From nobody Thu Apr 9 11:17:00 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 C65A03859CC for ; Mon, 9 Mar 2026 11:55:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773057356; cv=none; b=KkOR65n/WAwZmqeDIFhYiRhL9UvrboyMjCQu9YdDBE48WUgu+8/HZH1zZ5wAIlulXeZKBNL/ySZHB8OTLWQNHYtijbv3jTIlrq46Jg9AB2v6qcwI4s7DSThQ0wIdDM3xlGhsS1gynlOIQ05GBlqAyv+GVV6OtmMSSMy9aKyDmDc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773057356; c=relaxed/simple; bh=Tkc2G5v7MJj/0+toMiZPKrDMqernsxUrrJDbe2DWPYM=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=jHZnq43f6tD4q10CLiglE7t3KlsdrtrwfV0E0M91Mel535TgKEtfqIFrPjB4opYuAkR6/vI5IR2sSeJQINwQZSOCW8JW3FAh0nMlJdqGfjGKc77uWUxmG/EnzNxwA5RgYqSIpxFT3RsuPDk2HYO+1NYl1eP2On+uK41JabZu9uk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sRIUkNWG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="sRIUkNWG" Received: by smtp.kernel.org (Postfix) with ESMTPS id 7D3EBC2BC86; Mon, 9 Mar 2026 11:55:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773057356; bh=Tkc2G5v7MJj/0+toMiZPKrDMqernsxUrrJDbe2DWPYM=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=sRIUkNWGsABFa8kdDDrR33aTDFr/sXXQOoLU63pncZ/FqAQzJYRvhu6qjK5UFcYlJ 6Qenp9K4h9HV3UMFvL/MslPrggOsM6rmK5ucf9Tbm0JEvyevEDG6roA0BqAOHg+Ew9 7uGjcT/OKSi72L3mFMVgTn8hwLjROUAOjA9Z37tUtbVMs4KSenJontUo5flAOWbNcM J3gE3K2YIs+XC73DKFau0KJiw9U79kgy4WyuSVMhfWoUoDtGIYYoCtdgPdtAU/Np0H l1AWbI+vXxyWfXZJD6soigm8fzdKlwNfZDcTzvrVxeEph7FbtKgLl/g2HjLOHIrkdq hv8tT8ljnLHrA== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6FED5EFCD9C; Mon, 9 Mar 2026 11:55:56 +0000 (UTC) From: Shivam Kalra via B4 Relay Date: Mon, 09 Mar 2026 17:25:45 +0530 Subject: [PATCH v3 1/2] mm/vmalloc: extract vmalloc_free_pages() helper from vfree() 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="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260309-vmalloc-shrink-v3-1-5590fd8de2eb@zohomail.in> References: <20260309-vmalloc-shrink-v3-0-5590fd8de2eb@zohomail.in> In-Reply-To: <20260309-vmalloc-shrink-v3-0-5590fd8de2eb@zohomail.in> To: Andrew Morton , Uladzislau Rezki Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alice Ryhl , Danilo Krummrich , Shivam Kalra X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1773057354; l=2510; i=shivamkalra98@zohomail.in; s=20260212; h=from:subject:message-id; bh=K+fKY35rqal1HjSu0w8XUZyvTIb7GSRojmpzX5n0cKs=; b=tMvxDF4NmGBn266aUsP+BKfmmmHzs/OZbd58axuJ2Mp3ZLEdgFFSuV5XELVT1XA29RKBD299L /+X1aDNpFovBk90VI4PO/fFT8dyB3TnaE17p1U4Enf3NXpoaaJacXwE X-Developer-Key: i=shivamkalra98@zohomail.in; a=ed25519; pk=9Q+S1LD/xjbjL7bEaLIlwRADBwU/6LJq7lYm8LFrkQE= X-Endpoint-Received: by B4 Relay for shivamkalra98@zohomail.in/20260212 with auth_id=633 X-Original-From: Shivam Kalra Reply-To: shivamkalra98@zohomail.in From: Shivam Kalra Extract the page-freeing loop and NR_VMALLOC stat accounting from vfree() into a reusable vmalloc_free_pages() helper. The helper operates on a range [start, end) of pages from a vm_struct, making it suitable for both full free (vfree) and partial free (upcoming vrealloc shrink). No functional change. Signed-off-by: Shivam Kalra --- mm/vmalloc.c | 46 ++++++++++++++++++++++++++++++++-------------- 1 file changed, 32 insertions(+), 14 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index c607307c657a..42ae68450a90 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3416,6 +3416,36 @@ void vfree_atomic(const void *addr) schedule_work(&p->wq); } =20 +/* + * vmalloc_free_pages - free a range of pages from a vmalloc allocation + * @vm: the vm_struct containing the pages + * @start: first page index to free (inclusive) + * @end: last page index to free (exclusive) + * + * Free pages [start, end) updating NR_VMALLOC stat accounting. + * Caller is responsible for unmapping (vunmap_range) and KASAN + * poisoning before calling this. + */ +static void vmalloc_free_pages(struct vm_struct *vm, unsigned int start, + unsigned int end) +{ + unsigned int i; + + for (i =3D start; i < end; i++) { + struct page *page =3D vm->pages[i]; + + BUG_ON(!page); + /* + * High-order allocs for huge vmallocs are split, so + * can be freed as an array of order-0 allocations + */ + if (!(vm->flags & VM_MAP_PUT_PAGES)) + mod_lruvec_page_state(page, NR_VMALLOC, -1); + __free_page(page); + cond_resched(); + } +} + /** * vfree - Release memory allocated by vmalloc() * @addr: Memory base address @@ -3436,7 +3466,6 @@ void vfree_atomic(const void *addr) void vfree(const void *addr) { struct vm_struct *vm; - int i; =20 if (unlikely(in_interrupt())) { vfree_atomic(addr); @@ -3459,19 +3488,8 @@ void vfree(const void *addr) =20 if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS)) vm_reset_perms(vm); - for (i =3D 0; i < vm->nr_pages; i++) { - struct page *page =3D vm->pages[i]; - - BUG_ON(!page); - /* - * High-order allocs for huge vmallocs are split, so - * can be freed as an array of order-0 allocations - */ - if (!(vm->flags & VM_MAP_PUT_PAGES)) - mod_lruvec_page_state(page, NR_VMALLOC, -1); - __free_page(page); - cond_resched(); - } + if (vm->nr_pages) + vmalloc_free_pages(vm, 0, vm->nr_pages); kvfree(vm->pages); kfree(vm); } --=20 2.43.0 From nobody Thu Apr 9 11:17:00 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 C66C13A4F2D for ; 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charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260309-vmalloc-shrink-v3-2-5590fd8de2eb@zohomail.in> References: <20260309-vmalloc-shrink-v3-0-5590fd8de2eb@zohomail.in> In-Reply-To: <20260309-vmalloc-shrink-v3-0-5590fd8de2eb@zohomail.in> To: Andrew Morton , Uladzislau Rezki Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alice Ryhl , Danilo Krummrich , Shivam Kalra X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1773057354; l=2543; i=shivamkalra98@zohomail.in; s=20260212; h=from:subject:message-id; bh=Y6w6SdmqyOX+lKwpSwN3cQqWUNCycwjirQc9nEik+Gw=; b=L/WqM1MJYwB7vVbM9AOGxxZTpnHqTAxqZxh0e6lKXHQvPLuZXyjB0b+6gFXrLrBkH/mTyqQkL aS9B5mwSnayA6paU3NhhXeQ9aA0U2x05yDdAvgHLU3Oya8ycfErgZZd X-Developer-Key: i=shivamkalra98@zohomail.in; a=ed25519; pk=9Q+S1LD/xjbjL7bEaLIlwRADBwU/6LJq7lYm8LFrkQE= X-Endpoint-Received: by B4 Relay for shivamkalra98@zohomail.in/20260212 with auth_id=633 X-Original-From: Shivam Kalra Reply-To: shivamkalra98@zohomail.in From: Shivam Kalra When vrealloc() shrinks an allocation and the new size crosses a page boundary, unmap and free the tail pages that are no longer needed. This reclaims physical memory that was previously wasted for the lifetime of the allocation. The heuristic is simple: always free when at least one full page becomes unused. Huge page allocations (page_order > 0) are skipped, as partial freeing would require splitting. The virtual address reservation (vm->size / vmap_area) is intentionally kept unchanged, preserving the address for potential future grow-in-place support. Fix the grow-in-place check to compare against vm->nr_pages rather than get_vm_area_size(), since the latter reflects the virtual reservation which does not shrink. Without this fix, a grow after shrink would access freed pages. Signed-off-by: Shivam Kalra --- mm/vmalloc.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 42ae68450a90..114e0bd1030e 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4344,14 +4344,23 @@ void *vrealloc_node_align_noprof(const void *p, siz= e_t size, unsigned long align goto need_realloc; } =20 - /* - * TODO: Shrink the vm_area, i.e. unmap and free unused pages. What - * would be a good heuristic for when to shrink the vm_area? - */ if (size <=3D old_size) { + unsigned int new_nr_pages =3D PAGE_ALIGN(size) >> PAGE_SHIFT; + /* Zero out "freed" memory, potentially for future realloc. */ if (want_init_on_free() || want_init_on_alloc(flags)) memset((void *)p + size, 0, old_size - size); + + /* Free tail pages when shrink crosses a page boundary. */ + if (new_nr_pages < vm->nr_pages && !vm_area_page_order(vm)) { + unsigned long addr =3D (unsigned long)p; + + vunmap_range(addr + (new_nr_pages << PAGE_SHIFT), + addr + (vm->nr_pages << PAGE_SHIFT)); + + vmalloc_free_pages(vm, new_nr_pages, vm->nr_pages); + vm->nr_pages =3D new_nr_pages; + } vm->requested_size =3D size; kasan_vrealloc(p, old_size, size); return (void *)p; @@ -4360,7 +4369,7 @@ 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 <=3D alloced_size) { + if (size <=3D (size_t)vm->nr_pages << PAGE_SHIFT) { /* * No need to zero memory here, as unused memory will have * already been zeroed at initial allocation time or during --=20 2.43.0