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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 68290C46475 for ; Tue, 20 Nov 2018 21:09:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EB62920685 for ; Tue, 20 Nov 2018 21:09:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EB62920685 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-btrfs-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726201AbeKUHkO (ORCPT ); Wed, 21 Nov 2018 02:40:14 -0500 Received: from mx2.suse.de ([195.135.220.15]:43454 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725865AbeKUHkN (ORCPT ); Wed, 21 Nov 2018 02:40:13 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7EBBEACFF; Tue, 20 Nov 2018 21:09:04 +0000 (UTC) Subject: Re: [PATCH v2] btrfs: Fix error handling in btrfs_cleanup_ordered_extents To: Josef Bacik Cc: dsterba@suse.com, linux-btrfs@vger.kernel.org, wqu@suse.com References: <1540554115-11226-1-git-send-email-nborisov@suse.com> <20181120190050.u4pyaa6m5p5tck27@macbook-pro-91.dhcp.thefacebook.com> From: Nikolay Borisov Openpgp: preference=signencrypt Autocrypt: addr=nborisov@suse.com; prefer-encrypt=mutual; keydata= xsFNBFiKBz4BEADNHZmqwhuN6EAzXj9SpPpH/nSSP8YgfwoOqwrP+JR4pIqRK0AWWeWCSwmZ T7g+RbfPFlmQp+EwFWOtABXlKC54zgSf+uulGwx5JAUFVUIRBmnHOYi/lUiE0yhpnb1KCA7f u/W+DkwGerXqhhe9TvQoGwgCKNfzFPZoM+gZrm+kWv03QLUCr210n4cwaCPJ0Nr9Z3c582xc bCUVbsjt7BN0CFa2BByulrx5xD9sDAYIqfLCcZetAqsTRGxM7LD0kh5WlKzOeAXj5r8DOrU2 GdZS33uKZI/kZJZVytSmZpswDsKhnGzRN1BANGP8sC+WD4eRXajOmNh2HL4P+meO1TlM3GLl EQd2shHFY0qjEo7wxKZI1RyZZ5AgJnSmehrPCyuIyVY210CbMaIKHUIsTqRgY5GaNME24w7h TyyVCy2qAM8fLJ4Vw5bycM/u5xfWm7gyTb9V1TkZ3o1MTrEsrcqFiRrBY94Rs0oQkZvunqia c+NprYSaOG1Cta14o94eMH271Kka/reEwSZkC7T+o9hZ4zi2CcLcY0DXj0qdId7vUKSJjEep c++s8ncFekh1MPhkOgNj8pk17OAESanmDwksmzh1j12lgA5lTFPrJeRNu6/isC2zyZhTwMWs k3LkcTa8ZXxh0RfWAqgx/ogKPk4ZxOXQEZetkEyTFghbRH2BIwARAQABzSJOaWtvbGF5IEJv cmlzb3YgPG5ib3Jpc292QHN1c2UuZGU+wsF4BBMBAgAiBQJYijkSAhsDBgsJCAcDAgYVCAIJ CgsEFgIDAQIeAQIXgAAKCRBxvoJG5T8oV/B6D/9a8EcRPdHg8uLEPywuJR8URwXzkofT5bZE IfGF0Z+Lt2ADe+nLOXrwKsamhweUFAvwEUxxnndovRLPOpWerTOAl47lxad08080jXnGfYFS Dc+ew7C3SFI4tFFHln8Y22Q9075saZ2yQS1ywJy+TFPADIprAZXnPbbbNbGtJLoq0LTiESnD w/SUC6sfikYwGRS94Dc9qO4nWyEvBK3Ql8NkoY0Sjky3B0vL572Gq0ytILDDGYuZVo4alUs8 LeXS5ukoZIw1QYXVstDJQnYjFxYgoQ5uGVi4t7FsFM/6ykYDzbIPNOx49Rbh9W4uKsLVhTzG BDTzdvX4ARl9La2kCQIjjWRg+XGuBM5rxT/NaTS78PXjhqWNYlGc5OhO0l8e5DIS2tXwYMDY LuHYNkkpMFksBslldvNttSNei7xr5VwjVqW4vASk2Aak5AleXZS+xIq2FADPS/XSgIaepyTV tkfnyreep1pk09cjfXY4A7qpEFwazCRZg9LLvYVc2M2eFQHDMtXsH59nOMstXx2OtNMcx5p8 0a5FHXE/HoXz3p9bD0uIUq6p04VYOHsMasHqHPbsMAq9V2OCytJQPWwe46bBjYZCOwG0+x58 fBFreP/NiJNeTQPOa6FoxLOLXMuVtpbcXIqKQDoEte9aMpoj9L24f60G4q+pL/54ql2VRscK d87BTQRYigc+ARAAyJSq9EFk28++SLfg791xOh28tLI6Yr8wwEOvM3wKeTfTZd+caVb9gBBy wxYhIopKlK1zq2YP7ZjTP1aPJGoWvcQZ8fVFdK/1nW+Z8/NTjaOx1mfrrtTGtFxVBdSCgqBB jHTnlDYV1R5plJqK+ggEP1a0mr/rpQ9dFGvgf/5jkVpRnH6BY0aYFPprRL8ZCcdv2DeeicOO YMobD5g7g/poQzHLLeT0+y1qiLIFefNABLN06Lf0GBZC5l8hCM3Rpb4ObyQ4B9PmL/KTn2FV Xq/c0scGMdXD2QeWLePC+yLMhf1fZby1vVJ59pXGq+o7XXfYA7xX0JsTUNxVPx/MgK8aLjYW hX+TRA4bCr4uYt/S3ThDRywSX6Hr1lyp4FJBwgyb8iv42it8KvoeOsHqVbuCIGRCXqGGiaeX Wa0M/oxN1vJjMSIEVzBAPi16tztL/wQtFHJtZAdCnuzFAz8ue6GzvsyBj97pzkBVacwp3/Mw qbiu7sDz7yB0d7J2tFBJYNpVt/Lce6nQhrvon0VqiWeMHxgtQ4k92Eja9u80JDaKnHDdjdwq FUikZirB28UiLPQV6PvCckgIiukmz/5ctAfKpyYRGfez+JbAGl6iCvHYt/wAZ7Oqe/3Cirs5 KhaXBcMmJR1qo8QH8eYZ+qhFE3bSPH446+5oEw8A9v5oonKV7zMAEQEAAcLBXwQYAQIACQUC WIoHPgIbDAAKCRBxvoJG5T8oV1pyD/4zdXdOL0lhkSIjJWGqz7Idvo0wjVHSSQCbOwZDWNTN JBTP0BUxHpPu/Z8gRNNP9/k6i63T4eL1xjy4umTwJaej1X15H8Hsh+zakADyWHadbjcUXCkg OJK4NsfqhMuaIYIHbToi9K5pAKnV953xTrK6oYVyd/Rmkmb+wgsbYQJ0Ur1Ficwhp6qU1CaJ mJwFjaWaVgUERoxcejL4ruds66LM9Z1Qqgoer62ZneID6ovmzpCWbi2sfbz98+kW46aA/w8r 7sulgs1KXWhBSv5aWqKU8C4twKjlV2XsztUUsyrjHFj91j31pnHRklBgXHTD/pSRsN0UvM26 lPs0g3ryVlG5wiZ9+JbI3sKMfbdfdOeLxtL25ujs443rw1s/PVghphoeadVAKMPINeRCgoJH zZV/2Z/myWPRWWl/79amy/9MfxffZqO9rfugRBORY0ywPHLDdo9Kmzoxoxp9w3uTrTLZaT9M KIuxEcV8wcVjr+Wr9zRl06waOCkgrQbTPp631hToxo+4rA1jiQF2M80HAet65ytBVR2pFGZF zGYYLqiG+mpUZ+FPjxk9kpkRYz61mTLSY7tuFljExfJWMGfgSg1OxfLV631jV1TcdUnx+h3l Sqs2vMhAVt14zT8mpIuu2VNxcontxgVr1kzYA/tQg32fVRbGr449j1gw57BV9i0vww== Message-ID: <1af84f15-4ef4-0aaf-60a4-f4c3275e08ba@suse.com> Date: Tue, 20 Nov 2018 23:09:03 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181120190050.u4pyaa6m5p5tck27@macbook-pro-91.dhcp.thefacebook.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 20.11.18 г. 21:00 ч., Josef Bacik wrote: > On Fri, Oct 26, 2018 at 02:41:55PM +0300, Nikolay Borisov wrote: >> Running btrfs/124 in a loop hung up on me sporadically with the >> following call trace: >> btrfs D 0 5760 5324 0x00000000 >> Call Trace: >> ? __schedule+0x243/0x800 >> schedule+0x33/0x90 >> btrfs_start_ordered_extent+0x10c/0x1b0 [btrfs] >> ? wait_woken+0xa0/0xa0 >> btrfs_wait_ordered_range+0xbb/0x100 [btrfs] >> btrfs_relocate_block_group+0x1ff/0x230 [btrfs] >> btrfs_relocate_chunk+0x49/0x100 [btrfs] >> btrfs_balance+0xbeb/0x1740 [btrfs] >> btrfs_ioctl_balance+0x2ee/0x380 [btrfs] >> btrfs_ioctl+0x1691/0x3110 [btrfs] >> ? lockdep_hardirqs_on+0xed/0x180 >> ? __handle_mm_fault+0x8e7/0xfb0 >> ? _raw_spin_unlock+0x24/0x30 >> ? __handle_mm_fault+0x8e7/0xfb0 >> ? do_vfs_ioctl+0xa5/0x6e0 >> ? btrfs_ioctl_get_supported_features+0x30/0x30 [btrfs] >> do_vfs_ioctl+0xa5/0x6e0 >> ? entry_SYSCALL_64_after_hwframe+0x3e/0xbe >> ksys_ioctl+0x3a/0x70 >> __x64_sys_ioctl+0x16/0x20 >> do_syscall_64+0x60/0x1b0 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> >> Turns out during page writeback it's possible that the code in >> writepage_delalloc can instantiate a delalloc range which doesn't >> belong to the page currently being written back. This happens since >> find_lock_delalloc_range returns up to BTRFS_MAX_EXTENT_SIZE delalloc >> range when asked and doens't really consider the range of the passed >> page. When such a foregin range is found the code proceeds to >> run_delalloc_range and calls the appropriate function to fill the >> delalloc and create ordered extents. If, however, a failure occurs >> while this operation is in effect then the clean up code in >> btrfs_cleanup_ordered_extents will be called. This function has the >> wrong assumption that caller of run_delalloc_range always properly >> cleans the first page of the range hence when it calls >> __endio_write_update_ordered it explicitly ommits the first page of >> the delalloc range. This is wrong because this function could be >> cleaning a delalloc range that doesn't belong to the current page. This >> in turn means that the page cleanup code in __extent_writepage will >> not really free the initial page for the range, leaving a hanging >> ordered extent with bytes_left set to 4k. This bug has been present >> ever since the original introduction of the cleanup code in 524272607e88. >> >> Fix this by correctly checking whether the current page belongs to the >> range being instantiated and if so correctly adjust the range parameters >> passed for cleaning up. If it doesn't, then just clean the whole OE >> range directly. >> >> Signed-off-by: Nikolay Borisov >> Fixes: 524272607e88 ("btrfs: Handle delalloc error correctly to avoid ordered extent hang") > > Can we just remove the endio cleanup in __extent_writepage() and make this do > the proper cleanup? I'm not sure if that is feasible or not, but seems like it > would make the cleanup stuff less confusing and more straightforward. If not > you can add Quickly skimming the code I think the cleanup in __extent_writepage could be moved into __extent_writepage_io where we have 2 branches that set PageError. So I guess it could be done, but I will have to experiment with it. > > Reviewed-by: Josef Bacik > > Thanks, > > Josef >