There is concern that READA may do more than simply reorder the queue.
There may be an increased chance that a requested marked READA will
fail because the elevator considers it optional. For this reason, all
read requests, even speculative ones, have been converted back to READ.
The 2.6.30 kernel build systems sets -Wframe-larger-than=2048 which causes
a warning to be generated when an individual stack frame exceeds 2048.
This caught the spa_history_log() and dmu_objset_snapshot() functions
which declared a data structure on the stack which contained a char
array of MAXPATHLEN. This in defined to be 4096 in the linux kernel
and I imagine it is quite large under Solaris as well. Regardless, the
offending data structures were moved to the heap to correctly keep the
stack depth to a minimum. We might consider setting this value even
lower to catch additional offenders because we are expecting deep stacks.
Tested under CHAOS4.2, RHEL5, SLES11, and FC11 (all x86_64)
Features:
Honor spa_mode() when opening the block device. Previously this
was ignored and devices were always opened read/write.
Integrated DKIOCFLUSHWRITECACHE zio operation with linux WRITE_BARRIER
for kernels post 2.6.24 where empty bio requests are supported. For
earlier kernels ENOTSUP is returned and no barriers are performed. If
RHEL5 based kernels are intended to be supported long term we may need
make use of the old akward API.
With the addition of WRITE_BARRIER support all writes which were
WRITE_SYNC can now be safely made WRITE bios. They will now take
advantage of aggregation in the elevator and improved write performance
is likely.
Notice the ZIO_FLAG_SPECULATIVE flag and pass along the hint to the
elevator by using READA instead of READ. This provides the elevator
the ability to prioritize the real READs ahead of the speculative IO
if needed.
Implement an initial version of vdev_disk_io_done() which in the case
of an EIO error triggers a media change check. If it determines a
media change has occured we fail the device and remove it from the
config. This logic I'm sure can be improved further but for now it
is an improvement over the VERIFY() that no error will ever happen.
APIs:
2.6.22 API change
Unused destroy_dirty_buffers arg removed from prototype.
2.6.24 API change
Empty write barriers are now supported and we should use them.
2.6.24 API change
Size argument dropped from bio_endio and bi_end_io, because the
bi_end_io is only called once now when the request is complete.
There is no longer any need for a size argument. This also means
that partial IO's are no longer possibe and the end_io callback
should not check bi->bi_size. Finally, the return type was updated
to void.
2.6.28 API change
open/close_bdev_excl() renamed to open/close_bdev_exclusive().
2.6.29 API change
BIO_RW_SYNC renamed to BIO_RW_SYNCIO.
Use the legacy BIO_RW_FAILFAST flag if it exists. If it is missing it
means we are running against a kernel with the newer API. We should
be able to enable some fairly smart behavior one we intergrate with the
new API, but until I get around to writing that code just remove the
flag entirely. It's not critical for correctness.
Kernel commit 6712ecf8f648118c3363c142196418f89a510b90 which removes the
size argument from bio_endio and bi_end_io, also removes the need to
handle partial IOs in the handler.
The intent here is to fully remove the previous Solaris thread
implementation so we don't need to simulate both Solaris kernel
and user space thread APIs. The few user space consumers of the
thread API have been updated to use the kthread API. In order
to support this we needed to more fully support the kthread API
and that means not doing crazy things like casting a thread id
to a pointer and using that as was done before. This first
implementation is not effecient but it does provide all the
corrent semantics. If/when performance becomes and issue we
can and should just natively adopt pthreads which is portable.
Let me finish by saying I'm not proud of any of this and I would
love to see it improved. However, this slow implementation does
at least provide all the correct kthread API semantics whereas
the previous method of casting the thread ID to a pointer was
dodgy at best.
gcc-unused and gcc-uninit topic branches at the same time and
then ran 'tg update'. I'll need to keep that sort of thing
in mind when updating multiple topic branches between updates.
within an ASSERT with the ASSERTV macro which will ensure it will
be removed when the ASSERTs are commented out. This makes gcc much
happier, makes the variables usage explicit, and removes the need
for the compiler to detect it is unused and do the right thing.
These changes bring the zfs-0.4.4 tree in to compliance with
the spl-0.4.4 packaging changes. The bottom line is 2 source
rpms and 4 binary rpms will now be generated when creating
packages there will be:
zfs-<version>.src.rpm
- Fully rebuildable source rpm for libzfs and utils.
zfs-modules-<version>.src.rpm
- Fully rebuildable source rpm for kernel modules.
zfs-<version>.<arch>.rpm
- Binary rpm for libzfs and utils. The utils in this package are
compatible with all zfs-module rpms of the same version.
zfs-devel-<version>.<arch>.rpm
- Binary rpm containing headers for building against libzfs libraries.
zfs-modules-<verion>-<kernel>.arch.rpm
- Binary rpm containing the kernel modules for a specific kernel build.
The package name contains the kernel version and you should have one
of these packages installed to match every kernel on your system.
zfs-modules-devel-<verion>-<kernel>.arch.rpm
- Binary rpm containing development header and module symbols needed
for building additional kernel modules which are dependent on the
zfs module stack.
Expect minor interations on these changes as I validate they work
properly on CHAOS, RHEL, Fedora, and SLES style distros.
The extra call to the constructor was there to reinitialize the non-
trivial primatives in the dnode (lists, mutexs, condvars, avl tree, etc).
This was safe, although not exactly clean, on Solaris because none of
the primitives allocate memory. In the Linux port this is not true.
To keep stack usage to a minimum several of the primatives dynamically
allocate memory thus initializing them twice results in a memory leak.
This patch resolves this problem for Solaris and Linux by ensuring all
*_inits are called in the constructor, and all *_destroys are called
in the destructor. Additionally we ensure that all dnode objects are
properly deconstructed before being freed to the slab, and when the
objects are allocated from the slab all required data members are
explicity initialized to correct values.
Most of these fixes appear to be harmless and should never occur.
However, there were a few cases in this patch which do concern me,
I doubt we're seeing them but they look possible... mainly in the
user tools.
The previous code was not wrong, but this prevents gcc from warning
us about missing cases for these known safe switch statements. The
-Wno-missing-cases can now be removed to detect places where we
accidentally forgot a case.
compile option. In most case the variables are only unused when
debugging is disabled (ASSERT) however they do waste stack if that
case if the compiler doesn't optimize it out (it should). But more
importantly disabling this warning prevent us from noticing legit
unused variables accidentally left in other place of the code.
Brian Behlendorf