From: Jan Kara Subject: Re: [v4.14-rc3 bug] scheduling while atomic in generic/451 test on extN Date: Thu, 12 Oct 2017 17:07:40 +0200 Message-ID: <20171012150740.GD31488@quack2.suse.cz> References: <20171005060700.GF8034@eguan.usersys.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, lczerner@redhat.com To: Eryu Guan Return-path: Received: from mx2.suse.de ([195.135.220.15]:48584 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751040AbdJLPHm (ORCPT ); Thu, 12 Oct 2017 11:07:42 -0400 Content-Disposition: inline In-Reply-To: <20171005060700.GF8034@eguan.usersys.redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: Hi Eryu! On Thu 05-10-17 14:07:00, Eryu Guan wrote: > I hit "scheduling while atomic" bug by running fstests generic/451 on > extN filesystems in v4.14-rc3 testing, but it didn't reproduce for me on > every host I tried, but I've seen it multiple times on multiple hosts. A > test vm of mine with 4 vcpus and 8G memory reproduced the bug reliably, > while a bare metal host with 8 cpus and 8G mem couldn't. > > This is due to commit 332391a9935d ("fs: Fix page cache inconsistency > when mixing buffered and AIO DIO"), which defers AIO DIO io completion > to a workqueue if the inode has mapped pages and does page cache > invalidation in process context. I think that the problem is that the > pages can be mapped after the dio->inode->i_mapping->nrpages check, so > we're doing page cache invalidation, which could sleep, in interrupt > context, thus "scheduling while atomic" bug happens. > > Defering all AIO DIO completion to workqueue unconditionally (as what > the iomap based path does) fixed the problem for me. But there're > performance concerns to do so in the original discussions. > > https://www.spinics.net/lists/linux-fsdevel/msg112669.html Thanks for report and the detailed analysis. I think your analysis is correct and the nrpages check in dio_bio_end_aio() is racy. My solution to this would be to pass to dio_complete() as an argument whether invalidation is required or not (and set it to true for deferred completion and to false when we decide not to defer completion since nrpages is 0 at that moment). Lukas? Honza > [17087.868644] BUG: scheduling while atomic: swapper/0/0/0x00000100 > [17087.875363] Modules linked in: dm_thin_pool dm_persistent_data dm_bio_prison dm_snapshot dm_bufio loop dm_flakey dm_mod ses enclosure ext4 mbcache jbd2 intel_rapl sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul mpt3sas ghash_clmulni_intel raid_class sg scsi_transport_sas pcbc ipmi_ssif shpchp aesni_intel crypto_simd iTCO_wdt glue_helper ipmi_si cryptd iTCO_vendor_support cdc_ether ipmi_devintf ipmi_msghandler usbnet mii pcspkr acpi_pad wmi dcdbas joydev acpi_power_meter lpc_ich mei_me mei nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c mgag200 drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops sd_mod igb ttm ahci ptp libahci drm libata pps_core crc32c_intel dca megaraid_sas i2c_algo_bit i2c_core [last unloaded: scsi_debug] > [17087.955757] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W 4.14.0-rc3 #1 > [17087.964110] Hardware name: Dell Inc. PowerEdge R620/01W23F, BIOS 2.5.4 01/22/2016 > [17087.972460] Call Trace: > [17087.975189] > [17087.977441] dump_stack+0x63/0x89 > [17087.981143] __schedule_bug+0x62/0x70 > [17087.985232] __schedule+0x7bb/0x890 > [17087.989125] schedule+0x36/0x80 > [17087.992629] io_schedule+0x16/0x40 > [17087.996429] __lock_page+0x10a/0x150 > [17088.000420] ? page_cache_tree_insert+0xb0/0xb0 > [17088.005470] invalidate_inode_pages2_range+0x240/0x500 > [17088.011208] ? kmem_cache_free+0x1ad/0x1c0 > [17088.015778] ? mempool_free_slab+0x17/0x20 > [17088.020347] ? mempool_free+0x2b/0x80 > [17088.024438] dio_complete+0x14f/0x1d0 > [17088.028526] dio_bio_end_aio+0xcb/0x120 > [17088.032800] bio_endio+0xa1/0x120 > [17088.036501] blk_update_request+0xb7/0x310 > [17088.041076] scsi_end_request+0x34/0x200 > [17088.045454] scsi_io_completion+0x133/0x5f0 > [17088.050123] scsi_finish_command+0xd9/0x120 > [17088.054782] scsi_softirq_done+0x145/0x170 > [17088.059355] blk_done_softirq+0xa1/0xd0 > [17088.063627] __do_softirq+0xc9/0x269 > [17088.067619] irq_exit+0xd9/0xf0 > [17088.071123] do_IRQ+0x51/0xd0 > [17088.074434] common_interrupt+0x9d/0x9d > [17088.078713] -- Jan Kara SUSE Labs, CR