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From:   Yang Shi <shy828301@gmail.com>
Date:   Mon, 13 Apr 2020 15:10:22 -0700
Message-ID: <CAHbLzkpJjpOjizxhG6oS1OsbdycwaRdLeA8nb1R4Y2C4F7nV+g@mail.gmail.com>
Subject: Re: possible deadlock in shmem_uncharge
To:     syzbot <syzbot+c8a8197c8852f566b9d9@syzkaller.appspotmail.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>, syzkaller-bugs@googlegroups.com,
        Linus Torvalds <torvalds@linux-foundation.org>
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On Sun, Apr 12, 2020 at 3:11 AM syzbot
<syzbot+c8a8197c8852f566b9d9@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    ae46d2aa mm/gup: Let __get_user_pages_locked() return -EIN..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14a30a77e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ca75979eeebf06c2
> dashboard link: https://syzkaller.appspot.com/bug?extid=c8a8197c8852f566b9d9
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15f5632be00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132ade57e00000
>
> The bug was bisected to:
>
> commit 71725ed10c40696dc6bdccf8e225815dcef24dba
> Author: Hugh Dickins <hughd@google.com>
> Date:   Tue Apr 7 03:07:57 2020 +0000
>
>     mm: huge tmpfs: try to split_huge_page() when punching hole
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=120a752be00000
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=110a752be00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=160a752be00000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+c8a8197c8852f566b9d9@syzkaller.appspotmail.com
> Fixes: 71725ed10c40 ("mm: huge tmpfs: try to split_huge_page() when punching hole")
>
> =====================================================
> WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
> 5.6.0-syzkaller #0 Not tainted
> -----------------------------------------------------
> syz-executor428/8337 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
> ffff8880a851c778 (&info->lock){....}-{2:2}, at: shmem_uncharge+0x24/0x270 mm/shmem.c:341
>
> and this task is already holding:
> ffff8880a851cac8 (&xa->xa_lock#4){..-.}-{2:2}, at: spin_lock include/linux/spinlock.h:353 [inline]
> ffff8880a851cac8 (&xa->xa_lock#4){..-.}-{2:2}, at: split_huge_page_to_list+0xad0/0x33b0 mm/huge_memory.c:2864
> which would create a new lock dependency:
>  (&xa->xa_lock#4){..-.}-{2:2} -> (&info->lock){....}-{2:2}
>
> but this new dependency connects a SOFTIRQ-irq-safe lock:
>  (&xa->xa_lock#4){..-.}-{2:2}

It looks shmem_uncharge() is just called by __split_huge_page() and
collapse_file(). The collapse_file() has acquired xa_lock with irq
disabled before acquiring info->lock, so it is safe.
__split_huge_page() is called with holding xa_lock with irq enabled,
but lru_lock is acquired with irq disabled before acquiring xa_lock.

So, it is unnecessary to acquire info->lock with irq disabled in
shmem_uncharge(). Can syzbot try the below patch?

diff --git a/mm/shmem.c b/mm/shmem.c
index d722eb8..100117b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -334,15 +334,14 @@ bool shmem_charge(struct inode *inode, long pages)
 void shmem_uncharge(struct inode *inode, long pages)
 {
        struct shmem_inode_info *info = SHMEM_I(inode);
-       unsigned long flags;

        /* nrpages adjustment done by __delete_from_page_cache() or caller */

-       spin_lock_irqsave(&info->lock, flags);
+       spin_lock(&info->lock);
        info->alloced -= pages;
        inode->i_blocks -= pages * BLOCKS_PER_PAGE;
        shmem_recalc_inode(inode);
-       spin_unlock_irqrestore(&info->lock, flags);
+       spin_unlock(&info->lock);

        shmem_inode_unacct_blocks(inode, pages);
 }


>
> ... which became SOFTIRQ-irq-safe at:
>   lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>   __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>   _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
>   test_clear_page_writeback+0x1d7/0x11e0 mm/page-writeback.c:2728
>   end_page_writeback+0x239/0x520 mm/filemap.c:1317
>   end_buffer_async_write+0x442/0x5c0 fs/buffer.c:384
>   end_bio_bh_io_sync+0xe2/0x140 fs/buffer.c:3012
>   bio_endio+0x473/0x820 block/bio.c:1422
>   req_bio_endio block/blk-core.c:245 [inline]
>   blk_update_request+0x3e1/0xdc0 block/blk-core.c:1472
>   scsi_end_request+0x80/0x7b0 drivers/scsi/scsi_lib.c:575
>   scsi_io_completion+0x1e7/0x1300 drivers/scsi/scsi_lib.c:959
>   scsi_softirq_done+0x31e/0x3b0 drivers/scsi/scsi_lib.c:1454
>   blk_done_softirq+0x2db/0x440 block/blk-softirq.c:37
>   __do_softirq+0x26c/0x9f7 kernel/softirq.c:292
>   invoke_softirq kernel/softirq.c:373 [inline]
>   irq_exit+0x192/0x1d0 kernel/softirq.c:413
>   exiting_irq arch/x86/include/asm/apic.h:546 [inline]
>   do_IRQ+0xda/0x270 arch/x86/kernel/irq.c:263
>   ret_from_intr+0x0/0x2b
>   arch_local_irq_restore arch/x86/include/asm/paravirt.h:759 [inline]
>   lock_acquire+0x267/0x8f0 kernel/locking/lockdep.c:4926
>   down_write+0x8d/0x150 kernel/locking/rwsem.c:1531
>   inode_lock include/linux/fs.h:797 [inline]
>   process_measurement+0x68a/0x1750 security/integrity/ima/ima_main.c:228
>   ima_file_check+0xb9/0x100 security/integrity/ima/ima_main.c:440
>   do_open fs/namei.c:3231 [inline]
>   path_openat+0x1997/0x27d0 fs/namei.c:3346
>   do_filp_open+0x192/0x260 fs/namei.c:3373
>   do_sys_openat2+0x585/0x7d0 fs/open.c:1148
>   do_sys_open+0xc3/0x140 fs/open.c:1164
>   do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>   entry_SYSCALL_64_after_hwframe+0x49/0xb3
>
> to a SOFTIRQ-irq-unsafe lock:
>  (shmlock_user_lock){+.+.}-{2:2}
>
> ... which became SOFTIRQ-irq-unsafe at:
> ...
>   lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>   __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>   _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>   spin_lock include/linux/spinlock.h:353 [inline]
>   user_shm_lock+0xab/0x230 mm/mlock.c:855
>   hugetlb_file_setup+0x4e1/0x677 fs/hugetlbfs/inode.c:1416
>   newseg+0x460/0xe60 ipc/shm.c:652
>   ipcget_new ipc/util.c:344 [inline]
>   ipcget+0xf0/0xcb0 ipc/util.c:643
>   ksys_shmget ipc/shm.c:742 [inline]
>   __do_sys_shmget ipc/shm.c:747 [inline]
>   __se_sys_shmget ipc/shm.c:745 [inline]
>   __x64_sys_shmget+0x139/0x1a0 ipc/shm.c:745
>   do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>   entry_SYSCALL_64_after_hwframe+0x49/0xb3
>
> other info that might help us debug this:
>
> Chain exists of:
>   &xa->xa_lock#4 --> &info->lock --> shmlock_user_lock
>
>  Possible interrupt unsafe locking scenario:
>
>        CPU0                    CPU1
>        ----                    ----
>   lock(shmlock_user_lock);
>                                local_irq_disable();
>                                lock(&xa->xa_lock#4);
>                                lock(&info->lock);
>   <Interrupt>
>     lock(&xa->xa_lock#4);
>
>  *** DEADLOCK ***
>
> 5 locks held by syz-executor428/8337:
>  #0: ffff8880a7948450 (sb_writers#7){.+.+}-{0:0}, at: sb_start_write include/linux/fs.h:1655 [inline]
>  #0: ffff8880a7948450 (sb_writers#7){.+.+}-{0:0}, at: do_sys_ftruncate+0x29f/0x570 fs/open.c:190
>  #1: ffff8880a851c9d0 (&sb->s_type->i_mutex_key#16){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:797 [inline]
>  #1: ffff8880a851c9d0 (&sb->s_type->i_mutex_key#16){+.+.}-{3:3}, at: do_truncate+0x125/0x1f0 fs/open.c:62
>  #2: ffff8880a851cb90 (&mapping->i_mmap_rwsem){++++}-{3:3}, at: i_mmap_lock_read include/linux/fs.h:541 [inline]
>  #2: ffff8880a851cb90 (&mapping->i_mmap_rwsem){++++}-{3:3}, at: split_huge_page_to_list+0x4c3/0x33b0 mm/huge_memory.c:2825
>  #3: ffff88812ffffcd8 (&pgdat->lru_lock){....}-{2:2}, at: split_huge_page_to_list+0x8da/0x33b0 mm/huge_memory.c:2855
>  #4: ffff8880a851cac8 (&xa->xa_lock#4){..-.}-{2:2}, at: spin_lock include/linux/spinlock.h:353 [inline]
>  #4: ffff8880a851cac8 (&xa->xa_lock#4){..-.}-{2:2}, at: split_huge_page_to_list+0xad0/0x33b0 mm/huge_memory.c:2864
>
> the dependencies between SOFTIRQ-irq-safe lock and the holding lock:
> -> (&xa->xa_lock#4){..-.}-{2:2} {
>    IN-SOFTIRQ-W at:
>                     lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                     __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>                     _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
>                     test_clear_page_writeback+0x1d7/0x11e0 mm/page-writeback.c:2728
>                     end_page_writeback+0x239/0x520 mm/filemap.c:1317
>                     end_buffer_async_write+0x442/0x5c0 fs/buffer.c:384
>                     end_bio_bh_io_sync+0xe2/0x140 fs/buffer.c:3012
>                     bio_endio+0x473/0x820 block/bio.c:1422
>                     req_bio_endio block/blk-core.c:245 [inline]
>                     blk_update_request+0x3e1/0xdc0 block/blk-core.c:1472
>                     scsi_end_request+0x80/0x7b0 drivers/scsi/scsi_lib.c:575
>                     scsi_io_completion+0x1e7/0x1300 drivers/scsi/scsi_lib.c:959
>                     scsi_softirq_done+0x31e/0x3b0 drivers/scsi/scsi_lib.c:1454
>                     blk_done_softirq+0x2db/0x440 block/blk-softirq.c:37
>                     __do_softirq+0x26c/0x9f7 kernel/softirq.c:292
>                     invoke_softirq kernel/softirq.c:373 [inline]
>                     irq_exit+0x192/0x1d0 kernel/softirq.c:413
>                     exiting_irq arch/x86/include/asm/apic.h:546 [inline]
>                     do_IRQ+0xda/0x270 arch/x86/kernel/irq.c:263
>                     ret_from_intr+0x0/0x2b
>                     arch_local_irq_restore arch/x86/include/asm/paravirt.h:759 [inline]
>                     lock_acquire+0x267/0x8f0 kernel/locking/lockdep.c:4926
>                     down_write+0x8d/0x150 kernel/locking/rwsem.c:1531
>                     inode_lock include/linux/fs.h:797 [inline]
>                     process_measurement+0x68a/0x1750 security/integrity/ima/ima_main.c:228
>                     ima_file_check+0xb9/0x100 security/integrity/ima/ima_main.c:440
>                     do_open fs/namei.c:3231 [inline]
>                     path_openat+0x1997/0x27d0 fs/namei.c:3346
>                     do_filp_open+0x192/0x260 fs/namei.c:3373
>                     do_sys_openat2+0x585/0x7d0 fs/open.c:1148
>                     do_sys_open+0xc3/0x140 fs/open.c:1164
>                     do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>                     entry_SYSCALL_64_after_hwframe+0x49/0xb3
>    INITIAL USE at:
>                    lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                    __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
>                    _raw_spin_lock_irq+0x5b/0x80 kernel/locking/spinlock.c:167
>                    spin_lock_irq include/linux/spinlock.h:378 [inline]
>                    __add_to_page_cache_locked+0x607/0xe00 mm/filemap.c:855
>                    add_to_page_cache_lru+0x1aa/0x700 mm/filemap.c:921
>                    do_read_cache_page+0x9ab/0x1810 mm/filemap.c:2755
>                    read_mapping_page include/linux/pagemap.h:397 [inline]
>                    read_part_sector+0xf6/0x600 block/partitions/core.c:643
>                    adfspart_check_ICS+0x9d/0xc80 block/partitions/acorn.c:360
>                    check_partition block/partitions/core.c:140 [inline]
>                    blk_add_partitions+0x474/0xe50 block/partitions/core.c:571
>                    bdev_disk_changed+0x1fb/0x380 fs/block_dev.c:1544
>                    __blkdev_get+0xb15/0x1530 fs/block_dev.c:1647
>                    blkdev_get+0x41/0x2b0 fs/block_dev.c:1749
>                    register_disk block/genhd.c:763 [inline]
>                    __device_add_disk+0xa4f/0x1170 block/genhd.c:853
>                    add_disk include/linux/genhd.h:294 [inline]
>                    brd_init+0x297/0x463 drivers/block/brd.c:533
>                    do_one_initcall+0x10a/0x7d0 init/main.c:1158
>                    do_initcall_level init/main.c:1231 [inline]
>                    do_initcalls init/main.c:1247 [inline]
>                    do_basic_setup init/main.c:1267 [inline]
>                    kernel_init_freeable+0x501/0x5ae init/main.c:1451
>                    kernel_init+0xd/0x1bb init/main.c:1358
>                    ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
>  }
>  ... key      at: [<ffffffff8c67b1e0>] __key.18007+0x0/0x40
>  ... acquired at:
>    lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>    __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>    _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
>    shmem_uncharge+0x24/0x270 mm/shmem.c:341
>    __split_huge_page mm/huge_memory.c:2613 [inline]
>    split_huge_page_to_list+0x274b/0x33b0 mm/huge_memory.c:2886
>    split_huge_page include/linux/huge_mm.h:204 [inline]
>    shmem_punch_compound+0x13e/0x1e0 mm/shmem.c:814
>    shmem_undo_range+0x5f1/0x1b80 mm/shmem.c:870
>    shmem_truncate_range+0x27/0xa0 mm/shmem.c:980
>    shmem_setattr+0x8b6/0xc80 mm/shmem.c:1039
>    notify_change+0xb6d/0x1020 fs/attr.c:336
>    do_truncate+0x134/0x1f0 fs/open.c:64
>    do_sys_ftruncate+0x4a5/0x570 fs/open.c:195
>    do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>    entry_SYSCALL_64_after_hwframe+0x49/0xb3
>
>
> the dependencies between the lock to be acquired
>  and SOFTIRQ-irq-unsafe lock:
>  -> (shmlock_user_lock){+.+.}-{2:2} {
>     HARDIRQ-ON-W at:
>                       lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>                       _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>                       spin_lock include/linux/spinlock.h:353 [inline]
>                       user_shm_lock+0xab/0x230 mm/mlock.c:855
>                       hugetlb_file_setup+0x4e1/0x677 fs/hugetlbfs/inode.c:1416
>                       newseg+0x460/0xe60 ipc/shm.c:652
>                       ipcget_new ipc/util.c:344 [inline]
>                       ipcget+0xf0/0xcb0 ipc/util.c:643
>                       ksys_shmget ipc/shm.c:742 [inline]
>                       __do_sys_shmget ipc/shm.c:747 [inline]
>                       __se_sys_shmget ipc/shm.c:745 [inline]
>                       __x64_sys_shmget+0x139/0x1a0 ipc/shm.c:745
>                       do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>                       entry_SYSCALL_64_after_hwframe+0x49/0xb3
>     SOFTIRQ-ON-W at:
>                       lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>                       _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>                       spin_lock include/linux/spinlock.h:353 [inline]
>                       user_shm_lock+0xab/0x230 mm/mlock.c:855
>                       hugetlb_file_setup+0x4e1/0x677 fs/hugetlbfs/inode.c:1416
>                       newseg+0x460/0xe60 ipc/shm.c:652
>                       ipcget_new ipc/util.c:344 [inline]
>                       ipcget+0xf0/0xcb0 ipc/util.c:643
>                       ksys_shmget ipc/shm.c:742 [inline]
>                       __do_sys_shmget ipc/shm.c:747 [inline]
>                       __se_sys_shmget ipc/shm.c:745 [inline]
>                       __x64_sys_shmget+0x139/0x1a0 ipc/shm.c:745
>                       do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>                       entry_SYSCALL_64_after_hwframe+0x49/0xb3
>     INITIAL USE at:
>                      lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                      __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>                      _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>                      spin_lock include/linux/spinlock.h:353 [inline]
>                      user_shm_lock+0xab/0x230 mm/mlock.c:855
>                      shmem_lock+0x1dd/0x2d0 mm/shmem.c:2184
>                      shmctl_do_lock+0x73f/0x8f0 ipc/shm.c:1111
>                      ksys_shmctl.constprop.0+0x203/0x350 ipc/shm.c:1188
>                      do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>                      entry_SYSCALL_64_after_hwframe+0x49/0xb3
>   }
>   ... key      at: [<ffffffff89a5e858>] shmlock_user_lock+0x18/0x5c0
>   ... acquired at:
>    __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>    _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>    spin_lock include/linux/spinlock.h:353 [inline]
>    user_shm_lock+0xab/0x230 mm/mlock.c:855
>    shmem_lock+0x1dd/0x2d0 mm/shmem.c:2184
>    shmctl_do_lock+0x73f/0x8f0 ipc/shm.c:1111
>    ksys_shmctl.constprop.0+0x203/0x350 ipc/shm.c:1188
>    do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>    entry_SYSCALL_64_after_hwframe+0x49/0xb3
>
> -> (&info->lock){....}-{2:2} {
>    INITIAL USE at:
>                    lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>                    __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
>                    _raw_spin_lock_irq+0x5b/0x80 kernel/locking/spinlock.c:167
>                    spin_lock_irq include/linux/spinlock.h:378 [inline]
>                    shmem_getpage_gfp+0x937/0x2a10 mm/shmem.c:1882
>                    shmem_getpage mm/shmem.c:154 [inline]
>                    shmem_write_begin+0x102/0x1e0 mm/shmem.c:2483
>                    generic_perform_write+0x20a/0x4e0 mm/filemap.c:3302
>                    __generic_file_write_iter+0x24c/0x610 mm/filemap.c:3431
>                    generic_file_write_iter+0x3f3/0x630 mm/filemap.c:3463
>                    call_write_iter include/linux/fs.h:1907 [inline]
>                    new_sync_write+0x4a2/0x700 fs/read_write.c:483
>                    __vfs_write+0xc9/0x100 fs/read_write.c:496
>                    vfs_write+0x268/0x5d0 fs/read_write.c:558
>                    ksys_write+0x12d/0x250 fs/read_write.c:611
>                    do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>                    entry_SYSCALL_64_after_hwframe+0x49/0xb3
>  }
>  ... key      at: [<ffffffff8c667e80>] __key.56422+0x0/0x40
>  ... acquired at:
>    lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>    __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>    _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
>    shmem_uncharge+0x24/0x270 mm/shmem.c:341
>    __split_huge_page mm/huge_memory.c:2613 [inline]
>    split_huge_page_to_list+0x274b/0x33b0 mm/huge_memory.c:2886
>    split_huge_page include/linux/huge_mm.h:204 [inline]
>    shmem_punch_compound+0x13e/0x1e0 mm/shmem.c:814
>    shmem_undo_range+0x5f1/0x1b80 mm/shmem.c:870
>    shmem_truncate_range+0x27/0xa0 mm/shmem.c:980
>    shmem_setattr+0x8b6/0xc80 mm/shmem.c:1039
>    notify_change+0xb6d/0x1020 fs/attr.c:336
>    do_truncate+0x134/0x1f0 fs/open.c:64
>    do_sys_ftruncate+0x4a5/0x570 fs/open.c:195
>    do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>    entry_SYSCALL_64_after_hwframe+0x49/0xb3
>
>
> stack backtrace:
> CPU: 0 PID: 8337 Comm: syz-executor428 Not tainted 5.6.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x188/0x20d lib/dump_stack.c:118
>  print_bad_irq_dependency kernel/locking/lockdep.c:2132 [inline]
>  check_irq_usage.cold+0x566/0x6de kernel/locking/lockdep.c:2330
>  check_prev_add kernel/locking/lockdep.c:2519 [inline]
>  check_prevs_add kernel/locking/lockdep.c:2620 [inline]
>  validate_chain kernel/locking/lockdep.c:3237 [inline]
>  __lock_acquire+0x2c39/0x4e00 kernel/locking/lockdep.c:4344
>  lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
>  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>  _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
>  shmem_uncharge+0x24/0x270 mm/shmem.c:341
>  __split_huge_page mm/huge_memory.c:2613 [inline]
>  split_huge_page_to_list+0x274b/0x33b0 mm/huge_memory.c:2886
>  split_huge_page include/linux/huge_mm.h:204 [inline]
>  shmem_punch_compound+0x13e/0x1e0 mm/shmem.c:814
>  shmem_undo_range+0x5f1/0x1b80 mm/shmem.c:870
>  shmem_truncate_range+0x27/0xa0 mm/shmem.c:980
>  shmem_setattr+0x8b6/0xc80 mm/shmem.c:1039
>  notify_change+0xb6d/0x1020 fs/attr.c:336
>  do_truncate+0x134/0x1f0 fs/open.c:64
>  do_sys_ftruncate+0x4a5/0x570 fs/open.c:195
>  do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
>  entry_SYSCALL_64_after_hwframe+0x49/0xb3
> RIP: 0033:0x44e769
> Code: 4d c9 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 1b c9 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fe511b3fce8 EFLAGS: 00000246 ORIG_RAX: 000000000000004d
> RAX: ffffffffffffffda RBX: 00000000006e1c68 RCX: 000000000044e769
> RDX: 000000000044e769 RSI: 00000000000001ff RDI: 0000000000000006
> RBP: 00000000006e1c60 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e1c6c
> R13: 00007ffce699f92f R14: 00007fe511b409c0 R15: 0000000000000000
>
>
> ---
> This bug 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 bug report. See:
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> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>