Re: [PATCH -next] PM: hibernate: Get block device exclusively when do swsusp_check

[Rafael J. Wysocki]

On Wed, Oct 13, 2021 at 2:06 PM Ye Bin <yebin10@xxxxxxxxxx> wrote:
>
> We got follow issue:
> [   89.266592] ------------[ cut here ]------------
> [   89.267427] kernel BUG at fs/buffer.c:3020!
> [   89.268264] invalid opcode: 0000 [#1] SMP KASAN PTI
> [   89.269116] CPU: 7 PID: 1750 Comm: kmmpd-loop0 Not tainted 5.10.0-862.14.0.6.x86_64-08610-gc932cda3cef4-dirty #20
> [   89.273169] RIP: 0010:submit_bh_wbc.isra.0+0x538/0x6d0
> [   89.277157] RSP: 0018:ffff888105ddfd08 EFLAGS: 00010246
> [   89.278093] RAX: 0000000000000005 RBX: ffff888124231498 RCX: ffffffffb2772612
> [   89.279332] RDX: 1ffff11024846293 RSI: 0000000000000008 RDI: ffff888124231498
> [   89.280591] RBP: ffff8881248cc000 R08: 0000000000000001 R09: ffffed1024846294
> [   89.281851] R10: ffff88812423149f R11: ffffed1024846293 R12: 0000000000003800
> [   89.283095] R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881161f7000
> [   89.284342] FS:  0000000000000000(0000) GS:ffff88839b5c0000(0000) knlGS:0000000000000000
> [   89.285711] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   89.286701] CR2: 00007f166ebc01a0 CR3: 0000000435c0e000 CR4: 00000000000006e0
> [   89.287919] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [   89.289138] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [   89.290368] Call Trace:
> [   89.290842]  write_mmp_block+0x2ca/0x510
> [   89.292218]  kmmpd+0x433/0x9a0
> [   89.294902]  kthread+0x2dd/0x3e0
> [   89.296268]  ret_from_fork+0x22/0x30
> [   89.296906] Modules linked in:
>
> We can reproduce this issue as follow:
> 1. mkfs.ext4 -O mmp  /dev/sda -b 1024
> 2. mount /dev/sda /home/test
> 3. echo "/dev/sda" > /sys/power/resume
> 4. wait a moment we will get exception
>
> The sequence of issue is as follows:
>        Thread1                       Thread2
> mount /dev/sda /home/test
> get s_mmp_bh  --> has mapped flag
> start kmmpd thread
>                                 echo "/dev/sda" > /sys/power/resume
>                                   resume_store
>                                     software_resume
>                                       swsusp_check
>                                         set_blocksize
>                                           truncate_inode_pages_range
>                                             truncate_cleanup_page
>                                               block_invalidatepage
>                                                 discard_buffer --> clean mapped flag
> write_mmp_block
>   submit_bh
>     submit_bh_wbc
>       BUG_ON(!buffer_mapped(bh)) --> trigger bug_on
>
> To solve this issue, get block device exclusively when do swsusp_check.

And why exactly is this going to help?

>
> Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
> ---
>  kernel/power/swap.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/power/swap.c b/kernel/power/swap.c
> index 9ec418955556..26c0bd2a50da 100644
> --- a/kernel/power/swap.c
> +++ b/kernel/power/swap.c
> @@ -1521,9 +1521,10 @@ int swsusp_read(unsigned int *flags_p)
>  int swsusp_check(void)
>  {
>         int error;
> +       void *holder;
>
>         hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device,
> -                                           FMODE_READ, NULL);
> +                                           FMODE_READ | FMODE_EXCL, &holder);

So you need to explain to me how this works.

>         if (!IS_ERR(hib_resume_bdev)) {
>                 set_blocksize(hib_resume_bdev, PAGE_SIZE);
>                 clear_page(swsusp_header);
> @@ -1545,7 +1546,7 @@ int swsusp_check(void)
>
>  put:
>                 if (error)
> -                       blkdev_put(hib_resume_bdev, FMODE_READ);
> +                       blkdev_put(hib_resume_bdev, FMODE_READ | FMODE_EXCL);
>                 else
>                         pr_debug("Image signature found, resuming\n");
>         } else {
> --