Direct IO via the O_DIRECT flag was originally introduced in XFS by
IRIX for database workloads. Its purpose was to allow the database
to bypass the page and buffer caches to prevent unnecessary IO
operations (e.g. readahead) while preventing contention for system
memory between the database and kernel caches.
On Illumos, there is a library function called directio(3C) that
allows user space to provide a hint to the file system that Direct IO
is useful, but the file system is free to ignore it. The semantics
are also entirely a file system decision. Those that do not
implement it return ENOTTY.
Since the semantics were never defined in any standard, O_DIRECT is
implemented such that it conforms to the behavior described in the
Linux open(2) man page as follows.
1. Minimize cache effects of the I/O.
By design the ARC is already scan-resistant which helps mitigate
the need for special O_DIRECT handling. Data which is only
accessed once will be the first to be evicted from the cache.
This behavior is in consistent with Illumos and FreeBSD.
Future performance work may wish to investigate the benefits of
immediately evicting data from the cache which has been read or
written with the O_DIRECT flag. Functionally this behavior is
very similar to applying the 'primarycache=metadata' property
per open file.
2. O_DIRECT _MAY_ impose restrictions on IO alignment and length.
No additional alignment or length restrictions are imposed.
3. O_DIRECT _MAY_ perform unbuffered IO operations directly
between user memory and block device.
No unbuffered IO operations are currently supported. In order
to support features such as transparent compression, encryption,
and checksumming a copy must be made to transform the data.
4. O_DIRECT _MAY_ imply O_DSYNC (XFS).
O_DIRECT does not imply O_DSYNC for ZFS. Callers must provide
O_DSYNC to request synchronous semantics.
5. O_DIRECT _MAY_ disable file locking that serializes IO
operations. Applications should avoid mixing O_DIRECT
and normal IO or mmap(2) IO to the same file. This is
particularly true for overlapping regions.
All I/O in ZFS is locked for correctness and this locking is not
disabled by O_DIRECT. However, concurrently mixing O_DIRECT,
mmap(2), and normal I/O on the same file is not recommended.
This change is implemented by layering the aops->direct_IO operations
on the existing AIO operations. Code already existed in ZFS on Linux
for bypassing the page cache when O_DIRECT is specified.
References:
* http://xfs.org/docs/xfsdocs-xml-dev/XFS_User_Guide/tmp/en-US/html/ch02s09.html
* https://blogs.oracle.com/roch/entry/zfs_and_directio
* https://ext4.wiki.kernel.org/index.php/Clarifying_Direct_IO's_Semantics
* https://illumos.org/man/3c/directio
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#224Closes#7823
Allow the 'zpool replace' to run slowly without overwhelming the vdev
queues by setting zfs_scan_vdev_limit=128k. This limits the number of
concurrent slow IOs which need to be handled. The net effect is the
test case runs approximately 3x faster putting it well under the 10
minute per-test time limit.
Rename import_cache* test cases to imprt_cachefile*. Originally
these were renamed due to a maximum tar name limit, this limit was
removed by commit 1dfde3d9b.
Replaced instances of /var/tmp in zpool_import.cfg with $TEST_BASE_DIR.
Reviewed-by: bunder2015 <omfgbunder@gmail.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#7765Closes#7802
* Both cli_root/zpool_import/import_cache_device_replaced, and
redundancy/redundancy_004_neg have been observed to fail for
spurious reasons ~1% of the time. Add them to the exception
list and reference the open Github issue.
* Speed up replacement/replacement_001_pos to prevent it from
exceeding the 10 minute per test limit and getting KILLED.
File vdev creation switched to truncate -s, redundant raidz1
testing pass dropped, fixed some minor formating issues.
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#7766
The reservation_008_pos test case has been observed to fail in
a non-dangerous way in approximately 5% of automated test runs.
Add the test case to the list of possible expected failures
until the test case can be made perfectly reliable.
Reviewed by: Giuseppe Di Natale <guss80@gmail.com>
Reviewed by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #7741Closes#7742
While the autoexpand property may seem like a small feature it
depends on a significant amount of system infrastructure. Enough
of that infrastructure is now in place that with a few modifications
for Linux it can be supported.
Auto-expand works as follows; when a block device is modified
(re-sized, closed after being open r/w, etc) a change uevent is
generated for udev. The ZED, which is monitoring udev events,
passes the change event along to zfs_deliver_dle() if the disk
or partition contains a zfs_member as identified by blkid.
From here the device is matched against all imported pool vdevs
using the vdev_guid which was read from the label by blkid. If
a match is found the ZED reopens the pool vdev. This re-opening
is important because it allows the vdev to be briefly closed so
the disk partition table can be re-read. Otherwise, it wouldn't
be possible to report the maximum possible expansion size.
Finally, if the property autoexpand=on a vdev expansion will be
attempted. After performing some sanity checks on the disk to
verify that it is safe to expand, the primary partition (-part1)
will be expanded and the partition table updated. The partition
is then re-opened (again) to detect the updated size which allows
the new capacity to be used.
In order to make all of the above possible the following changes
were required:
* Updated the zpool_expand_001_pos and zpool_expand_003_pos tests.
These tests now create a pool which is layered on a loopback,
scsi_debug, and file vdev. This allows for testing of non-
partitioned block device (loopback), a partition block device
(scsi_debug), and a file which does not receive udev change
events. This provided for better test coverage, and by removing
the layering on ZFS volumes there issues surrounding layering
one pool on another are avoided.
* zpool_find_vdev_by_physpath() updated to accept a vdev guid.
This allows for matching by guid rather than path which is a
more reliable way for the ZED to reference a vdev.
* Fixed zfs_zevent_wait() signal handling which could result
in the ZED spinning when a signal was not handled.
* Removed vdev_disk_rrpart() functionality which can be abandoned
in favor of kernel provided blkdev_reread_part() function.
* Added a rwlock which is held as a writer while a disk is being
reopened. This is important to prevent errors from occurring
for any configuration related IOs which bypass the SCL_ZIO lock.
The zpool_reopen_007_pos.ksh test case was added to verify IO
error are never observed when reopening. This is not expected
to impact IO performance.
Additional fixes which aren't critical but were discovered and
resolved in the course of developing this functionality.
* Added PHYS_PATH="/dev/zvol/dataset" to the vdev configuration for
ZFS volumes. This is as good as a unique physical path, while the
volumes are not used in the test cases anymore for other reasons
this improvement was included.
Reviewed by: Richard Elling <Richard.Elling@RichardElling.com>
Signed-off-by: Sara Hartse <sara.hartse@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#120Closes#2437Closes#5771Closes#7366Closes#7582Closes#7629
Remove the dependency on partitionable devices for the clean_mirror
and scrub_mirror test cases. This allows for the setup and cleanup
of the test cases to be simplified by removing the need for complex
partitioning.
This change also resolves a issue where the clean_mirror devices
were not being properly damaged since the device name was not a
full path. The result being loopX files were being left in the
top level test_results directory.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#7434Closes#7690
The enospc_002_pos test case would frequently fail due a command
succeeding when it was expected to fail due to lack of space.
In order to make this far less likely, files are created across
multiple transaction groups in order to consume as many unused
blocks as possible.
The dependency that the tests run on a partitioned block device
has been removed. It's simpler to use sparse files.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#7663
Adopt and extend the OpenZFS ZTS results analysis script for use
with ZFS on Linux. This allows for automatic analysis of tests
which may be skipped for a variety or reasons or which are not
entirely reliable.
In addition to the list of 'known' failures, which have been updated
for ZFS on Linux, there in a new 'maybe' section. This mapping
include tests which might be correctly skipped depending on the
test environment. This may be because of a missing dependency or
lack of required kernel support. This list also includes tests
which normally pass but might on occasion fail for a harmless
reason.
The script was also extended include a reason for why a given test
might be skipped or may fail. The reason will be included after
the test in the "results other than PASS that are expected" section.
For failures it is preferable to set the reason to the GitHub issue
number and for skipped tests several generic reasons are available.
You may also specify a custom reason if needed.
All tests were added back in to the linux.run file even if they are
expected to failed. There is value in running tests which may not
pass, the expected results for these tests has been encoded in
the new analysis script.
All tests which were disabled because they ran more slowly on a
32-bit system have been re-enabled. Developers working on 32-bit
systems should assess what it reasonable for their environment.
The unnecessary dependency on physical block devices was removed for
the checksum, grow_pool, and grow_replicas test groups so they are
no longer skipped. Updated the filetest_001_pos test case to run
properly now that it is enabled and moved the grow tests in to a
single directory.
Reviewed-by: Prakash Surya <prakash.surya@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#7638
