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Re: virtio-fs: Fix file ID collisions (was: 9p: Fix file ID collisions)
From: |
Christian Schoenebeck |
Subject: |
Re: virtio-fs: Fix file ID collisions (was: 9p: Fix file ID collisions) |
Date: |
Wed, 16 Oct 2019 11:42:52 +0200 |
On Dienstag, 15. Oktober 2019 11:20:39 CEST Greg Kurz wrote:
> On Tue, 08 Oct 2019 14:05:28 +0200
>
> Christian Schoenebeck <address@hidden> wrote:
> > I wonder though whether virtio-fs suffers from the same file ID collisions
> > problem when sharing multiple file systems.
>
> I gave a try and it seems that virtio-fs might expose the inode numbers from
> different devices in the host, unvirtualized AND with the same device in
> the guest:
>
> # mkdir -p /var/tmp/virtio-fs/proc
> # mount --bind /proc /var/tmp/virtio-fs/proc
> # virtiofsd -o vhost_user_socket=/tmp/vhostqemu -o source=/var/tmp/virtio-fs
> -o cache=always
>
> and then started QEMU with:
>
> -chardev socket,id=char0,path=/tmp/vhostqemu \
> -device vhost-user-fs-pci,queue-size=1024,chardev=char0,tag=myfs \
> -m 4G -object memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on
> \ -numa node,memdev=mem
>
> In the host:
>
> $ stat /var/tmp/virtio-fs
> File: /var/tmp/virtio-fs
> Size: 4096 Blocks: 8 IO Block: 4096 directory
> Device: fd00h/64768d Inode: 787796 Links: 4
> Access: (0775/drwxrwxr-x) Uid: ( 1000/ greg) Gid: ( 1000/ greg)
> Context: unconfined_u:object_r:user_tmp_t:s0
> Access: 2019-10-15 11:08:52.070080922 +0200
> Modify: 2019-10-15 11:02:09.887404446 +0200
> Change: 2019-10-15 11:02:09.887404446 +0200
> Birth: 2019-10-13 19:13:04.009699354 +0200
> [greg@bahia ~]$ stat /var/tmp/virtio-fs/FOO
> File: /var/tmp/virtio-fs/FOO
> Size: 0 Blocks: 0 IO Block: 4096 regular empty
> file Device: fd00h/64768d Inode: 790740 Links: 1
> Access: (0664/-rw-rw-r--) Uid: ( 1000/ greg) Gid: ( 1000/ greg)
> Context: unconfined_u:object_r:user_tmp_t:s0
> Access: 2019-10-15 11:02:09.888404448 +0200
> Modify: 2019-10-15 11:02:09.888404448 +0200
> Change: 2019-10-15 11:02:09.888404448 +0200
> Birth: 2019-10-15 11:02:09.887404446 +0200
> [greg@bahia ~]$ stat /var/tmp/virtio-fs/proc/fs
> File: /var/tmp/virtio-fs/proc/fs
> Size: 0 Blocks: 0 IO Block: 1024 directory
> Device: 4h/4d Inode: 4026531845 Links: 5
> Access: (0555/dr-xr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
> Context: system_u:object_r:proc_t:s0
> Access: 2019-10-01 14:50:09.223233901 +0200
> Modify: 2019-10-01 14:50:09.223233901 +0200
> Change: 2019-10-01 14:50:09.223233901 +0200
> Birth: -
>
> In the guest:
>
> [greg@localhost ~]$ stat /mnt
> File: /mnt
> Size: 4096 Blocks: 8 IO Block: 4096 directory
> Device: 2dh/45d Inode: 787796 Links: 4
> Access: (0775/drwxrwxr-x) Uid: ( 1000/ greg) Gid: ( 1000/ greg)
> Context: system_u:object_r:unlabeled_t:s0
> Access: 2019-10-15 11:08:52.070080922 +0200
> Modify: 2019-10-15 11:02:09.887404446 +0200
> Change: 2019-10-15 11:02:09.887404446 +0200
> Birth: -
> [greg@localhost ~]$ stat /mnt/FOO
> File: /mnt/FOO
> Size: 0 Blocks: 0 IO Block: 4096 regular empty
> file Device: 2dh/45d Inode: 790740 Links: 1
> Access: (0664/-rw-rw-r--) Uid: ( 1000/ greg) Gid: ( 1000/ greg)
> Context: system_u:object_r:unlabeled_t:s0
> Access: 2019-10-15 11:02:09.888404448 +0200
> Modify: 2019-10-15 11:02:09.888404448 +0200
> Change: 2019-10-15 11:02:09.888404448 +0200
> Birth: -
> [greg@localhost ~]$ stat /mnt/proc/fs
> File: /mnt/proc/fs
> Size: 0 Blocks: 0 IO Block: 1024 directory
> Device: 2dh/45d Inode: 4026531845 Links: 5
> Access: (0555/dr-xr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
> Context: system_u:object_r:unlabeled_t:s0
> Access: 2019-10-01 14:50:09.223233901 +0200
> Modify: 2019-10-01 14:50:09.223233901 +0200
> Change: 2019-10-01 14:50:09.223233901 +0200
> Birth: -
>
> Unless I'm missing something, it seems that "virtio-fs" has the same
> issue we had on 9pfs before Christian's patches... :-\
Is a fix for this desired for virtio-fs?
Greg, did you have to update kernel version on either host or guest side to
get virtio-fs running? Or were the discussed kernel changes just for optional
acceleration purposes (i.e. DAX)?
Best regards,
Christian Schoenebeck