As part of block polling support in Linux 4.4, make_request_fn should
return a cookie value of type blk_qc_t. For now, we make zvol_request
always return BLK_QC_T_NONE until we assess whether and how we want
to support block polling.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4021
On 32 bit, the calculation of zfs_dirty_data_max from phymem will overflow,
causing it to be smaller than zfs_dirty_data_sync, and will cause txg being
delayed while no one write to disk. The end result is horrendous write speed.
On 4G ram 32-bit VM, before this patch, simple dd results in ~7MB/s. Now it
can reach speed on par with 64-bit VM.
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3973
On 32 bit system, zio_buf_cache is limit to 1M. Larger than that is all NULL.
So we need to avoid reaping them.
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3973
When concurrent threads accessing the snapdir, one will succeed the user
helper mount while others will get EBUSY. However, the original code treats
those EBUSY threads as success and goes on to do zfsctl_snapshot_add, which
causes repeated avl_add and thus panic.
Also, if the snapshot is already mounted somewhere else, a thread accessing
the snapdir will also get EBUSY from user helper mount. And it will cause
strange things as doing follow_down_one will fail and then follow_up will jump
up to the mountpoint of the filesystem and confuse the hell out of VFS.
The patch fix both behavior by returning 0 immediately for the EBUSY threads.
Note, this will have a side effect for the second case where the VFS will
retry several times before returning ELOOP.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#4018
Because errors during module load are so rare it went unnoticed that
it was possible that a positive errno was returned. This would result
in the module being loaded, nothing being initialized, and a system
panic shortly thereafter. This is what was causing the hard failures
in the automated testing.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
When decreasing the maximum ARC size preserve the 3/4 default
ratio for the arc_meta_limit. Otherwise, the arc_meta_limit
may be set the same as arc_max.
Signed-off-by: AndCycle <andcycle@andcycle.idv.tw>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#4001
When sa_bulk_lookup() fails, unlock_new_inode() will spit out a WARNING. It
will also recursive deadlock on ZFS_OBJ_HOLD_ENTER in zfs_zinactive().
Since we never call insert_inode_locked in fail path, I_NEW is never set, the
inode is never hashed. So unlock_new_inode() can be safely remove it.
We set z_sa_hdl to NULL in fail path so that iput path will stop at
zfs_inactive() without entering zfs_zinactive(). This way we can avoid the
deadlock and prevent double sa_handle_destroy().
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3899
Currently, vdev_disk_physio_completion will try to wake up an waiter without
first checking the existence. This creates a race window in which complete is
called after dr is freed.
We add dr_wait in dio_request to indicate the existence of waiter. Also,
remove dr_rw since no one is using it, and reorder dr_ref to make the struct
more compact in 64bit.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3917
Issue #3880
Strictly enforce keeping 'arc_c >= arc_c_min'. The ASSERTs are
left in place to catch this in a debug build but logic has been
added to gracefully handle in a production build.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3904
We should never block when holding a spin lock, but zfs_inode_update can
block in the critical section of a spin lock in zfs_inode_update:
zfs_inode_update -> dmu_object_size_from_db -> zrl_add -> mutex_enter
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3858
All users of zv_lock were removed by 37f9dac, but we forgot to remove
it. Lets remove it as clean up.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3858
This reverts commit 5f8e1e8505. It
was determined that this patch introduced the quota regression
described in #3789.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3443
Issue #3789
Commit b39c22b set the READ_SYNC and WRITE_SYNC flags for a bio
based on the ZIO_PRIORITY_* flag passed in. This had the unnoticed
side-effect of making the vdev_disk_io_start() synchronous for
certain I/Os.
This in turn resulted in vdev_disk_io_start() being able to
re-dispatch zio's which would result in a RCU stalls when a disk
was removed from the system. Additionally, this could negatively
impact performance and explains the performance regressions reported
in both #3829 and #3780.
This patch resolves the issue by making the blocking behavior
dependent on a 'wait' flag being passed rather than overloading
the passed bio flags.
Finally, the WRITE_SYNC and READ_SYNC behavior is restricted to
non-rotational devices where there is no benefit to queuing to
aggregate the I/O.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3652
Issue #3780
Issue #3785
Issue #3817
Issue #3821
Issue #3829
Issue #3832
Issue #3870
As described in the comment above arc_reclaim_thread() it's critical
that the reclaim thread be careful about blocking. Just like it must
never wait on a hash lock, it must never wait on a task which can in
turn wait on the CV in arc_get_data_buf(). This will deadlock, see
issue #3822 for full backtraces showing the problem.
To resolve this issue arc_kmem_reap_now() has been updated to use the
asynchronous arc prune function. This means that arc_prune_async()
may now be called while there are still outstanding arc_prune_tasks.
However, this isn't a problem because arc_prune_async() already
keeps a reference count preventing multiple outstanding tasks per
registered consumer. Functionally, this behavior is the same as
the counterpart illumos function dnlc_reduce_cache().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Issue #3808
Issue #3834
Issue #3822
The zpl_nr_cached_objects() function has been disabled because in the
current code it doesn't provide any critical functionality and it may
result in a deadlock under certain circumstances. However, because
we expect to need these hooks in the future this code has not been
entirely removed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3719
Accessing a snapshot via NFS should cause an auto-unmount of that
snapshot to be deferred until such as time as the snapshot is idle.
This is analogous to the zpl_revalidate logic employed by locally
mounted snapshots.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3794
Commit torvalds/linux@4246a0b63b
("block: add a bi_error field to struct bio") dropped the error
argument from bio_endio in favor of newly introduced bio->bi_error.
This also replaces bio->bi_flags value BIO_UPTODATE.
bio_endio was a 3 argument function until Linux 2.6.24, which made it
a 2 argument function, and now the prototype has changed yet again to
a 1 argument function. Support for pre 2.6.24 kernels was already
dropped with 37f9dac592 ("zvol processing should use struct bio")
which assumed the 2 argument version in zvol_request(). Remaining code
to support the 3 argument version is hereby removed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Issue #3799
ZFS incorrectly uses directory-based extended attributes even when
xattr=sa is specified as a dataset property or mount option. Support to
honor temporary mount options including "xattr" was added in commit
0282c4137e. There are two issues with the
mount option handling:
* Libzfs has historically included "xattr" in its list of default mount
options. This overrides the dataset property, so the dataset is always
configured to use directory-based xattrs even when the xattr dataset
property is set to off or sa. Address this by removing "xattr" from
the set of default mount options in libzfs.
* There was no way to enable system attribute-based extended attributes
using temporary mount options. Add the mount options "saxattr" and
"dirxattr" which enable the xattr behavior their names suggest. This
approach has the advantages of mirroring the valid xattr dataset
property values and following existing conventions for mount option
names.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3787
Passing NULL for the mount data should not result in EINVAL. It
should be treated as if an empty string were passed and succeed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes#3771
37f9dac592 replaced the end-start
calculation with a cached value, but neglected to update it on discard
operations. This can cause us to discard data not requested, causing
data loss on zvols.
Reported-by: Richard Connon <richard.connon@zynstra.com>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3798
6214 zpools going south
Reviewed by: Igor Kozhukhov <ikozhukhov@gmail.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com>
References:
https://www.illumos.org/issues/6214http://cr.illumos.org/~webrev/sensille/6214_zpools_going_south/
Porting Notes:
Reintroduce b_compress to the l2arc_buf_hdr_t. In commit b9541d6
the compression flags were moved to the generic b_flags in the
arc_buf_hdr_t. This is a problem because l2arc_compress_buf()
may manipulate the compression flags and this can only be done
safely under the hash lock which is not held. See Illumos 6214
for a detailed analysis of the race.
HDR_GET_COMPRESS() macro was removed from arc_buf_info().
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3757
When adding a zvol to the system prefetch zvol_prefetch_bytes from the
start and end of the volume. Prefetching these regions of the volume is
desirable because they are likely to be accessed immediately by blkid(8),
the kernel scanning for a partition table, or another task which probes
the devices.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3659
zfsonlinux/zfs@e20cd6f7a8 caused us to
lose IO accounting on zvols. When I originally wrote that last year, the
symbols we needed to maintain IO accounting were GPL exported, but
torvalds/linux@394ffa503b provided
suitable symbols for restoring this functionality 4 months later. We
can call them to restore the IO accounting on Linux 3.19 and later as
well as any older kernels where that patch is backported.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3741
Internally ZFS keeps a small log to facilitate debugging. By default
the log is disabled, to enable it set zfs_dbgmsg_enable=1. The contents
of the log can be accessed by reading the /proc/spl/kstat/zfs/dbgmsg file.
Writing 0 to this proc file clears the log.
$ echo 1 >/sys/module/zfs/parameters/zfs_dbgmsg_enable
$ echo 0 >/proc/spl/kstat/zfs/dbgmsg
$ zpool import tank
$ cat /proc/spl/kstat/zfs/dbgmsg
1 0 0x01 -1 0 2492357525542 2525836565501
timestamp message
1441141408 spa=tank async request task=1
1441141408 txg 70 open pool version 5000; software version 5000/5; ...
1441141409 spa=tank async request task=32
1441141409 txg 72 import pool version 5000; software version 5000/5; ...
1441141414 command: lt-zpool import tank
Note the zfs_dbgmsg() and dprintf() functions are both now mapped to
the same log. As mentioned above the kernel debug log can be accessed
though the /proc/spl/kstat/zfs/dbgmsg kstat. For user space consumers
log messages are immediately written to stdout after applying the
ZFS_DEBUG environment variable.
$ ZFS_DEBUG=on ./cmd/ztest/ztest -V
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes#3728
This patch is based on the previous work done by @andrey-ve and
@yshui. It triggers the automount by using kern_path() to traverse
to the known snapshout mount point. Once the snapshot is mounted
NFS can access the contents of the snapshot.
Allowing NFS clients to access to the .zfs/snapshot directory would
normally mean that a root user on a client mounting an export with
'no_root_squash' would be able to use mkdir/rmdir/mv to manipulate
snapshots on the server. To prevent configuration mistakes a
zfs_admin_snapshot module option was added which disables the
mkdir/rmdir/mv functionally. System administators desiring this
functionally must explicitly enable it.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2797Closes#1655Closes#616
Prevents NFS client from detection of different fileids of snapshot root dentry
before & after snapshot mount.
Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Linux 2.6.36 introduced REQ_SECURE to indicate when discards *must* be
processed, such that we cannot do optimizations like block alignment.
Consequently, the discard semantics prior to 2.6.36 require us to always
process unaligned discards. Previously, we would do this optimization
regardless. This patch changes things to correctly restrict this
optimization to situations where REQ_SECURE exists, but is not included
in the flags.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Internally, zvols are files exposed through the block device API. This
is intended to reduce overhead when things require block devices.
However, the ZoL zvol code emulates a traditional block device in that
it has a top half and a bottom half. This is an unnecessary source of
overhead that does not exist on any other OpenZFS platform does this.
This patch removes it. Early users of this patch reported double digit
performance gains in IOPS on zvols in the range of 50% to 80%.
Comments in the code suggest that the current implementation was done to
obtain IO merging from Linux's IO elevator. However, the DMU already
does write merging while arc_read() should implicitly merge read IOs
because only 1 thread is permitted to fetch the buffer into ARC. In
addition, commercial ZFSOnLinux distributions report that regular files
are more performant than zvols under the current implementation, and the
main consumers of zvols are VMs and iSCSI targets, which have their own
elevators to merge IOs.
Some minor refactoring allows us to register zfs_request() as our
->make_request() handler in place of the generic_make_request()
function. This eliminates the layer of code that broke IO requests on
zvols into a top half and a bottom half. This has several benefits:
1. No per zvol spinlocks.
2. No redundant IO elevator processing.
3. Interrupts are disabled only when actually necessary.
4. No redispatching of IOs when all taskq threads are busy.
5. Linux's page out routines will properly block.
6. Many autotools checks become obsolete.
An unfortunate consequence of eliminating the layer that
generic_make_request() is that we no longer calls the instrumentation
hooks for block IO accounting. Those hooks are GPL-exported, so we
cannot call them ourselves and consequently, we lose the ability to do
IO monitoring via iostat. Since zvols are internally files mapped as
block devices, this should be okay. Anyone who is willing to accept the
performance penalty for the block IO layer's accounting could use the
loop device in between the zvol and its consumer. Alternatively, perf
and ftrace likely could be used. Also, tools like latencytop will still
work. Tools such as latencytop sometimes provide a better view of
performance bottlenecks than the traditional block IO accounting tools
do.
Lastly, if direct reclaim occurs during spacemap loading and swap is on
a zvol, this code will deadlock. That deadlock could already occur with
sync=always on zvols. Given that swap on zvols is not yet production
ready, this is not a blocker.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Reclaim in the traverse prefetch thread, which is run on the system
taskq, can overrun the stack.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes#3733
Add the required kernel side infrastructure to parse arbitrary
mount options. This enables us to support temporary mount
options in largely the same way it is handled on other platforms.
See the 'Temporary Mount Point Properties' section of zfs(8)
for complete details.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#985Closes#3351
Commit 49ddb31506 added the
zfs_arc_average_blocksize parameter to allow control over the size of
the arc hash table. The dbuf hash table's size should be determined
similarly.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3721
Allow for easy turning of a pools reserved free space. Previous
versions of ZFS (v0.6.4 and earlier) held 1/64 of the pools capacity
in reserve. Commits 3d45fdd and 0c60cc3 increased this to 1/32.
Setting spa_slop_shift=6 will restore the previous default setting.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3724
The LBA weighting makes sense on rotational media where the outer tracks
have twice the bandwidth of the inner tracks. However, it is detrimental
on nonrotational media such as solid state disks, where the only effect
is to ensure that metaslabs enter the best-fit allocation behavior
sooner, which is detrimental to performance. It also makes no sense on
files where the underlying filesystem can arrange things however it
wants.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3712
Before read locking z_teardown_inactive_lock, we need to check if we have
already had write lock on it. Otherwise, we would deadlock on ourself when
doing rollback:
zfs_ioc_rollback
->zfs_suspend_fs (z_teardown_inactive_lock, RW_WRITER)
->zfs_resume_fs->zfs_rezget->zfs_iput_async->iput-> ...
->zfs_inactive (z_teardown_inactive_lock, RW_READER)
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2869
The misc_deregister() function was changed to a void return type.
Rather than add compatibility code to detect this change simply
ignore the return code on all kernels. It was only used to log
an informational error message of no real value.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Re-factor the .zfs/snapshot auto-mouting code to take in to account
changes made to the upstream kernels. And to lay the groundwork for
enabling access to .zfs snapshots via NFS clients. This patch makes
the following core improvements.
* All actively auto-mounted snapshots are now tracked in two global
trees which are indexed by snapshot name and objset id respectively.
This allows for fast lookups of any auto-mounted snapshot regardless
without needing access to the parent dataset.
* Snapshot entries are added to the tree in zfsctl_snapshot_mount().
However, they are now removed from the tree in the context of the
unmount process. This eliminates the need complicated error logic
in zfsctl_snapshot_unmount() to handle unmount failures.
* References are now taken on the snapshot entries in the tree to
ensure they always remain valid while a task is outstanding.
* The MNT_SHRINKABLE flag is set on the snapshot vfsmount_t right
after the auto-mount succeeds. This allows to kernel to unmount
idle auto-mounted snapshots if needed removing the need for the
zfsctl_unmount_snapshots() function.
* Snapshots in active use will not be automatically unmounted. As
long as at least one dentry is revalidated every zfs_expire_snapshot/2
seconds the auto-unmount expiration timer will be extended.
* Commit torvalds/linux@bafc9b7 caused snapshots auto-mounted by ZFS
to be immediately unmounted when the dentry was revalidated. This
was a consequence of ZFS invaliding all snapdir dentries to ensure that
negative dentries didn't mask new snapshots. This patch modifies the
behavior such that only negative dentries are invalidated. This solves
the issue and may result in a performance improvement.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3589Closes#3344Closes#3295Closes#3257Closes#3243Closes#3030Closes#2841
There's no metadata to write to disk for ctldir inodes. So we check if
a inode belongs to the ctldir in zpl_commit_metadata, and returns
immediately if it is.
Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2797
zvols should not be an entropy source for the kernel. Disable it to be
consistent with the upstream kernel.
torvalds/linux@b277da0a8a
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3713
Add a missing space to the zfs_vdev_sync_write_min_active module
parameter description.
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3714
As part of the stack reduction effort in
50b25b2187, a zio_t containing a taskq_ent
was added to struct vdev_queue which itself is part of struct vdev.
The taskq entry should be initialized as is currently done in zio_create()
for newly-created bare zio_t object. The rationale is the same as is
described in f467b05a26.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3709
If the ZAP object containing a snapshot map is corrupted due to an
unrecoverable checksum error or otherwise, dsl_dataset_name() will
normally panic the system due to its VERIFY.
This patch attempts to allow a recovery avenue from such situations by
manufacturing a descriptive snapshot name and then ignoring the error.
Scrubbing a pool with this type of corruption will then show the affected
object in the error list rather than panicking.
The recovery code is only enabled when the zfs_recover module parameter
is set.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3705
Since ZoL allows large blocks to be used by volumes, unlike upstream
illumos, the feature flag must be checked prior to volume creation.
This is critical because unlike filesystems, volumes will create a
object which uses large blocks as part of the create. Therefore, it
cannot be safely checked in zfs_check_settable() after the dataset
can been created.
In addition this patch updates the relevant error messages to use
zfs_nicenum() to print the maximum blocksize.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3591
When support for large blocks was added DMU_MAX_ACCESS was increased
to allow for blocks of up to 16M to fit in a transaction handle.
This had the side effect of increasing the max_hw_sectors_kb for
volumes, which are scaled off DMU_MAX_ACCESS, to 64M from 10M.
This is an issue for volumes which by default use an 8K block size
because it results in dmu_buf_hold_array_by_dnode() allocating a
64K array for the dbufs. The solution is to restore the maximum
size to ~10M. This patch specifically changes it to 16M which is
close enough.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3684
Starting from Linux 4.1 allows iov_iter with bio_vec to be passed into
iter_read/iter_write. Notably, the loop device will pass bio_vec to backend
filesystem. However, current ZFS code assumes iovec without any check, so it
will always crash when using loop device.
With the restructured uio_t, we can safely pass bio_vec in uio_t with UIO_BVEC
set. The uio* functions are modified to handle bio_vec case separately.
The const uio_iov causes some warning in xuio related stuff, so explicit
convert them to non const.
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3511Closes#3640
The spa_config_write() function relies on the classic method of
making sure updates to the /etc/zfs/zpool.cache file are atomic.
It writes out a temporary version of the file and then uses
vn_rename() to switch it in to place. This way there can never
exist a partial version of the file, it's all or nothing.
Conceptually this is a good strategy and it makes good sense
for platforms where it's easy to do a rename within the kernel.
Unfortunately, Linux is not one of those platforms. Even doing
basic I/O to a file system from within the kernel is strongly
discouraged. In order to support this at all the vn_rename()
implementation ends up being complex and fragile. So fragile
that recent Linux 4.2 changes have broken it.
While it is possible to update vn_rename() to work with the
latest kernels a better long term strategy is to stop using
vn_rename() entirely. Then all this complex, fragile code can
be removed. Achieving this is straight forward because
config_write() is the only consumer of vn_rename().
This patch reworks spa_config_write() to update the cache file
in place. The file will be truncated, written out, and then
synced to disk. If an error is encountered the file will be
unlinked leaving the system in a consistent state.
This does expose a tiny tiny tiny window where a system could
crash at exactly the wrong moment could leave a partially written
cache file. However, this is highly unlikely because the cache
file is 1) infrequently updated, 2) only a few kilobytes in size,
and 3) written with a single vn_rdwr() call.
If this were to somehow happen it poses no risk to pool. Simply
removing the cache file will allow the pool to be imported cleanly.
Going forward this will be even less of an issue as we intend to
disable the use of a cache file by default.
Bottom line not using vn_rename() allows us to make ZoL more
robust against upstream kernel changes.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3653
Failing to lookup a name in the spa_ddt_stat_object should not result
in a panic in ddt_object_load(). The error can be safely returned to
the caller for handling resulting in a useful user error message.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3370
Without the parenthesis, this particular ASSERT will evaluate to
"(RW_READER == (!zap->zap_ismicro && fatreader)) ? RW_READER : lti"
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3685
This brings the behavior of arc_memory_throttle() back in sync with
illumos. The updated memory throttling policy roughly goes like this:
* Never throttle if more than 10% of memory is free. This threshold
is configurable with the zfs_arc_lotsfree_percent module option.
* Minimize any throttling of kswapd even when free memory is below
the set threshold. Allow it to write out pages as quickly as
possible to help alleviate the memory pressure.
* Delay all other threads when free memory is below the set threshold
in order to avoid compounding the memory pressure. Buffers will be
evicted from the ARC to reduce the issue.
The Linux specific zfs_arc_memory_throttle_disable module option has
been removed in favor of the existing zfs_arc_lotsfree_percent tuning.
Setting zfs_arc_lotsfree_percent=0 will have the same effect as
zfs_arc_memory_throttle_disable and it was therefore redundant.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3637
