Message-ID: <20171005060700.GF8034@eguan.usersys.redhat.com>
Date:   Thu, 5 Oct 2017 14:07:00 +0800
From:   Eryu Guan <eguan@...hat.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-ext4@...r.kernel.org, lczerner@...hat.com
Subject: [v4.14-rc3 bug] scheduling while atomic in generic/451 test on extN

Hi all,

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,
Eryu

[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]  <IRQ> 
[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]  </IRQ> 

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