Re: [syzbot] [block?] WARNING in blkdev_put (2)

[Yu Kuai]

Hi,

在 2023/03/06 23:00, Julian Ruess 写道:
> On Thu, 2023-03-02 at 20:33 +0100, Alexander Egorenkov wrote:
> > Hi,
> >
> > we are seeing a similar problem on s390x architecture when
> > partitioning
> > a NVMe disk on linux-next.
> >
> >
> >    [   70.403015]  nvme0n1: p1
> >    [   70.403197] ------------[ cut here ]------------
> >    [   70.403199] WARNING: CPU: 8 PID: 2452 at block/bdev.c:845
> > blkdev_put+0x280/0x298
>
> ...
>
> > The problem appeared about a week ago.
> >
> > Regards
> > Alex
>
> Hi all,
>
> I bisected this to:
>
> commit e5cfefa97bccf956ea0bb6464c1f6c84fd7a8d9f
> Author: Yu Kuai <yukuai3@xxxxxxxxxx>
> Date:   Fri Feb 17 10:22:00 2023 +0800
>                                                                                        
>      block: fix scan partition for exclusively open device again

Yes, thanks for the report, I figure out that I made a mistake here.

Following patch should fix this problem:

diff --git a/block/genhd.c b/block/genhd.c
index 3ee5577e1586..02d9cfb9e077 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -385,7 +385,7 @@ int disk_scan_partitions(struct gendisk *disk, 
fmode_t mode)
        if (IS_ERR(bdev))
                ret =  PTR_ERR(bdev);
        else
-               blkdev_put(bdev, mode);
+               blkdev_put(bdev, mode & ~FMODE_EXCL);

Thanks,
Kuai
>                                                                                        
>      As explained in commit 36369f46e917 ("block: Do not reread
> partition table
>      on exclusively open device"), reread partition on the device that
> is
>      exclusively opened by someone else is problematic.
>                                                                                        
>      This patch will make sure partition scan will only be proceed if
> current
>      thread open the device exclusively, or the device is not opened
>      exclusively, and in the later case, other scanners and exclusive
> openers
>      will be blocked temporarily until partition scan is done.
>                                                                                        
>      Fixes: 10c70d95c0f2 ("block: remove the bd_openers checks in
> blk_drop_partitions")
>      Cc: <stable@xxxxxxxxxxxxxxx>
>      Suggested-by: Jan Kara <jack@xxxxxxx>
>      Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
>      Reviewed-by: Christoph Hellwig <hch@xxxxxx>
>      Link:
> https://lore.kernel.org/r/20230217022200.3092987-3-yukuai1@xxxxxxxxxxxxxxx
>   
>      Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
>
>
>
> Regards
> Julian