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Sun, 11 Sep 2022 23:55:12 -0700 (PDT) Date: Mon, 12 Sep 2022 00:55:08 -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: <20220906194824.2110408-68-Liam.Howlett@oracle.com> ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=ddKn14bs; spf=pass (imf12.hostedemail.com: domain of yuzhao@google.com designates 209.85.166.181 as permitted sender) smtp.mailfrom=yuzhao@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662965713; a=rsa-sha256; cv=none; b=ySB5Y6vjSwLa3jbgnzIkBA578gf+YzxFn8skiGDDbFAQNKtFid5ACyjbpbZulmdtDX5XxP Od98U+uZTDDN2ZeOKY7UaUxEufwTaP4v5elWCMUw+osI0iPnpT1Y8wE2jnHoW/SrH79vrd 9u6qnpgdw0gpAifPIE2+GP/hEccPyxw= ARC-Message-Signature: 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. 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