 yesterday. > > > - > > - if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args)) { > > - args->vma = args->vma->vm_next; > > - continue; > > - } > > > > *vm_start = max(start, args->vma->vm_start); > > *vm_end = min(end - 1, args->vma->vm_end - 1) + 1; > > The following should work properly. Please take a look. Thanks! > > --- > mm/vmscan.c | 12 +++--------- > 1 file changed, 3 insertions(+), 9 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 11a86d47e85e..b22d3efe3031 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3776,23 +3776,17 @@ static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk > { > unsigned long start = round_up(*vm_end, size); > unsigned long end = (start | ~mask) + 1; > + VMA_ITERATOR(vmi, args->mm, start); > > VM_WARN_ON_ONCE(mask & size); > VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask)); > > - while (args->vma) { > - if (start >= args->vma->vm_end) { > - args->vma = args->vma->vm_next; > - continue; > - } > - > + for_each_vma(vmi, args->vma) { > if (end && end <= args->vma->vm_start) > return false; > > - if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args)) { > - args->vma = args->vma->vm_next; > + if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args)) > continue; > - } > > *vm_start = max(start, args->vma->vm_start); > *vm_end = min(end - 1, args->vma->vm_end - 1) + 1; > -- > 2.37.2.789.g6183377224-goog