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 35EEE256E; Fri, 6 Dec 2024 18:16:46 +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=1733509007; cv=none; b=YVwylflXfT67C/I2wYk2/B2qRPNNarrGqmJk1P50bslW0/S4mtvME7N9rv3EhE8/y2jV+Uqg3AnjO9Om89/ZfoMuCEZ7DDeDJepULLTcyqdt1oUx4YeifKqw5OuAeq41zHYKK+E7Q7m2eRgm87fSeoDaomDDoGDqEHJG2Y6Mf1k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733509007; c=relaxed/simple; bh=lGINZh+0lSO+fouVKk+htbdhq62SzZUm82oIXJU7XWU=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Cxe+6vf9JuGO3XM2ptfOan3Hh4bYOIV+MBCVuDwanPhvDlCnOC5wDyZahm8OtJBKHSfljvjrBDbPghpYF5X5LeolXvmqBi06LQmka7RayIAgrE05Txidz3Lw3F3h1a+uDLaNouzyS1/QaQsiC/yjjQy6A7sO2uCLVGCw9mUPc9w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=P9pxE4Gg; 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="P9pxE4Gg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93C15C4CED1; Fri, 6 Dec 2024 18:16:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733509006; bh=lGINZh+0lSO+fouVKk+htbdhq62SzZUm82oIXJU7XWU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P9pxE4GgBC5HXHNSVIq9zZOVCAgT0XffH+dkwiQCo9OcjFcz3VYBd22OdR6uVr+5f enw4DQK6w6c5vpJpM755jmWxa7h1vwhFJigKEJ3XTjTA2TJwAM+1QNepx2J91ewqvS r3zp0tyMb2A/6ZO2BohYpiUpdtq0C4hxsz+wmmNS0neQn4WOI378HiU6a7+ZPWxt82 xOPq8C3RpxJmNEhpt7vxQ3Odn0qgAgJeMMFJtnGlmYvyze661Umr7QjuywxDukWiNu npq4lU9wNmr2GaB6wN72J0moTvFFmPd0ThX64AawhHw82vOMx1gXKXjNVYytaCZgtm V4IrBTMb4PcBg== From: SeongJae Park To: stable@vger.kernel.org Cc: Zheng Yejian , damon@lists.linux.dev, linux-mm@kvack.org, SeongJae Park , Fernand Sieber , Leonard Foerster , Shakeel Butt , Ye Weihua , Andrew Morton Subject: [PATCH 5.15.y 2/2] mm/damon/vaddr: fix issue in damon_va_evenly_split_region() Date: Fri, 6 Dec 2024 10:16:20 -0800 Message-Id: <20241206181620.91603-3-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20241206181620.91603-1-sj@kernel.org> References: <2024120625-recycling-till-0cca@gregkh> <20241206181620.91603-1-sj@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Zheng Yejian 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 (cherry picked from commit f3c7a1ede435e2e45177d7a490a85fb0a0ec96d1) --- mm/damon/vaddr-test.h | 1 + mm/damon/vaddr.c | 4 ++-- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/damon/vaddr-test.h b/mm/damon/vaddr-test.h index 95ec362cdc37..5531766ff09f 100644 --- a/mm/damon/vaddr-test.h +++ b/mm/damon/vaddr-test.h @@ -306,6 +306,7 @@ static void damon_test_split_evenly(struct kunit *test) 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); damon_destroy_ctx(c); diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c index 6ad96da15081..6d8036671e60 100644 --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -69,6 +69,7 @@ static int damon_va_evenly_split_region(struct damon_target *t, 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; @@ -82,8 +83,7 @@ static int damon_va_evenly_split_region(struct damon_target *t, 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; -- 2.39.5