Commit Graph

619 Commits

Author SHA1 Message Date
Albert Lee
22cd4a4653 Illumos #1475: zfs spill block hold can access invalid spill blkptr
Reviewed by: Dan McDonald <danmcd@nexenta.com>
Reviewed by: Gordon Ross <gwr@nexenta.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <gwilson@zfsmail.com>
Approved by: Garrett D'Amore <garrett@nexenta.com>

References to Illumos issue:
  https://www.illumos.org/issues/1475

Ported-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #648
2012-04-11 11:46:30 -07:00
George Wilson
5ffb9d1d05 Illumos #1951: leaking a vdev when removing an l2cache device
1952 memory leak when adding a file-based l2arc device
1954 leak in ZFS from metaslab_group_create and zfs_ereport_checksum

Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Bill Pijewski <wdp@joyent.com>
Reviewed by: Dan McDonald <danmcd@nexenta.com>
Approved by: Eric Schrock <eric.schrock@delphix.com>

References to Illumos issues:
  https://www.illumos.org/issues/1951
  https://www.illumos.org/issues/1952
  https://www.illumos.org/issues/1954

Ported-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #650
2012-04-11 11:32:06 -07:00
Martin Matuska
b129c6590e OS-926: zfs panic in zfs_fill_zplprops_impl()
This change appears to be exclusive to SmartOS. It is not present in
illumos-gate but it just adds some needed error handling.  This is
clearly preferable to simply ASSERTING which is what would occur
prior to the patch.

Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Ported-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #652
2012-04-11 11:29:19 -07:00
Andriy Gapon
3adfc400f5 Illumos #1680: zfs vdev_file_io_start: validate vdev before using vdev_tsd
vdev_tsd can be NULL for certain vdev states.
At least in userland testing with ztest.

References to Illumos issue:
  https://www.illumos.org/issues/1680

Ported-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #655
2012-04-11 11:23:18 -07:00
Richard Laager
109491a897 Improve error message consistency
Signed-off-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-04-11 10:43:17 -07:00
Richard Laager
f4605f07a2 Document the zle compression algorithm
Signed-off-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-04-11 10:42:02 -07:00
Brian Behlendorf
f0fd83be65 Export additional dsl symbols
Principly these symbols were exported to get access to the
dsl_prop_register/dsl_prop_unregister functions.  They allow
us to cleanly register a callback which is called when a
dataset property is modified.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-04-11 09:26:55 -07:00
Gunnar Beutner
1f0d8a566f Fixed a NULL pointer dereference bug in zfs_preumount
When zpl_fill_super -> zfs_domount fails (e.g. because the dataset
was destroyed before it could be successfully mounted) the subsequent
call to zpl_kill_sb -> zfs_preumount would derefence a NULL pointer.

This bug can be reproduced using this shell script:

 #!/bin/sh
 (
 while true; do
 	zfs create -o mountpoint=legacz tank/bar
 	zfs destroy tank/bar
 done
 ) &

 (
 while true; do
 	mount -t zfs tank/bar /mnt
 	umount /mnt
 done
 ) &

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #639
2012-04-05 11:29:42 -07:00
Richard Yao
2ce9d0ec61 Make Gentoo initscript use modinfo
The -l parameter to modprobe has been removed from the latest upstream
code and this change has entered Gentoo. Using modinfo as a substitute
addresses this.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #636
2012-04-03 10:37:18 -07:00
Richard Yao
847de12271 Print human readable error message for ENOENT
A cryptic error code is printed when mounting a legacy dataset to a
non-existent mountpoint. This patch changes this behavior to print
"mount point '%s' does not exist", which is similar to the error
message printed when mounting procfs.

The single quotes were added to be consistent with the existing EBUSY
error message, which is the only difference between this error message
and the one that is printed when the same condition occurs when mounting
procfs.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #633
2012-04-03 10:24:34 -07:00
Brian Behlendorf
fc41c6402b Properly expose the mfu ghost list kstats
Due to a typo the mru ghost lists stats were accidentally being
exposed as the mfu ghost list stats.  This was harmless but
confusing since memory usage could be over reported.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-03-27 15:08:22 -07:00
Craig Sanders
9fc60702c6 Remove hard-coded 80 column output
When stdout is detected to be a tty use the number of columns
specified by the terminal.  If that fails fall back to a default
80 column width.  In the non-tty case allow for 999 column lines.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-03-27 15:01:08 -07:00
Brian Behlendorf
2008ab88dd ZFS 0.6.0-rc8 2012-03-26 11:55:32 -07:00
Brian Behlendorf
f47e1351db Fix executable permissions
Caught by lint, this permission change was accidentally introduced
by commit 42cb3819f1.  Restore the
correct permissions and while I'm at it add a missing whack-bang
to config/ltmain.sh.

  lint: executable-not-elf-or-script: zpool_main.c zfs_main.c

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #620
2012-03-26 11:52:44 -07:00
Brian Behlendorf
1c5de20ae2 Add --enable-debug-dmu-tx configure option
Allow rigorous (and expensive) tx validation to be enabled/disabled
indepentantly from the standard zfs debugging.  When enabled these
checks ensure that all txs are constructed properly and that a dbuf
is never dirtied without taking the correct tx hold.

This checking is particularly helpful when adding new dmu consumers
like Lustre.  However, for established consumers such as the zpl
with no known outstanding tx construction problems this is just
overhead.

--enable-debug-dmu-tx  - Enable/disable validation of each tx as
--disable-debug-dmu-tx   it is constructed.  By default validation
                         is disabled due to performance concerns.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-03-23 12:25:17 -07:00
Brian Behlendorf
99ea23c583 Enhance a dmu_tx_dirty_buf() assertion
The following assertion is good to validate the correctness of
new DMU consumers, but it doesn't quite provide enough information.
Slightly rework the assertion so that when it is hit the actual
offending values will be included in the output.

  SPLError: 4787:0:(dmu_tx.c:828:dmu_tx_dirty_buf())
  ASSERTION(dn == NULL || dn->dn_assigned_txg == tx->tx_txg) failed

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-03-23 12:24:05 -07:00
Brian Behlendorf
4b5d425f14 Add ZFS_META_RELEASE to module load/unload messages
Include the ZFS_META_RELEASE in the module load/unload messages
to more clearly indidcate exactly what version of ZFS has been
loaded.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-03-23 12:14:35 -07:00
Brian Behlendorf
9ed86e7cc7 Account for .zfs ctldir inodes
Because the .zfs ctldir inodes are not backed by physical storage
they use a different create path which was not properly accounting
for them as used.  This could result in ->nr_cached_objects()
returning 0 and cause a divide by zero error in prune_super().

In my option there's a kernel bug here too which allows this to
happen.  They should either be checking for 0 or adding +1 like
they correctly do earlier in the function.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #617
2012-03-22 15:43:55 -07:00
Brian Behlendorf
ebe7e575ea Add .zfs control directory
Add support for the .zfs control directory.  This was accomplished
by leveraging as much of the existing ZFS infrastructure as posible
and updating it for Linux as required.  The bulk of the core
functionality is now all there with the following limitations.

*) The .zfs/snapshot directory automount support requires a 2.6.37
   or newer kernel.  The exception is RHEL6.2 which has backported
   the d_automount patches.

*) Creating/destroying/renaming snapshots with mkdir/rmdir/mv
   in the .zfs/snapshot directory works as expected.  However,
   this functionality is only available to root until zfs
   delegations are finished.

      * mkdir - create a snapshot
      * rmdir - destroy a snapshot
      * mv    - rename a snapshot

The following issues are known defeciences, but we expect them to
be addressed by future commits.

*) Add automount support for kernels older the 2.6.37.  This should
   be possible using follow_link() which is what Linux did before.

*) Accessing the .zfs/snapshot directory via NFS is not yet possible.
   The majority of the ground work for this is complete.  However,
   finishing this work will require resolving some lingering
   integration issues with the Linux NFS kernel server.

*) The .zfs/shares directory exists but no futher smb functionality
   has yet been implemented.

Contributions-by: Rohan Puri <rohan.puri15@gmail.com>
Contributiobs-by: Andrew Barnes <barnes333@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #173
2012-03-22 13:03:47 -07:00
Brian Behlendorf
49be0ccf1f Add zio constructor/destructor
Add a standard zio constructor and destructor.  Normally, this is
done to reduce to cost of allocating a new structure by reducing
expensive operations such as memory allocations.  However, in this
case none of the operations moved out of zio_create() were really
very expensive.

This change was principly made as a debug patch (and workaround)
for a zio_destroy() race.  The is good evidence that zio_create()
is reinitializing a mutex which is really still in use by another
thread.  This would completely explain the observed symptoms in
the issue report.

This patch doesn't fix the root cause of the race, but it should
make it less likely by only initializing the mutex once in the
constructor.  Also, this particular flaw might have gone unnoticed
in other zfs implementations due to the specific implementation
details of Linux ticket spinlocks.

Once the real root cause is determined and resolved this change
can be safely reverted.  Until then this should help workaround
the issue.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #496
2012-03-21 14:51:44 -07:00
Brian Behlendorf
c8df41538d Revert "Add zio constructor/destructor"
This patch was slightly flawed and allowed for zio->io_logical
to potentially not be reinitialized for a new zio.  This could
lead to assertion failures in specific cases when debugging is
enabled (--enable-debug) and I/O errors are encountered.  It
may also have caused problems when issues logical I/Os.

Since we want to make sure this workaround can be easily removed
in the future (when we have the real fix).  I'm reverting this
change and applying a new version of the patch which includes
the zio->io_logical fix.

This reverts commit 2c6d0b1e07.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #602
Issue #604
2012-03-21 14:51:01 -07:00
Brian Behlendorf
43c8454724 ZFS 0.6.0-rc7 2012-03-16 11:25:13 -07:00
Brian Behlendorf
77a405ae52 Add missing NULL in zpl_xattr_handlers
The xattr_resolve_name() helper function expects the registered
list of xattr handlers to be NULL terminated.  This NULL was
accidentally missing which could result in a NULL dereference.

Interestingly this issue only manifested itself on certain 32-bit
systems.  Presumably on 64-bit kernels we just always happen to
get lucky and the memory following the structure is zeroed.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #594
2012-03-15 15:18:29 -07:00
Gregor Kopka
42cb3819f1 Use stderr for 'no pools/datasets available' error
The 'zfs list' and 'zpool list' commands output the message
'no datasets/pools available' to stdout.  This should go to
stderr and only the available datasets/pools should go to
stdout.  Returning nothing to stdout is expected behavior
when there is nothing to list.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #581
2012-03-15 10:24:00 -07:00
Brian Behlendorf
0ece356db5 Add sa_spill_rele() interface
Add a SA interface which allows us to release the spill block
from a SA handle without destroying the handle.  This is useful
because we can then ensure that a copy of the dirty spill block
is not made at sync time due to the extra hold.  Susequent calls
to sa_update() or sa_lookup() with transparently refetch the
spill block dbuf from the ARC hash.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-03-07 16:28:00 -08:00
Brian Behlendorf
2c6d0b1e07 Add zio constructor/destructor
Add a standard zio constructor and destructor.  Normally, this is
done to reduce to cost of allocating a new structure by reducing
expensive operations such as memory allocations.  However, in this
case none of the operations moved out of zio_create() were really
very expensive.

This change was principly made as a debug patch (and workaround)
for a zio_destroy() race.  The is good evidence that zio_create()
is reinitializing a mutex which is really still in use by another
thread.  This would completely explain the observed symptoms in
the issue report.

This patch doesn't fix the root cause of the race, but it should
make it less likely by only initializing the mutex once in the
constructor.  Also, this particular flaw might have gone unnoticed
in other zfs implementations due to the specific implementation
details of Linux ticket spinlocks.

Once the real root cause is determined and resolved this change
can be safely reverted.  Until then this should help workaround
the issue.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #496
2012-03-07 16:06:23 -08:00
Richard Yao
76c2b24c61 Fix distribution detection
Improve the distribution detection by moving the tests for
distribution specific files first.  The Ubuntu and Debian
checks are left for last because they are the least likely
to be unique.  This is particularly true in the case of Debian
since so many distributions are based on Debian.

Since this is currently only used to identify the correct
packaging method for this system the result in many instances
is simply cosmetic.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-03-05 10:38:27 -08:00
Ned Bass
613d88eda8 Align parition end on 1 MiB boundary
Some devices have exhibited sensitivity to the ending alignment of
partitions.  In particular, even if the first partition begins at 1
MiB, we have seen many sd driver task abort errors with certain SSDs
if the first partition doesn't end on a 1 MiB boundary.  This occurs
when the vdev label is read during pool creation or importation and
causes a delay of about 30 seconds per device.  It can also be
simulated with dd when the pool isn't imported:

  dd if=/dev/sda1 of=/dev/null bs=262144 count=1

For the record, this problem was observed with SMARTMOD
SG9XCA2E200GE01 200GB SSDs.  Unfortunately I don't have a good
explanation for this behavior. It seems to have something to do with
highly fragmented single-sector requests being issued to the device,
which it may not support.  With end-aligned partitions at least
page-sized requests were queued and issued to the driver according
to blktrace. In any case, aligning the partition end is a fairly
innocuous work-around, wasting at most 1 MiB of space.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #574
2012-03-05 09:49:50 -08:00
Brian Behlendorf
ec2626ad3f Use SA_HDL_PRIVATE for SA xattrs
A private SA handle must be used to ensure we can drop the dbuf
hold on the spill block prior to calling dmu_tx_commit().  If we
call dmu_tx_commit() before sa_handle_destroy(), then our hold
will trigger a copy of the dbuf to be made.  This is done to
prevent data from leaking in to the syncing txg.  As a result
the original dirty spill block will remain cached.

Additionally, relying on the shared zp->z_sa_hdl is unsafe in
the xattr context because the znode may be asynchronously dropped
from the cache.  It's far safer and simpler just to use a private
handle for xattrs.  Plus any additional overhead is offset by
the avoidance of the previously mentioned memory copy.

These forever dirty buffers can be noticed in the arcstats under
the anon_size.  On a quiescent system the value should be zero.
Without this fix and a SA xattr write workload you will see
anon_size increase.  Eventually, if enough dirty data builds up
your system it will appear to hang.  This occurs because the dmu
won't allow new txs to be assigned until that dirty data is
flushed, and it won't be because it's not part of an assigned tx.

As an aside, I typically see anon_size lurk around 16k so I think
there is another place in the code which needs a similar fix.
However, this value doesn't grow over time so it isn't critical.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #503
Issue #513
2012-03-02 13:20:48 -08:00
Brian Behlendorf
4b787d75c8 Cleanly support debug packages
Allow a source rpm to be rebuilt with debugging enabled.  This
avoids the need to have to manually modify the spec file.  By
default debugging is still largely disabled.  To enable specific
debugging features use the following options with rpmbuild.

  '--with debug'               - Enables ASSERTs

  # For example:
  $ rpmbuild --rebuild --with debug zfs-modules-0.6.0-rc6.src.rpm

Additionally, ZFS_CONFIG has been added to zfs_config.h for
packages which build against these headers.  This is critical
to ensure both zfs and the dependant package are using the same
prototype and structure definitions.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-27 14:08:17 -08:00
Brian Behlendorf
570827e129 Add 'dmu_tx' kstats entry
Keep counters for the various reasons that a thread may end up
in txg_wait_open() waiting on a new txg.  This can be useful
when attempting to determine why a particular workload is
under performing.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-27 08:59:10 -08:00
Brian Behlendorf
13be560d89 Add arc_state_t stats to arcstats
To ensure the arc is behaving properly we need greater visibility
in to exactly how it's managing the systems memory.  This patch
takes one step in that direction be adding the current arc_state_t
for the anon, mru, mru_ghost, mfu, and mfs_ghost lists.  The l2
arc_state_t is already well represented in the arcstats.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-27 08:58:59 -08:00
Ned Bass
3a4f6caf08 Return success from check_slice() if device doesn't exist
When creating a new pool, make_root_vdev() calls check_in_use() to
ensure that none of the consituent disks are in use.  If the disk
contains a valid vdev label it is read to retrieve the list of its
child vdevs and these are checked recursively.  However, the
partitions stored in the vdev label my no longer exist, for example
if the partition table has since been altered.  In any such case we
would want the pool creation to proceed, so this change removes the
check from check_slice() that returns an error if the device doesn't
exist.  As an added assurance, the Solaris implementation also
returns sucess on ENOENT.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-27 08:52:38 -08:00
Alex Zhuravlev
a473d90cee Export symbols for zero-copy
Export additional symbols to make use of the DMU's zero-copy
API.  This allows external modules to move data in to and out of
the ARC without incurring the cost of a memory copy.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-17 12:43:02 -08:00
Richard Yao
b41c9906dc Support ashift=13 for 8KB SSD block sizes
New SSDs are now available which use an internal 8k block size.
To make sure ZFS can get the maximum performance out of these
devices we're increasing the maximum ashift to 13 (8KB).

This value is still small enough that we can fit 16 uberblocks
in the vdev ring label.  However, I don't want to increase this
any futher or it will limit the ability the safely roll back a
pool to recover it.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #565
2012-02-13 12:25:27 -08:00
Turbo Fredriksson
d2e032ca9c Add 'fsid' mount option to allowed options.
Resolves nfs-utils-1.0.x compatibility issue which requires
that the fsid be set in the export options.

  exportfs: Warning: /tank/dir requires fsid= for NFS export

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #570
2012-02-13 09:43:57 -08:00
Brian Behlendorf
b10c77f70a Export symbols for zero-copy
Exported the required symbols to make use of the DMU's zero-copy
API.  This allows external modules to move data in to and out of
the ARC without incurring the cost of a memory copy.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-10 11:56:55 -08:00
Brian Behlendorf
a31acb462d Use spl_debug_* helpers
When configuring the spl debug log support use the provided wrapper
functions.  This ensures that if --disable-debug-log was used when
buiding the spl the functions will have no effect.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-09 16:37:48 -08:00
Etienne Dechamps
30930fba21 Add support for DISCARD to ZVOLs.
DISCARD (REQ_DISCARD, BLKDISCARD) is useful for thin provisioning.
It allows ZVOL clients to discard (unmap, trim) block ranges from
a ZVOL, thus optimizing disk space usage by allowing a ZVOL to
shrink instead of just grow.

We can't use zfs_space() or zfs_freesp() here, since these functions
only work on regular files, not volumes. Fortunately we can use the
low-level function dmu_free_long_range() which does exactly what we
want.

Currently the discard operation is not added to the log. That's not
a big deal since losing discard requests cannot result in data
corruption. It would however result in disk space usage higher than
it should be. Thus adding log support to zvol_discard() is probably
a good idea for a future improvement.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-09 16:19:38 -08:00
Etienne Dechamps
cb2d19010d Support the fallocate() file operation.
Currently only the (FALLOC_FL_PUNCH_HOLE) flag combination is
supported, since it's the only one that matches the behavior of
zfs_space(). This makes it pretty much useless in its current
form, but it's a start.

To support other flag combinations we would need to modify
zfs_space() to make it more flexible, or emulate the desired
functionality in zpl_fallocate().

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #334
2012-02-09 16:19:32 -08:00
Etienne Dechamps
aec69371a6 Check permissions in zfs_space().
This isn't done on Solaris because on this OS zfs_space() can
only be called with an opened file handle. Since the addition of
zpl_truncate_range() this isn't the case anymore, so we need to
enforce access rights.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #334
2012-02-09 15:20:37 -08:00
Etienne Dechamps
5cb63a57f8 Implement the truncate_range() inode operation.
This operation allows "hole punching" in ZFS files. On Solaris this
is done via the vop_space() system call, which maps to the zfs_space()
function. So we just need to write zpl_truncate_range() as a wrapper
around zfs_space().

Note that this only works for regular files, not ZVOLs.

This is currently an insecure implementation without permission
checking, although this isn't that big of a deal since truncate_range()
isn't even callable from userspace.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #334
2012-02-09 15:20:32 -08:00
Brian Behlendorf
93648f314c Fix zconfig.sh non-optimal alignment
The recent zvol improvements have changed default suggested alignment
for zvols from 512b (default) to 8k (zvol blocksize).  Because of this
the zconfig.sh tests which create paritions are now generating a
warning about non-optimal alignments.

This change updates the need zconfig.sh tests such that a partition
will be properly aligned.  In the process, it shifts from using the
sfdisk utility to the parted utility to create partitions.  It also
moves the creation of labels, partitions, and filesystems in to
generic functions in common.sh.in.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-09 13:23:28 -08:00
Etienne Dechamps
dde9380a1b Use 32 as the default number of zvol threads.
Currently, the `zvol_threads` variable, which controls the number of worker
threads which process items from the ZVOL queues, is set to the number of
available CPUs.

This choice seems to be based on the assumption that ZVOL threads are
CPU-bound. This is not necessarily true, especially for synchronous writes.
Consider the situation described in the comments for `zil_commit()`, which is
called inside `zvol_write()` for synchronous writes:

> itxs are committed in batches. In a heavily stressed zil there will be a
> commit writer thread who is writing out a bunch of itxs to the log for a
> set of committing threads (cthreads) in the same batch as the writer.
> Those cthreads are all waiting on the same cv for that batch.
>
> There will also be a different and growing batch of threads that are
> waiting to commit (qthreads). When the committing batch completes a
> transition occurs such that the cthreads exit and the qthreads become
> cthreads. One of the new cthreads becomes he writer thread for the batch.
> Any new threads arriving become new qthreads.

We can easily deduce that, in the case of ZVOLs, there can be a maximum of
`zvol_threads` cthreads and qthreads. The default value for `zvol_threads` is
typically between 1 and 8, which is way too low in this case. This means
there will be a lot of small commits to the ZIL, which is very inefficient
compared to a few big commits, especially since we have to wait for the data
to be on stable storage. Increasing the number of threads will increase the
amount of data waiting to be commited and thus the size of the individual
commits.

On my system, in the context of VM disk image storage (lots of small
synchronous writes), increasing `zvol_threads` from 8 to 32 results in a 50%
increase in sequential synchronous write performance.

We should choose a more sensible default for `zvol_threads`. Unfortunately
the optimal value is difficult to determine automatically, since it depends
on the synchronous write latency of the underlying storage devices. In any
case, a hardcoded value of 32 would probably be better than the current
situation. Having a lot of ZVOL threads doesn't seem to have any real
downside anyway.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Fixes #392
2012-02-08 13:58:10 -08:00
Etienne Dechamps
34037afe24 Improve ZVOL queue behavior.
The Linux block device queue subsystem exposes a number of configurable
settings described in Linux block/blk-settings.c. The defaults for these
settings are tuned for hard drives, and are not optimized for ZVOLs. Proper
configuration of these options would allow upper layers (I/O scheduler) to
take better decisions about write merging and ordering.

Detailed rationale:

 - max_hw_sectors is set to unlimited (UINT_MAX). zvol_write() is able to
   handle writes of any size, so there's no reason to impose a limit. Let the
   upper layer decide.

 - max_segments and max_segment_size are set to unlimited. zvol_write() will
   copy the requests' contents into a dbuf anyway, so the number and size of
   the segments are irrelevant. Let the upper layer decide.

 - physical_block_size and io_opt are set to the ZVOL's block size. This
   has the potential to somewhat alleviate issue #361 for ZVOLs, by warning
   the upper layers that writes smaller than the volume's block size will be
   slow.

 - The NONROT flag is set to indicate this isn't a rotational device.
   Although the backing zpool might be composed of rotational devices, the
   resulting ZVOL often doesn't exhibit the same behavior due to the COW
   mechanisms used by ZFS. Setting this flag will prevent upper layers from
   making useless decisions (such as reordering writes) based on incorrect
   assumptions about the behavior of the ZVOL.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-07 16:23:06 -08:00
Etienne Dechamps
b18019d2d8 Fix synchronicity for ZVOLs.
zvol_write() assumes that the write request must be written to stable storage
if rq_is_sync() is true. Unfortunately, this assumption is incorrect. Indeed,
"sync" does *not* mean what we think it means in the context of the Linux
block layer. This is well explained in linux/fs.h:

    WRITE:       A normal async write. Device will be plugged.
    WRITE_SYNC:  Synchronous write. Identical to WRITE, but passes down
                 the hint that someone will be waiting on this IO
                 shortly.
    WRITE_FLUSH: Like WRITE_SYNC but with preceding cache flush.
    WRITE_FUA:   Like WRITE_SYNC but data is guaranteed to be on
                 non-volatile media on completion.

In other words, SYNC does not *mean* that the write must be on stable storage
on completion. It just means that someone is waiting on us to complete the
write request. Thus triggering a ZIL commit for each SYNC write request on a
ZVOL is unnecessary and harmful for performance. To make matters worse, ZVOL
users have no way to express that they actually want data to be written to
stable storage, which means the ZIL is broken for ZVOLs.

The request for stable storage is expressed by the FUA flag, so we must
commit the ZIL after the write if the FUA flag is set. In addition, we must
commit the ZIL before the write if the FLUSH flag is set.

Also, we must inform the block layer that we actually support FLUSH and FUA.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-07 16:23:06 -08:00
Etienne Dechamps
56c34bac44 Support "sync=always" for ZVOLs.
Currently the "sync=always" property works for regular ZFS datasets, but not
for ZVOLs. This patch remedies that.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Fixes #374.
2012-02-07 16:23:06 -08:00
Darik Horn
e67329d8e0 Let libnvpair be linked independently of libzfs.
Autoconf will fail to detect the ZoL libnvpair on systems that do not
implicitly link library runtime dependencies, which is anything that
has the GCC 4.5 DCO update.

Build libuutil before libnvpair, and put it on the the LDADD line of
the libnvpair automake template.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes: #560
2012-02-07 11:37:15 -08:00
Brian Behlendorf
47621f3d76 Linux 3.3 compat, sops->show_options()
The second argument of sops->show_options() was changed from a
'struct vfsmount *' to a 'struct dentry *'.  Add an autoconf check
to detect the API change and then conditionally define the expected
interface.  In either case we are only interested in the zfs_sb_t.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #549
2012-02-03 10:02:01 -08:00
Brian Behlendorf
d7e398ce1a Cleanup ZFS debug infrastructure
Historically the internal zfs debug infrastructure has been
scattered throughout the code.  Since we expect to start making
more use of this code this patch performs some cleanup.

* Consolidate the zfs debug infrastructure in the zfs_debug.[ch]
  files.  This includes moving the zfs_flags and zfs_recover
  variables, plus moving the zfs_panic_recover() function.

* Remove the existing unused functionality in zfs_debug.c and
  replace it with code which correctly utilized the spl logging
  infrastructure.

* Remove the __dprintf() function from zfs_ioctl.c.  This is
  dead code, the dprintf() functionality in the kernel relies
  on the spl log support.

* Remove dprintf() from hdr_recl().  This wasn't particularly
  useful and was missing the required format specifier anyway.

* Subsequent patches should unify the dprintf() and zfs_dbgmsg()
  functions.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-02 11:24:30 -08:00