rsync w/ fake-super -> crashes zfs

[javocado]

Gathering more info here...

When re-running the rsync command, stripped down:
rsync -av --rsync-path="rsync --fake-super" /src /dst

we're not seeing any system crashes, yet, but rsync is choking/quitting
quite a bit saying a file here or there has a corrupt extattr. Does this
point to a problem with ZFS or more with rsync.

Any thoughts on the fake-super impact and how it leads to crashing?


On Fri, Mar 14, 2014 at 4:57 PM, javocado <javocado at gmail.com> wrote:

> System specifics:
> ZFS version 28
> FreeBSD 8.3-RELEASE
>
> We're seeing a repeatable outcome where a remote rsync command like:
>
> rsync -axzHAXS --rsync-path="rsync --fake-super" --exclude '*/rsync.%stat'
>
> backing up to our zfs filesystem (with 15M inodes) will lead to a panic
> with output like:
>
> Fatal trap 12: page fault while in kernel modecpuid = 4; apic id = 04fault virtual address   = 0x160fault code              = supervisor read data, page not presentinstruction pointer     = 0x20:0xffffffff80abb546stack pointer           = 0x28:0xffffff976c62b910frame pointer           = 0x28:0xffffff976c62b9d0code segment            = base 0x0, limit 0xfffff, type 0x1b                        = DPL 0, pres 1, long 1, def32 0, gran 1processor eflags        = interrupt enabled, resume, IOPL = 0current process         = 7295 (rsync)[thread pid 7295 tid 101008 ]Stopped at      zfs_freebsd_remove+0x426:       movq    0x160(%rax),%rsi
>
>
> On the sending side (RHEL, ext3), rsync reports errors like:
>
> rsync: failed to read xattr rsync.%statrsync: failed to write xattr rsync.%statrsync: get_xattr_names: llistxattr
>
> which we've seen occasionally with other systems when running rsync with fake-super, but it usually doesn't lead to a crash.*
>
> On the receiving side, other than the crashes, we are seeing a few new files (that don't exist on the source) named:
>
> rsync.%stat
>
> which correspond to and contain the owner and permission attributes that should have been stored in the extattr's for the file or directory. Not sure if they are a red herring, but they're usually not something we see (perhaps that's related to the --exclude '*/rsync.%stat' and rsync not being able to cleanup properly).
>
> We are still testing to see if any options in the rsync command (above) may be contributing to the crash, since fake-super in and of itself runs fine under basic (rsync -av --rsync-path="rsync --fake-super" /src /dst) circumstances. But we suspect that the problem is related to fake-super and its reliance upon extattr's.
>
> What we really need is a solution to the crashing - some way to make ZFS stop choking on whatever --fake-super produces and/or how it's interacting with extattr's on ZFS.
>
>
> Thanks!
>
> * we sometimes also see on the sending side w/ fake-super:
> rsync: failed to write xattr rsync.%stat for "xxxxxx/file" : No such file
> or directory (2)
>
> when (1) the file exists, (2) it's a symlink
> but that isn't happening in this instance. We only mention it here as
> another oddity of fake-super + ZFS + extattr
>
>