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 D70342210FB; Thu, 12 Dec 2024 15:50:22 +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=1734018622; cv=none; b=qlUzvLylLJoNyGK6vgMbgTI7xup/Z7B2cu9b3KPexJUmn/tuQQ8K73+hn78GnNX1oS5EwwluqgBs7KKHKxiyy24B6LhwCKB+d0g/rzXA76A2SSIN8aS7l/67X/mf9zKPupOWAuYn9Ompz4ZnC6jK41kTA5LQGLFSuOGFMPQl348= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734018622; c=relaxed/simple; bh=2nNpABws69uasDsd1CuJgbO3WjorKreCrZsGJyJfuiQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=g3IMHBuapDX7z0DvOyrkn1zQUKFX6fssE3lNyisVP1sKZCTAnzkxVBg4Kx5SWkqU4L/YihEzdf1JFQ9Jz7FbxZDt+tee4dP5o1fMPjTEWZnO5SrJEDgnCkyU0ILD//2DYZzQKT97Q9TIwxD4puqU2yh9xJk9el4bfkOfGcu02MQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=R9gYFrdI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="R9gYFrdI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 41ED3C4CECE; Thu, 12 Dec 2024 15:50:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1734018622; bh=2nNpABws69uasDsd1CuJgbO3WjorKreCrZsGJyJfuiQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=R9gYFrdISafq+LmVlrOB/DYsyT4iYkCAbcjei6jNTC9GCGOfENWBrkSs0ggGSWFrO E6JgXqpPPq3FkZJ00g4r0FEChGTfqmZDCNoEcsEpLuUvI8BKP42vsrE6r4yDuJzM/R UZD+uPezS7mJzCQCTkH5NVqekm+f6nGZs1+UMYTY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Zheng Yejian , SeongJae Park , Fernand Sieber , Leonard Foerster , Shakeel Butt , Ye Weihua , Andrew Morton Subject: [PATCH 6.6 342/356] mm/damon/vaddr: fix issue in damon_va_evenly_split_region() Date: Thu, 12 Dec 2024 16:01:01 +0100 Message-ID: <20241212144258.080988235@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241212144244.601729511@linuxfoundation.org> References: <20241212144244.601729511@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zheng Yejian commit f3c7a1ede435e2e45177d7a490a85fb0a0ec96d1 upstream. Patch series "mm/damon/vaddr: Fix issue in damon_va_evenly_split_region()". v2. According to the logic of damon_va_evenly_split_region(), currently following split case would not meet the expectation: Suppose DAMON_MIN_REGION=0x1000, Case: Split [0x0, 0x3000) into 2 pieces, then the result would be acutually 3 regions: [0x0, 0x1000), [0x1000, 0x2000), [0x2000, 0x3000) but NOT the expected 2 regions: [0x0, 0x1000), [0x1000, 0x3000) !!! The root cause is that when calculating size of each split piece in damon_va_evenly_split_region(): `sz_piece = ALIGN_DOWN(sz_orig / nr_pieces, DAMON_MIN_REGION);` both the dividing and the ALIGN_DOWN may cause loss of precision, then each time split one piece of size 'sz_piece' from origin 'start' to 'end' would cause more pieces are split out than expected!!! To fix it, count for each piece split and make sure no more than 'nr_pieces'. In addition, add above case into damon_test_split_evenly(). And add 'nr_piece == 1' check in damon_va_evenly_split_region() for better code readability and add a corresponding kunit testcase. This patch (of 2): According to the logic of damon_va_evenly_split_region(), currently following split case would not meet the expectation: Suppose DAMON_MIN_REGION=0x1000, Case: Split [0x0, 0x3000) into 2 pieces, then the result would be acutually 3 regions: [0x0, 0x1000), [0x1000, 0x2000), [0x2000, 0x3000) but NOT the expected 2 regions: [0x0, 0x1000), [0x1000, 0x3000) !!! The root cause is that when calculating size of each split piece in damon_va_evenly_split_region(): `sz_piece = ALIGN_DOWN(sz_orig / nr_pieces, DAMON_MIN_REGION);` both the dividing and the ALIGN_DOWN may cause loss of precision, then each time split one piece of size 'sz_piece' from origin 'start' to 'end' would cause more pieces are split out than expected!!! To fix it, count for each piece split and make sure no more than 'nr_pieces'. In addition, add above case into damon_test_split_evenly(). After this patch, damon-operations test passed: # ./tools/testing/kunit/kunit.py run damon-operations [...] ============== damon-operations (6 subtests) =============== [PASSED] damon_test_three_regions_in_vmas [PASSED] damon_test_apply_three_regions1 [PASSED] damon_test_apply_three_regions2 [PASSED] damon_test_apply_three_regions3 [PASSED] damon_test_apply_three_regions4 [PASSED] damon_test_split_evenly ================ [PASSED] damon-operations ================= Link: https://lkml.kernel.org/r/20241022083927.3592237-1-zhengyejian@huaweicloud.com Link: https://lkml.kernel.org/r/20241022083927.3592237-2-zhengyejian@huaweicloud.com Fixes: 3f49584b262c ("mm/damon: implement primitives for the virtual memory address spaces") Signed-off-by: Zheng Yejian Reviewed-by: SeongJae Park Cc: Fernand Sieber Cc: Leonard Foerster Cc: Shakeel Butt Cc: Ye Weihua Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/damon/vaddr-test.h | 1 + mm/damon/vaddr.c | 4 ++-- 2 files changed, 3 insertions(+), 2 deletions(-) --- a/mm/damon/vaddr-test.h +++ b/mm/damon/vaddr-test.h @@ -300,6 +300,7 @@ static void damon_test_split_evenly(stru damon_test_split_evenly_fail(test, 0, 100, 0); damon_test_split_evenly_succ(test, 0, 100, 10); damon_test_split_evenly_succ(test, 5, 59, 5); + damon_test_split_evenly_succ(test, 0, 3, 2); damon_test_split_evenly_fail(test, 5, 6, 2); } --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -67,6 +67,7 @@ static int damon_va_evenly_split_region( unsigned long sz_orig, sz_piece, orig_end; struct damon_region *n = NULL, *next; unsigned long start; + unsigned int i; if (!r || !nr_pieces) return -EINVAL; @@ -80,8 +81,7 @@ static int damon_va_evenly_split_region( r->ar.end = r->ar.start + sz_piece; next = damon_next_region(r); - for (start = r->ar.end; start + sz_piece <= orig_end; - start += sz_piece) { + for (start = r->ar.end, i = 1; i < nr_pieces; start += sz_piece, i++) { n = damon_new_region(start, start + sz_piece); if (!n) return -ENOMEM;