Re: Blocked tasks on 3.15.1

[Cody P Schafer <dev@codyps.com>]

On Thu, Jul 17, 2014 at 8:18 AM, Chris Mason <clm@fb.com> wrote:
>
> [ deadlocks during rsync in 3.15 with compression enabled ]
>
> Hi everyone,
>
> I still haven't been able to reproduce this one here, but I'm going
> through a series of tests with lzo compression foraced and every
> operation forced to ordered.  Hopefully it'll kick it out soon.
>
> While I'm hammering away, could you please try this patch.  If this is
> the buy you're hitting, the deadlock will go away and you'll see this
> printk in the log.
>
> thanks!
>
> -chris
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 3668048..8ab56df 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -8157,6 +8157,13 @@ void btrfs_destroy_inode(struct inode *inode)
>                 spin_unlock(&root->fs_info->ordered_root_lock);
>         }
>
> +       spin_lock(&root->fs_info->ordered_root_lock);
> +       if (!list_empty(&BTRFS_I(inode)->ordered_operations)) {
> +               list_del_init(&BTRFS_I(inode)->ordered_operations);
> +printk(KERN_CRIT "racing inode deletion with ordered operations!!!!!!!!!!!\n");
> +       }
> +       spin_unlock(&root->fs_info->ordered_root_lock);
> +
>         if (test_bit(BTRFS_INODE_HAS_ORPHAN_ITEM,
>                      &BTRFS_I(inode)->runtime_flags)) {
>                 btrfs_info(root->fs_info, "inode %llu still on the orphan list",

Thanks Chris.

Running 3.15.6 with this patch applied on top:
 - still causes a hang with `rsync -hPaHAXx --del /mnt/home/nyx/ /home/nyx/`
 - no extra error messages printed (`dmesg | grep racing`) compared to
without the patch

To recap some details (so I can have it all in one place):
 - /home/ is btrfs with compress=lzo
 - /mnt/home is btrfs with no compression enabled.
 - I have _not_ created any nodatacow files.
 - Both filesystems are on different physical disks.
 - Full stack is: sata <-> dmcrypt <-> lvm <-> btrfs (I noticed others
mentioning the use of dmcrypt)