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Tue, 10 Sep 2019 15:18:16 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com X-SMAIL-MID: 54868954920922 From: Hillf Danton To: syzbot Cc: hughd@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, Peter Zijlstra , Omar Sandoval Subject: Re: possible deadlock in shmem_fallocate (3) Date: Tue, 10 Sep 2019 15:18:04 +0800 Message-Id: <20190910071804.2944-1-hdanton@sina.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > syzbot found the following crash on Mon, 09 Sep 2019 20:38:05 -0700 >=20 > HEAD commit: 6d028043 Add linux-next specific files for 20190830 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=3D12359ec6600= 000 > kernel config: https://syzkaller.appspot.com/x/.config?x=3D82a6bec43ab= 0cb69 > dashboard link: https://syzkaller.appspot.com/bug?extid=3D5d04068d02b9d= a8a0947 > compiler: gcc (GCC) 9.0.0 20181231 (experimental) >=20 > Unfortunately, I don't have any reproducer for this crash yet. >=20 > IMPORTANT: if you fix the bug, please add the following tag to the comm= it: > Reported-by: syzbot+5d04068d02b9da8a0947@syzkaller.appspotmail.com >=20 > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D > WARNING: possible circular locking dependency detected > 5.3.0-rc6-next-20190830 #75 Not tainted > ------------------------------------------------------ > kswapd0/1770 is trying to acquire lock: > ffff8880a0b9b780 (&sb->s_type->i_mutex_key#13){+.+.}, at: inode_lock =20 > include/linux/fs.h:789 [inline] > ffff8880a0b9b780 (&sb->s_type->i_mutex_key#13){+.+.}, at: =20 > shmem_fallocate+0x15a/0xc60 mm/shmem.c:2728 >=20 > but task is already holding lock: > ffffffff89042f80 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 = =20 > mm/page_alloc.c:4889 >=20 > which lock already depends on the new lock. >=20 >=20 > the existing dependency chain (in reverse order) is: >=20 > -> #1 (fs_reclaim){+.+.}: > __fs_reclaim_acquire mm/page_alloc.c:4075 [inline] > fs_reclaim_acquire.part.0+0x24/0x30 mm/page_alloc.c:4086 > fs_reclaim_acquire mm/page_alloc.c:4662 [inline] > prepare_alloc_pages mm/page_alloc.c:4659 [inline] > __alloc_pages_nodemask+0x52f/0x900 mm/page_alloc.c:4711 > alloc_pages_vma+0x1bc/0x3f0 mm/mempolicy.c:2114 > shmem_alloc_page+0xbd/0x180 mm/shmem.c:1496 > shmem_alloc_and_acct_page+0x165/0x990 mm/shmem.c:1521 > shmem_getpage_gfp+0x598/0x2680 mm/shmem.c:1835 > shmem_getpage mm/shmem.c:152 [inline] > shmem_write_begin+0x105/0x1e0 mm/shmem.c:2480 > generic_perform_write+0x23b/0x540 mm/filemap.c:3304 > __generic_file_write_iter+0x25e/0x630 mm/filemap.c:3433 > generic_file_write_iter+0x420/0x690 mm/filemap.c:3465 > call_write_iter include/linux/fs.h:1890 [inline] > new_sync_write+0x4d3/0x770 fs/read_write.c:483 > __vfs_write+0xe1/0x110 fs/read_write.c:496 > vfs_write+0x268/0x5d0 fs/read_write.c:558 > ksys_write+0x14f/0x290 fs/read_write.c:611 > __do_sys_write fs/read_write.c:623 [inline] > __se_sys_write fs/read_write.c:620 [inline] > __x64_sys_write+0x73/0xb0 fs/read_write.c:620 > do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe >=20 > -> #0 (&sb->s_type->i_mutex_key#13){+.+.}: > check_prev_add kernel/locking/lockdep.c:2476 [inline] > check_prevs_add kernel/locking/lockdep.c:2581 [inline] > validate_chain kernel/locking/lockdep.c:2971 [inline] > __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955 > lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4487 > down_write+0x93/0x150 kernel/locking/rwsem.c:1534 > inode_lock include/linux/fs.h:789 [inline] > shmem_fallocate+0x15a/0xc60 mm/shmem.c:2728 > ashmem_shrink_scan drivers/staging/android/ashmem.c:462 [inline= ] > ashmem_shrink_scan+0x370/0x510 drivers/staging/android/ashmem.c= :437 > do_shrink_slab+0x40f/0xa30 mm/vmscan.c:560 > shrink_slab mm/vmscan.c:721 [inline] > shrink_slab+0x19a/0x680 mm/vmscan.c:694 > shrink_node+0x223/0x12e0 mm/vmscan.c:2807 > kswapd_shrink_node mm/vmscan.c:3549 [inline] > balance_pgdat+0x57c/0xea0 mm/vmscan.c:3707 > kswapd+0x5c3/0xf30 mm/vmscan.c:3958 > kthread+0x361/0x430 kernel/kthread.c:255 > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 >=20 > other info that might help us debug this: >=20 > Possible unsafe locking scenario: >=20 > CPU0 CPU1 > ---- ---- > lock(fs_reclaim); > lock(&sb->s_type->i_mutex_key#13); > lock(fs_reclaim); > lock(&sb->s_type->i_mutex_key#13); >=20 > *** DEADLOCK *** >=20 > 2 locks held by kswapd0/1770: > #0: ffffffff89042f80 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0= /0x30 =20 > mm/page_alloc.c:4889 > #1: ffffffff8901ffe8 (shrinker_rwsem){++++}, at: shrink_slab =20 > mm/vmscan.c:711 [inline] > #1: ffffffff8901ffe8 (shrinker_rwsem){++++}, at: shrink_slab+0xe6/0x6= 80 =20 > mm/vmscan.c:694 >=20 > stack backtrace: > CPU: 0 PID: 1770 Comm: kswapd0 Not tainted 5.3.0-rc6-next-20190830 #75 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS= =20 > Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x172/0x1f0 lib/dump_stack.c:113 > print_circular_bug.isra.0.cold+0x163/0x172 kernel/locking/lockdep.c:1= 685 > check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1809 > check_prev_add kernel/locking/lockdep.c:2476 [inline] > check_prevs_add kernel/locking/lockdep.c:2581 [inline] > validate_chain kernel/locking/lockdep.c:2971 [inline] > __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955 > lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4487 > down_write+0x93/0x150 kernel/locking/rwsem.c:1534 > inode_lock include/linux/fs.h:789 [inline] > shmem_fallocate+0x15a/0xc60 mm/shmem.c:2728 > ashmem_shrink_scan drivers/staging/android/ashmem.c:462 [inline] > ashmem_shrink_scan+0x370/0x510 drivers/staging/android/ashmem.c:437 > do_shrink_slab+0x40f/0xa30 mm/vmscan.c:560 > shrink_slab mm/vmscan.c:721 [inline] > shrink_slab+0x19a/0x680 mm/vmscan.c:694 > shrink_node+0x223/0x12e0 mm/vmscan.c:2807 > kswapd_shrink_node mm/vmscan.c:3549 [inline] > balance_pgdat+0x57c/0xea0 mm/vmscan.c:3707 > kswapd+0x5c3/0xf30 mm/vmscan.c:3958 > kthread+0x361/0x430 kernel/kthread.c:255 > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 It burns more than pure cpu cycles to check anything against kswapd in terms of __GFP_FS, so fix 93781325da6e and d92a8cfcb37e. --- works/jj/vmscan.c 2019-09-10 14:52:00.602771300 +0800 +++ works/zz/vmscan.c 2019-09-10 14:54:48.101915500 +0800 @@ -3593,7 +3593,6 @@ static int balance_pgdat(pg_data_t *pgda =20 set_task_reclaim_state(current, &sc.reclaim_state); psi_memstall_enter(&pflags); - __fs_reclaim_acquire(); =20 count_vm_event(PAGEOUTRUN); =20 @@ -3718,9 +3717,7 @@ restart: wake_up_all(&pgdat->pfmemalloc_wait); =20 /* Check if kswapd should be suspending */ - __fs_reclaim_release(); ret =3D try_to_freeze(); - __fs_reclaim_acquire(); if (ret || kthread_should_stop()) break; =20 @@ -3770,7 +3767,6 @@ out: } =20 snapshot_refaults(NULL, pgdat); - __fs_reclaim_release(); psi_memstall_leave(&pflags); set_task_reclaim_state(current, NULL); =20 --