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Fri, 17 Apr 2026 10:24:52 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Fri, 17 Apr 2026 19:24:50 +0200 To: Shivam Kalra Cc: Uladzislau Rezki , Alice Ryhl , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Danilo Krummrich Subject: Re: [PATCH v10 0/4] mm/vmalloc: free unused pages on vrealloc() shrink Message-ID: References: <20260404-vmalloc-shrink-v10-0-335759165dfa@zohomail.in> <7d16f260-ffd0-4e45-b66e-9e7f71332466@zohomail.in> <85a9f419-7f1e-41a0-9e8e-67aae7a1b0fe@zohomail.in> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <85a9f419-7f1e-41a0-9e8e-67aae7a1b0fe@zohomail.in> X-Rspamd-Queue-Id: 2FB401C0014 X-Stat-Signature: mtaickkgktrgnpp6kgzienzrt4shfaie X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1776446694-971674 X-HE-Meta: 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 vxBaUfWm PObtOuLIOB1BNO6T264vm4nx9E7XVIIY9IhTg86Cm1rUS8n1vMFqO2K66Vnhdkt47pbn6xEYutdY0f2slCJU1jOscDJidRVjVELlH7zl43q0z3f32Hbu/3anLP6FUUhrWSDJyZf+gRgkmy1vMeLRS48p7pVMDv4s/fBDuz43cRonvUAgkb+64GHQYJokqChwcuZzw9QcGr5dEYYbFWARVBWu249ScEcEER8nji0pooKQAQg3PuVq79eJDj+8TqL5D2J8E+wYs4CNYC+m5Q5BysYzzJaR89q1pjvbel+przKW1RTyPbr8I8vxeF6HkajEiMY+PzdaCFTNEQRmpOUQ0utdz4UdxqOpfUhdrno++ZCb+2x5xhNN/vPuLjSfayL3dquE4H0IS/gx4RNyas39GuzzN/t/6TsBxPKgo5NtjNeIGuWN/wIC0N01VrMxjwPiCKeJdXVcMuVq18bLxZyhvEbsnPbp7g0o/Y9Et Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 17, 2026 at 07:05:09PM +0530, Shivam Kalra wrote: > On 16/04/26 00:14, Uladzislau Rezki wrote: > > Yep, the problem reported by Sashiko regarding area->size and vread_iter() > > is correct. V10 does not address this. > > > > I am not sure that reducing vma size is a good approach here. It is > > widely used and we might end up with fixing even more corner cases. > > > > vread_iter() and vm-size calculation there should be fixed. > > > > -- > > Uladzislau Rezki > Proposed Change for v11: > > long vread_iter(struct iov_iter *iter, const char *addr, size_t count) > { > struct vmap_node *vn; > struct vmap_area *va; > struct vm_struct *vm; > char *vaddr; > > vaddr = (char *) va->va_start; > size = vm ? get_vm_area_size(vm) : va_size(va); > > if (vm && vm->nr_pages) > size = min(size, (size_t)vm->nr_pages << PAGE_SHIFT); > > > I have some questions to clarify. Why should we use min()? Checking vm->nr_pages, can it be 0? Can we just do: if (vm) /* Can not use get_vm_area_size() because of realloc(). */ size = vm->nr_pages << PAGE_SHIFT; else size = va_size(va); or i am missing something? Thanks! -- Uladzislau Rezki