From mboxrd@z Thu Jan 1 00:00:00 1970 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 E91D82459C5 for ; Sat, 14 Mar 2026 09:06:06 +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=1773479167; cv=none; b=KVBpdJx8LJOJi2dA79OWhlVb7peIRaSGAvbaNO2camhUPLm2unXeWOALPfgEFLPUM/0fv6MZG4fSZBzt9vfNQieRs9LO6pAzwuHftRl8eHSC1zrsfTKdxuYiR3DYmYv1H87BMfWOMQZf2ZAXOu31a8kjE1k0Jnltu/sWtA+sh4Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773479167; c=relaxed/simple; bh=FpWmOp0KrMNBjh4gR56azZfEz9z4IdeZPVymGFzqY4k=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=B4gtr/asUQ2qM72SU+GrGp2Y0d1MRmgaajiz9QB0EjJQOIXzH6kiwwaB6Py3cjWDYZwol2Z4bkCGgds2Gz8yYhwI02wi3UfyKjWpyy/44bJuvLRyiqGAeU5cGvgiyeVNIFgxdXduex3hJ3u8WlZPhaFqwUDF8Org+OBfXbhUwE4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IzrDyOWS; 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="IzrDyOWS" Received: by smtp.kernel.org (Postfix) with ESMTPS id 9098DC116C6; Sat, 14 Mar 2026 09:06:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773479166; bh=FpWmOp0KrMNBjh4gR56azZfEz9z4IdeZPVymGFzqY4k=; h=From:Subject:Date:To:Cc:Reply-To:From; b=IzrDyOWSA8ccGC7TBidzm3PGS99uNHQsya5UjJ3K4excCRvHYl7aD1XhYUfF+tprE 3W08mHVxB8UGDI78xGWJvlbKRimeW5jTE+QWFuZL3leU9RxFWvtWfQLVA1WffXqBRH cvRc510RDSR+GhO1sIDimwy0zFGJdlCnM890fY1Z+d0W4aS1gkzD9jWf+P7w9GO0Ei 6Mc3A6GxmDEg3bYMKD07ih218HJeRliq3d3GSmh9szkkguGT+e9C6e617gn1rZ3foT No7U18qQdXfeWJe0PN1rh01K9RPrCytU1+nk1d7Or9g8fFdY3cpcTUa+KLANEM6fZ1 4YZeMJ3BJT4ew== 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 869A5107BCE9; Sat, 14 Mar 2026 09:06:06 +0000 (UTC) From: Shivam Kalra via B4 Relay Subject: [PATCH v4 0/3] mm/vmalloc: free unused pages on vrealloc() shrink Date: Sat, 14 Mar 2026 14:34:12 +0530 Message-Id: <20260314-vmalloc-shrink-v4-0-c1e2e0bb5455@zohomail.in> 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: 7bit X-B4-Tracking: v=1; b=H4sIAIwktWkC/3XMza7CIBCG4VsxrMUMU8ppXXkfxgUtw+nEWgwY4 k9676IrTePy/ZLveYhEkSmJ7eohImVOHKYSer0S/WCnf5LsSgsENFABynyy4xh6mYbI01GC7tB b0zRWaVFO50ier29wfyg9cLqEeHv7Wb3Wn1RWEqQ2jrzXpu7+aHcPQzhZHjc8iReW8RPQCwALg E2PrXIGFMASqD6BdgFUBajrFrxrHCF138A8z0/7/oNpMAEAAA== X-Change-ID: 20260302-vmalloc-shrink-04b2fa688a14 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=1773479164; l=3149; i=shivamkalra98@zohomail.in; s=20260212; h=from:subject:message-id; bh=FpWmOp0KrMNBjh4gR56azZfEz9z4IdeZPVymGFzqY4k=; b=e2prkkhIrcliRDFynHQBoXYTe7vpo2xtunw0OR910D+c/ibdQa4FAC33JhJx9Dnw8+zWOfr2I 7gP21Z3WRcJBPU2CGo4ZHCBDBbZ2zMk/fnYzChdxC5pZZZxefIbyydi 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 This series implements the TODO in vrealloc() to unmap and free unused pages when shrinking across a page boundary. Problem: When vrealloc() shrinks an allocation, it updates bookkeeping (requested_size, KASAN shadow) but does not free the underlying physical pages. This wastes memory for the lifetime of the allocation. Solution: - Patch 1: Extracts a vm_area_free_pages(vm, start, end) helper from vfree() that frees a range of pages with memcg and nr_vmalloc_pages accounting. Freed page pointers are set to NULL to prevent stale references. - Patch 2: Uses the helper to free tail pages when vrealloc() shrinks across a page boundary. Skips huge page allocations (page_order > 0) since compound pages cannot be partially freed. Also fixes the grow-in-place path to check vm->nr_pages instead of get_vm_area_size(), which reflects the virtual reservation and does not change on shrink. - Patch 3: Adds a vrealloc test case to lib/test_vmalloc that exercises grow-realloc, shrink-across-boundary, shrink-within-page, and grow-in-place paths with data integrity validation. The virtual address reservation is kept intact to preserve the range for potential future grow-in-place support. A concrete user is the Rust binder driver's KVVec::shrink_to [1], which performs explicit vrealloc() shrinks for memory reclamation. Tested: - KASAN KUnit (vmalloc_oob passes) - lib/test_vmalloc stress tests (3/3, 1M iterations each) - checkpatch, sparse, W=1, allmodconfig, coccicheck clean [1] https://lore.kernel.org/all/20260216-binder-shrink-vec-v3-v6-0-ece8e8593e53@zohomail.in/ Signed-off-by: Shivam Kalra --- Changes in v4: - Rename vmalloc_free_pages() to vm_area_free_pages() to align with vm_area_alloc_pages() (Uladzislau Rezki) - NULL out freed vm->pages[] entries to prevent stale pointers (Alice Ryhl) - Remove redundant if (vm->nr_pages) guard in vfree() (Uladzislau Rezki) - Add vrealloc test case to lib/test_vmalloc (new patch 3/3) - Link to v3: https://lore.kernel.org/r/20260309-vmalloc-shrink-v3-0-5590fd8de2eb@zohomail.in Changes in v3: - Restore the comment. - Rebase to the latest mm-new - Link to v2: https://lore.kernel.org/r/20260304-vmalloc-shrink-v2-0-28c291d60100@zohomail.in Changes in v2: - Updated the base-commit to mm-new - Fix conflicts after rebase - Ran `clang-format` on the changes made - Use a single `kasan_vrealloc` (Alice Ryhl) - Link to v1: https://lore.kernel.org/r/20260302-vmalloc-shrink-v1-0-46deff465b7e@zohomail.in --- Shivam Kalra (3): mm/vmalloc: extract vm_area_free_pages() helper from vfree() mm/vmalloc: free unused pages on vrealloc() shrink lib/test_vmalloc: add vrealloc test case lib/test_vmalloc.c | 52 ++++++++++++++++++++++++++++++++++++++++++ mm/vmalloc.c | 66 ++++++++++++++++++++++++++++++++++++++---------------- 2 files changed, 99 insertions(+), 19 deletions(-) --- base-commit: 593fab843afbd6800243552aebcc61d02d3cdcb2 change-id: 20260302-vmalloc-shrink-04b2fa688a14 Best regards, -- Shivam Kalra