* [syzbot] divide error in wb_update_dirty_ratelimit
@ 2021-08-02 18:24 syzbot
2021-08-02 20:31 ` Andrew Morton
0 siblings, 1 reply; 4+ messages in thread
From: syzbot @ 2021-08-02 18:24 UTC (permalink / raw)
To: akpm, linux-kernel, linux-mm, syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: 8d4b477da1a8 Add linux-next specific files for 20210730
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=128ede56300000
kernel config: https://syzkaller.appspot.com/x/.config?x=4adf4987f875c210
dashboard link: https://syzkaller.appspot.com/bug?extid=6a04d6ba849df9d81239
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
Unfortunately, I don't have any reproducer for this issue yet.
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6a04d6ba849df9d81239@syzkaller.appspotmail.com
divide error: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 10430 Comm: syz-executor.3 Not tainted 5.14.0-rc3-next-20210730-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:wb_update_dirty_ratelimit+0x18d/0x7d0 mm/page-writeback.c:1197
Code: 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 af 05 00 00 4c 2b b5 30 02 00 00 49 8d 7f 58 31 d2 49 6b c6 64 <48> f7 f3 48 89 fa 48 89 04 24 48 b8 00 00 00 00 00 fc ff df 48 c1
RSP: 0018:ffffc9000551f750 EFLAGS: 00010206
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000fdb1000
RDX: 0000000000000000 RSI: 0000000000006377 RDI: ffffc9000551f9a0
RBP: ffff888089632060 R08: 0000000000000000 R09: ffffffff9023d363
R10: fffffbfff2047a6c R11: 0000000000000000 R12: 0000000000006400
R13: 000000000003c2b1 R14: 0000000000000000 R15: ffffc9000551f948
FS: 00007fdc4e708700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000206000bf CR3: 0000000073f41000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__wb_update_bandwidth+0x3d7/0x5a0 mm/page-writeback.c:1350
balance_dirty_pages+0x12ab/0x29d0 mm/page-writeback.c:1719
balance_dirty_pages_ratelimited+0xda2/0x1820 mm/page-writeback.c:1920
generic_perform_write+0x320/0x510 mm/filemap.c:3789
__generic_file_write_iter+0x24e/0x610 mm/filemap.c:3882
generic_file_write_iter+0xd7/0x220 mm/filemap.c:3914
fuse_cache_write_iter fs/fuse/file.c:1298 [inline]
fuse_file_write_iter+0x56c/0xcd0 fs/fuse/file.c:1601
call_write_iter include/linux/fs.h:2152 [inline]
new_sync_write+0x426/0x650 fs/read_write.c:518
vfs_write+0x75a/0xa40 fs/read_write.c:605
ksys_write+0x12d/0x250 fs/read_write.c:658
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665e9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdc4e708188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665e9
RDX: 00000000fffffdef RSI: 00000000200000c0 RDI: 0000000000000006
RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
R13: 00007fff2d6f27cf R14: 00007fdc4e708300 R15: 0000000000022000
Modules linked in:
---[ end trace 01891e5696647ce8 ]---
RIP: 0010:wb_update_dirty_ratelimit+0x18d/0x7d0 mm/page-writeback.c:1197
Code: 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 af 05 00 00 4c 2b b5 30 02 00 00 49 8d 7f 58 31 d2 49 6b c6 64 <48> f7 f3 48 89 fa 48 89 04 24 48 b8 00 00 00 00 00 fc ff df 48 c1
RSP: 0018:ffffc9000551f750 EFLAGS: 00010206
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000fdb1000
RDX: 0000000000000000 RSI: 0000000000006377 RDI: ffffc9000551f9a0
RBP: ffff888089632060 R08: 0000000000000000 R09: ffffffff9023d363
R10: fffffbfff2047a6c R11: 0000000000000000 R12: 0000000000006400
R13: 000000000003c2b1 R14: 0000000000000000 R15: ffffc9000551f948
FS: 00007fdc4e708700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000206000bf CR3: 0000000073f41000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [syzbot] divide error in wb_update_dirty_ratelimit
2021-08-02 18:24 [syzbot] divide error in wb_update_dirty_ratelimit syzbot
@ 2021-08-02 20:31 ` Andrew Morton
2021-08-03 10:58 ` Jan Kara
0 siblings, 1 reply; 4+ messages in thread
From: Andrew Morton @ 2021-08-02 20:31 UTC (permalink / raw)
To: syzbot; +Cc: linux-kernel, linux-mm, syzkaller-bugs, Jan Kara
On Mon, 02 Aug 2021 11:24:20 -0700 syzbot <syzbot+6a04d6ba849df9d81239@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 8d4b477da1a8 Add linux-next specific files for 20210730
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=128ede56300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=4adf4987f875c210
> dashboard link: https://syzkaller.appspot.com/bug?extid=6a04d6ba849df9d81239
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+6a04d6ba849df9d81239@syzkaller.appspotmail.com
>
> divide error: 0000 [#1] PREEMPT SMP KASAN
> CPU: 0 PID: 10430 Comm: syz-executor.3 Not tainted 5.14.0-rc3-next-20210730-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:wb_update_dirty_ratelimit+0x18d/0x7d0 mm/page-writeback.c:1197
Thanks.
Presumably wb_update_dirty_ratelimit() was passed elapsed==0. Jan,
could your changes have caused this?
> Code: 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 af 05 00 00 4c 2b b5 30 02 00 00 49 8d 7f 58 31 d2 49 6b c6 64 <48> f7 f3 48 89 fa 48 89 04 24 48 b8 00 00 00 00 00 fc ff df 48 c1
> RSP: 0018:ffffc9000551f750 EFLAGS: 00010206
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000fdb1000
> RDX: 0000000000000000 RSI: 0000000000006377 RDI: ffffc9000551f9a0
> RBP: ffff888089632060 R08: 0000000000000000 R09: ffffffff9023d363
> R10: fffffbfff2047a6c R11: 0000000000000000 R12: 0000000000006400
> R13: 000000000003c2b1 R14: 0000000000000000 R15: ffffc9000551f948
> FS: 00007fdc4e708700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000206000bf CR3: 0000000073f41000 CR4: 00000000001506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> __wb_update_bandwidth+0x3d7/0x5a0 mm/page-writeback.c:1350
> balance_dirty_pages+0x12ab/0x29d0 mm/page-writeback.c:1719
> balance_dirty_pages_ratelimited+0xda2/0x1820 mm/page-writeback.c:1920
> generic_perform_write+0x320/0x510 mm/filemap.c:3789
> __generic_file_write_iter+0x24e/0x610 mm/filemap.c:3882
> generic_file_write_iter+0xd7/0x220 mm/filemap.c:3914
> fuse_cache_write_iter fs/fuse/file.c:1298 [inline]
> fuse_file_write_iter+0x56c/0xcd0 fs/fuse/file.c:1601
> call_write_iter include/linux/fs.h:2152 [inline]
> new_sync_write+0x426/0x650 fs/read_write.c:518
> vfs_write+0x75a/0xa40 fs/read_write.c:605
> ksys_write+0x12d/0x250 fs/read_write.c:658
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x4665e9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fdc4e708188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665e9
> RDX: 00000000fffffdef RSI: 00000000200000c0 RDI: 0000000000000006
> RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
> R13: 00007fff2d6f27cf R14: 00007fdc4e708300 R15: 0000000000022000
> Modules linked in:
> ---[ end trace 01891e5696647ce8 ]---
> RIP: 0010:wb_update_dirty_ratelimit+0x18d/0x7d0 mm/page-writeback.c:1197
> Code: 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 af 05 00 00 4c 2b b5 30 02 00 00 49 8d 7f 58 31 d2 49 6b c6 64 <48> f7 f3 48 89 fa 48 89 04 24 48 b8 00 00 00 00 00 fc ff df 48 c1
> RSP: 0018:ffffc9000551f750 EFLAGS: 00010206
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000fdb1000
> RDX: 0000000000000000 RSI: 0000000000006377 RDI: ffffc9000551f9a0
> RBP: ffff888089632060 R08: 0000000000000000 R09: ffffffff9023d363
> R10: fffffbfff2047a6c R11: 0000000000000000 R12: 0000000000006400
> R13: 000000000003c2b1 R14: 0000000000000000 R15: ffffc9000551f948
> FS: 00007fdc4e708700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000206000bf CR3: 0000000073f41000 CR4: 00000000001506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [syzbot] divide error in wb_update_dirty_ratelimit
2021-08-02 20:31 ` Andrew Morton
@ 2021-08-03 10:58 ` Jan Kara
2021-08-03 12:32 ` Jan Kara
0 siblings, 1 reply; 4+ messages in thread
From: Jan Kara @ 2021-08-03 10:58 UTC (permalink / raw)
To: Andrew Morton; +Cc: syzbot, linux-kernel, linux-mm, syzkaller-bugs, Jan Kara
On Mon 02-08-21 13:31:06, Andrew Morton wrote:
> On Mon, 02 Aug 2021 11:24:20 -0700 syzbot <syzbot+6a04d6ba849df9d81239@syzkaller.appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: 8d4b477da1a8 Add linux-next specific files for 20210730
> > git tree: linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=128ede56300000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=4adf4987f875c210
> > dashboard link: https://syzkaller.appspot.com/bug?extid=6a04d6ba849df9d81239
> > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+6a04d6ba849df9d81239@syzkaller.appspotmail.com
> >
> > divide error: 0000 [#1] PREEMPT SMP KASAN
> > CPU: 0 PID: 10430 Comm: syz-executor.3 Not tainted 5.14.0-rc3-next-20210730-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > RIP: 0010:wb_update_dirty_ratelimit+0x18d/0x7d0 mm/page-writeback.c:1197
>
> Thanks.
>
> Presumably wb_update_dirty_ratelimit() was passed elapsed==0. Jan,
> could your changes have caused this?
Right, they could have if wb_update_bandwidth_workfn() got called in the
same jiffie as some other update. Thanks for letting me know. I'll send a
fix.
Honza
> > Code: 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 af 05 00 00 4c 2b b5 30 02 00 00 49 8d 7f 58 31 d2 49 6b c6 64 <48> f7 f3 48 89 fa 48 89 04 24 48 b8 00 00 00 00 00 fc ff df 48 c1
> > RSP: 0018:ffffc9000551f750 EFLAGS: 00010206
> > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000fdb1000
> > RDX: 0000000000000000 RSI: 0000000000006377 RDI: ffffc9000551f9a0
> > RBP: ffff888089632060 R08: 0000000000000000 R09: ffffffff9023d363
> > R10: fffffbfff2047a6c R11: 0000000000000000 R12: 0000000000006400
> > R13: 000000000003c2b1 R14: 0000000000000000 R15: ffffc9000551f948
> > FS: 00007fdc4e708700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00000000206000bf CR3: 0000000073f41000 CR4: 00000000001506f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> > __wb_update_bandwidth+0x3d7/0x5a0 mm/page-writeback.c:1350
> > balance_dirty_pages+0x12ab/0x29d0 mm/page-writeback.c:1719
> > balance_dirty_pages_ratelimited+0xda2/0x1820 mm/page-writeback.c:1920
> > generic_perform_write+0x320/0x510 mm/filemap.c:3789
> > __generic_file_write_iter+0x24e/0x610 mm/filemap.c:3882
> > generic_file_write_iter+0xd7/0x220 mm/filemap.c:3914
> > fuse_cache_write_iter fs/fuse/file.c:1298 [inline]
> > fuse_file_write_iter+0x56c/0xcd0 fs/fuse/file.c:1601
> > call_write_iter include/linux/fs.h:2152 [inline]
> > new_sync_write+0x426/0x650 fs/read_write.c:518
> > vfs_write+0x75a/0xa40 fs/read_write.c:605
> > ksys_write+0x12d/0x250 fs/read_write.c:658
> > do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> > entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x4665e9
> > Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> > RSP: 002b:00007fdc4e708188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> > RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665e9
> > RDX: 00000000fffffdef RSI: 00000000200000c0 RDI: 0000000000000006
> > RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
> > R13: 00007fff2d6f27cf R14: 00007fdc4e708300 R15: 0000000000022000
> > Modules linked in:
> > ---[ end trace 01891e5696647ce8 ]---
> > RIP: 0010:wb_update_dirty_ratelimit+0x18d/0x7d0 mm/page-writeback.c:1197
> > Code: 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 af 05 00 00 4c 2b b5 30 02 00 00 49 8d 7f 58 31 d2 49 6b c6 64 <48> f7 f3 48 89 fa 48 89 04 24 48 b8 00 00 00 00 00 fc ff df 48 c1
> > RSP: 0018:ffffc9000551f750 EFLAGS: 00010206
> > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000fdb1000
> > RDX: 0000000000000000 RSI: 0000000000006377 RDI: ffffc9000551f9a0
> > RBP: ffff888089632060 R08: 0000000000000000 R09: ffffffff9023d363
> > R10: fffffbfff2047a6c R11: 0000000000000000 R12: 0000000000006400
> > R13: 000000000003c2b1 R14: 0000000000000000 R15: ffffc9000551f948
> > FS: 00007fdc4e708700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00000000206000bf CR3: 0000000073f41000 CR4: 00000000001506f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [syzbot] divide error in wb_update_dirty_ratelimit
2021-08-03 10:58 ` Jan Kara
@ 2021-08-03 12:32 ` Jan Kara
0 siblings, 0 replies; 4+ messages in thread
From: Jan Kara @ 2021-08-03 12:32 UTC (permalink / raw)
To: Andrew Morton; +Cc: syzbot, linux-kernel, linux-mm, syzkaller-bugs, Jan Kara
[-- Attachment #1: Type: text/plain, Size: 5504 bytes --]
On Tue 03-08-21 12:58:12, Jan Kara wrote:
> On Mon 02-08-21 13:31:06, Andrew Morton wrote:
> > On Mon, 02 Aug 2021 11:24:20 -0700 syzbot <syzbot+6a04d6ba849df9d81239@syzkaller.appspotmail.com> wrote:
> >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit: 8d4b477da1a8 Add linux-next specific files for 20210730
> > > git tree: linux-next
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=128ede56300000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=4adf4987f875c210
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=6a04d6ba849df9d81239
> > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+6a04d6ba849df9d81239@syzkaller.appspotmail.com
> > >
> > > divide error: 0000 [#1] PREEMPT SMP KASAN
> > > CPU: 0 PID: 10430 Comm: syz-executor.3 Not tainted 5.14.0-rc3-next-20210730-syzkaller #0
> > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > > RIP: 0010:wb_update_dirty_ratelimit+0x18d/0x7d0 mm/page-writeback.c:1197
> >
> > Thanks.
> >
> > Presumably wb_update_dirty_ratelimit() was passed elapsed==0. Jan,
> > could your changes have caused this?
>
> Right, they could have if wb_update_bandwidth_workfn() got called in the
> same jiffie as some other update. Thanks for letting me know. I'll send a
> fix.
Attached patch should fix the problem. Can you add this as a fixup for
"writeback: Fix bandwidth estimate for spiky workload" please? Thanks!
Honza
> > > Code: 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 af 05 00 00 4c 2b b5 30 02 00 00 49 8d 7f 58 31 d2 49 6b c6 64 <48> f7 f3 48 89 fa 48 89 04 24 48 b8 00 00 00 00 00 fc ff df 48 c1
> > > RSP: 0018:ffffc9000551f750 EFLAGS: 00010206
> > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000fdb1000
> > > RDX: 0000000000000000 RSI: 0000000000006377 RDI: ffffc9000551f9a0
> > > RBP: ffff888089632060 R08: 0000000000000000 R09: ffffffff9023d363
> > > R10: fffffbfff2047a6c R11: 0000000000000000 R12: 0000000000006400
> > > R13: 000000000003c2b1 R14: 0000000000000000 R15: ffffc9000551f948
> > > FS: 00007fdc4e708700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: 00000000206000bf CR3: 0000000073f41000 CR4: 00000000001506f0
> > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > Call Trace:
> > > __wb_update_bandwidth+0x3d7/0x5a0 mm/page-writeback.c:1350
> > > balance_dirty_pages+0x12ab/0x29d0 mm/page-writeback.c:1719
> > > balance_dirty_pages_ratelimited+0xda2/0x1820 mm/page-writeback.c:1920
> > > generic_perform_write+0x320/0x510 mm/filemap.c:3789
> > > __generic_file_write_iter+0x24e/0x610 mm/filemap.c:3882
> > > generic_file_write_iter+0xd7/0x220 mm/filemap.c:3914
> > > fuse_cache_write_iter fs/fuse/file.c:1298 [inline]
> > > fuse_file_write_iter+0x56c/0xcd0 fs/fuse/file.c:1601
> > > call_write_iter include/linux/fs.h:2152 [inline]
> > > new_sync_write+0x426/0x650 fs/read_write.c:518
> > > vfs_write+0x75a/0xa40 fs/read_write.c:605
> > > ksys_write+0x12d/0x250 fs/read_write.c:658
> > > do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> > > entry_SYSCALL_64_after_hwframe+0x44/0xae
> > > RIP: 0033:0x4665e9
> > > Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> > > RSP: 002b:00007fdc4e708188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> > > RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665e9
> > > RDX: 00000000fffffdef RSI: 00000000200000c0 RDI: 0000000000000006
> > > RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000
> > > R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
> > > R13: 00007fff2d6f27cf R14: 00007fdc4e708300 R15: 0000000000022000
> > > Modules linked in:
> > > ---[ end trace 01891e5696647ce8 ]---
> > > RIP: 0010:wb_update_dirty_ratelimit+0x18d/0x7d0 mm/page-writeback.c:1197
> > > Code: 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 af 05 00 00 4c 2b b5 30 02 00 00 49 8d 7f 58 31 d2 49 6b c6 64 <48> f7 f3 48 89 fa 48 89 04 24 48 b8 00 00 00 00 00 fc ff df 48 c1
> > > RSP: 0018:ffffc9000551f750 EFLAGS: 00010206
> > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000fdb1000
> > > RDX: 0000000000000000 RSI: 0000000000006377 RDI: ffffc9000551f9a0
> > > RBP: ffff888089632060 R08: 0000000000000000 R09: ffffffff9023d363
> > > R10: fffffbfff2047a6c R11: 0000000000000000 R12: 0000000000006400
> > > R13: 000000000003c2b1 R14: 0000000000000000 R15: ffffc9000551f948
> > > FS: 00007fdc4e708700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: 00000000206000bf CR3: 0000000073f41000 CR4: 00000000001506f0
> > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >
> --
> Jan Kara <jack@suse.com>
> SUSE Labs, CR
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
[-- Attachment #2: 0001-writeback-Avoid-division-by-0-in-wb_update_dirty_rat.patch --]
[-- Type: text/x-patch, Size: 1263 bytes --]
From 9c16cd6b3353e39c0d596a7baf9f9067aa1a05b5 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Tue, 3 Aug 2021 14:24:32 +0200
Subject: [PATCH] writeback: Avoid division by 0 in wb_update_dirty_ratelimit()
Fixup patch "writeback: Fix bandwidth estimate for spiky workload" which
introduced possibility of __wb_update_bandwidth() getting called at a
moment when 'elapsed' evaluates to 0.
Signed-off-by: Jan Kara <jack@suse.cz>
---
mm/page-writeback.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index d55a3a7411b3..b2fa9f20c764 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1342,7 +1342,13 @@ static void __wb_update_bandwidth(struct dirty_throttle_control *gdtc,
unsigned long written;
spin_lock(&wb->list_lock);
- elapsed = now - wb->bw_time_stamp;
+ /*
+ * Lockless checks for elapsed time are racy and delayed update after
+ * IO completion doesn't do it at all (to make sure written pages are
+ * accounted reasonably quickly). Make sure elapsed >= 1 to avoid
+ * division errors.
+ */
+ elapsed = max(now - wb->bw_time_stamp, 1UL);
dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED]);
written = wb_stat_sum(wb, WB_WRITTEN);
--
2.26.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-08-03 12:32 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-08-02 18:24 [syzbot] divide error in wb_update_dirty_ratelimit syzbot
2021-08-02 20:31 ` Andrew Morton
2021-08-03 10:58 ` Jan Kara
2021-08-03 12:32 ` Jan Kara
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