Re: Deadlock in ZFS @ FreeBSD 15.0-RELEASE-p3 handling of extended attributes?

On Sun, Feb 15, 2026 at 10:51 AM Peter Eriksson <[email protected]> wrote:
>
> I would have entered this into the freebsd bugzilla, but that seems to be down right now…
It might be better to report this to OpenZFS. See below..

>
> Anyway, I’m trying to copy some 30000 ZFS filesystems (home directories) on a new server running FreeBSD 15.0-RELEASE-p3. The server has 10 15TB NVMEe SSD drives configured as mirrors in one big Zpool. The copy is basically a loop over the 30000 directories and the doing a zfs create … ; tar cpf - | (cd /new/home; tar xpf -)
>
> The first 495 directories copied without problem, but now it seems the bsdtar process writing to the new home directory has deadlocked in:
>
>
> # procstat -kka|egrep bsdtar
>
> 63997 103752 bsdtar              -                   mi_switch+0xbc sleepq_catch_signals+0x27d sleepq_wait_sig+0x9 _sleep+0x197 uipc_sosend_stream_or_seqpacket+0x475 sousrsend+0x5f dofilewrite+0x81 sys_write+0x127 amd64_syscall+0x126 fast_syscall_common+0xf8
>
> 63998 290883 bsdtar              -                   mi_switch+0xbc _sleep+0x19e rms_rlock_fallback+0x90 zfs_lookup+0x74 zfs_deleteextattr_dir+0x38 zfs_setextattr+0x7dc VOP_SETEXTATTR_APV+0x24 extattr_set_vp+0x11d kern_extattr_set_path+0x14e sys_extattr_set_link+0x6b amd64_syscall+0x126 fast_syscall_common+0xf8
>
> I’m guessing some kind of problem with the handling of extended attributes…
I think the hang has occurred because zfs_enter() has done a
ZFS_TEARDOWN_ENTER_READ(),
which tries to acquire a read lock on z_teardown_lock.
Since this hangs, it suggests that something else is holding a write
lock on z_teardown_lock.

Looking at the code, I think a call to zfs_suspend_fs() might be what did this.
But, that is as far as my limited ZFS knowledge (almost none) goes, so I
don't know when/why zfs_suspend_fs() gets called.

You could try setting xattr=dir and see if that works better, but that would
just be a workaround if it does work better.

I've cc'd a couple of people that might know when zfs_suspend_fs() gets
called or if there are other/better explanations for this hang?

rick

>
> I created the home directory root like this:
>
> #!/bin/sh
>
> PROPS="\
> -o atime=off \
> -o relatime=on \
> -o dnodesize=auto \
> -o compression=zstd \
> -o utf8only=on \
> -o normalization=formC \
> -o xattr=sa \
> -o overlay=off \
> -o aclmode=passthrough \
> -o aclinherit=passthrough-x \
> -o sharenfs=sec=krb5:krb5i:krb5p"
>
> for ZFS in "$@"; do
>     zfs create $PROPS "$ZFS"
> done
>
>
> - Peter