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 13C70C433F5 for ; Wed, 27 Apr 2022 07:19:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358678AbiD0HW3 (ORCPT ); Wed, 27 Apr 2022 03:22:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357783AbiD0HW1 (ORCPT ); Wed, 27 Apr 2022 03:22:27 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B83A45D5CE for ; Wed, 27 Apr 2022 00:19:17 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 6495E1F380 for ; Wed, 27 Apr 2022 07:19:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1651043956; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=UpifccS/B0BpiUqPyiKZqQxaGD13VggDMzYqPi4UUPo=; b=S1Utw9cEhdTFUsAk1d09TSC1rbBIqJ2Qd58n8e1Sp+MlSJjp2KAsjh80en8ykfBZN8j9sF 8vqyhdEc0W/hbVEC4InzOkrRFrZPOiBTjdErUP/CPZ96Q5TeQpFSYXJSZOWMmUyZEb0NrH l07m5M3qOu3C89ZBmZKrkxuRpCr6zqM= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id A7AFD13A39 for ; Wed, 27 Apr 2022 07:19:15 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id nEL3GnPuaGIbJAAAMHmgww (envelope-from ) for ; Wed, 27 Apr 2022 07:19:15 +0000 From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH RFC v2 00/12] btrfs: make read repair work in synchronous mode Date: Wed, 27 Apr 2022 15:18:46 +0800 Message-Id: X-Mailer: git-send-email 2.36.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org [CHANGELOG] RFC v1 -> RFC v2: - Assemble a bio list for read/write bios and submit them in one go This allows less submit bio hooks, while still allow us to wait for them all to finish. - Completely remove io_failure_tree infrastructure Now we don't need to remember which mirror we hit error. At end_bio_extent_readpage() we either get good data and done the repair already, or we there aren't enough mirrors for us to recover all data. This is mostly trading on-stack memory of end_bio_extent_readpage() with btrfs_inode::io_failure_tree. The latter tree has a much longer lifespan, thus I think it's still a win overall [RFC POINTS] - How to improve read_repair_get_sector()? Currently we always iterate the whole bio to grab the target page/pgoff. Is there any better cached method to avoid such iteration? - Is this new code logically more reader-friendly? It's more for sure straight-forward, but I doubt if it's any easier to read compared to the old code. - btrfs/157 failure Need extra check to find out why btrfs/157 failed. In theory, we should just iterate through all mirrors, I guess it's we have no way to exhaust all combinations, thus the extra 2 "mirrors" can gave us wrong result for RAID6. [BEFORE] For corrupted sectors, we just record the logical bytenr and mirror number into io_failure_tree, then re-queue the same block with different mirror number and call it a day. The re-queued read will trigger enter the same endio function, with extra failrec handling to either continue re-queue (csum mismatch/read failure), or clear the current failrec and submit a write to fix the corrupted mirror (read succeeded and csum match/no csum). This is harder to read, as we need to enter the same river twice or even more. [AFTER] For corrupted sectors, we record the following things into an on-stack structure in end_bio_extent_readpage(): - The original bio - The original file offset of the bio This is for direct IO case, as we can not grab file offset just using page_offset() - Offset inside the bio of the corrupted sector - Corrupted mirror Then in the new btrfs_read_repair_ctrl structure, we hold those info like: Original bio logical = X, file_offset = Y, inode=(R/I) Offset inside bio: 0 4k 8K 12K 16K cur_bad_bitmap | X| X| | X| Each set bit will indicate we have a corrupted sector inside the original bio. During endio function, we only populate the cur_bad_bitmap. After we have iterated all sectors of the original bio, then we call btrfs_read_repair_finish() to do the real repair by: - Build a list of bios for cur_bad_bitmap For above case, bio offset [0, 8K) will be inside one bio, while another bio for bio offset [12K, 16K). And the page/pgoff will be extracted from the orignial bio. This is a little different from the old behavior, as old behavior will submit a new bio for each sector. The new behavior will save some btrfs_map_bio() calls. - Submit all the bios in the bio list and wait them to finish - Re-verify the read result - Submit write for the corrupted mirror Currently the write is still submitted for each sector and we will wait for each sector to finish. This needs some optimization. And for repaired sectors, remove them from @cur_bad_bitmap. - Do the same loop until either 1) we tried all mirrors, or 2) no more corrupted sectors - Handle the remaining corrupted sectors Either mark them error for buffered read, or just return an error for direct IO. By this we can: - Remove the re-entry behavior of endio function Now everything is handled inside end_bio_extent_readpage(). - Remove the io_failure_tree completely As we don't need to record which mirror has failed. - Slightly reduced overhead on read repair Now we won't call btrfs_map_bio() for each corrupted sector, as we can merge the sectors into a much larger bio. Qu Wenruo (12): btrfs: introduce a pure data checksum checking helper btrfs: always save bio::bi_iter into btrfs_bio::iter before submitting btrfs: remove duplicated parameters from submit_data_read_repair() btrfs: add btrfs_read_repair_ctrl to record corrupted sectors btrfs: add a helper to queue a corrupted sector for read repair btrfs: introduce a helper to repair from one mirror btrfs: allow btrfs read repair to submit all writes in one go btrfs: switch buffered read to the new btrfs_read_repair_* based repair routine btrfs: switch direct IO routine to use btrfs_read_repair_ctrl btrfs: cleanup btrfs_repair_one_sector() btrfs: remove io_failure_record infrastructure completely btrfs: remove btrfs_inode::io_failure_tree fs/btrfs/btrfs_inode.h | 5 - fs/btrfs/compression.c | 12 +- fs/btrfs/ctree.h | 2 + fs/btrfs/extent-io-tree.h | 15 - fs/btrfs/extent_io.c | 744 ++++++++++++++++++----------------- fs/btrfs/extent_io.h | 89 +++-- fs/btrfs/inode.c | 108 +++-- include/trace/events/btrfs.h | 1 - 8 files changed, 518 insertions(+), 458 deletions(-) -- 2.36.0