Refresh the autogen.sh products based on the versions which are
installed by default in the GA RHEL6.0 release.
autoconf (GNU Autoconf) 2.63
automake (GNU automake) 1.11.1
ltmain.sh (GNU libtool) 2.2.6b
As of the 0.5.2 tag, names of whole-disk vdevs must be specified to
the command line tools without partition identifiers. This commit
fixes a 'zpool online' command in zfault.sh that incorrectly includes
he partition in the vdev name, causing test 9 to fail.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
If libblkid does not contain ZFS support, then 'zpool import' will scan
all block devices in /dev/ to determine which ones are components of a
ZFS filesystem. It does this by opening all the devices and stat'ing
them to determine which ones are block devices. If the device turns
out not to be a block device it is skipped.
Usually, this whole process is pretty harmless (although slow). But
there are certain devices in /dev/ which must be handled in a very
specific way or your system may crash. For example, if /dev/watchdog
is simply opened the watchdog timer will be started and your system
will panic when the timer expires.
It turns out the /dev/hpet causes similiar problems although only when
accessed under a virtual machine. For some reason accessing /dev/hpet
causes qemu to crash. To address this issue this commit adds /dev/hpet
to the device blacklist, it will be skipped solely based on its name.
When adding this functionality originally the options to only
run specific tests (-t), or conversely skip specific tests (-s)
were omitted from the usage page. This commit adds the missing
documentation.
The idea behind the '-c' flag is to cleanup everything from a
previous test run which might cause the test script to fail.
This should also include removing the previously loaded module.
This makes it a little easier to run 'zconfig.sh -c', however
remember this is a test script and it will take all of your
other zpools offline for the purposes of the test. This notion
has also been extended to the default 'make check' behavior.
Loading and unloading the zlib modules as part of the zfs.sh
script has proven a little problematic for a few reasons.
* First, your kernel may not need to load either zlib_inflate
or zlib_deflate. This functionality may be built directly in
to your kernel. It depends entirely on what your distribution
decided was the right thing to do.
* Second, even if you do manage to load the correct modules you
may not be able to unload them. There may other consumers
of the modules with a reference preventing the unload.
To avoid both of these issues the test scripts have been updated to
attempt to unconditionally load all modules listed in KERNEL_MODULES.
If the module is successfully loaded you must have needed it. If
the module can't be loaded that almost certainly means either it is
built in to your kernel or is already being used by another consumer.
In both cases this is not an issue and we can move on to the spl/zfs
modules.
Finally, by removing these kernel modules from the MODULES list
we ensure they are never unloaded during 'zfs.sh -u'. This avoids
the issue of the script failing because there is another consumer
using the module we were not aware of. In other words the script
restricts unloading modules to only the spl/zfs modules.
Closes#78
This commit fixes a sign extension bug affecting l2arc devices. Extremely
large offsets may be passed down to the low level block device driver on
reads, generating errors similar to
attempt to access beyond end of device
sdbi1: rw=14, want=36028797014862705, limit=125026959
The unwanted sign extension occurrs because the function arc_read_nolock()
stores the offset as a daddr_t, a 32-bit signed int type in the Linux kernel.
This offset is then passed to zio_read_phys() as a uint64_t argument, causing
sign extension for values of 0x80000000 or greater. To avoid this, we store
the offset in a uint64_t.
This change also changes a few daddr_t struct members to uint64_t in the libspl
headers to avoid similar bugs cropping up in the future. We also add an ASSERT
to __vdev_disk_physio() to check for invalid offsets.
Closes#66
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
As of linux-2.6.36 the last in-tree consumer of fops->ioctl() has
been removed and thus fops()->ioctl() has also been removed. The
replacement hook is fops->unlocked_ioctl() which has existed in
kernel since 2.6.12. Since the ZFS code only contains support
back to 2.6.18 vintage kernels, I'm not adding an autoconf check
for this and simply moving everything to use fops->unlocked_ioctl().
Most of the blk_* macros were removed in 2.6.36. Ostensibly this was
done to improve readability and allow easier grepping. However, from
a portability stand point the macros are helpful. Therefore the needed
macros are redefined here if they are missing from the kernel.
The name of the flag used to mark a bio as synchronous has changed
again in the 2.6.36 kernel due to the unification of the BIO_RW_*
and REQ_* flags. The new flag is called REQ_SYNC. To simplify
checking this flag I have introduced the vdev_disk_dio_is_sync()
helper function. Based on the results of several new autoconf
tests it uses the correct mask to check for a synchronous bio.
Preferred interface for flagging a synchronous bio:
2.6.12-2.6.29: BIO_RW_SYNC
2.6.30-2.6.35: BIO_RW_SYNCIO
2.6.36-2.6.xx: REQ_SYNC
As of linux-2.6.36 the BIO_RW_FAILFAST and REQ_FAILFAST flags
have been unified under the REQ_* names. These flags always had
to be kept in-sync so this is a nice step forward, unfortunately
it means we need to be careful to only use the new unified flags
when the BIO_RW_* flags are not defined. Additional autoconf
checks were added for this and if it is ever unclear which method
to use no flags are set. This is safe but may result in longer
delays before a disk is failed.
Perferred interface for setting FAILFAST on a bio:
2.6.12-2.6.27: BIO_RW_FAILFAST
2.6.28-2.6.35: BIO_RW_FAILFAST_{DEV|TRANSPORT|DRIVER}
2.6.36-2.6.xx: REQ_FAILFAST_{DEV|TRANSPORT|DRIVER}
Commit 3ee56c292b changed an ENOTSUP return value
in one location to ENOTSUPP to fix user programs seeing an invalid ioctl()
error code. However, use of ENOTSUP is widespread in the zfs module. Instead
of changing all of those uses, we fixed the ENOTSUP definition in the SPL to be
consistent with user space. The changed return value in the above commit is
therefore no longer needed, so this commit reverses it to maintain consistency.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The lustre zpios-test simulates a reasonable lustre workload. It will
create 128 threads, the same as a Lustre OSS, and then 4096 individual
objects. Each objects is 16MiB in size and will be written/read in 1MiB
from a random thread. This is fundamentally how we expect Lustre to behave
for large IO intensive workloads.
To streamline testing I have in the past added several custom configs
to the zpool-config directory. This change reverts those custom configs
and replaces them with three generic config which can do the same thing.
The generic config behavior can be set by setting various environment
variables when calling either the zpool-create.sh or zpios.sh scripts.
For example if you wanted to create and test a single 4-disk Raid-Z2
configuration using disks [A-D]1 with dedicated ZIL and L2ARC devices
you could run the following.
$ ZIL="log A2" L2ARC="cache B2" RANKS=1 CHANNELS=4 LEVEL=2 \
zpool-create.sh -c zpool-raidz
$ zpool status tank
pool: tank
state: ONLINE
scan: none requested
config:
NAME STATE READ WRITE CKSUM
tank ONLINE 0 0 0
raidz2-0 ONLINE 0 0 0
A1 ONLINE 0 0 0
B1 ONLINE 0 0 0
C1 ONLINE 0 0 0
D1 ONLINE 0 0 0
logs
A2 ONLINE 0 0 0
cache
B2 ONLINE 0 0 0
errors: No known data errors
Support for rolling back datasets require a functional ZPL, which we currently
do not have. The zfs command does not check for ZPL support before attempting
a rollback, and in preparation for rolling back a zvol it removes the minor
node of the device. To prevent the zvol device node from disappearing after a
failed rollback operation, this change wraps the zfs_do_rollback() function in
an #ifdef HAVE_ZPL and returns ENOSYS in the absence of a ZPL. This is
consistent with the behavior of other ZPL dependent commands such as mount.
The orginal error message observed with this bug was rather confusing:
internal error: Unknown error 524
Aborted
This was because zfs_ioc_rollback() returns ENOTSUP if we don't HAVE_ZPL, but
Linux actually has no such error code. It should instead return EOPNOTSUPP, as
that is how ENOTSUP is defined in user space. With that we would have gotten
the somewhat more helpful message
cannot rollback 'tank/fish': unsupported version
This is rather a moot point with the above changes since we will no longer make
that ioctl call without a ZPL. But, this change updates the error code just in
case.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Increasing the default zio_wr_int thread count from 8 to 16 improves
write performence by 13% on large systems. More testing need to be
done but I suspect the ideal tuning here is ZTI_BATCH() with a minimum
of 8 threads.
Linux kernel thread names are expected to be short. This change shortens
the zio thread names to 10 characters leaving a few chracters to append
the /<cpuid> to which the thread is bound. For example: z_wr_iss/0.
On some older kernels, i.e. 2.6.18, zvol_ioctl_by_inode() may get passed a NULL
file pointer if the user tries to mount a zvol without a filesystem on it.
This change adds checks to prevent a null pointer dereference.
Closes#73.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Some sudo configurations may not include /sbin in the PATH.
libzfs_load_module() currently does not call modprobe with an absolute path, so
it may fail under such configurations if called under sudo. This change adds
the absolute path to modprobe so we no longer rely on how PATH is set.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Creating whole-disk vdevs can intermittently fail if a udev-managed symlink to
the disk partition is already in place. To avoid this, we now remove any such
symlink before partitioning the disk. This makes zpool_label_disk_wait() truly
wait for the new link to show up instead of returning if it finds an old link
still in place. Otherwise there is a window between when udev deletes and
recreates the link during which access attempts will fail with ENOENT.
Also, clean up a comment about waiting for udev to create symlinks. It no
longer needs to describe the special cases for the link names, since that is
now handled in a separate helper function.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This test performs a sanity check of the zpool add and remove commands. It
tests adding and removing both a cache disk and a log disk to and from a zpool.
Usage of both a shorthand device path and a full path is covered. The test
uses a scsi_debug device as the disk to be added and removed. This is done so
that zpool will see it as a whole disk and partition it, which it does not
currently done for loopback devices. We want to verify that the manipulation
done to whole disks paths to hide the parition information does not break the
add/remove interface.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Portability between Solaris and Linux isn't really an issue for us anymore, and
removing sections like this one helps simplify the code.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
zpool status displays abbreviated vdev names without leading path components
and, in the case of whole disks, without partition information. Also, the
zpool subcommands 'create' and 'add' support using shorthand devices names
without qualified paths. Prior to this change, however, removing a device
generally required specifying its name as it is stored in the vdev label. So
while zpool status might list a cache disk with a name like A16, removing it
would require a full path such as /dev/disk/zpool/A16-part1, which is
non-intuitive.
This change adds support for shorthand device names with the remove subcommand
so one can simply type, for example,
zpool remove tank A16
A consequence of this change is that including the partition information when
removing a whole-disk vdev now results in an error. While this is arguably the
correct behavior, it is a departure from how zpool previously worked in this
project.
This change removes the only reference to ctd_check_path(), so that function is
also removed to avoid compiler warnings.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This change adds two helper functions for working with vdev names and paths.
zfs_resolve_shortname() resolves a shorthand vdev name to an absolute path
of a file in /dev, /dev/disk/by-id, /dev/disk/by-label, /dev/disk/by-path,
/dev/disk/by-uuid, /dev/disk/zpool. This was previously done only in the
function is_shorthand_path(), but we need a general helper function to
implement shorthand names for additional zpool subcommands like remove.
is_shorthand_path() is accordingly updated to call the helper function.
There is a minor change in the way zfs_resolve_shortname() tests if a file
exists. is_shorthand_path() effectively used open() and stat64() to test for
file existence, since its scope includes testing if a device is a whole disk
and collecting file status information. zfs_resolve_shortname(), on the other
hand, only uses access() to test for existence and leaves it to the caller to
perform any additional file operations. This seemed like the most general and
lightweight approach, and still preserves the semantics of is_shorthand_path().
zfs_append_partition() appends a partition suffix to a device path. This
should be used to generate the name of a whole disk as it is stored in the vdev
label. The user-visible names of whole disks do not contain the partition
information, while the name in the vdev label does. The code was lifted from
the function make_disks(), which now just calls the helper function. Again,
having a helper function to do this supports general handling of shorthand
names in the user interface.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Eleven new zpool configurations were added to allow testing of various
failure cases. The first 5 zpool configurations leverage the 'faulty'
md device type which allow us to simuluate IO errors at the block layer.
The last 6 zpool configurations leverage the scsi_debug module provided
by modern kernels. This device allows you to create virtual scsi
devices which are backed by a ram disk. With this setup we can verify
the full IO stack by injecting faults at the lowest layer. Both methods
of fault injection are important to verifying the IO stack.
The zfs code itself also provides a mechanism for error injection
via the zinject command line tool. While we should also take advantage
of this appraoch to validate the code it does not address any of the
Linux integration issues which are the most concerning. For the
moment we're trusting that the upstream Solaris guys are running
zinject and would have caught internal zfs logic errors.
Currently, there are 6 r/w test cases layered on top of the 'faulty'
md devices. They include 3 writes tests for soft/transient errors,
hard/permenant errors, and all writes error to the device. There
are 3 matching read tests for soft/transient errors, hard/permenant
errors, and fixable read error with a write. Although for this last
case zfs doesn't do anything special.
The seventh test case verifies zfs detects and corrects checksum
errors. In this case one of the drives is extensively damaged and
by dd'ing over large sections of it. We then ensure zfs logs the
issue and correctly rebuilds the damage.
The next test cases use the scsi_debug configuration to injects error
at the bottom of the scsi stack. This ensures we find any flaws in the
scsi midlayer or our usage of it. Plus it stresses the device specific
retry, timeout, and error handling outside of zfs's control.
The eighth test case is to verify that the system correctly handles an
intermittent device timeout. Here the scsi_debug device drops 1 in N
requests resulting in a retry either at the block level. The ZFS code
does specify the FAILFAST option but it turns out that for this case
the Linux IO stack with still retry the command. The FAILFAST logic
located in scsi_noretry_cmd() does no seem to apply to the simply
timeout case. It appears to be more targeted to specific device or
transport errors from the lower layers.
The ninth test case handles a persistent failure in which the device
is removed from the system by Linux. The test verifies that the failure
is detected, the device is made unavailable, and then can be successfully
re-add when brought back online. Additionally, it ensures that errors
and events are logged to the correct places and the no data corruption
has occured due to the failure.
It turns out that 'zpool events' over 1024 bytes in size where being
silently dropped. This was discovered while writing the zfault.sh
tests to validate common failure modes.
This could occur because the zfs interface for passing an arbitrary
size nvlist_t over an ioctl() is to provide a buffer for the packed
nvlist which is usually big enough. In this case 1024 byte is the
default. If the kernel determines the buffer is to small it returns
ENOMEM and the minimum required size of the nvlist_t. This was
working properly but in the case of 'zpool events' the event stream
was advanced dispite the error. Thus the retry with the bigger
buffer would succeed but it would skip over the previous event.
The fix is to pass this size to zfs_zevent_next() and determine
before removing the event from the list if it will fit. This was
preferable to checking after the event was returned because this
avoids the need to rewind the stream.
While there is no right maximum timeout for a disk IO we can start
laying the ground work to measure how long they do take in practice.
This change simply measures the IO time and if it exceeds 30s an
event is posted for 'zpool events'.
This value was carefully selected because for sd devices it implies
that at least one timeout (SD_TIMEOUT) has occured. Unfortunately,
even with FAILFAST set we may retry and request and not get an
error. This behavior is strongly dependant on the device driver
and how it is hooked in to the scsi error handling stack. However
by setting the limit at 30s we can log the event even if no error
was returned.
Slightly longer term we can start recording these delays perhaps
as a simple power-of-two histrogram. This histogram can then be
reported as part of the 'zpool status' command when given an command
line option.
None of this code changes the internal behavior of ZFS. Currently
it is simply for reporting excessively long delays.
ZFS works best when it is notified as soon as possible when a device
failure occurs. This allows it to immediately start any recovery
actions which may be needed. In theory Linux supports a flag which
can be set on bio's called FAILFAST which provides this quick
notification by disabling the retry logic in the lower scsi layers.
That's the theory at least. In practice is turns out that while the
flag exists you oddly have to set it with the BIO_RW_AHEAD flag.
And even when it's set it you may get retries in the low level
drivers decides that's the right behavior, or if you don't get the
right error codes reported to the scsi midlayer.
Unfortunately, without additional kernels patchs there's not much
which can be done to improve this. Basically, this just means that
it may take 2-3 minutes before a ZFS is notified properly that a
device has failed. This can be improved and I suspect I'll be
submitting patches upstream to handle this.
To make the 'zpool events' output simple to parse with awk the extra
newline after embedded nvlists has been dropped. This allows the
entire event to be parsed as a single whitespace seperated record.
The -H option has been added to operate in scripted mode. For the
'zpool events' command this means don't print the header. The usage
of -H is consistent with scripted mode for other zpool commands.
By default the Solaris code does not log speculative or soft io errors
in either 'zpool status' or post an event. Under Linux we don't want
to change the expected behavior of 'zpool status' so these io errors
are still suppressed there.
However, since we do need to know about these events for Linux FMA and
the 'zpool events' interface is new we do post the events. With the
addition of the zio_flags field the posted events now contain enough
information that a user space consumer can identify and discard these
events if it sees fit.
All the upper layers of zfs expect zio->io_error to be positive. I was
careful but I missed one instance in vdev_disk_physio_completion() which
could return a negative error. To ensure all cases are always caught I
had additionally added an ASSERT() to check this before zio_interpret().
Finally, as a debugging aid when zfs is build with --enable-debug all
errors from the backing block devices will be reported to the console
with an error message like this:
ZFS: zio error=5 type=1 offset=4217856 size=8192 flags=60440
Observed during failure mode testing, dsl_scan_setup_sync() allocates
73920 bytes. This is way over the limit of what is wise to do with a
kmem_alloc() and it should probably be moved to a slab. For now I'm
just flagging it with KM_NODEBUG to quiet the error until this can be
revisited.
The string array 'char dirs[5][8]' was too small to accomodate the terminating
NUL character in "by-label". This change adds the needed additional byte.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit modifies libzfs_init() to attempt to load the zfs kernel module if
it is not already loaded. This is done to simplify initialization by letting
users simply import their zpools without having to first load the module.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Under Solaris, the slice number is chopped off when displaying the device name
if the vdev is a whole disk. Under Linux we should similarly discard the
partition number. This commit adds the logic to perform the name truncation
for devices ending in -partX, XpX, or X, where X is a string of digits. The
second case handles devices like md0p0. The third case is limited to scsi and
ide disks, i.e. those beginning with "sd" or "hd", in order to avoid stripping
the number from names like "loop0".
This commit removes the Solaris-specific code for removing slices, since we no
longer reasonably expect our changes to be merged in upstream. The partition
stripping code was moved off to a helper function to improve readability.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit fixes a bug in vdev_disk_open() in which the whole_disk property
was getting set to 0 for disk devices, even when it was stored as a 1 when the
zpool was created. The whole_disk property lets us detect when the partition
suffix should be stripped from the device name in CLI output. It is also used
to determine how writeback cache should be set for a device.
When an existing zpool is imported its configuration is read from the vdev
label by user space in zpool_read_label(). The whole_disk property is saved in
the nvlist which gets passed into the kernel, where it in turn gets saved in
the vdev struct in vdev_alloc(). Therefore, this value is available in
vdev_disk_open() and should not be overridden by checking the provided device
path, since that path will likely point to a partition and the check will
return the wrong result.
We also add an ASSERT that the whole_disk property is set. We are not aware of
any cases where vdev_disk_open() should be called with a config that doesn't
have this property set. The ASSERT is there so that when debugging is enabled
we can identify any legitimate cases that we are missing. If we never hit the
ASSERT, we can at some point remove it along with the conditional whole_disk
check.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This callback is needed for properly accounting the per-uid and per-gid
space usage. Even if we don't have the ZPL, we still need this callback
in order to have proper on-disk ZPL compatibility and to be able to use
Lustre quotas.
Fortunately, the callback doesn't have any ZPL/VFS dependencies so we
can just move it out of #ifdef HAVE_ZPL.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Top-level vdev names in zpool status output should follow a <type-id> naming
convention. In the case of raidz devices, the type portion of the name was
missing.
This commit fixes a bug in zpool_vdev_name() where in this snprintf call
(void) snprintf(buf, sizeof (buf), "%s-%llu", path,
(u_longlong_t)id);
buf and path may point to the same location. The result is that buf ends up
containing only the "-id" part. This only occurred for raidz devices because
the code for appending the parity level to the type string stored its result in
buf then set path to point there. To fix this we allocate a new temporary
buffer on the stack instead of reusing buf.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#57
Required for the DB_DNODE_ENTER()/DB_DNODE_EXIT() helpers.
Signed-off-by: Ricardo M. Correia <ricardo.correia@oracle.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
In my machine, dnode_hold_impl() allocates 9992 bytes in DEBUG mode and it
causes a large stream of stack traces in the logs. Instead, use KM_NODEBUG
to quiet down this known large alloc.
Signed-off-by: Ricardo M. Correia <ricardo.correia@oracle.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
By default the zpool_layout command would always use the slot
number assigned by Linux when generating the zdev.conf file.
This is a reasonable default there are cases when it makes
sense to remap the slot id assigned by Linux using your own
custom mapping.
This commit adds support to zpool_layout to provide a custom
slot mapping file. The file contains in the first column the
Linux slot it and in the second column the custom slot mapping.
By passing this map file with '-m map' to zpool_config the
mapping will be applied when generating zdev.conf.
Additionally, two sample mapping have been added which reflect
different ways to map the slots in the dragon drawers.
These two lines were being rendered incorrectly on the GitHub
site. To fix the issue there needs to be leading whitespace
before each line to ensure each command is rendered on its
own line.
$ ./configure
$ make pkg
The wiki contents have been converted to html and made available
at their new home http://zfsonlinux.org. The wiki has also been
disabled the html pages are now the official documentation.
Occasional failures were observed in zconfig.sh because udev
could be delayed for a few seconds. To handle this the wait_udev
function has been added to wait for timeout seconds for an
expected device before returning an error. By default callers
currently use a 30 seconds timeout which should be much longer
than udev ever needs but not so long to worry the test suite
is hung.
Commit 6283f55ea1 updated _almost_
everything to use the correct top level object directory. This
was done to correctly supporting building in custom directories.
Unfortunately, I missed this one instance in the zfs-module.spec.in
rpm spec file. Fix it.
The zfs package supports the option --with-config=srpm which
is used to bootstrap configure to allow the 'make srpm' target
to work. This has the advantage of allowing creation of source
rpms without having all your -devel packages installed. This
source package can then be feed back in to an automated build
farm which only installs the required packages listed by the
srpm. This ensures that all proper dependencies are expressed
by the source package, because if they are not you will get
configure/build failures.
The trouble here is that --with-config=srpm prevents the
architecture check from running resulting in TARGET_ASM_DIR
being set to the default asm-generic. The 'make dist' rule
then fails because there is no asm-generic/atomic.S file
because it is generated at build time. To handle this I
have added an empty file asm-generic/atomic.S simply as a
place holder for 'make dist'.
Previously the project contained who zfs_context.h files,
one for user space builds and one for kernel space builds.
It was the responsibility of the source including the file
to ensure the right one was included based on the order of
the include paths.
This was the way it was done in OpenSolaris but for our
purposes I felt it was overly obscure. The user and kernel
zfs_context.h files have been combined in to a single file
and a #define determines if you get the user or kernel
context.
The issue here was that I used the _KERNEL macro which is
defined as part of the spl which will only be defined for
most builds after you include the right zfs_context. It is
safer to use the __KERNEL__ macro which is automatically
defined as part of the kernel build process and passed as
a command line compiler option. It will always be defined
if your building in the kernel and never for user space.
