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 D99FDC77B78 for ; Thu, 4 May 2023 19:58:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232108AbjEDT6T (ORCPT ); Thu, 4 May 2023 15:58:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232480AbjEDT4I (ORCPT ); Thu, 4 May 2023 15:56:08 -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 78CC81C0F7; Thu, 4 May 2023 12:49:25 -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 D244163801; Thu, 4 May 2023 19:49:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 50BE8C4339B; Thu, 4 May 2023 19:49:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1683229745; bh=KBbLHB3W595ZHLY9iyrj8ireU+PEvPjhLx1gv5CrqIA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BIPshuvvvQACfpAnjECI1L5Y+zB33lXx4Cxls+BlAemDdmKXphQ0E+4s7y20P7ikk zUW7GHdYjXVwupZQI6eSDIm1QeAatxy3gAq96KBS3DDcOdBNlH3rbAt+h9OXD722L0 NB9F+Xj6QKsZNa66ktnz9a+UUlKbRm0qfhdh8OU80G4Bq2H4HXRrg0eDeKqaxIHNJg 3lvohZ+EIWKPdOD2ysnh4V03iYgSsBOlIUuAoVMdddevjvEsXdBBwD8Xzkbnq6leSS kjTxer13+3iBOBIHsZ2rJ8L+6uB1YoD058+SxaXpMo9WH+0vnlDR7C2zIARGGo1eSr N91k0Bf0ndk1Q== 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 5.15 16/30] ext4: Fix best extent lstart adjustment logic in ext4_mb_new_inode_pa() Date: Thu, 4 May 2023 15:48:09 -0400 Message-Id: <20230504194824.3808028-16-sashal@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230504194824.3808028-1-sashal@kernel.org> References: <20230504194824.3808028-1-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 b737437618047..c8dfea7c4ba43 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -4308,6 +4308,7 @@ 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(ac->ac_sb, "use %llu/%d from inode pa %p\n", start, len, pa); @@ -4632,10 +4633,8 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac) pa = ac->ac_pa; 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 @@ -4643,26 +4642,40 @@ 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