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 2EAD853365; Thu, 12 Dec 2024 17:12:40 +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=1734023561; cv=none; b=cR1VK1wPncNTsx3fqK96g2gw9hJZy1aEXVPkjYkXUD37c7Ia7dF+GbzZjfIuQX6EhDjikHJZ1PJjVqCJg5J8ZrL54Q2t59bZ3PxE/JV6FYVZwwu0Ai+sIcQMbVgi40QJ53NeT1uj7b+/SsbV1VmPCU6Xe7cORTZiUKayZ7WIe1w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734023561; c=relaxed/simple; bh=Gs1geyviPmFJhxYgw+R2iIfXXwHeZ0tYwQToTIRXvEk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PitAw+5KcksrsAnSbtmMV9TmBKXGCJocTMe+lshGemAO9XNvrjOj2BdeDIzpKo57Z1ltE+PPIKDWDcn8jHzdTUC/29swyYWUtilOkNmqgQk0AzAIbtkP2uZTI7d25/wxXHHEBiAZOsTuXgMEGDrn7ziyQ6rxn1lozLSiN3CGdAs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Ib9ptz2t; 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="Ib9ptz2t" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6599AC4CED0; Thu, 12 Dec 2024 17:12:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1734023560; bh=Gs1geyviPmFJhxYgw+R2iIfXXwHeZ0tYwQToTIRXvEk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ib9ptz2tESxqcQF+VXWsjF6sTIkfD0XlH48YH0WvOKr/hiM4ex0XDbEbH38IEPFIL p2o0orJb8bAer8kR2Bm9EOWrcjf1i/EwPLV7uPp2UR6AUidVoaOgyBNmzy4n7ZQwWB SkQCaLPfnzIUpSHIRIXGp7YpwriojnfkFYv2d6e4= 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 5.15 545/565] mm/damon/vaddr: fix issue in damon_va_evenly_split_region() Date: Thu, 12 Dec 2024 16:02:20 +0100 Message-ID: <20241212144333.398839906@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241212144311.432886635@linuxfoundation.org> References: <20241212144311.432886635@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 5.15-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 @@ -306,6 +306,7 @@ 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); damon_destroy_ctx(c); --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -69,6 +69,7 @@ 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; @@ -82,8 +83,7 @@ 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;