To accomindate the updated Linux 3.0 shrinker API the spl
shrinker compatibility code was updated. Unfortunately, this
couldn't be done cleanly without slightly adjusting the comapt
API. See spl commit a55bcaad18.
This commit updates the ZFS code to use the slightly modified
API. You must use the latest SPL if your building ZFS.
The problem here is that prune_icache() tries to evict/delete
both the xattr directory inode as well as at least one xattr
inode contained in that directory. Here's what happens:
1. File is created.
2. xattr is created for that file (behind the scenes a xattr
directory and a file in that xattr directory are created)
3. File is deleted.
4. Both the xattr directory inode and at least one xattr
inode from that directory are evicted by prune_icache();
prune_icache() acquires a lock on both inodes before it
calls ->evict() on the inodes
When the xattr directory inode is evicted zfs_zinactive attempts
to delete the xattr files contained in that directory. While
enumerating these files zfs_zget() is called to obtain a reference
to the xattr file znode - which tries to lock the xattr inode.
However that very same xattr inode was already locked by
prune_icache() further up the call stack, thus leading to a
deadlock.
This can be reliably reproduced like this:
$ touch test
$ attr -s a -V b test
$ rm test
$ echo 3 > /proc/sys/vm/drop_caches
This patch fixes the deadlock by moving the zfs_purgedir() call to
zfs_unlinked_drain(). Instead zfs_rmnode() now checks whether the
xattr dir is empty and leaves the xattr dir in the unlinked set if
it finds any xattrs.
To ensure zfs_unlinked_drain() never accesses a stale super block
zfsvfs_teardown() has been update to block until the iput taskq
has been drained. This avoids a potential race where a file with
an xattr directory is removed and the file system is immediately
unmounted.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#266
iput_final() already calls zpl_inode_destroy() -> zfs_inode_destroy()
for us after zfs_zinactive(), thus making sure that the inode is
properly cleaned up.
The zfs_inode_destroy() calls in zfs_rmnode() would lead to a
double-free.
Fixes#282
Some disks with internal sectors larger than 512 bytes (e.g., 4k) can
suffer from bad write performance when ashift is not configured
correctly. This is caused by the disk not reporting its actual sector
size, but a sector size of 512 bytes. The drive may behave this way
for compatibility reasons. For example, the WDC WD20EARS disks are
known to exhibit this behavior.
When creating a zpool, ZFS takes that wrong sector size and sets the
"ashift" property accordingly (to 9: 1<<9=512), whereas it should be
set to 12 for 4k sectors (1<<12=4096).
This patch allows an adminstrator to manual specify the known correct
ashift size at 'zpool create' time. This can significantly improve
performance in certain cases. However, it will have an impact on your
total pool capacity. See the updated ashift property description
in the zpool.8 man page for additional details.
Valid values for the ashift property range from 9 to 17 (512B-128KB).
Additionally, you may set the ashift to 0 if you wish to auto-detect
the sector size based on what the disk reports, this is the default
behavior. The most common ashift values are 9 and 12.
Example:
zpool create -o ashift=12 tank raidz2 sda sdb sdc sdd
Closes#280
Original-patch-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The WRITE_FLUSH, WRITE_FUA, and WRITE_FLUSH_FUA flags have been
introduced as a replacement for WRITE_BARRIER. This was done
to allow richer semantics to be expressed to the block layer.
It is the block layers responsibility to choose the correct way
to implement these semantics.
This change simply updates the bio's to use the new kernel API
which should be absolutely safe. However, since ZFS depends
entirely on this working as designed for correctness we do
want to be careful.
Closes#281
Stack usage for ddt_class_contains() reduced from 524 bytes to 68
bytes. This large stack allocation significantly contributed to
the likelyhood of a stack overflow when scrubbing/resilvering
dedup pools.
Stack usage for ddt_zap_lookup() reduced from 368 bytes to 120
bytes. This large stack allocation significantly contributed to
the likelyhood of a stack overflow when scrubbing/resilvering
dedup pools.
This abomination is no longer required because the zio's issued
during this recursive call path will now be handled asynchronously
by the taskq thread pool.
This reverts commit 6656bf5621.
The majority of the recursive operations performed by the dsl
are done either in the context of the tgx_sync_thread or during
pool import. It is these recursive operations which contribute
greatly to the stack depth. When this recursion is coupled with
a synchronous I/O in the same context overflow becomes possible.
Previously to handle this case I have focused on keeping the
individual stack frames as light as possible. This is a good
idea as long as it can be done in a way which doesn't overly
complicate the code. However, there is a better solution.
If we treat all zio's issued by the tgx_sync_thread as async then
we can use the tgx_sync_thread stack for the recursive parts, and
the zio_* threads for the I/O parts. This effectively doubles our
available stack space with the only drawback being a small delay
to schedule the I/O. However, in practice the scheduling time
is so much smaller than the actual I/O time this isn't an issue.
Another benefit of making the zio async is that the zio pipeline
is now parallel. That should mean for CPU intensive pipelines
such as compression or dedup performance may be improved.
With this change in place the worst case stack usage observed so
far is 6902 bytes. This is still higher than I'd like but
significantly improved. Additional changes to specific functions
should improve this further. This change allows us to revent
commit 6656bf5 which did some horrible things to the recursive
traverse_visitbp() callpath in the name of saving stack.
Yesterday I ran across a 3TB drive which exposed 4K sectors to
Linux. While I thought I had gotten this support correct it
turns out there were 2 subtle bugs which prevented it from
working.
sudo ./cmd/zpool/zpool create -f large-sector /dev/sda
cannot create 'large-sector': one or more devices is currently unavailable
1) The first issue was that it was possible that bdev_capacity()
would return the number of 512 byte sectors rather than the number
of 4096 sectors. Internally, certain Linux functions only operate
with 512 byte sectors so you need to be careful. To avoid any
confusion in the future I've updated bdev_capacity() to simply
return the device (or partition) capacity in bytes. The higher
levels of ZFS want the value in bytes anyway so this is cleaner.
2) When creating a bio the ->bi_sector count must always be
expressed in 512 byte sectors. The existing code would scale
the byte offset by the logical sector size. Until now this was
always 512 so it never caused problems. Trying a 4K sector drive
clearly exposed the issue. The problem has been fixed by
hard coding the 512 byte sector which is exactly what the bio
code does internally.
With these changes I'm now able to create ZFS pools using 4K
sector drives. No issues were observed during fairly extensive
testing. This is also a low risk change if your using 512b
sectors devices because none of the logic changes.
Closes#256
The default buffer size when requesting multiple quota entries
is 100 times the zfs_useracct_t size. In practice this works out
to exactly 27200 bytes. Since this will be a short lived buffer
in a non-performance critical path it is preferable to vmem_alloc()
the needed memory.
Initially when zfsdev_ioctl() was ported to Linux we didn't have
any credential support implemented. So at the time we simply
passed NULL which wasn't much of a problem since most of the
secpolicy code was disabled.
However, one exception is quota handling which does require the
credential. Now that proper credentials are supported we can
safely start passing the callers credential. This is also an
initial step towards fully implemented the zfs secpolicy.
Normally when the arc_shrinker_func() function is called the return
value should be:
>=0 - To indicate the number of freeable objects in the cache, or
-1 - To indicate this cache should be skipped
However, when the shrinker callback is called with 'nr_to_scan' equal
to zero. The caller simply wants the number of freeable objects in
the cache and we must never return -1. This patch reorders the
first two conditionals in arc_shrinker_func() to ensure this behavior.
This patch also now explictly casts arc_size and arc_c_min to signed
int64_t types so MAX(x, 0) works as expected. As unsigned types
we would never see an negative value which defeated the purpose of
the MAX() lower bound and broke the shrinker logic.
Finally, when nr_to_scan is non-zero we explictly prevent all reclaim
below arc_c_min. This is done to prevent the Linux page cache from
completely crowding out the ARC. This limit is tunable and some
experimentation is likely going to be required to set it exactly right.
For now we're sticking with the OpenSolaris defaults.
Closes#218Closes#243
The comment in zfs_close() pertaining to decrementing the synchronous
open count needs to be updated for Linux. The code was already
updated to be correct, but the comment was missed and is now misleading.
Under Linux the zfs_close() hook is only called once when the final
reference is dropped. This differs from Solaris where zfs_close()
is called for each close.
Closes#237
Update the handling of named pipes and sockets to be consistent with
other platforms with regard to the rdev attribute. While all ZFS
ipmlementations store the rdev for device files in a system attribute
(SA), this is not the case for FIFOs and sockets. Indeed, Linux always
passes rdev=0 to mknod() for FIFOs and sockets, so the value is not
needed. Add an ASSERT that rdev==0 for FIFOs and sockets to detect if
the expected behavior ever changes.
Closes#216
The direct reclaim path in the z_wr_* threads must be disabled
to ensure forward progress is always maintained for txg processing.
This ensures that a txg will never get stuck waiting on itself
because it entered the following memory reclaim callpath.
->prune_icache()->dispose_list()->zpl_clear_inode()->zfs_inactive()
->dmu_tx_assign()->dmu_tx_wait()->tgx_wait_open()
It would be preferable to target this exact code path but the
kernel offers no way to do this without custom patches. To avoid
this we are forced to disable all reclaim for these threads. It
should not be necessary to do this for other other z_* threads
because they will not hold a txg open.
Closes#232
How nfsd handles .fsync() has been changed a couple of times in the
recent kernels. But basically there are three cases we need to
consider.
Linux 2.6.12 - 2.6.33
* The .fsync() hook takes 3 arguments
* The nfsd will call .fsync() with a NULL file struct pointer.
Linux 2.6.34
* The .fsync() hook takes 3 arguments
* The nfsd no longer calls .fsync() but instead used sync_inode()
Linux 2.6.35 - 2.6.x
* The .fsync() hook takes 2 arguments
* The nfsd no longer calls .fsync() but instead used sync_inode()
For once it looks like we've gotten lucky. The first two cases can
actually be collased in to one if we stop using the file struct
pointer entirely. Since the dentry is still passed in both cases
this is possible. The last case can then be safely handled by
unconditionally using the dentry in the file struct pointer now
that we know the nfsd caller has been removed.
Closes#230
The default buffer size when requesting history is 128k. This
is far to large for a kmem_alloc() so instead use the slower
vmem_alloc(). This path has no performance concerns and the
buffer is immediately free'd after its contents are copied to
the user space buffer.
This commit adds module options for all existing zfs tunables.
Ideally the average user should never need to modify any of these
values. However, in practice sometimes you do need to tweak these
values for one reason or another. In those cases it's nice not to
have to resort to rebuilding from source. All tunables are visable
to modinfo and the list is as follows:
$ modinfo module/zfs/zfs.ko
filename: module/zfs/zfs.ko
license: CDDL
author: Sun Microsystems/Oracle, Lawrence Livermore National Laboratory
description: ZFS
srcversion: 8EAB1D71DACE05B5AA61567
depends: spl,znvpair,zcommon,zunicode,zavl
vermagic: 2.6.32-131.0.5.el6.x86_64 SMP mod_unload modversions
parm: zvol_major:Major number for zvol device (uint)
parm: zvol_threads:Number of threads for zvol device (uint)
parm: zio_injection_enabled:Enable fault injection (int)
parm: zio_bulk_flags:Additional flags to pass to bulk buffers (int)
parm: zio_delay_max:Max zio millisec delay before posting event (int)
parm: zio_requeue_io_start_cut_in_line:Prioritize requeued I/O (bool)
parm: zil_replay_disable:Disable intent logging replay (int)
parm: zfs_nocacheflush:Disable cache flushes (bool)
parm: zfs_read_chunk_size:Bytes to read per chunk (long)
parm: zfs_vdev_max_pending:Max pending per-vdev I/Os (int)
parm: zfs_vdev_min_pending:Min pending per-vdev I/Os (int)
parm: zfs_vdev_aggregation_limit:Max vdev I/O aggregation size (int)
parm: zfs_vdev_time_shift:Deadline time shift for vdev I/O (int)
parm: zfs_vdev_ramp_rate:Exponential I/O issue ramp-up rate (int)
parm: zfs_vdev_read_gap_limit:Aggregate read I/O over gap (int)
parm: zfs_vdev_write_gap_limit:Aggregate write I/O over gap (int)
parm: zfs_vdev_scheduler:I/O scheduler (charp)
parm: zfs_vdev_cache_max:Inflate reads small than max (int)
parm: zfs_vdev_cache_size:Total size of the per-disk cache (int)
parm: zfs_vdev_cache_bshift:Shift size to inflate reads too (int)
parm: zfs_scrub_limit:Max scrub/resilver I/O per leaf vdev (int)
parm: zfs_recover:Set to attempt to recover from fatal errors (int)
parm: spa_config_path:SPA config file (/etc/zfs/zpool.cache) (charp)
parm: zfs_zevent_len_max:Max event queue length (int)
parm: zfs_zevent_cols:Max event column width (int)
parm: zfs_zevent_console:Log events to the console (int)
parm: zfs_top_maxinflight:Max I/Os per top-level (int)
parm: zfs_resilver_delay:Number of ticks to delay resilver (int)
parm: zfs_scrub_delay:Number of ticks to delay scrub (int)
parm: zfs_scan_idle:Idle window in clock ticks (int)
parm: zfs_scan_min_time_ms:Min millisecs to scrub per txg (int)
parm: zfs_free_min_time_ms:Min millisecs to free per txg (int)
parm: zfs_resilver_min_time_ms:Min millisecs to resilver per txg (int)
parm: zfs_no_scrub_io:Set to disable scrub I/O (bool)
parm: zfs_no_scrub_prefetch:Set to disable scrub prefetching (bool)
parm: zfs_txg_timeout:Max seconds worth of delta per txg (int)
parm: zfs_no_write_throttle:Disable write throttling (int)
parm: zfs_write_limit_shift:log2(fraction of memory) per txg (int)
parm: zfs_txg_synctime_ms:Target milliseconds between tgx sync (int)
parm: zfs_write_limit_min:Min tgx write limit (ulong)
parm: zfs_write_limit_max:Max tgx write limit (ulong)
parm: zfs_write_limit_inflated:Inflated tgx write limit (ulong)
parm: zfs_write_limit_override:Override tgx write limit (ulong)
parm: zfs_prefetch_disable:Disable all ZFS prefetching (int)
parm: zfetch_max_streams:Max number of streams per zfetch (uint)
parm: zfetch_min_sec_reap:Min time before stream reclaim (uint)
parm: zfetch_block_cap:Max number of blocks to fetch at a time (uint)
parm: zfetch_array_rd_sz:Number of bytes in a array_read (ulong)
parm: zfs_pd_blks_max:Max number of blocks to prefetch (int)
parm: zfs_dedup_prefetch:Enable prefetching dedup-ed blks (int)
parm: zfs_arc_min:Min arc size (ulong)
parm: zfs_arc_max:Max arc size (ulong)
parm: zfs_arc_meta_limit:Meta limit for arc size (ulong)
parm: zfs_arc_reduce_dnlc_percent:Meta reclaim percentage (int)
parm: zfs_arc_grow_retry:Seconds before growing arc size (int)
parm: zfs_arc_shrink_shift:log2(fraction of arc to reclaim) (int)
parm: zfs_arc_p_min_shift:arc_c shift to calc min/max arc_p (int)
When a new znode/inode pair is created both the znode and the inode
should be immediately updated to the correct values. This was done
for the znode and for most of the values in the inode, but not all
of them. This normally wasn't a problem because most subsequent
operations would cause the inode to be immediately updated. This
change ensures the inode is now fully updated before it is inserted
in to the inode hash.
Closes#116Closes#146Closes#164
This change fixes a kernel panic which would occur when resizing
a dataset which was not open. The objset_t stored in the
zvol_state_t will be set to NULL when the block device is closed.
To avoid this issue we pass the correct objset_t as the third arg.
The code has also been updated to correctly notify the kernel
when the block device capacity changes. For 2.6.28 and newer
kernels the capacity change will be immediately detected. For
earlier kernels the capacity change will be detected when the
device is next opened. This is a known limitation of older
kernels.
Online ext3 resize test case passes on 2.6.28+ kernels:
$ dd if=/dev/zero of=/tmp/zvol bs=1M count=1 seek=1023
$ zpool create tank /tmp/zvol
$ zfs create -V 500M tank/zd0
$ mkfs.ext3 /dev/zd0
$ mkdir /mnt/zd0
$ mount /dev/zd0 /mnt/zd0
$ df -h /mnt/zd0
$ zfs set volsize=800M tank/zd0
$ resize2fs /dev/zd0
$ df -h /mnt/zd0
Original-patch-by: Fajar A. Nugraha <github@fajar.net>
Closes#68Closes#84
The vdev_metaslab_init() function has been observed to allocate
larger than 8k chunks. However, they are not much larger than 8k
and it does this infrequently so it is allowed and the warning is
supressed.
The dsl_scan_visit() function is a little heavy weight taking 464
bytes on the stack. This can be easily reduced for little cost by
moving zap_cursor_t and zap_attribute_t off the stack and on to the
heap. After this change dsl_scan_visit() has been reduced in size
by 320 bytes.
This change was made to reduce stack usage in the dsl_scan_sync()
callpath which is recursive and has been observed to overflow the
stack.
Issue #174
This function is called recursively so everything possible must be
done to limit its stack consumption. The dprintf_bp() debugging
function adds 30 bytes of local variables to the function we cannot
afford. By commenting out this debugging we save 30 bytes per
recursion and depths of 13 are not uncommon. This yeilds a total
stack saving of 390 bytes on our 8k stack.
Issue #174
The recursive call chain dsl_scan_visitbp() -> dsl_scan_recurse() ->
dsl_scan_visitdnode() -> dsl_scan_visitbp has been observed to consume
considerable stack resulting in a stack overflow (>8k). The cleanest
way I see to fix this with minimal impact to the existing flow of
code, and with the fewest performance concerns, is to always inline
dsl_scan_recurse() and dsl_scan_visitdnode(). While this will increase
the function size of dsl_scan_visitbp(), by 4660 bytes, it also reduces
the stack requirements by removing the function call overhead.
Issue #174
It's possible for a zvol_write thread to enter direct memory reclaim
while holding open a transaction group. This results in the system
attempting to write out data to the disk to free memory. Unfortunately,
this can't succeed because the the thread doing reclaim is holding open
the txg which must be closed to be synced to disk. To prevent this
the offending allocation is marked KM_PUSHPAGE which will prevent it
from attempting writeback.
Closes#191
Occasionally we would see an -EFAULT returned when setting the
I/O scheduler on a vdev. This was caused an improperly formatted
user mode helper command.
This commit restructures the command to something simpler, allocates
space for it dynamically to save stack, and removes the retry logic
which is no longer needed.
Closes#169
This change ensures the ARC meta-data limits are enforced. Without
this enforcement meta-data can grow to consume all of the ARC cache
pushing out data and hurting performance. The cache is aggressively
reclaimed but this is a soft and not a hard limit. The cache may
exceed the set limit briefly before being brought under control.
By default 25% of the ARC capacity can be used for meta-data. This
limit can be tuned by setting the 'zfs_arc_meta_limit' module option.
Once this limit is exceeded meta-data reclaim will occur in 3 percent
chunks, or may be tuned using 'arc_reduce_dnlc_percent'.
Closes#193
Fixed a bug where zfs_zget could access a stale znode pointer when
the inode had already been removed from the inode cache via iput ->
iput_final -> ... -> zfs_zinactive but the corresponding SA handle
was still alive.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#180
As part of zfs_ioc_recv() a zfs_cmd_t is allocated in the kernel
which is 17808 bytes in size. This sort of thing in general should
be avoided. However, since this should be an infrequent event for
now we allow it and simply suppress the warning with the KM_NODEBUG
flag. This can be revisited latter if/when it becomes an issue.
Closes#178
If the attribute's new value was shorter than the old one the old
code would leave parts of the old value in the xattr znode.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#203
Without this we may mistakenly believe we have a dentry and try to
d_instantiate() it. This will result in the following BUG. It's
important to note that while the xattr directory has an inode
assoicated with it we never create a dentry for it.
kernel BUG at fs/dcache.c:1418!
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#202
When compiling ZFS in user space gcc-4.6.0 correctly identifies
the variable 'os' as being set but never used. This generates a
warning and a build failure when using --enable-debug. However,
the code is correct we only want to use 'os' for the kernel space
builds. To suppress the warning the call was wrapped with a
VERIFY() which has the nice side effect of ensuring the 'os'
actually never is NULL. This was observed under Fedora 15.
module/zfs/dsl_pool.c: In function ‘dsl_pool_create’:
module/zfs/dsl_pool.c:229:12: error: variable ‘os’ set but not used
[-Werror=unused-but-set-variable]
Update code to use the spl_invalidate_inodes() wrapper. This hides
some of the complexity of determining if invalidate_inodes() was
exported, and if so what is its prototype. The second argument
of spl_invalidate_inodes() determined the behavior of how dirty
inodes are handled. By passing a zero we are indicated that we
want those inodes to be treated as busy and skipped.
The .sync_fs fix as applied did not use the updated SPL credential
API. This broke builds on Debian Lenny, this change applies the
needed fix to use the portable API. The original credential changes
are part of commit 81e97e2187.
Disable the normal reclaim path for the txg_sync thread. This
ensures the thread will never enter dmu_tx_assign() which can
otherwise occur due to direct reclaim. If this is allowed to
happen the system can deadlock. Direct reclaim call path:
->shrink_icache_memory->prune_icache->dispose_list->
clear_inode->zpl_clear_inode->zfs_inactive->dmu_tx_assign
Under OpenSolaris all memory reclaim is done asyncronously. Under
Linux memory reclaim is done asynchronously _and_ synchronously.
When a process allocates memory with GFP_KERNEL it explicitly allows
the kernel to do reclaim on its behalf to satify the allocation.
If that GFP_KERNEL allocation fails the kernel may take more drastic
measures to reclaim the memory such as killing user space processes.
This was observed to happen with ZFS because the ARC could consume
a large fraction of the system memory but no synchronous reclaim
could be performed on it. The result was GFP_KERNEL allocations
could fail resulting in OOM events, and only moments latter the
arc_reclaim thread would free unused memory from the ARC.
This change leaves the arc_thread in place to manage the fundamental
ARC behavior. But it adds a synchronous (direct) reclaim path for
the ARC which can be called when memory is badly needed. It also
adds an asynchronous (indirect) reclaim path which is called
much more frequently to prune the ARC slab caches.
The following useful values were missing the arcstats. This change
adds them in to provide greater visibility in to the arcs behavior.
arc_no_grow 4 0
arc_tempreserve 4 0
arc_loaned_bytes 4 0
arc_meta_used 4 624774592
arc_meta_limit 4 400785408
arc_meta_max 4 625594176
Under Linux a dentry referencing an inode must be instantiated before
the inode is unlocked. To accomplish this without overly modifing
the core ZFS code the dentry it passed via the vattr_t. There are
cases such as replay when a dentry is not available. In which case
it is obviously not initialized at inode creation time, if a dentry
is needed it will be spliced as when required via d_lookup().
Making distclean in module
make[1]: Entering directory `/zfs/module'
make -C SUBDIRS=`pwd` clean
make: Entering an unknown directory
make: *** SUBDIRS=/zfs/module: No such file or directory. Stop.
When using --with-config=user the 'distclean' target would fail
because it assumes the kernel configuration infrastrure is set up.
This is not the case, nor does it need to be, because the
'--with-config=user' option will prune the entire ./module subtree
from SUBDIRS. This prevents most build rules from operating in the
./module directory.
However, the 'dist*' rules will still traverse this directory
because it is listed in DIST_SUBDIRS. This is correct because we
need to ensure the dist rules package the directory contents
regardless of the configuration for the 'dist' rule. The correct
way to handle this is to only invoke the kernel build system as
part of the 'clean' rule when CONFIG_KERNEL_TRUE is set.
Initial fix provided by Darik Horn <dajhorn@vanadac.com>.
This commit is a slightly refined form of the original.
Kernel threads which sleep uninterruptibly on Linux are marked in the (D)
state. These threads are usually in the process of performing IO and are
thus counted against the load average. The txg_quiesce and txg_sync threads
were always sleeping uninterruptibly and thus inflating the load average.
This change makes them sleep interruptibly. Some care is required however
because these threads may now be woken early by signals. In this case the
callers are all careful to check that the required conditions are met after
waking up. If we're woken early due to a signal they will simply go back
to sleep. In this case these changes are safe.
Closes#175
The .freeze_fs/.unfreeze_fs hooks were not added until Linux 2.6.29
Since these hooks are currently unused they are being removed to
allow support of older kernels.
As of Linux 2.6.29 a clean credential API was added to the Linux kernel.
Previously the credential was embedded in the task_struct. Because the
SPL already has considerable support for handling this API change the
ZPL code has been updated to use the Solaris credential API.
Now that KM_SLEEP is not defined as GFP_NOFS there is the possibility
of synchronous reclaim deadlocks. These deadlocks never existed in the
original OpenSolaris code because all memory reclaim on Solaris is done
asyncronously. Linux does both synchronous (direct) and asynchronous
(indirect) reclaim.
This commit addresses a deadlock caused by inode eviction. A KM_SLEEP
allocation may trigger direct memory reclaim and shrink the inode cache.
This can occur while a mutex in the array of ZFS_OBJ_HOLD mutexes is
held. Through the ->shrink_icache_memory()->evict()->zfs_inactive()->
zfs_zinactive() call path the same mutex may be reacquired resulting
in a deadlock. To avoid this deadlock the process must not reacquire
the mutex when it is already holding it.
This is a reasonable fix for now but longer term the ZFS_OBJ_HOLD
mutex locking should be reevaluated. This infrastructure already
prevents us from ever using the Linux lock dependency analysis tools,
and it may limit scalability.
It used to be the case that all KM_SLEEP allocations were GFS_NOFS.
Unfortunately this often resulted in the kernel being unable to
reclaim the ARC, inode, and dentry caches in a timely manor.
The fix was to make KM_SLEEP a GFP_KERNEL allocation in the SPL.
However, this increases the posibility of deadlocking the system
on a zfs write thread. If a zfs write thread attempts to perform
an allocation it may trigger synchronous reclaim. This reclaim
may attempt to flush dirty data/inode to disk to free memory.
Unforunately, this write cannot finish because the write thread
which would handle it is holding the previous transaction open.
Deadlock.
To avoid this all allocations in the zfs write thread path must
use KM_PUSHPAGE which prohibits synchronous reclaim for that
thread. In this way forward progress in ensured. The risk
with this change is I missed updating an allocation for the
write threads leaving an increased posibility of deadlock. If
any deadlocks remain they will be unlikely but we'll have to
make sure they all get fixed.
Register the missing .remount_fs handler. This handler isn't strictly
required because the VFS does a pretty good job updating most of the
MS_* flags. However, there's no harm in using the hook to call the
registered zpl callback for various MS_* flags. Additionaly, this
allows us to lay the ground work for more complicated argument parsing
in the future.
Register the missing .sync_fs handler. This is a noop in most cases
because the usual requirement is that sync just be initiated. As part
of the DMU's normal transaction processing txgs will be frequently
synced. However, when the 'wait' flag is set the requirement is that
.sync_fs must not return until the data is safe on disk. With the
addition of the .sync_fs handler this is now properly implemented.
ZFS should only change the i/o scheduler for a disk when it has
ownership of the whole disk. This is basically the same logic as
adjusting the write cache behavior on a disk. This change updates
the vdev disk code to skip partitions when setting the i/o scheduler.
Closes#152
Due to an uninitialized variable files opened with O_APPEND may
overwrite the start of the file rather than append to it. This
was introduced accidentally when I removed the Solaris vnodes.
The zfs_range_lock_writer() function used to key off zf->z_vnode
to determine if a znode_t was for a zvol of zpl object. With
the removal of vnodes this was replaced by the flag zp->z_is_zvol.
This flag was used to control the append behavior for range locks.
Unfortunately, this value was never properly initialized after
the vnode removal. However, because most of memory is usually
zeros it happened to be set correctly most of the time making
the bug appear racy. Properly initializing zp->z_is_zvol to
zero completely resolves the problem with O_APPEND.
Closes#126
Move 'bulk' and 'xattr_bulk' from the stack to the heap to minimize
stack space usage. These two arrays consumed 448 bytes on the stack
and have been replaced by two 8 byte points for a total stack space
saving of 432 bytes. The zfs_setattr() path had been previously
observed to overrun the stack in certain circumstances.
The original range lock implementation had to be modified by commit
8926ab7 because it was unsafe on Linux. In particular, calling
cv_destroy() immediately after cv_broadcast() is dangerous because
the waiters may still be asleep. Thus the following cv_destroy()
will free memory which may still be in use.
This was fixed by updating cv_destroy() to block on waiters but
this in turn introduced a deadlock. The deadlock was resolved
with the use of a taskq to move the offending free outside the
range lock. This worked well but using the taskq for the free
resulted in a serious performace hit. This is somewhat ironic
because at the time I felt using the taskq might improve things
by making the free asynchronous.
This patch refines the original fix and moves the free from the
taskq to a private free list. Then items which must be free'd
are simply inserted in to the list. When the range lock is dropped
it's safe to free the items. The list is walked and all rl_t
entries are freed.
This change improves small cached read performance by 26x. This
was expected because for small reads the number of locking calls
goes up significantly. More surprisingly this change significantly
improves large cache read performance. This probably attributable
to better cpu/memory locality. Very likely the same processor
which allocated the memory is now freeing it.
bs ext3 zfs zfs+fix faster
----------------------------------------------
512 435 3 79 26x
1k 820 7 160 22x
2k 1536 14 305 21x
4k 2764 28 572 20x
8k 3788 50 1024 20x
16k 4300 86 1843 21x
32k 4505 138 2560 18x
64k 5324 252 3891 15x
128k 5427 276 4710 17x
256k 5427 413 5017 12x
512k 5427 497 5324 10x
1m 5427 521 5632 10x
Closes#142
In the original implementation the zfs_open()/zfs_close() hooks
were dropped for simplicity. This was functional but not 100%
correct with the expected ZFS sematics. Updating and re-adding the
zfs_open()/zfs_close() hooks resolves the following issues.
1) The ZFS_APPENDONLY file attribute is once again honored. While
there are still no Linux tools to set/clear these attributes once
there are it should behave correctly.
2) Minimal virus scan file attribute hooks were added. Once again
this support in disabled but the infrastructure is back in place.
3) Most importantly correctly handle assigning files which were
opened syncronously to the intent log. Without this change O_SYNC
modifications could be lost during a system crash even though they
were marked synchronous.
Filesystems like ZFS must use what the kernel calls an anonymous super
block. Basically, this is just a filesystem which is not backed by a
single block device. Normally this block device's dev_t is stored in
the super block. For anonymous super blocks a unique reserved dev_t
is assigned as part of get_sb().
This sb->s_dev must then be set in the returned stat structures as
stat->st_dev. This allows userspace utilities to easily detect the
boundries of a specific filesystem. Tools such as 'du' depend on this
for proper accounting.
Additionally, under OpenSolaris the statfs->f_fsid is set to the device
id. To preserve consistency with OpenSolaris we also set the fsid to
the device id. Other Linux filesystem (ext) set the fsid to a unique
value determined by the filesystems uuid. This value is unique but
maintains no relationship to the device id. This may be desirable
when exporting NFS filesystem because it minimizes to chance of a
client observing the same fsid from two different servers.
Closes#140
The AT_ versions of these macros are used on Solaris and while they
map to their Linux equivilants the code has been updated to use the
ATTR_ versions.
Move 'tmpxvattr' from the stack to the heap to minimize stack
space usage. This is enough to get us below the 1024 byte stack
frame warning. That however is still a large stack frame and it
should be further reduced by moving the 'bulk' and 'xattr_bulk'
sa_bulk_attr_t variables to the heap in a future patch.
When I began work on the Posix layer it immediately became clear to
me that to integrate cleanly with the Linux VFS certain Solaris
specific things would have to go. One of these things was to elimate
as many Solaris specific types from the ZPL layer as possible. They
would be replaced with their Linux equivalents. This would not only
be good for performance, but for the general readability and health of
the code. The Solaris and Linux VFS are different beasts and should
be treated as such. Most of the code remains common for constructing
transactions and such, but there are subtle and important differenced
which need to be repsected.
This policy went quite for for certain types such as the vnode_t,
and it initially seemed to be working out well for the vattr_t. There
was a relatively small amount of related xvattr_t code I was forced to
comment out with HAVE_XVATTR. But it didn't look that hard to come
back soon and replace it all with a native Linux type.
However, after going doing this path with xvattr some distance it
clear that this code was woven in the ZPL more deeply than I thought.
In particular its hooks went very deep in to the ZPL replay code
and replacing it would not be as easy as I originally thought.
Rather than continue persuing replacing and removing this code I've
taken a step back and reevaluted things. This commit reverts many of
my previous commits which removed xvattr related code. It restores
much of the code to its original upstream state and now relies on
improved xvattr_t support in the zfs package itself.
The result of this is that much of the code which I had commented
out, which accidentally broke things like replay, is now back in
place and working. However, there may be a small performance
impact for getattr/setattr operations because they now require
a translation from native Linux to Solaris types. For now that's
a price I'm willing to pay. Once everything is completely functional
we can revisting the issue of removing the vattr_t/xvattr_t types.
Closes#111
Print the supported zpool and filesystem versions at module load
time. This change removes an ambiguity and adds information that
system administrators care about. The phrase "ZFS pool version %s"
is the same as zpool upgrade -v so that the operator is familiar
with the message.
ZFS: Loaded module v0.6.0, ZFS pool version 28, ZFS filesystem version 5
ZFS: Unloaded module v0.6.0
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
There were two cases when attempting to set the vdev block device
scheduler which would causes console warnings.
The first case was when the vdev used a loop, ram, dm, or other
such device which doesn't support a configurable scheduler. In
these cases attempting to set a scheduler is pointless and can
be safely skipped.
The secord case is slightly more troubling. We were seeing
transient cases where setting the elevator would return -EFAULT.
On retry everything is fine so there appears to be a small window
where this is possible. To handle that case we silently retry
up to three times before reporting the warning.
In all of the above cases the warning is harmless and at worse you
may see slightly different performance characteristics from one
or more of your vdevs.
This commit allows zvols with names longer than 32 characters, which
fixes issue on https://github.com/behlendorf/zfs/issues/#issue/102.
Changes include:
- use /dev/zd* device names for zvol, where * is the device minor
(include/sys/fs/zfs.h, module/zfs/zvol.c).
- add BLKZNAME ioctl to get dataset name from userland
(include/sys/fs/zfs.h, module/zfs/zvol.c, cmd/zvol_id).
- add udev rule to create /dev/zvol/[dataset_name] and the legacy
/dev/[dataset_name] symlink. For partitions on zvol, it will create
/dev/zvol/[dataset_name]-part* (etc/udev/rules.d/60-zvol.rules,
cmd/zvol_id).
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Remove custom code to pack/unpack dev_t's. Under Linux all dev_t's
are an unsigned 32-bit value even on 64-bit platforms. The lower
20 bits are used for the minor number and the upper 12 for the major
number.
This means if your importing a pool from Solaris you may get strange
major/minor numbers. But it doesn't really matter because even if
we add compatibility code to translate the encoded Solaris major/minor
they won't do you any good under Linux. You will still need to
recreate the dev_t with a major/minor which maps to reserved major
numbers used under Linux.
Dropping this code also resolves 32-bit builds by removing the
offending 32-bit compatibility code.
ASSERT3P should be used instead of ASSERT3U when comparing
pointers. Using ASSERT3U with the cast causes a compiler
warning for 32-bit builds which is fatal with --enable-debug.
The underlying storage pool actually uses multiple block
size. Under Solaris frsize (fragment size) is reported as
the smallest block size we support, and bsize (block size)
as the filesystem's maximum block size. Unfortunately,
under Linux the fragment size and block size are often used
interchangeably. Thus we are forced to report both of them
as the filesystem's maximum block size.
Closes#112
Because the secpolicy_* macros are all currently defined to (0).
And because the caller of this function does not check the return
code. The compiler complains that this statement has no effect
which is correct and OK. To suppress the warning explictly cast
the result to (void).
Generally it's a good idea to use enums for switch statements,
but in this case it causes warning because the enum is really a
set of flags. These flags are OR'ed together in some cases
resulting in values which are not part of the original enum.
This causes compiler warning such as this about invalid cases.
error: case value ‘33’ not in enumerated type ‘zprop_source_t’
To handle this we simply case the enum to an int for the switch
statement. This leaves all other enum type checking in place
and effectively disabled these warnings.
For legacy reasons the zvol.c and vdev_disk.c Linux compatibility
code ended up in sys/blkdev.h and sys/vdev_disk.h headers. While
there are worse places for this code to live it should be in a
linux/blkdev_compat.h header. This change moves this block device
Linux compatibility code in to the linux/blkdev_compat.h header
and updates all the correct #include locations. This is not a
functional change or bug fix, it is just code cleanup.
When changing the uid/gid of a file via zfs_setattr() use the
Posix id passed in iattr->ia_uid/gid. While the zfs_fuid_create()
code already had the fuid support disabled for Linux it was
returning the uid/gid from the credential. With this change
the 'chown' command which relies on setxattr is now working
properly.
Also remove a little stray white space which was in front of
zfs_update_inode() call and the end of zfs_setattr().
Under Linux sys_symlink(2) should result in a inode being created
with one reference for the inode itself, and a second reference on
the inode which is held by the new dentry. Under Solaris this
appears not to be the case. Their zfs_symlink() handler drops
the inode reference before returning.
The result of this under Linux is that the reference count for
symlinks is always one smaller than it should have been. This
results in a BUG() when the symlink is unlinked. To handle this
the Linux port now keeps the inode reference which differs from
the Solaris behavior. This results in correct reference counts.
Closes#96
The zfs_readlink() function returns a Solaris positive error value
and that needs to be converted to a Linux negative error value.
While in this case nothing would actually go wrong, it's still
incorrect and should be fixed if for no other reason than clarity.
This patch addresses three issues related to symlinks.
1) Revert the zfs_follow_link() function to a modified version
of the original zfs_readlink(). The only changes from the
original OpenSolaris version relate to using Linux types.
For the moment this means no vnode's and no zfsvfs_t. The
caller zpl_follow_link() was also updated accordingly. This
change was reverted because it was slightly gratuitious.
2) Update zpl_follow_link() to use local variables for the
link buffer. I'd forgotten that iov.iov_base is updated by
uiomove() so after the call to zfs_readlink() it can not longer
be used. We need our own private copy of the link pointer.
3) Allocate MAXPATHLEN instead of MAXPATHLEN+1. By default
MAXPATHLEN is 4096 bytes which is a full page, adding one to
it pushes it slightly over a page. That means you'll likely
end up allocating 2 pages which is wasteful of memory and
possibly slightly slower.
This adds an API to wait for pending commit callbacks of already-synced
transactions to finish processing. This is needed by the DMU-OSD in
Lustre during device finalization when some callbacks may still not be
called, this leads to non-zero reference count errors. See lustre.org
bug 23931.
While the attr/xattr hooks were already in place for regular
files this hooks can also apply to directories and special files.
While they aren't typically used in this way, it should be
supported. This patch registers these additional callbacks
for both directory and special inode types.
Under Linux when creating a fifo or socket type device in the ZFS
filesystem it's critical that the rdev is stored in a SA. This
was already being correctly done for character and block devices,
but that logic needed to be extended to include FIFOs and sockets.
This patch takes care of device creation but a follow on patch
may still be required to verify that the dev_t is being correctly
packed/unpacked from the SA.
It was noticed that when you have zvols in multiple datasets
not all of the zvol devices are created at module load time.
Fajarnugraha did the leg work to identify that the root cause of
this bug is a non-zero return value from zvol_create_minors_cb().
Returning a non-zero value from the dmu_objset_find_spa() callback
function results in aborting processing the remaining children in
a dataset. Since we want to ensure that the callback in run on
all children regardless of error simply unconditionally return
zero from the zvol_create_minors_cb(). This callback function
is solely used for this purpose so surpressing the error is safe.
Closes#96
The new prefered inteface for evicting an inode from the inode cache
is the ->evict_inode() callback. It replaces both the ->delete_inode()
and ->clear_inode() callbacks which were previously used for this.
The xattr handler prototypes were sanitized with the idea being that
the same handlers could be used for multiple methods. The result of
this was the inode type was changes to a dentry, and both the get()
and set() hooks had a handler_flags argument added. The list()
callback was similiarly effected but no autoconf check was added
because we do not use the list() callback.
The fsync() callback in the file_operations structure used to take
3 arguments. The callback now only takes 2 arguments because the
dentry argument was determined to be unused by all consumers. To
handle this a compatibility prototype was added to ensure the right
prototype is used. Our implementation never used the dentry argument
either so it's just a matter of using the right prototype.
The const keyword was added to the 'struct xattr_handler' in the
generic Linux super_block structure. To handle this we define an
appropriate xattr_handler_t typedef which can be used. This was
the preferred solution because it keeps the code clean and readable.
Initial testing has shown the the right IO scheduler to use under Linux
is noop. This strikes the ideal balance by allowing the zfs elevator
to do all request ordering and prioritization. While allowing the
Linux elevator to do the maximum front/back merging allowed by the
physical device. This yields the largest possible requests for the
device with the lowest total overhead.
While 'noop' should be right for your system you can choose a different
IO scheduler with the 'zfs_vdev_scheduler' option. You may set this
value to any of the standard Linux schedulers: noop, cfq, deadline,
anticipatory. In addition, if you choose 'none' zfs will not attempt
to change the IO scheduler for the block device.
The following warning was observed under normal operation. It's
not fatal but it's something to be addressed long term. Flag the
offending allocation with KM_NODEBUG to suppress the warning and
flag the call site.
SPL: Showing stack for process 21761
Pid: 21761, comm: iozone Tainted: P ----------------
2.6.32-71.14.1.el6.x86_64 #1
Call Trace:
[<ffffffffa05465a7>] spl_debug_dumpstack+0x27/0x40 [spl]
[<ffffffffa054a84d>] kmem_alloc_debug+0x11d/0x130 [spl]
[<ffffffffa05de166>] dmu_buf_hold_array_by_dnode+0xa6/0x4e0 [zfs]
[<ffffffffa05de825>] dmu_buf_hold_array+0x65/0x90 [zfs]
[<ffffffffa05de891>] dmu_read_uio+0x41/0xd0 [zfs]
[<ffffffffa0654827>] zfs_read+0x147/0x470 [zfs]
[<ffffffffa06644a2>] zpl_read_common+0x52/0x70 [zfs]
[<ffffffffa0664503>] zpl_read+0x43/0x70 [zfs]
[<ffffffff8116d905>] vfs_read+0xb5/0x1a0
[<ffffffff8116da41>] sys_read+0x51/0x90
[<ffffffff81013172>] system_call_fastpath+0x16/0x1b
When performing a 'zfs rollback' it's critical to invalidate
the previous dcache and inode cache. If we don't there will
stale cache entries which when accessed will result in EIOs.
With the recent SPL change (d599e4fa) that forces cv_destroy()
to block until all waiters have been woken. It is now unsafe
to call cv_destroy() under the zp->z_range_lock() because it
is used as the condition variable mutex. If there are waiters
cv_destroy() will block until they wake up and aquire the mutex.
However, they will never aquire the mutex because cv_destroy()
will not return allowing it's caller to drop the lock. Deadlock.
To avoid this cv_destroy() is now run asynchronously in a taskq.
This solves two problems:
1) It is no longer run under the zp->z_range_lock so no deadlock.
2) Since cv_destroy() may now block we don't want this slowing
down zfs_range_unlock() and throttling the system.
This was not as much of an issue under OpenSolaris because their
cv_destroy() implementation does not do anything. They do however
risk a bad paging request if cv_destroy() returns, the memory holding
the condition variable is free'd, and then the waiters wake up and
try to reference it. It's a very small unlikely race, but it is
possible.
It's worth taking a moment to describe how mmap is implemented
for zfs because it differs considerably from other Linux filesystems.
However, this issue is handled the same way under OpenSolaris.
The issue is that by design zfs bypasses the Linux page cache and
leaves all caching up to the ARC. This has been shown to work
well for the common read(2)/write(2) case. However, mmap(2)
is problem because it relies on being tightly integrated with the
page cache. To handle this we cache mmap'ed files twice, once in
the ARC and a second time in the page cache. The code is careful
to keep both copies synchronized.
When a file with an mmap'ed region is written to using write(2)
both the data in the ARC and existing pages in the page cache
are updated. For a read(2) data will be read first from the page
cache then the ARC if needed. Neither a write(2) or read(2) will
will ever result in new pages being added to the page cache.
New pages are added to the page cache only via .readpage() which
is called when the vfs needs to read a page off disk to back the
virtual memory region. These pages may be modified without
notifying the ARC and will be written out periodically via
.writepage(). This will occur due to either a sync or the usual
page aging behavior. Note because a read(2) of a mmap'ed file
will always check the page cache first even when the ARC is out
of date correct data will still be returned.
While this implementation ensures correct behavior it does have
have some drawbacks. The most obvious of which is that it
increases the required memory footprint when access mmap'ed
files. It also adds additional complexity to the code keeping
both caches synchronized.
Longer term it may be possible to cleanly resolve this wart by
mapping page cache pages directly on to the ARC buffers. The
Linux address space operations are flexible enough to allow
selection of which pages back a particular index. The trick
would be working out the details of which subsystem is in
charge, the ARC, the page cache, or both. It may also prove
helpful to move the ARC buffers to a scatter-gather lists
rather than a vmalloc'ed region.
Additionally, zfs_write/read_common() were used in the readpage
and writepage hooks because it was fairly easy. However, it
would be better to update zfs_fillpage and zfs_putapage to be
Linux friendly and use them instead.
The Linux specific xattr operations have all been located in the
file zpl_xattr.c. These functions primarily rely on the reworked
zfs_* functions to do their job. They are also responsible for
converting the possible Solaris style error codes to negative
Linux errors.
The Linux specific super block operations have all been located in the
file zpl_super.c. These functions primarily rely on the reworked
zfs_* functions to do their job. They are also responsible for
converting the possible Solaris style error codes to negative
Linux errors.
The Linux specific inode operations have all been located in the
file zpl_inode.c. These functions primarily rely on the reworked
zfs_* functions to do their job. They are also responsible for
converting the possible Solaris style error codes to negative
Linux errors.
The Linux specific file operations have all been located in the
file zpl_file.c. These functions primarily rely on the reworked
zfs_* functions to do their job. They are also responsible for
converting the possible Solaris style error codes to negative
Linux errors.
This first zpl_* commit also includes a common zpl.h header with
minimal entries to register the Linux specific hooks. In also
adds all the new zpl_* file to the Makefile.in. This is not a
standalone commit, you required the following zpl_* commits.
For the moment exactly how to handle xvattr is not clear. This
change largely consists of the code to comment out the offending
bits until something reasonable can be done.
A new flag is required for the zfs_rlock code to determine if
it is operation of the zvol of zpl dataset. This used to be
keyed off the zp->z_vnode, which was a hack to begin with, but
with the removal of vnodes we needed a dedicated flag.
I appologize in advance why to many things ended up in this commit.
When it could be seperated in to a whole series of commits teasing
that all apart now would take considerable time and I'm not sure
there's much merrit in it. As such I'll just summerize the intent
of the changes which are all (or partly) in this commit. Broadly
the intent is to remove as much Solaris specific code as possible
and replace it with native Linux equivilants. More specifically:
1) Replace all instances of zfsvfs_t with zfs_sb_t. While the
type is largely the same calling it private super block data
rather than a zfsvfs is more consistent with how Linux names
this. While non critical it makes the code easier to read when
your thinking in Linux friendly VFS terms.
2) Replace vnode_t with struct inode. The Linux VFS doesn't have
the notion of a vnode and there's absolutely no good reason to
create one. There are in fact several good reasons to remove it.
It just adds overhead on Linux if we were to manage one, it
conplicates the code, and it likely will lead to bugs so there's
a good change it will be out of date. The code has been updated
to remove all need for this type.
3) Replace all vtype_t's with umode types. Along with this shift
all uses of types to mode bits. The Solaris code would pass a
vtype which is redundant with the Linux mode. Just update all the
code to use the Linux mode macros and remove this redundancy.
4) Remove using of vn_* helpers and replace where needed with
inode helpers. The big example here is creating iput_aync to
replace vn_rele_async. Other vn helpers will be addressed as
needed but they should be be emulated. They are a Solaris VFS'ism
and should simply be replaced with Linux equivilants.
5) Update znode alloc/free code. Under Linux it's common to
embed the inode specific data with the inode itself. This removes
the need for an extra memory allocation. In zfs this information
is called a znode and it now embeds the inode with it. Allocators
have been updated accordingly.
6) Minimal integration with the vfs flags for setting up the
super block and handling mount options has been added this
code will need to be refined but functionally it's all there.
This will be the first and last of these to large to review commits.
For the moment we do not use dmu_write_pages() to write pages
directly in to a dmu object. It may be required at some point
in the future, but for now is simplest and cleanest to drop it.
It can be easily readded if/when needed.
For portability reasons it's handy to be able to create a root
znode and basic filesystem components without requiring the full
cooperation of the VFS. We are committing to this to simply the
filesystem creations code.
This code is used for snapshot and heavily leverages Solaris
functionality we do not want to reimplement. These files have
been removed, including references to them, and will be replaced
by a zfs_snap.c/zpl_snap.c implementation which handles snapshots.
Minor update to ensure zfs_sync() is disabled if a kernel oops/panic
is triggered. As the comment says 'data integrity is job one'. This
change could have been done by defining panicstr to oops_in_progress
in the SPL. But I felt it was better to use the native Linux API
here since to be clear.
This flag does not need to be support under Linux. As the comment
says it was only there to support fsflush() for old filesystem like
UFS. This is not needed under Linux.
Brian Behlendorf
Gunnar Beutner
Christian Kohlschütter
Ned A. Bass
Darik Horn
Fajar A. Nugraha
Ricardo M. Correia