At present zfs_domount() acquires a reference on the filesystem's root vnode
and that reference is kept until zfs_umount.
The latter calls vflush(rootrefs = 1) to dispose of the extra reference.
There is no explanation of why that reference is kept - what problem it
solves or what behavior it improves.
Also, that logic is FreeBSD specific.
There is one real problem with that reference, though.
zfs recv -F may receive a full, non-incremental stream to a mounted filesystem.
In that case the received root object is likely to have a different z_gen
attribute value. Because of that, zfs_rezget will leave the previous root znode
and vnode disassociated from the actual object (z_sa_hdl == NULL).
Thus, future calls to VFS_ROOT() -> zfs_root() will produce a new vnode-znode
pair, while the old one will be kept alive by the outstanding reference.
So, the outstanding reference will not actually be for the new root vnode
(or, more precisely, vnodes - because a root vnode may be recycled and a newer
one can be created).
As a result, when vflush(rootrefs = 1) s called there will be two problems:
- a leaked reference on the old root vnode preventing a graceful unmount
- insufficient references on the actual root vnode leading to a crash upon
access to the vnode after it is destroyed by vgone() + vdrop()
The second issue will actually override the first one.
Differential Revision: https://reviews.freebsd.org/D2353
Reviewed by: delphij, kib, smh
MFC after: 17 days
In traverse_visitbp(), the input argument dnp is modified in the middle
to point to a temporary buffer. Originally this doesn't matter, because
no user of TRAVERSE_POST dereferences it. However, in fbeddd6 a piece of
code is added dereferencing dnp after the modification, creating a possible
bug.
We fix this by creating a new local variable cdnp for the DMU_OT_DNODE case,
so we don't modify the input argument. Also we introduce different local
variables in the DMU_OT_OBJSET case to prevent confusion between the input
argument.
Obtained from: zfsonlinux (a585f2f844ed3d4270221fed88f5e494eb55d932)
MFC after: 2 weeks
Sponsored by: Multiplay
The old comment in zfs_rezget explains what situation the code handles,
the new comment also describes how the situation can arise.
Also, re-join a line that became sufficiently shorti some time ago.
Differential Revision: https://reviews.freebsd.org/D2352
Reviewed by: delphij, smh
MFC after: 12 days
/dev/zfs always has per-open data, so when it is missing the file
descriptor is for some other file. Returning ENOENT in this case
is confusing as a variety of other conditions (like a missing dataset)
may result in the same error. It's better to consistently return
EBADF for any problems with the file descriptor.
Note that zfs_onexit_fd_hold() is used with 'automatic cleanup fd'
- when that fd is closed, typically because a process is terminated,
some cleanup action is taken by ZFS driver. E.g. a temporary
snapshot hold is released.
Perhaps, it would even be worthwhile changing devfs_get_cdevpriv()
to return EBADF if there is no associated data.
Differential Revision: https://reviews.freebsd.org/D2370
Reviewed by: delphij, smh
MFC after: 12 days
skip 10, rather than 9, frames. This appears to work quite well in
practice on the BeagleBone Black, so remove a comment about the value
being bogus and replace it with a slightly less negative one. However,
the number of frames to skip is quite sensitive to details of the timer
and interrupt handling paths, so this is necessarily fragile -- but no
more so than on x86.
Sponsored by: DARPA, AFRL
It would previously call into some unfinished Solaris compatibility code and
return without actually calling panic(9). The compatibility code is
unneeded, however, so just remove it and have dtrace_panic() call vpanic(9)
directly.
Differential Revision: https://reviews.freebsd.org/D2349
Reviewed by: avg
MFC after: 2 weeks
Sponsored by: EMC / Isilon Storage Division
Passing "-x lazyload" to dtrace -G during compilation causes dtrace(1) to
not link drti.o into the output object file, so the USDT probes are not created
during process startup. Instead, dtrace(1) will automatically discover and
create probes on the process' behalf when attaching.
Differential Revision: https://reviews.freebsd.org/D2203
Reviewed by: rpaulo
MFC after: 1 month
Even on Illumos, with its much larger KVA, ZFS ARC steps back if KVA usage
reaches certain threshold (3/4 on i386 or 16/17 otherwise). FreeBSD has
even less KVA, but had no such limit on archs with direct map as amd64.
As result, on machines with a lot of RAM, during load with very small user-
space memory pressure, such as `zfs send`, it was possible to reach state,
when there is enough both physical RAM and KVA (I've seen up to 25-30%),
but no continuous KVA range to allocate even single 128KB I/O request.
Address this situation from two sides:
- restore KVA usage limitations in a way the most close to Illumos;
- introduce new requirement for KVA fragmentation, specifying that we
should have at least one sequential KVA range of zfs_max_recordsize bytes.
Experiments show that first limitation done alone is not sufficient. On
machine with 64GB of RAM it is sometimes needed to drop up to half of ARC
size to get at leats one 1MB KVA chunk. Statically limiting ARC to half
of KVA/RAM is too strict, so second limitation makes it to work in cycles:
accumulate trash up to certain critical mass, do massive spring-cleaning,
and then start littering again. :)
MFC after: 1 month
This adds an upper bound, dtrace_ustackdepth_max, to the number of frames
traversed when computing the userland stack depth. Some programs - notably
firefox - are otherwise able to trigger an infinite loop in
dtrace_getustack_common(), causing a panic.
MFC after: 1 week
traps do appear in the regular call stack, rather than only in a special
trap frame, so we don't need to inject the trap-frame $pc into a returned
stack trace in DTrace.
MFC after: 3 days
Sponsored by: DARPA, AFRL
skip using the DTrace 'profile' provider on ARM. This causes stack traces
to skip various driver-and callout-related things as they do on x86, where
the likewise arbitrary values are '6' (32-bit) and '10' (64-bit) for
similar sorts of reasons.
MFC after: 3 days
Sponsored by: DARPA, AFRL
If zvol_geom_start is called with a BIO_DELETE from a thread which can
sleep it queues it for later processing by the zvol_geom_worker. The
zvol_geom_worker didn't have a delete case so would simply loose the bio
hence preventing the original caller from every completing. In addition
an other unknown types would suffer the same fate.
Allow zvol_geom_worker to process BIO_DELETE's via zvol_strategy and
return unsupported for all unknown bio types.
MFC after: 2 weeks
Sponsored by: Multiplay
emulate the instructions used in function entry and exit.
For function entry ARM will use a push instruction to push up to 16
registers to the stack. While we don't expect all 16 to be used we need to
handle any combination the compiler may generate, even if it doesn't make
sense (e.g. pushing the program counter).
On function return we will either have a pop or branch instruction. The
former is similar to the push instruction, but with care to make sure we
update the stack pointer and program counter correctly in the cases they
are either in the list of registers or not. For branch we need to take the
24-bit offset, sign-extend it, and add that number of 4-byte words to the
program counter. Care needs to be taken as, due to historical reasons, the
address the branch is relative to is not the current instruction, but 8
bytes later.
This allows us to use the following probes on ARM boards:
dtrace -n 'fbt::malloc:entry { stack() }'
and
dtrace -n 'fbt:🆓return { stack() }'
Differential Revision: https://reviews.freebsd.org/D2007
Reviewed by: gnn, rpaulo
Sponsored by: ABT Systems Ltd
expected to return the data in the memory location pointed at by target
after the operation. The FreeBSD atomic functions previously used return
either 0 or 1 to indicate if the comparison succeeded or not respectively.
With this change these functions only support ARMv6 and later are supported
by these functions.
Sponsored by: ABT Systems Ltd
dtrace is able to display a stack trace similar to the one below.
# dtrace -p 603 -n 'tcp:kernel::receive { stack(); }'
0 70 :receive
kernel`ip_input+0x140
kernel`netisr_dispatch_src+0xb8
kernel`ether_demux+0x1c4
kernel`ether_nh_input+0x3a8
kernel`netisr_dispatch_src+0xb8
kernel`ether_input+0x60
kernel`cpsw_intr_rx+0xac
kernel`intr_event_execute_handlers+0x128
kernel`ithread_loop+0xb4
kernel`fork_exit+0x84
kernel`swi_exit
kernel`swi_exit
Tested by: gnn
Sponsored by: ABT Systems Ltd
cannot happen on FreeBSD. r278136 overlooked the fact that a destructor
registered with devfs_set_cdevpriv(9) is invoked even in the case of an
error.
X-MFC-With: r278136
This allows dtrace to monitor the calls to txg_quiesce which can be really
helpful.
Also standardise __noinline order for arc_kmem_reap_now.
Sponsored by: Multiplay
ZFS already commits outstanding data every zfs_txg_timeout seconds, so these
syncs are unnecessarily intrusive.
Submitted by: gibbs
Sponsored by: Spectra Logic
MFSpectraBSD: 1105759 on 2014/12/11
Since allow_mounted is a FreeBSD-specific change, default to B_TRUE, then
locally check for the magic bit. Unconditionally check allow_mounted below.
Convert the setting of allow_mounted to an explicit boolean.
MFC after: 1 week
Sponsored by: Spectra Logic
MFSpectraBSD: 672578 (in part) on 2013/07/19
This is primarily for developer/debugging use; it enables built-in tagged
tracking of refcounts inside ZFS. It can only be enabled from the loader,
since it modifies how in-core state is managed. Default remains disabled.
MFC after: 1 week
Sponsored by: Spectra Logic
Remove the unnecessary #ifdef _KERNEL, which did not differ in the true or
false cases. Actually set the value of to_free before using it.
MFC after: 1 week
Sponsored by: Spectra Logic
