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 X-Spam-Level: X-Spam-Status: No, score=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BE105C433EF for ; Thu, 9 Sep 2021 12:22:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A2EF3611BF for ; Thu, 9 Sep 2021 12:22:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243871AbhIIMXi (ORCPT ); Thu, 9 Sep 2021 08:23:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:56662 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351663AbhIIMTL (ORCPT ); Thu, 9 Sep 2021 08:19:11 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1F27461A8F; Thu, 9 Sep 2021 11:50:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631188217; bh=EO5WTZ8O4LLdufi6+e6+MagC1+NkIj5HFqVjt36Xhxs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=soouTyLhUBZC1aPkLHBVIL+Va/u2C58Fi1XjD5Yi3sK3WjMnAmsjB6OZwPx0H83UT PdrMBO7d4DNQQGwAOKqpfqP5R20GPiWSxQeXUrQvb6ePyeIqf0LyZNcoExj+hOGman tIYCNjsYRPfu6napHtewYMo7CpE3s6ZoQzRlKv854eQFriASBoHHRs78crGAK0onAr QpL7AAb0VkOLy9+iuu4vx0gI46mPl+8xu275ZURpU+OTEySs+STCADaWWamf2uzIaS jEmIEMmpi3ZX5NFBvWzFk4v92KyWPV9rWDMeXPZTGAbj9vIhFfiJe6drYTyu+zHuth SvdWvUxfq28PA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Qu Wenruo , Anand Jain , David Sterba , Sasha Levin , linux-btrfs@vger.kernel.org Subject: [PATCH AUTOSEL 5.13 172/219] btrfs: grab correct extent map for subpage compressed extent read Date: Thu, 9 Sep 2021 07:45:48 -0400 Message-Id: <20210909114635.143983-172-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210909114635.143983-1-sashal@kernel.org> References: <20210909114635.143983-1-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-btrfs@vger.kernel.org From: Qu Wenruo [ Upstream commit 557023ea9f06baf2659b232b08b8e8711f7001a6 ] [BUG] When subpage compressed read write support is enabled, btrfs/038 always fails with EIO. A simplified script can easily trigger the problem: mkfs.btrfs -f -s 4k $dev mount $dev $mnt -o compress=lzo xfs_io -f -c "truncate 118811" $mnt/foo xfs_io -c "pwrite -S 0x0d -b 39987 92267 39987" $mnt/foo > /dev/null sync btrfs subvolume snapshot -r $mnt $mnt/mysnap1 xfs_io -c "pwrite -S 0x3e -b 80000 200000 80000" $mnt/foo > /dev/null sync xfs_io -c "pwrite -S 0xdc -b 10000 250000 10000" $mnt/foo > /dev/null xfs_io -c "pwrite -S 0xff -b 10000 300000 10000" $mnt/foo > /dev/null sync btrfs subvolume snapshot -r $mnt $mnt/mysnap2 cat $mnt/mysnap2/foo # Above cat will fail due to EIO [CAUSE] The problem is in btrfs_submit_compressed_read(). When it tries to grab the extent map of the read range, it uses the following call: em = lookup_extent_mapping(em_tree, page_offset(bio_first_page_all(bio)), fs_info->sectorsize); The problem is in the page_offset(bio_first_page_all(bio)) part. The offending inode has the following file extent layout item 10 key (257 EXTENT_DATA 131072) itemoff 15639 itemsize 53 generation 8 type 1 (regular) extent data disk byte 13680640 nr 4096 extent data offset 0 nr 4096 ram 4096 extent compression 0 (none) item 11 key (257 EXTENT_DATA 135168) itemoff 15586 itemsize 53 generation 8 type 1 (regular) extent data disk byte 0 nr 0 item 12 key (257 EXTENT_DATA 196608) itemoff 15533 itemsize 53 generation 8 type 1 (regular) extent data disk byte 13676544 nr 4096 extent data offset 0 nr 53248 ram 86016 extent compression 2 (lzo) And the bio passed in has the following parameters: page_offset(bio_first_page_all(bio)) = 131072 bio_first_bvec_all(bio)->bv_offset = 65536 If we use page_offset(bio_first_page_all(bio) without adding bv_offset, we will get an extent map for file offset 131072, not 196608. This means we read uncompressed data from disk, and later decompression will definitely fail. [FIX] Take bv_offset into consideration when trying to grab an extent map. And add an ASSERT() to ensure we're really getting a compressed extent. Thankfully this won't affect anything but subpage, thus we only need to ensure this patch get merged before we enabled basic subpage support. Reviewed-by: Anand Jain Signed-off-by: Qu Wenruo Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/compression.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index f69b8d332574..f25ea4764ea1 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -683,6 +683,7 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, struct page *page; struct bio *comp_bio; u64 cur_disk_byte = bio->bi_iter.bi_sector << 9; + u64 file_offset; u64 em_len; u64 em_start; struct extent_map *em; @@ -692,15 +693,17 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, em_tree = &BTRFS_I(inode)->extent_tree; + file_offset = bio_first_bvec_all(bio)->bv_offset + + page_offset(bio_first_page_all(bio)); + /* we need the actual starting offset of this extent in the file */ read_lock(&em_tree->lock); - em = lookup_extent_mapping(em_tree, - page_offset(bio_first_page_all(bio)), - fs_info->sectorsize); + em = lookup_extent_mapping(em_tree, file_offset, fs_info->sectorsize); read_unlock(&em_tree->lock); if (!em) return BLK_STS_IOERR; + ASSERT(em->compress_type != BTRFS_COMPRESS_NONE); compressed_len = em->block_len; cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS); if (!cb) -- 2.30.2