This commit used PF_MEMALLOC to prevent a memory reclaim deadlock.
However, commit 49be0ccf1f eliminated
the invocation of __cv_init(), which was the cause of the deadlock.
PF_MEMALLOC has the side effect of permitting pages from ZONE_DMA
to be allocated. The use of PF_MEMALLOC was found to cause stability
problems when doing swap on zvols. Since this technique is known to
cause problems and no longer fixes anything, we revert it.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #726
Under certain circumstances the following functions may be called
in a context where KM_SLEEP is unsafe and can result in a deadlocked
system. To avoid this problem the unconditional KM_SLEEPs are
converted to KM_PUSHPAGEs. This will prevent them from attempting
to initiate any I/O during direct reclaim.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Generate an assertion if we're going to deadlock the system by
attempting to acquire a mutex the process is already holding.
There are currently no known instances of this under normal
operation, but it _might_ be possible when using a ZVOL as a
swap device. I want to ensure we catch this immediately if it
were to occur.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
PF_NOFS is a per-process debug flag which is set in current->flags to
detect when a process is performing an unsafe allocation. All tasks
with PF_NOFS set must strictly use KM_PUSHPAGE for allocations because
if they enter direct reclaim and initiate I/O they may deadlock.
When debugging is disabled, any incorrect usage will be detected and
a call stack with a warning will be printed to the console. The flags
will then be automatically corrected to allow for safe execution. If
debugging is enabled this will be treated as a fatal condition.
To avoid any risk of conflicting with the existing PF_ flags. The
PF_NOFS bit shadows the rarely used PF_MUTEX_TESTER bit. Only when
CONFIG_RT_MUTEX_TESTER is not set, and we know this bit is unused,
will the PF_NOFS bit be valid. Happily, most existing distributions
ship a kernel with CONFIG_RT_MUTEX_TESTER disabled.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This reverts commit 372c257233. The
use of the PF_MEMALLOC flag was always a hack to work around memory
reclaim deadlocks. Those issues are believed to be resolved so this
workaround can be safely reverted.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This patch is designed to resolve a deadlock which can occur with
__vmalloc() based slabs. The issue is that the Linux kernel does
not honor the flags passed to __vmalloc(). This makes it unsafe
to use in a writeback context. Unfortunately, this is a use case
ZFS depends on for correct operation.
Fixing this issue in the upstream kernel was pursued and patches
are available which resolve the issue.
https://bugs.gentoo.org/show_bug.cgi?id=416685
However, these changes were rejected because upstream felt that
using __vmalloc() in the context of writeback should never be done.
Their solution was for us to rewrite parts of ZFS to accomidate
the Linux VM.
While that is probably the right long term solution, and it is
something we want to pursue, it is not a trivial task and will
likely destabilize the existing code. This work has been planned
for the 0.7.0 release but in the meanwhile we want to improve the
SPL slab implementation to accomidate this expected ZFS usage.
This is accomplished by performing the __vmalloc() asynchronously
in the context of a work queue. This doesn't prevent the posibility
of the worker thread from deadlocking. However, the caller can now
safely block on a wait queue for the slab allocation to complete.
Normally this will occur in a reasonable amount of time and the
caller will be woken up when the new slab is available,. The objects
will then get cached in the per-cpu magazines and everything will
proceed as usual.
However, if the __vmalloc() deadlocks for the reasons described
above, or is just very slow, then the callers on the wait queues
will timeout out. When this rare situation occurs they will attempt
to kmalloc() a single minimally sized object using the GFP_NOIO flags.
This allocation will not deadlock because kmalloc() will honor the
passed flags and the caller will be able to make forward progress.
As long as forward progress can be maintained then even if the
worker thread is deadlocked the critical thread will make progress.
This will eventually allow the deadlocked worker thread to complete
and normal operation will resume.
These emergency allocations will likely be slow since they require
contiguous pages. However, their use should be rare so the impact
is expected to be minimal. If that turns out not to be the case in
practice further optimizations are possible.
One additional concern is if these emergency objects are long lived.
Right now they are simply tracked on a list which must be walked when
an object is freed. Is they accumulate on a system and the list
grows freeing objects will become more expensive. This could be
handled relatively easily by using a hash instead of a list, but that
optimization (if needed) is left for a follow up patch.
Additionally, these emeregency objects could be repacked in to existing
slabs as objects are freed if the kmem_cache_set_move() functionality
was implemented. See issue https://github.com/zfsonlinux/spl/issues/26
for full details. This work would also help reduce ZFS's memory
fragmentation problems.
The /proc/spl/kmem/slab file has had two new columns added at the
end. The 'emerg' column reports the current number of these emergency
objects in use for the cache, and the following 'max' column shows
the historical worst case. These value should give us a good idea
of how often these objects are needed. Based on these values under
real use cases we can tune the default behavior.
Lastly, as a side benefit using a single work queue for the slab
allocations should reduce cpu contention on the global virtual address
space lock. This should manifest itself as reduced cpu usage for
the system.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Remove all of the generated autotools products from the repository
and update the .gitignore files accordingly.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#718
Remove all of the generated autotools products from the repository
and update the .gitignore files accordingly.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue zfsonlinux/zfs#718
To support preempt enabled kernels in ZFS on Linux, there are a couple
places where the ZFS code needs to disable interrupts. This change adds
the Solaris preempt functions and maps them to the equivalent ZFS
functions, allowing the ZFS to make use of them.
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #98
After surveying the code, the few places where smp_processor_id is used
were deemed to be safe to use with a preempt enabled kernel. As such, no
core logic had to be changed. These smp_processor_id call sites are simply
are wrapped in kpreempt_disable and kpreempt_enabled to prevent the
Linux kernel from emitting scary warnings.
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Issue #83
The spl_magazine_age function had the implied assumption that it will
remain on its current cpu through its execution. In order to support
preempt enabled kernels, this assumption had to be removed.
The spl_kmem_magazine structure now holds the cpu id of the cpu it is
local to. This allows spl_magazine_age to use this field when scheduling
work to be done by the magazine's local cpu.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #98
When building SPL support into the kernel, ./copy-builtin will copy
non-toplevel .gitignore files. These files list /Makefile, which causes
git-archive to omit ./module/{spl,splat}/Makefile. The absence of these
files result in build failures when SPL is selected. ZFS is unaffected
because it puts Makefile in the toplevel .gitignore, which is not
copied. We fix SPL by emulating that behavior.
Reported-by: Fabio Erculiani <lxnay@gentoo.org>
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#152
Export these symbols so they may be used by other ZFS consumers
besides the ZPL.
Remove three stale prototype definites from dbuf.h. The actual
implementations of these functions were removed/renamed long ago.
It would be good in the long term to remove the existing pragmas
we inherited from Solaris and simply use the dbuf_* names.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Currently, zvols have a discard granularity set to 0, which suggests to
the upper layer that discard requests of arbirarily small size and
alignment can be made efficiently.
In practice however, ZFS does not handle unaligned discard requests
efficiently: indeed, it is unable to free a part of a block. It will
write zeros to the specified range instead, which is both useless and
inefficient (see dnode_free_range).
With this patch, zvol block devices expose volblocksize as their discard
granularity, so the upper layer is aware that it's not supposed to send
discard requests smaller than volblocksize.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#862
A preprocessor definition renders this harmless. However, it is a good
idea to change this to be consistent.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
The end_writeback() function was changed by moving the call to
inode_sync_wait() earlier in to evict(). This effecitvely changes
the ordering of the sync but it does not impact the details of
the zfs implementation.
However, as part of this change end_writeback() was renamed to
clear_inode() to reflect the new semantics. This change does
impact us and clear_inode() now maps to end_writeback() for
kernels prior to 3.5.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#784
The vmtruncate_range() support has been removed from the kernel in
favor of using the fallocate method in the file_operations table.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #784
The export_operations member ->encode_fh() has been updated to
take both the child and parent inodes. This interface used to
take the child dentry and a bool describing if the parent is needed.
NOTE: While updating this code I noticed that we do not currently
cleanly handle the case where we're passed a connectable parent.
This code should be audited to make sure we're doing the right thing.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #784
Gentoo Hardened kernels include the PaX/GRSecurity patches. They use a
dialect of C that relies on a GCC plugin. In particular, struct
file_operations has been marked do_const in the PaX/GRSecurity dialect,
which causes GCC to consider all instances of it as const. This caused
failures in the autotools checks and the ZFS source code.
To address this, we modify the autotools checks to take into account
differences between the PaX C dialect and the regular C dialect. We also
modify struct zfs_acl's z_ops member to be a pointer to a function
pointer table. Lastly, we modify zpl_put_link() to address a PaX change
to the function prototype of nd_get_link(). This avoids compiler errors
in the PaX/GRSecurity dialect.
Note that the change in zpl_put_link() causes a warning that becomes a
build failure when debugging is enabled. Fixing that warning requires
ryao/spl@5ca50ef459.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#484
Currently, zpool online -e (dynamic vdev expansion) doesn't work on
whole disks because we're invoking ioctl(BLKRRPART) from userspace
while ZFS still has a partition open on the disk, which results in
EBUSY.
This patch moves the BLKRRPART invocation from the zpool utility to the
module. Specifically, this is done just before opening the device in
vdev_disk_open() which is called inside vdev_reopen(). This requires
jumping through some hoops to get to the disk device from the partition
device, and to make sure we can still open the partition after the
BLKRRPART call.
Note that this new code path is triggered on dynamic vdev expansion
only; other actions, like creating a new pool, are unchanged and still
call BLKRRPART from userspace.
This change also depends on API changes which are available in 2.6.37
and latter kernels. The build system has been updated to detect this,
but there is no compatibility mode for older kernels. This means that
online expansion will NOT be available in older kernels. However, it
will still be possible to expand the vdev offline.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#808
The spl_rwsem_is_locked() compatibility function has been observed
to be a hot spot. The root cause of this is that we must check the
rwsem activity under the rwsem->wait_lock to avoid a race. When
the lock is busy significant contention can occur.
The upstream kernel fix for this race had the insight that by using
spin_trylock_irqsave() this contention could be avoided. When the
lock is contended it's reasonable to return that it is locked.
This change updates the SPLs implemention to be like the upstream
kernel. Since the kernel code has been in use for years now this
a low risk change.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: George Wilson <gwilson@zfsmail.com>
Reviewed by: Igor Kozhukhov <ikozhukhov@gmail.com>
Reviewed by: Alexander Eremin <alexander.eremin@nexenta.com>
Reviewed by: Alexander Stetsenko <ams@nexenta.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
References:
https://www.illumos.org/issues/1748
This commit modifies the user to kernel space ioctl ABI. Extra
care should be taken when updating to ensure both the kernel
modules and utilities are updated. If only the user space
component is updated both the 'zpool events' command and the
'zpool reguid' command will not work until the kernel modules
are updated.
Ported by: Martin Matuska <martin@matuska.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#665
The lack of the ULL suffix causes warnings such as the following on
32-bit systems:
In function 'zfsctl_is_snapdir':
zfs-0.6.0//module/zfs/zfs_ctldir.c:151: warning: integer constant
is too large for 'long' type
We add the ULL suffix to fix that.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#813
This prevents warnings in ZFS that were caused by changes necessary to
support PaX patched kernels. When debugging is enabled, these warnings
become build failures.
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#131
Usage of get_current() is not supported across all architectures.
The correct interface to use is the '#define current' which will
map to the appropriate function, usually current_thread_info().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#119
The performance of the ZIL is usually the main bottleneck when dealing with
synchronous, write-heavy workloads (e.g. databases). Understanding the
behavior of the ZIL is required to diagnose performance issues for these
workloads, and to tune ZIL parameters (like zil_slog_limit) accordingly.
This commit adds a new kstat page dedicated to the ZIL with some counters
which, hopefully, scheds some light into what the ZIL is doing, and how it is
doing it.
Currently, these statistics are available in /proc/spl/kstat/zfs/zil.
A description of the fields can be found in zil.h.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#786
FreeBSD #xxx: Dramatically optimize listing snapshots when user
requests only snapshot names and wants to sort them by name, ie.
when executes:
# zfs list -t snapshot -o name -s name
Because only name is needed we don't have to read all snapshot
properties.
Below you can find how long does it take to list 34509 snapshots
from a single disk pool before and after this change with cold and
warm cache:
before:
# time zfs list -t snapshot -o name -s name > /dev/null
cold cache: 525s
warm cache: 218s
after:
# time zfs list -t snapshot -o name -s name > /dev/null
cold cache: 1.7s
warm cache: 1.1s
NOTE: This patch only appears in FreeBSD. If/when Illumos picks up
the change we may want to drop this patch and adopt their version.
However, for now this addresses a real issue.
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #450
torvalds/linux@1dce27c5aa introduced
__clear_close_on_exec() as a replacement for FD_CLR. Further commits
appear to have removed FD_CLR from the Linux source tree. This
causes the following failure:
error: implicit declaration of function '__FD_CLR'
[-Werror=implicit-function-declaration]
To correct this we update the code to use the current
__clear_close_on_exec() interface for readability. Then we introduce
an autotools check to determine if __clear_close_on_exec() is available.
If it isn't then we define some compatibility logic which used the older
FD_CLR() interface.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#124
torvalds/linux@adc0e91ab1 introduced
introduced d_make_root() as a replacement for d_alloc_root(). Further
commits appear to have removed d_alloc_root() from the Linux source
tree. This causes the following failure:
error: implicit declaration of function 'd_alloc_root'
[-Werror=implicit-function-declaration]
To correct this we update the code to use the current d_make_root()
interface for readability. Then we introduce an autotools check
to determine if d_make_root() is available. If it isn't then we
define some compatibility logic which used the older d_alloc_root()
interface.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#776
Originally I believed that these interfaces would be needed.
However, in practice it turned out that it was more straight
forward and maintainable to use the native Linux interfaces.
As such, this is all dead code and can be safely removed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#109
The resolution of issue #31 made KM_PUSHPAGE imply GFP_NOFS. This
was done to prevent situations where filesystem operations which are
holding locks enter direct reclaim and attempt to reaquire those
same locks. This clearly will result in a deadlock.
This works for datasets which are implemented in terms for filesystem
operations. But unfortunately, swapping to a zvol will encounter
many of the same deadlocks and GFP_NOFS will not prevent this. As
such, it is appropriate to extend KM_PUSHPAGE to use the broader
GFP_NOIO mask to handle these non-filesystem cases.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue zfsonlinux/zfs#342Closes#105
Previously, the SPL tried to maintain Solaris semantics by freeing
all available (empty) slabs from its slab caches when the shrinker
was called. This is not desirable when running on Linux. To make
the SPL shrinker more Linux friendly, the actual number of freed
slabs from each of the slab caches is now derived from nr_to_scan
and skc_slab_objs.
Additionally, an accounting bug was fixed in spl_slab_reclaim()
which could cause us to reclaim one more slab than requested.
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#101
The mode argument of iops->create()/mkdir()/mknod() was changed from
an 'int' to a 'umode_t'. To prevent a compiler warning an autoconf
check was added to detect the API change and then correctly set a
zpl_umode_t typedef. There is no functional change.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#701
Long ago I added support to the spl for condition variable names
because I thought they might be needed. It turns out they aren't.
In fact the official Solaris cv_init(9F) man page discourages
their use in the kernel.
cv_init(9F)
Parameters
name - Descriptive string. This is obsolete and should be
NULL. (Non-NULL strings are legal, but they're a
waste of kernel memory.)
Therefore, I'm removing them from the spl to reclaim this memory
and adding an ASSERT() to ensure no new consumers are added which
make use of the name.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
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>
Include the ZFS_META_RELEASE in the module load/unload messages
to more clearly indicate exactly what version of the SPL has
been loaded.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
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
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>
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
'--with debug-log' - Enables the internal debug log
'--with debug-kmem' - Enables basic memory accounting
'--with debug-kmem-tracking' - Enables detailed memory tracking
# For example:
$ rpmbuild --rebuild --with debug spl-modules-0.6.0-rc6.src.rpm
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
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>
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>
When building the spl with --disable-debug-log the __SDEBUG()
macro and spl_debug_* helper functions were undefined. This
change adds the missing functions so the upper layers compiling
against the spl don't need to be aware of how the spl was built.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
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>
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
Richard Yao