Comment 16 for bug 1839521

Verification done for zfs-linux on xenial-proposed.

The inodes for file, xattr dir, and xattr child are all evicted at file removal time, not making it to any disposal list after file removal.

So the window/scenario for the problem to occur is not present anymore.

Log
---

$ echo 'deb http://archive.ubuntu.com/ubuntu xenial-proposed main restricted universe' | sudo tee /etc/apt/sources.list.d/xenial-proposed-universe.list
$ sudo apt-get update

$ apt-cache madison zfs-dkms | grep proposed
  zfs-dkms | 0.6.5.6-0ubuntu28 | http://archive.ubuntu.com/ubuntu xenial-proposed/universe amd64 Packages

$ sudo apt-get install -y spl-dkms zfs-dkms

$ modinfo zfs | head
filename: /lib/modules/4.4.0-157-generic/updates/dkms/zfs.ko
version: 0.6.5.6-0ubuntu28
...

$ sudo ./zfs-mount.sh

$ echo 2 | sudo tee /proc/sys/vm/drop_caches
2

$ sudo ./zfs-kprobes.sh

$ touch /zfs/file
           <...>-26587 [001] d... 1196.781161: p_zfs_mknode_0: (zfs_mknode+0x0/0xe00 [zfs]) flag=0x0 dzp=0xffff88004ccfc000
           <...>-26587 [001] d... 1196.781306: p_zfs_znode_alloc_0: (zfs_znode_alloc+0x0/0x520 [zfs]) obj=0xa
           <...>-26587 [001] d... 1196.781336: r_zfs_znode_alloc_0: (zfs_mknode+0x8a3/0xe00 [zfs] <- zfs_znode_alloc) zpp=0xffff88004cd04cc0

$ setfattr -n user.debug -v 1 /zfs/file
        setfattr-26588 [000] d... 1199.095554: p_zfs_mknode_0: (zfs_mknode+0x0/0xe00 [zfs]) flag=0x2 dzp=0xffff88004cd04cc0
        setfattr-26588 [000] d... 1199.095937: p_zfs_znode_alloc_0: (zfs_znode_alloc+0x0/0x520 [zfs]) obj=0xb
        setfattr-26588 [000] d... 1199.096145: r_zfs_znode_alloc_0: (zfs_mknode+0x8a3/0xe00 [zfs] <- zfs_znode_alloc) zpp=0xffff88004c567740
        setfattr-26588 [000] d... 1199.096539: p_zfs_zget_0: (zfs_zget+0x0/0x230 [zfs]) zsb=0xffff88004d1c8000 obj=0xa
        setfattr-26588 [000] d... 1199.096779: r_zfs_zget_0: (zfs_zaccess+0x12b/0x220 [zfs] <- zfs_zget)
        setfattr-26588 [000] d... 1199.097139: p_zfs_zget_0: (zfs_zget+0x0/0x230 [zfs]) zsb=0xffff88004d1c8000 obj=0xa
        setfattr-26588 [000] d... 1199.097352: r_zfs_zget_0: (zfs_zaccess+0x12b/0x220 [zfs] <- zfs_zget)
        setfattr-26588 [000] d... 1199.097661: p_zfs_zget_0: (zfs_zget+0x0/0x230 [zfs]) zsb=0xffff88004d1c8000 obj=0xa
        setfattr-26588 [000] d... 1199.097892: r_zfs_zget_0: (zfs_zaccess+0x12b/0x220 [zfs] <- zfs_zget)
        setfattr-26588 [000] d... 1199.098217: p_zfs_mknode_0: (zfs_mknode+0x0/0xe00 [zfs]) flag=0x0 dzp=0xffff88004c567740
        setfattr-26588 [000] d... 1199.098449: p_zfs_znode_alloc_0: (zfs_znode_alloc+0x0/0x520 [zfs]) obj=0xc
        setfattr-26588 [000] d... 1199.098652: r_zfs_znode_alloc_0: (zfs_mknode+0x8a3/0xe00 [zfs] <- zfs_znode_alloc) zpp=0xffff88004c567300

$ rm /zfs/file
           <...>-26589 [001] d... 1201.376695: p_zfs_zget_0: (zfs_zget+0x0/0x230 [zfs]) zsb=0xffff88004d1c8000 obj=0xa
           <...>-26589 [001] d... 1201.376749: r_zfs_zget_0: (zfs_dirent_lock+0x56c/0x6c0 [zfs] <- zfs_zget)
              rm-26589 [001] d... 1201.376772: p_zfs_zget_0: (zfs_zget+0x0/0x230 [zfs]) zsb=0xffff88004d1c8000 obj=0xb
              rm-26589 [001] d... 1201.376778: r_zfs_zget_0: (zfs_remove+0x22b/0x4c0 [zfs] <- zfs_zget)
              rm-26589 [001] d... 1201.376904: p_zpl_evict_inode_0: (zpl_evict_inode+0x0/0x60 [zfs]) inode=0xffff88004cd04ed0
              rm-26589 [001] d... 1201.376922: p_zfs_inactive_0: (zfs_inactive+0x0/0x270 [zfs]) inode=0xffff88004cd04ed0
              rm-26589 [001] d... 1201.376923: p_zfs_zinactive_0: (zfs_zinactive+0x0/0xe0 [zfs]) znode=0xffff88004cd04cc0 obj=0xa
              rm-26589 [001] d... 1201.376927: p_zfs_rmnode_0: (zfs_rmnode+0x0/0x360 [zfs]) znode=0xffff88004cd04cc0
              rm-26589 [001] d... 1201.376942: p_zfs_zget_0: (zfs_zget+0x0/0x230 [zfs]) zsb=0xffff88004d1c8000 obj=0xb
              rm-26589 [001] d... 1201.376999: r_zfs_zget_0: (zfs_rmnode+0x25b/0x360 [zfs] <- zfs_zget)
              rm-26589 [001] d... 1201.377043: p_zfs_iput_async_0: (zfs_iput_async+0x0/0x60 [zfs]) inode=0xffff88004c567950 obj=0x0
          z_iput-26241 [001] d... 1201.377065: p_zpl_evict_inode_0: (zpl_evict_inode+0x0/0x60 [zfs]) inode=0xffff88004c567950
          z_iput-26241 [001] d... 1201.377067: p_zfs_inactive_0: (zfs_inactive+0x0/0x270 [zfs]) inode=0xffff88004c567950
          z_iput-26241 [001] d... 1201.377067: p_zfs_zinactive_0: (zfs_zinactive+0x0/0xe0 [zfs]) znode=0xffff88004c567740 obj=0xb
          z_iput-26241 [001] d... 1201.377070: p_zfs_rmnode_0: (zfs_rmnode+0x0/0x360 [zfs]) znode=0xffff88004c567740
          z_iput-26241 [001] d... 1201.377072: p_zfs_purgedir_0: (zfs_purgedir+0x0/0x230 [zfs]) znode=0xffff88004c567740
          z_iput-26241 [001] d... 1201.377079: p_zfs_zget_0: (zfs_zget+0x0/0x230 [zfs]) zsb=0xffff88004d1c8000 obj=0xc
          z_iput-26241 [001] d... 1201.377085: r_zfs_zget_0: (zfs_purgedir+0xb4/0x230 [zfs] <- zfs_zget)
          z_iput-26241 [001] d... 1201.377117: p_zfs_iput_async_0: (zfs_iput_async+0x0/0x60 [zfs]) inode=0xffff88004c567510 obj=0x0
          z_iput-26241 [001] d... 1201.377123: r_zfs_purgedir_0: (zfs_rmnode+0x272/0x360 [zfs] <- zfs_purgedir)
          z_iput-26241 [001] d... 1201.377160: p_zpl_evict_inode_0: (zpl_evict_inode+0x0/0x60 [zfs]) inode=0xffff88004c567510
          z_iput-26241 [001] d... 1201.377161: p_zfs_inactive_0: (zfs_inactive+0x0/0x270 [zfs]) inode=0xffff88004c567510
          z_iput-26241 [001] d... 1201.377162: p_zfs_zinactive_0: (zfs_zinactive+0x0/0xe0 [zfs]) znode=0xffff88004c567300 obj=0xc
          z_iput-26241 [001] d... 1201.377164: p_zfs_rmnode_0: (zfs_rmnode+0x0/0x360 [zfs]) znode=0xffff88004c567300

$ echo 2 | sudo tee /proc/sys/vm/drop_caches
2
           <...>-26592 [001] d... 1204.543205: p_dispose_list_0: (dispose_list+0x0/0x50)
             tee-26592 [001] dN.. 1204.543357: p_dispose_list_0: (dispose_list+0x0/0x50)
             tee-26592 [001] d... 1204.543652: p_dispose_list_0: (dispose_list+0x0/0x50)
             tee-26592 [001] d... 1204.543799: p_dispose_list_0: (dispose_list+0x0/0x50)
             tee-26592 [001] d... 1204.544250: p_dispose_list_0: (dispose_list+0x0/0x50)
             tee-26592 [001] d... 1204.544429: p_dispose_list_0: (dispose_list+0x0/0x50)