From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4AE4EC77B78 for ; Thu, 4 May 2023 20:11:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232977AbjEDUJu (ORCPT ); Thu, 4 May 2023 16:09:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232786AbjEDUJU (ORCPT ); Thu, 4 May 2023 16:09:20 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 48D931A105; Thu, 4 May 2023 12:54:42 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 15E706386D; Thu, 4 May 2023 19:52:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 86039C4339B; Thu, 4 May 2023 19:52:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1683229952; bh=xYrx8c4EG0HeFGp5LDwwZL0KcMzUPrcmpGA1rkAKKRs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aQEheBUHZx6uNsCmTQOMv5BXwKVXPcJ67JhQss53BH37RqhEsvWXhGxIuuUl9V+jS Gem2CXwi3CM3bqcXzLHNKuDXaEy6dPeLIoYnB/5EPutDAA259Fa8aP8DzevB0ZZSAY DmASkcPuPVwi0mQDITf1S+JLHJt4ksgTDm7+xDD4gSST/HoaN9EUInmW+KmwgmJ8jw LuGZp5BzclcZGKkfY7dECLeCgoacsBQhH+5VDVgEAmrV+VIuyOY6mKm8P/lY7PaK5D XAUesDeLP1nEnAfXduMO6TfIebtgHxxN7gKlSG2Lbj6bRMj20z+W8ImPEjm1HAMTaz 6eebeg+pXKwDw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Ojaswin Mujoo , Jan Kara , Ritesh Harjani , Theodore Ts'o , Sasha Levin , adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org Subject: [PATCH AUTOSEL 4.14 10/13] ext4: Fix best extent lstart adjustment logic in ext4_mb_new_inode_pa() Date: Thu, 4 May 2023 15:52:02 -0400 Message-Id: <20230504195207.3809116-10-sashal@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230504195207.3809116-1-sashal@kernel.org> References: <20230504195207.3809116-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ojaswin Mujoo [ Upstream commit 93cdf49f6eca5e23f6546b8f28457b2e6a6961d9 ] When the length of best extent found is less than the length of goal extent we need to make sure that the best extent atleast covers the start of the original request. This is done by adjusting the ac_b_ex.fe_logical (logical start) of the extent. While doing so, the current logic sometimes results in the best extent's logical range overflowing the goal extent. Since this best extent is later added to the inode preallocation list, we have a possibility of introducing overlapping preallocations. This is discussed in detail here [1]. As per Jan's suggestion, to fix this, replace the existing logic with the below logic for adjusting best extent as it keeps fragmentation in check while ensuring logical range of best extent doesn't overflow out of goal extent: 1. Check if best extent can be kept at end of goal range and still cover original start. 2. Else, check if best extent can be kept at start of goal range and still cover original start. 3. Else, keep the best extent at start of original request. Also, add a few extra BUG_ONs that might help catch errors faster. [1] https://lore.kernel.org/r/Y+OGkVvzPN0RMv0O@li-bb2b2a4c-3307-11b2-a85c-8fa5c3a69313.ibm.com Suggested-by: Jan Kara Signed-off-by: Ojaswin Mujoo Reviewed-by: Ritesh Harjani (IBM) Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/f96aca6d415b36d1f90db86c1a8cd7e2e9d7ab0e.1679731817.git.ojaswin@linux.ibm.com Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- fs/ext4/mballoc.c | 49 ++++++++++++++++++++++++++++++----------------- 1 file changed, 31 insertions(+), 18 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 60f202e63eebd..374862666128b 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -3403,6 +3403,7 @@ static void ext4_mb_use_inode_pa(struct ext4_allocation_context *ac, BUG_ON(start < pa->pa_pstart); BUG_ON(end > pa->pa_pstart + EXT4_C2B(sbi, pa->pa_len)); BUG_ON(pa->pa_free < len); + BUG_ON(ac->ac_b_ex.fe_len <= 0); pa->pa_free -= len; mb_debug(1, "use %llu/%u from inode pa %p\n", start, len, pa); @@ -3707,10 +3708,8 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac) return -ENOMEM; if (ac->ac_b_ex.fe_len < ac->ac_g_ex.fe_len) { - int winl; - int wins; - int win; - int offs; + int new_bex_start; + int new_bex_end; /* we can't allocate as much as normalizer wants. * so, found space must get proper lstart @@ -3718,26 +3717,40 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac) BUG_ON(ac->ac_g_ex.fe_logical > ac->ac_o_ex.fe_logical); BUG_ON(ac->ac_g_ex.fe_len < ac->ac_o_ex.fe_len); - /* we're limited by original request in that - * logical block must be covered any way - * winl is window we can move our chunk within */ - winl = ac->ac_o_ex.fe_logical - ac->ac_g_ex.fe_logical; + /* + * Use the below logic for adjusting best extent as it keeps + * fragmentation in check while ensuring logical range of best + * extent doesn't overflow out of goal extent: + * + * 1. Check if best ex can be kept at end of goal and still + * cover original start + * 2. Else, check if best ex can be kept at start of goal and + * still cover original start + * 3. Else, keep the best ex at start of original request. + */ + new_bex_end = ac->ac_g_ex.fe_logical + + EXT4_C2B(sbi, ac->ac_g_ex.fe_len); + new_bex_start = new_bex_end - EXT4_C2B(sbi, ac->ac_b_ex.fe_len); + if (ac->ac_o_ex.fe_logical >= new_bex_start) + goto adjust_bex; - /* also, we should cover whole original request */ - wins = EXT4_C2B(sbi, ac->ac_b_ex.fe_len - ac->ac_o_ex.fe_len); + new_bex_start = ac->ac_g_ex.fe_logical; + new_bex_end = + new_bex_start + EXT4_C2B(sbi, ac->ac_b_ex.fe_len); + if (ac->ac_o_ex.fe_logical < new_bex_end) + goto adjust_bex; - /* the smallest one defines real window */ - win = min(winl, wins); + new_bex_start = ac->ac_o_ex.fe_logical; + new_bex_end = + new_bex_start + EXT4_C2B(sbi, ac->ac_b_ex.fe_len); - offs = ac->ac_o_ex.fe_logical % - EXT4_C2B(sbi, ac->ac_b_ex.fe_len); - if (offs && offs < win) - win = offs; +adjust_bex: + ac->ac_b_ex.fe_logical = new_bex_start; - ac->ac_b_ex.fe_logical = ac->ac_o_ex.fe_logical - - EXT4_NUM_B2C(sbi, win); BUG_ON(ac->ac_o_ex.fe_logical < ac->ac_b_ex.fe_logical); BUG_ON(ac->ac_o_ex.fe_len > ac->ac_b_ex.fe_len); + BUG_ON(new_bex_end > (ac->ac_g_ex.fe_logical + + EXT4_C2B(sbi, ac->ac_g_ex.fe_len))); } /* preallocation can change ac_b_ex, thus we store actually -- 2.39.2