The sa_modify_attrs() function can add, remove or replace an SA.
The main loop in the function uses the index "i" to iterate over the
existing SAs and uses the index "j" for writing them into a new buffer
via SA_ADD_BULK_ATTR(). The write index, "j" is incremented on remove
(SA_REMOVE) operations which leads to a corruption in the new SA buffer.
This patch remove the increment for SA_REMOVE operations.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes#3028
An attempt to debug zfsonlinux/zfs#2781 revealed that this code could be
simplified by using kmem_asprintf(). It is not clear that switching to
kmem_asprintf() addresses zfsonlinux/zfs#2781. However, switching to
kmem_asprintf() is cleanup that simplifies debugging such that it would
become clear that this is a bug in glibc should the issue persist.
It also brings this function almost back in sync with Illumos. This
was possible due to the recently reworked kmem code which allows us
to use KM_SLEEP in the same fashion as Illumos.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2791
Issue #2781
The kmem_vasprintf(), kmem_vsprintf(), kobj_open_file(), and vn_openat()
functions should all use the kmem_flags_convert() function to generate
the GFP_* flags. This ensures that they can be safely called in any
context and the correct flags will be used.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#426
The split count/scan shrinker callbacks introduced in 3.12 broke the
test for HAVE_SHRINK, effectively disabling the per-superblock shrinkers.
This patch re-enables the per-superblock shrinkers when the split shrinker
callbacks have been detected.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2975
The core motivation behind these changes is to minimize the
memory management differences between ZFS on Linux and other
platforms. This simplifies the process of porting changes to
Linux from other platforms. This is good for code quality
and is expected to reduce the number of defects accidentally
introduced due to porting. The following key Linux specific
changes have been reverted.
* KM_PUSHPAGE changed back to KM_SLEEP. All contexts where
it is unsafe to perform IO have been marked with PF_FSTRANS.
This context specific mechanism is now used exclusively
and the KM_PUSHPAGE mechanism has been retired.
* The KM_NODEBUG flag has been retired. Allocations larger
than 32K should use vmem_alloc()/vmem_free(). Depending
on the size of the allocation either kmalloc() or vmalloc()
will be used internally, but no warning will be printed.
* Pre-allocated vdev IO buffers and the dedicated SA spill
block cache have been retired. It is now safe and reliable
to allocate buffers of the needed size without fear of
deadlocking. This reduces our memory footprint and paves
the way for larger block sizes.
Depends on zfsonlinux/spl#414.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes#2918
The SA spill_cache was originally introduced to avoid the need to
perform large kmem or vmem allocations. Instead a small dedicated
cache of preallocated SA buffers was kept.
This solution was viable while the maximum block size was limited
to 128K. But with the planned increase of the maximum block size
to 16M callers need to migrate to the zio_buf_alloc(). However,
they should be aware this interface is expected to change again
once the zio buffers are fully backed by scatter-gather lists.
Alternately, if the callers know these buffers will never be large
or be infrequently accessed they may kmem_alloc() or vmem_alloc()
the needed temporary space.
This change has the additional benegit of bringing the code back
inline with the upstream Illumos source.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Commit 86dd0fd added preallocated I/O buffers. This is no longer
required after the recent kmem changes designed to make our memory
allocation interfaces behave more like those found on Illumos. A
deadlock in this situation is no longer possible.
However, these allocations still have the potential to be expensive.
So a potential future optimization might be to perform then KM_NOSLEEP
so that they either succeed of fail quicky. Either case is acceptable
here because we can safely abort the aggregation.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
As part of the spl kmem/vmem refactoring the kmem_cache_* functions
were split in to their own kmem_cache.h header. This was done in
part so that kmem_* consumers would not be forced to include the
kmem_cache_* functions which mask several Linux SLAB/SLAB functions.
Because of this we now much explicitly include kmem_cache.h in the
zfs_context.h. However, consumers such as Lustre which need access
to the KM_FLAGS but not the kmem_cache_* functions can now safely
just include kmem.h.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
By marking DMU transaction processing contexts with PF_FSTRANS
we can revert the KM_PUSHPAGE -> KM_SLEEP changes. This brings
us back in line with upstream. In some cases this means simply
swapping the flags back. For others fnvlist_alloc() was replaced
by nvlist_alloc(..., KM_PUSHPAGE) and must be reverted back to
fnvlist_alloc() which assumes KM_SLEEP.
The one place KM_PUSHPAGE is kept is when allocating ARC buffers
which allows us to dip in to reserved memory. This is again the
same as upstream.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Callers of kmem_alloc() which passed the KM_NODEBUG flag to suppress
the large allocation warning have been replaced by vmem_alloc() as
appropriate. The updated vmem_alloc() call will not print a warning
regardless of the size of the allocation.
A careful reader will notice that not all callers have been changed
to vmem_alloc(). Some have only had the KM_NODEBUG flag removed.
This was possible because the default warning threshold has been
increased to 32k. This is desirable because it minimizes the need
for Linux specific code changes.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The initial port of ZFS to Linux required a way to identify virtual
memory to make IO to virtual memory backed slabs work, so kmem_virt()
was created. Linux 2.6.25 introduced is_vmalloc_addr(), which is
logically equivalent to kmem_virt(). Support for kernels before 2.6.26
was later dropped and more recently, support for kernels before Linux
2.6.32 has been dropped. We retire kmem_virt() in favor of
is_vmalloc_addr() to cleanup the code.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
In order to avoid deadlocking in the IO pipeline it is critical that
pageout be avoided during direct memory reclaim. This ensures that
the pipeline threads can always make forward progress and never end
up blocking on a DMU transaction. For this very reason Linux now
provides the PF_FSTRANS flag which may be set in the process context.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The core motivation behind these changes is to minimize the
memory management differences between ZFS on Linux and other
platforms. This simplifies the process of porting changes to
Linux from other platforms. This is good for code quality
and is expected to reduce the number of defects accidentally
introduced due to porting.
The key reason this is now possible is due to the addition of
Linux features such as the thread-specific PF_FSTRANS bit which
was introduced for XFS.
This patch stack also performs some refactoring and cleanup
designed to make the code more maintainable and understandable.
Finally, in the context of making and testing these changes
several bugs were identified and resolved resulting in a
more robust implementation.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes#414
The __get_free_pages() function must be used in place of kmalloc()
to ensure the __GFP_COMP is strictly honored. This is due to
kmalloc() being layered on the generic Linux slab caches. It
wasn't until recently that all caches were created using __GFP_COMP.
This means that it is possible for a kmalloc() which passed the
__GFP_COMP flag to be returned a non-compound allocation.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The kmem cache implementation always adds new slabs by dispatching a
task to the spl_kmem_cache taskq to perform the allocation. This is
done because large slabs must be allocated using vmalloc(). It is
possible these allocations will block on IO because the GFP_NOIO flag
is not honored. This can result in a deadlock.
Therefore, a deadlock detection strategy was implemented to deal with
this case. When it is determined, by timeout, that the spl_kmem_cache
thread has deadlocked attempting to add a new slab. Then all callers
attempting to allocate from the cache fall back to using kmalloc()
which does honor all passed flags.
This logic was correct but an optimization in the code allowed for a
deadlock. Because only slabs backed by vmalloc() can deadlock in the
way described above. An optimization was made to only invoke this
deadlock detection code for vmalloc() backed caches. This had the
advantage of making it easy to distinguish these objects when they
were freed.
But this isn't strictly safe. If all the spl_kmem_cache threads end
up deadlocked than we can't grow any of the other caches either. This
can once again result in a deadlock if memory needs to be allocated
from one of these other caches to ensure forward progress.
The fix here is to remove the optimization which limits this fall back
allocation stratagy to vmalloc() backed caches. Doing this means we
may need to take the cache lock in spl_kmem_cache_free() call path.
But this small cost can be mitigated by ignoring objects with virtual
addresses.
For good measure the default number of spl_kmem_cache threads has been
increased from 1 to 4, and made tunable. This alone wouldn't resolve
the original issue since it's still possible for all the threads to be
deadlocked. However, it does help responsiveness by ensuring that a
single deadlocked spl_kmem_cache thread doesn't block allocations from
other caches until the timeout is reached.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This change is designed to improve the memory utilization of
slabs by more carefully setting their size. The way the code
currently works is problematic for slabs which contain large
objects (>1MB). This is due to slabs being unconditionally
rounded up to a power of two which may result in unused space
at the end of the slab.
The reason the existing code rounds up every slab is because it
assumes it will backed by the buddy allocator. Since the buddy
allocator can only performs power of two allocations this is
desirable because it avoids wasting any space. However, this
logic breaks down if slab is backed by vmalloc() which operates
at a page level granularity. In this case, the optimal thing to
do is calculate the minimum required slab size given certain
constraints (object size, alignment, objects/slab, etc).
Therefore, this patch reworks the spl_slab_size() function so
that it sizes KMC_KMEM slabs differently than KMC_VMEM slabs.
KMC_KMEM slabs are rounded up to the nearest power of two, and
KMC_VMEM slabs are allowed to be the minimum required size.
This change also reduces the default number of objects per slab.
This reduces how much memory a single cache object can pin, which
can result in significant memory saving for highly fragmented
caches. But depending on the workload it may result in slabs
being allocated and freed more frequently. In practice, this
has been shown to be a better default for most workloads.
Also the maximum slab size has been reduced to 4MB on 32-bit
systems. Due to the limited virtual address space it's critical
the we be as frugal as possible. A limit of 4M still lets us
reasonably comfortably allocate a limited number of 1MB objects.
Finally, the kmem:slab_small and kmem:slab_large SPLAT tests
were extended to provide better test coverage of various object
sizes and alignments. Caches are created with random parameters
and their basic functionality is verified by allocating several
slabs worth of objects.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reduce the threshold for detecting a kmem cache deadlock by 10x
from HZ to HZ/10. The reduced value is still several orders of
magnitude large enough to avoid being triggered incorrectly. By
reducing it we allow the system to resolve the issue more quickly.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The spl-module-parameters(5) was not kept up to date. Refresh
the man page so that it lists all the possible module options,
describes what the do, and justify why the default values are
set they way the are.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Many people have noticed that the kmem cache implementation is slow
to release its memory. This patch makes the reclaim behavior more
aggressive by immediately freeing a slab once it is empty. Unused
objects which are cached in the magazines will still prevent a slab
from being freed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The comment above the Linux 3.16 kernel's clear_bit() states:
/**
* clear_bit - Clears a bit in memory
* @nr: Bit to clear
* @addr: Address to start counting from
*
* clear_bit() is atomic and may not be reordered. However, it does
* not contain a memory barrier, so if it is used for locking purposes,
* you should call smp_mb__before_atomic() and/or smp_mb__after_atomic()
* in order to ensure changes are visible on other processors.
*/
This comment does not make sense in the context of x86 because x86 maps the
operations to barrier(), which is a compiler barrier. However, it does make
sense to me when I consider architectures that reorder around atomic
instructions. In such situations, a processor is allowed to execute the
wake_up_bit() before clear_bit() and we have a race. There are a few
architectures that suffer from this issue.
In such situations, the other processor would wake-up, see the bit is still
taken and go to sleep, while the one responsible for waking it up will
assume that it did its job and continue.
This patch implements a wrapper that maps smp_mb__{before,after}_atomic() to
smp_mb__{before,after}_clear_bit() on older kernels and changes our code to
leverage it in a manner consistent with the mainline kernel.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The port of XFS to Linux introduced a thread-specific PF_FSTRANS bit
that is used to mark contexts which are processing transactions. When
set, allocations in this context can dip into kernel memory reserves
to avoid deadlocks during writeback. Linux 3.9 provided the additional
PF_MEMALLOC_NOIO for disabling __GFP_IO in page allocations, which XFS
began using in 3.15.
This patch implements hooks for marking transactions via PF_FSTRANS.
When an allocation is performed in the context of PF_FSTRANS, any
KM_SLEEP allocation is transparently converted to a GFP_NOIO allocation.
Additionally, when using a Linux 3.9 or newer kernel, it will set
PF_MEMALLOC_NOIO to prevent direct reclaim from entering pageout() on
on any KM_PUSHPAGE or KM_NOSLEEP allocation. This effectively allows
the spl_vmalloc() helper function to be used safely in a thread which
is responsible for IO.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This patch achieves the following goals:
1. It replaces the preprocessor kmem flag to gfp flag mapping with
proper translation logic. This eliminates the potential for
surprises that were previously possible where kmem flags were
mapped to gfp flags.
2. It maps vmem_alloc() allocations to kmem_alloc() for allocations
sized less than or equal to the newly-added spl_kmem_alloc_max
parameter. This ensures that small allocations will not contend
on a single global lock, large allocations can still be handled,
and potentially limited virtual address space will not be squandered.
This behavior is entirely different than under Illumos due to
different memory management strategies employed by the respective
kernels. However, this functionally provides the semantics required.
3. The --disable-debug-kmem, --enable-debug-kmem (default), and
--enable-debug-kmem-tracking allocators have been unified in to
a single spl_kmem_alloc_impl() allocation function. This was
done to simplify the code and make it more maintainable.
4. Improve portability by exposing an implementation of the memory
allocations functions that can be safely used in the same way
they are used on Illumos. Specifically, callers may safely
use KM_SLEEP in contexts which perform filesystem IO. This
allows us to eliminate an entire class of Linux specific changes
which were previously required to avoid deadlocking the system.
This change will be largely transparent to existing callers but there
are a few caveats:
1. Because the headers were refactored and extraneous includes removed
callers may find they need to explicitly add additional #includes.
In particular, kmem_cache.h must now be explicitly includes to
access the SPL's kmem cache implementation. This behavior is
different from Illumos but it was done to avoid always masking
the Linux slab functions when kmem.h is included.
2. Callers, like Lustre, which made assumptions about the definitions
of KM_SLEEP, KM_NOSLEEP, and KM_PUSHPAGE will need to be updated.
Other callers such as ZFS which did not will not require changes.
3. KM_PUSHPAGE is no longer overloaded to imply GFP_NOIO. It retains
its original meaning of allowing allocations to access reserved
memory. KM_PUSHPAGE callers can be converted back to KM_SLEEP.
4. The KM_NODEBUG flags has been retired and the default warning
threshold increased to 32k.
5. The kmem_virt() functions has been removed. For callers which
need to distinguish between a physical and virtual address use
is_vmalloc_addr().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Address all cstyle issues in the kmem, vmem, and kmem_cache source
and headers. This will done to make it easier to review subsequent
changes which will rework the kmem/vmem implementation.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This change introduces no functional changes to the memory management
interfaces. It only restructures the existing codes by separating the
kmem, vmem, and kmem cache implementations in the separate source and
header files.
Splitting this functionality in to separate files required the addition
of spl_vmem_{init,fini}() and spl_kmem_cache_{initi,fini}() functions.
Additionally, several minor changes to the #include's were required to
accommodate the removal of extraneous header from kmem.h.
But again, while large this patch introduces no functional changes.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This reverts commit eb0f407a2b in
preperation for updating the kmem/vmem infrastructure to use the
PF_FSTRANS flag.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Since the Linux kernel's utimens family of functions uses
current_kernel_time(), we need to do the same in the context of ZFS
or else there can be discrepencies in timestamps (they go backward)
if userland code does:
fd = creat(FNAME, 0600);
(void) futimens(fd, NULL);
The getnstimeofday() function generally returns a slightly lower time
value.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closeszfsonlinux/zfs#3006
This is a follow up commit to 74328ee which correctly resolved a lock
inversion between zfs_putpage() and zfs_free_range(). Unfortunately,
in the process it accidentally introduced another inversion between
zfs_putpage() and zfs_read(). The page must be unlocked before taking
the range lock. This patch corrects that issue.
In addition, because the locking rules here are subtle a block comment
has been added clearly explaining why the ordering here is critical.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Issue #2976
Add a table describing the debugging flags that can be set in the zfs_flags
module parameter. Also change the module_param type to 'uint' so users aren't
shown a negative value. The updated man page text is reproduced below for
convenience.
zfs_flags (int)
Set additional debugging flags. The following flags may be
bitwise-or'd together.
+-------------------------------------------------------+
|Value Symbolic Name |
| Description |
+-------------------------------------------------------+
| 1 ZFS_DEBUG_DPRINTF |
| Enable dprintf entries in the debug log. |
+-------------------------------------------------------+
| 2 ZFS_DEBUG_DBUF_VERIFY * |
| Enable extra dbuf verifications. |
+-------------------------------------------------------+
| 4 ZFS_DEBUG_DNODE_VERIFY * |
| Enable extra dnode verifications. |
+-------------------------------------------------------+
| 8 ZFS_DEBUG_SNAPNAMES |
| Enable snapshot name verification. |
+-------------------------------------------------------+
| 16 ZFS_DEBUG_MODIFY |
| Check for illegally modified ARC buffers. |
+-------------------------------------------------------+
| 32 ZFS_DEBUG_SPA |
| Enable spa_dbgmsg entries in the debug log. |
+-------------------------------------------------------+
| 64 ZFS_DEBUG_ZIO_FREE |
| Enable verification of block frees. |
+-------------------------------------------------------+
| 128 ZFS_DEBUG_HISTOGRAM_VERIFY |
| Enable extra spacemap histogram verifications. |
+-------------------------------------------------------+
* Requires debug build.
Default value: 0.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2988
When running the SPLAT tests on a kernel with CONFIG_DEBUG_OBJECTS=y
enabled the following warning is generated.
ODEBUG: object is on stack, but not annotated
WARNING: at lib/debugobjects.c:300 __debug_object_init+0x221/0x480()
This is caused by the test cases placing a debug object on the stack
rather than the heap. This isn't harmful since they are small objects
but to make CONFIG_DEBUG_OBJECTS=y happy the objects have been relocated
to the heap. This impacted taskq tests 1, 3, and 7.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#424
Using AC_LANG_SOURCE with some versions of autoconf is problematic if
the given source is to be written to a header file. Such versions assume
the contents are to be written to conftest.c and generate shell code to
that effect. The contents of the test program to detect support for
Linux tracepoints were consequently malformed (containing the source for
conftest.h) so the build system incorrectly disabled tracepoints
support. Fix this in ZFS_LINUX_TRY_COMPILE_HEADER by passing the header
source directly to ZFS_LINUX_COMPILE_IFELSE.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2953
Older versions of GCC (e.g. GCC 4.4.7 on RHEL6) do not allow duplicate
typedef declarations with the same type. The trace.h header contains
some typedefs to avoid 'unknown type' errors for C files that haven't
declared the type in question. But this causes build failures for C
files that have already declared the type. Newer versions of GCC (e.g.
v4.6) allow duplicate typedefs with the same type unless pedantic error
checking is in force. To support the older versions we need to remove
the duplicate typedefs.
Removal of the typedefs means we can't built tracepoints code using
those types unless the required headers have been included. To
facilitate this, all tracepoint event declarations have been moved out
of trace.h into separate headers. Each new header is explicitly included
from the C file that uses the events defined therein. The trace.h header
is still indirectly included form zfs_context.h and provides the
implementation of the dprintf(), dbgmsg(), and SET_ERROR() interfaces.
This makes those interfaces readily available throughout the code base.
The macros that redefine DTRACE_PROBE* to use Linux tracepoints are also
still provided by trace.h, so it is a prerequisite for the other
trace_*.h headers.
These new Linux implementation-specific headers do introduce a small
divergence from upstream ZFS in several core C files, but this should
not present a significant maintenance burden.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2953
There exists a lock inversions involving the zfs range lock and the
individual page writeback bits which can result in a deadlock. To
prevent this we must always manipulate the writeback bit while
holding the range lock. The exact deadlock is as follows:
------ Process A ------ ------ Process B ------
zpl_writepages zpl_fallocate
write_cache_pages zpl_fallocate_common
zpl_putpage zfs_space
zfs_putpage (set bit) zfs_freesp
zfs_range_lock (wait on lock) zfs_free_range (take lock)
[has not yet initiated I/O, truncate_inode_pages_range
the bit will not be cleared] wait_on_page_writeback (wait on bit)
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Richard Yao <richard.yao@clusterhq.com>
Issue #2976
Slot mapping in vdev_id doesn't work on systems using mawk as the 'awk'
alternative. A regular expression in map_slot() contains an unquoted
empty string following the alternation (|) operator, which results in an
"missing operand" error with mawk. The solution is to rearrange the
expression so the alternation has two operands.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closeszfsonlinux/pkg-zfs#136Closeszfsonlinux/zfs#2965
Commit c66989b accidentally introduced a cstyle issue which went
unnoticed. This tiny patch corrects that oversight.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
It is known that mutexes in Linux are not safe when using them to
synchronize the freeing of object in which the mutex is embedded:
http://lwn.net/Articles/575477/
The known places in ZFS which are suspected to suffer from the race
condition are zio->io_lock and dbuf->db_mtx.
* zio uses zio->io_lock and zio->io_cv to synchronize freeing
between zio_wait() and zio_done().
* dbuf uses dbuf->db_mtx to protect reference counting.
This patch fixes this kind of race by forcing serialization on
mutex_exit() with a spin lock, making the mutex safe by sacrificing
a bit of performance and memory overhead.
This issue most commonly manifests itself as a deadlock in the zio
pipeline caused by a process spinning on the damaged mutex. Similar
deadlocks have been reported for the dbuf->db_mtx mutex. And it can
also cause a NULL dereference or bad paging request under the right
circumstances.
This issue any many like it are linked off the zfsonlinux/zfs#2523
issue. Specifically this fix resolves at least the following
outstanding issues:
zfsonlinux/zfs#401
zfsonlinux/zfs#2523
zfsonlinux/zfs#2679
zfsonlinux/zfs#2684
zfsonlinux/zfs#2704
zfsonlinux/zfs#2708
zfsonlinux/zfs#2517
zfsonlinux/zfs#2827
zfsonlinux/zfs#2850
zfsonlinux/zfs#2891
zfsonlinux/zfs#2897
zfsonlinux/zfs#2247
zfsonlinux/zfs#2939
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Closes#421
Missing space made the %post directive be part of the package
%description and not have a %post scriptlet defined.
Signed-off-by: Andy Bakun <github@thwartedefforts.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2961
The systemd script zfs-share.service does 'zfs share -a' to share
any required datasets. Unfortunately, /etc/dfs/sharetab is stale
from the previous boot. Delete it before we share.
Signed-off-by: Dan Swartzendruber <dswartz@druber.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2883
Filesystems which are mounted read-only or are immutable because
they are snapshots must not be allowed to dirty and inode. This
will result in a write which will correctly cause a kernel panic
because these filesystem are (and must be) immutable.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2812
Don't include the compatibility code in linux/*_compat.h in the public
header sys/types.h. This causes problems when an external code base
includes the ZFS headers and has its own conflicting compatibility code.
Lustre, in particular, defined SHRINK_STOP for compatibility with
pre-3.12 kernels in a way that conflicted with the SPL's definition.
Because Lustre ZFS OSD includes ZFS headers it fails to build due to a
'"SHRINK_STOP" redefined' compiler warning. To avoid such conflicts
only include the compat headers from .c files or private headers.
Also, for consistency, include sys/*.h before linux/*.h then sort by
header name.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#411
When the SPL was originally written Linux tracepoints were still
in their infancy. Therefore, an entire debugging subsystem was
added to facilite tracing which served us well for many years.
Now that Linux tracepoints have matured they provide all the
functionality of the previous tracing subsystem. Rather than
maintain parallel functionality it makes sense to fully adopt
tracepoints. Therefore, this patch retires the legacy debugging
infrastructure.
See zfsonlinux/zfs@bc9f413 for the tracepoint changes.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#408
The zfs-share.service rule needs to be modified to ensure that it
does not execute before zfs-mount.service.
Signed-off-by: Dan Swartzendruber <dswartz@druber.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ralf Ertzinger <ralf@skytale.net>
Closes#2893
Mark the error handling branch as unlikely() because the current
kernel interface can never return NULL. However, we want to keep
the error handling in case this behavior changes in the futre.
Plus fix a small style issue.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Isaac Huang <he.huang@intel.com>
Closes#2703
Inclusion of SPL compatibility headers was moved out of the public
header sys/types.h to avoid conflicts with external packages. Include a
few compatiblity headers explicitly to cope with that change. Also,
sort some linux-specific inclusions alphabetically.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2898
Fix a few cases where null-byte termination of strings was done
unnecessarily or incorrectly.
- The snprintf() function always produces a null-byte terminated string
for non-negative return values, so it is not necessary to write out a
null-byte as a separate step.
- Also, it is unsafe to use the return value of snprintf() as an offset
for placing a null-byte, because if the output was truncated the return
value is the number of bytes that _would_ have been written had enough
space been available. Therefore the return value may index beyond the
array boundaries.
- Finally, snprintf() accounts for the null-byte when limiting its output
size, so there is no need to pass it a size parameter that is one less
than the buffer size.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2875
When processing async destroys ZFS would leak space every txg timeout
(5 seconds by default), if no writes occurred, until the pool is totally
full. At this point it would be unfixable without a pool recreation.
In addition if the machine was rebooted with the pool in this situation
would fail to import on boot, hanging indefinitely, as the import process
requires the ability to write data to the pool. Any attempts to query
the pool status during the hung import would not return as the import
holds the pool lock.
The only way to import such a pool would be to specify -o readonly=on
to the zpool import.
zdb -bb <pool> can be used to check for "deferred free" size which is
where this lost space will be counted.
References:
https://github.com/freebsd/freebsd/commit/48431b7http://svnweb.freebsd.org/base?view=revision&revision=273158https://reviews.csiden.org/r/132/
Porting notes:
This issue was filed as illumos 5347 and a more comprehensive fix is
under review. Once that change is finalized it will be integrated, in
the meanwhile the FreeBSD fix has been merged to prevent the issue.
Ported by: Tim Chase <tim@chase2k.com>
Signed-off-by: Matthew Ahrens mahrens@delphix.com
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2896
If a spill block's dbuf hasn't yet been written when a spill block is
freed, the unwritten version will still be written. This patch handles
the case in which a spill block's dbuf is freed and undirties it to
prevent it from being written.
The most common case in which this could happen is when xattr=sa is being
used and a long xattr is immediately replaced by a short xattr as in:
setfattr -n user.test -v very_very_very..._long_value <file>
setfattr -n user.test -v short_value <file>
The first value must be sufficiently long that a spill block is generated
and the second value must be short enough to not require a spill block.
In practice, this would typically happen due to internal xattr operations
as a result of setting acltype=posixacl.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2663Closes#2700Closes#2701Closes#2717Closes#2863Closes#2884
This patch leverages Linux tracepoints from within the ZFS on Linux
code base. It also refactors the debug code to bring it back in sync
with Illumos.
The information exported via tracepoints can be used for a variety of
reasons (e.g. debugging, tuning, general exploration/understanding,
etc). It is advantageous to use Linux tracepoints as the mechanism to
export this kind of information (as opposed to something else) for a
number of reasons:
* A number of external tools can make use of our tracepoints
"automatically" (e.g. perf, systemtap)
* Tracepoints are designed to be extremely cheap when disabled
* It's one of the "accepted" ways to export this kind of
information; many other kernel subsystems use tracepoints too.
Unfortunately, though, there are a few caveats as well:
* Linux tracepoints appear to only be available to GPL licensed
modules due to the way certain kernel functions are exported.
Thus, to actually make use of the tracepoints introduced by this
patch, one might have to patch and re-compile the kernel;
exporting the necessary functions to non-GPL modules.
* Prior to upstream kernel version v3.14-rc6-30-g66cc69e, Linux
tracepoints are not available for unsigned kernel modules
(tracepoints will get disabled due to the module's 'F' taint).
Thus, one either has to sign the zfs kernel module prior to
loading it, or use a kernel versioned v3.14-rc6-30-g66cc69e or
newer.
Assuming the above two requirements are satisfied, lets look at an
example of how this patch can be used and what information it exposes
(all commands run as 'root'):
# list all zfs tracepoints available
$ ls /sys/kernel/debug/tracing/events/zfs
enable filter zfs_arc__delete
zfs_arc__evict zfs_arc__hit zfs_arc__miss
zfs_l2arc__evict zfs_l2arc__hit zfs_l2arc__iodone
zfs_l2arc__miss zfs_l2arc__read zfs_l2arc__write
zfs_new_state__mfu zfs_new_state__mru
# enable all zfs tracepoints, clear the tracepoint ring buffer
$ echo 1 > /sys/kernel/debug/tracing/events/zfs/enable
$ echo 0 > /sys/kernel/debug/tracing/trace
# import zpool called 'tank', inspect tracepoint data (each line was
# truncated, they're too long for a commit message otherwise)
$ zpool import tank
$ cat /sys/kernel/debug/tracing/trace | head -n35
# tracer: nop
#
# entries-in-buffer/entries-written: 1219/1219 #P:8
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
lt-zpool-30132 [003] .... 91344.200050: zfs_arc__miss: hdr...
z_rd_int/0-30156 [003] .... 91344.200611: zfs_new_state__mru...
lt-zpool-30132 [003] .... 91344.201173: zfs_arc__miss: hdr...
z_rd_int/1-30157 [003] .... 91344.201756: zfs_new_state__mru...
lt-zpool-30132 [003] .... 91344.201795: zfs_arc__miss: hdr...
z_rd_int/2-30158 [003] .... 91344.202099: zfs_new_state__mru...
lt-zpool-30132 [003] .... 91344.202126: zfs_arc__hit: hdr ...
lt-zpool-30132 [003] .... 91344.202130: zfs_arc__hit: hdr ...
lt-zpool-30132 [003] .... 91344.202134: zfs_arc__hit: hdr ...
lt-zpool-30132 [003] .... 91344.202146: zfs_arc__miss: hdr...
z_rd_int/3-30159 [003] .... 91344.202457: zfs_new_state__mru...
lt-zpool-30132 [003] .... 91344.202484: zfs_arc__miss: hdr...
z_rd_int/4-30160 [003] .... 91344.202866: zfs_new_state__mru...
lt-zpool-30132 [003] .... 91344.202891: zfs_arc__hit: hdr ...
lt-zpool-30132 [001] .... 91344.203034: zfs_arc__miss: hdr...
z_rd_iss/1-30149 [001] .... 91344.203749: zfs_new_state__mru...
lt-zpool-30132 [001] .... 91344.203789: zfs_arc__hit: hdr ...
lt-zpool-30132 [001] .... 91344.203878: zfs_arc__miss: hdr...
z_rd_iss/3-30151 [001] .... 91344.204315: zfs_new_state__mru...
lt-zpool-30132 [001] .... 91344.204332: zfs_arc__hit: hdr ...
lt-zpool-30132 [001] .... 91344.204337: zfs_arc__hit: hdr ...
lt-zpool-30132 [001] .... 91344.204352: zfs_arc__hit: hdr ...
lt-zpool-30132 [001] .... 91344.204356: zfs_arc__hit: hdr ...
lt-zpool-30132 [001] .... 91344.204360: zfs_arc__hit: hdr ...
To highlight the kind of detailed information that is being exported
using this infrastructure, I've taken the first tracepoint line from the
output above and reformatted it such that it fits in 80 columns:
lt-zpool-30132 [003] .... 91344.200050: zfs_arc__miss:
hdr {
dva 0x1:0x40082
birth 15491
cksum0 0x163edbff3a
flags 0x640
datacnt 1
type 1
size 2048
spa 3133524293419867460
state_type 0
access 0
mru_hits 0
mru_ghost_hits 0
mfu_hits 0
mfu_ghost_hits 0
l2_hits 0
refcount 1
} bp {
dva0 0x1:0x40082
dva1 0x1:0x3000e5
dva2 0x1:0x5a006e
cksum 0x163edbff3a:0x75af30b3dd6:0x1499263ff5f2b:0x288bd118815e00
lsize 2048
} zb {
objset 0
object 0
level -1
blkid 0
}
For the specific tracepoint shown here, 'zfs_arc__miss', data is
exported detailing the arc_buf_hdr_t (hdr), blkptr_t (bp), and
zbookmark_t (zb) that caused the ARC miss (down to the exact DVA!).
This kind of precise and detailed information can be extremely valuable
when trying to answer certain kinds of questions.
For anybody unfamiliar but looking to build on this, I found the XFS
source code along with the following three web links to be extremely
helpful:
* http://lwn.net/Articles/379903/
* http://lwn.net/Articles/381064/
* http://lwn.net/Articles/383362/
I should also node the more "boring" aspects of this patch:
* The ZFS_LINUX_COMPILE_IFELSE autoconf macro was modified to
support a sixth paramter. This parameter is used to populate the
contents of the new conftest.h file. If no sixth parameter is
provided, conftest.h will be empty.
* The ZFS_LINUX_TRY_COMPILE_HEADER autoconf macro was introduced.
This macro is nearly identical to the ZFS_LINUX_TRY_COMPILE macro,
except it has support for a fifth option that is then passed as
the sixth parameter to ZFS_LINUX_COMPILE_IFELSE.
These autoconf changes were needed to test the availability of the Linux
tracepoint macros. Due to the odd nature of the Linux tracepoint macro
API, a separate ".h" must be created (the path and filename is used
internally by the kernel's define_trace.h file).
* The HAVE_DECLARE_EVENT_CLASS autoconf macro was introduced. This
is to determine if we can safely enable the Linux tracepoint
functionality. We need to selectively disable the tracepoint code
due to the kernel exporting certain functions as GPL only. Without
this check, the build process will fail at link time.
In addition, the SET_ERROR macro was modified into a tracepoint as well.
To do this, the 'sdt.h' file was moved into the 'include/sys' directory
and now contains a userspace portion and a kernel space portion. The
dprintf and zfs_dbgmsg* interfaces are now implemented as tracepoint as
well.
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
