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Wed, 06 May 2026 11:47:25 -0700 (PDT) Received: from pc636 ([2001:9b1:d5a0:a500:de96:9acf:5dca:ede4]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a865c8bed6sm4299484e87.31.2026.05.06.11.47.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 May 2026 11:47:25 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 6 May 2026 20:47:24 +0200 To: shivamkalra98@zohomail.in Cc: Andrew Morton , Uladzislau Rezki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alice Ryhl , Danilo Krummrich Subject: Re: [PATCH v12 2/5] mm/vmalloc: use physical page count for vrealloc() grow-in-place check Message-ID: References: <20260428-vmalloc-shrink-v12-0-3c18c9172eb1@zohomail.in> <20260428-vmalloc-shrink-v12-2-3c18c9172eb1@zohomail.in> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260428-vmalloc-shrink-v12-2-3c18c9172eb1@zohomail.in> X-Stat-Signature: eng4um4hr9ffntgm7edqswstmk6awmur X-Rspam-User: X-Rspamd-Queue-Id: C729540009 X-Rspamd-Server: rspam07 X-HE-Tag: 1778093247-41127 X-HE-Meta: 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 7esoJMOE 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Apr 28, 2026 at 01:54:17AM +0530, Shivam Kalra via B4 Relay wrote: > From: Shivam Kalra > > Update the grow-in-place check in vrealloc() to compare the requested size > against the actual physical page count (vm->nr_pages) rather than the > virtual area size (alloced_size, derived from get_vm_area_size()). > > Currently both values are equivalent, but the upcoming vrealloc() shrink > functionality will free pages without reducing the virtual reservation > size. After such a shrink, the old alloced_size-based comparison would > incorrectly allow a grow-in-place operation to succeed and attempt to > access freed pages. Switch to vm->nr_pages now so the check remains > correct once shrink support is added. > > Signed-off-by: Shivam Kalra > --- > mm/vmalloc.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 1073abb6094e..9cb3e287a1e8 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -4338,6 +4338,12 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align > if (unlikely(flags & __GFP_THISNODE) && nid != NUMA_NO_NODE && > nid != page_to_nid(vmalloc_to_page(p))) > goto need_realloc; > + } else { > + /* > + * If p is NULL, vrealloc behaves exactly like vmalloc. > + * Skip the shrink and in-place grow paths. > + */ > + goto need_realloc; > } > > /* > @@ -4356,7 +4362,7 @@ void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align > /* > * We already have the bytes available in the allocation; use them. > */ > - if (size <= alloced_size) { > + if (size <= vm->nr_pages << PAGE_SHIFT) { > /* > Maybe we should consider Fujunjie approach and borrow his idea to shrink VA also? In that case, we do not need to switch to vm->nr_pages? And we do not need [PATCH v12 3/5] mm/vmalloc: use physical page count in vread_iter() ? -- Uladzislau Rezki