Commit Graph

9 Commits

Author SHA1 Message Date
Rob Norris
02f4b63db9 config: remove checks with unused defines
All of these set a #define that doesn't appear anywhere in the tree.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #16479
2024-09-18 11:23:35 -07:00
Brian Atkinson
a10e552b99
Adding Direct IO Support
Adding O_DIRECT support to ZFS to bypass the ARC for writes/reads.

O_DIRECT support in ZFS will always ensure there is coherency between
buffered and O_DIRECT IO requests. This ensures that all IO requests,
whether buffered or direct, will see the same file contents at all
times. Just as in other FS's , O_DIRECT does not imply O_SYNC. While
data is written directly to VDEV disks, metadata will not be synced
until the associated  TXG is synced.
For both O_DIRECT read and write request the offset and request sizes,
at a minimum, must be PAGE_SIZE aligned. In the event they are not,
then EINVAL is returned unless the direct property is set to always (see
below).

For O_DIRECT writes:
The request also must be block aligned (recordsize) or the write
request will take the normal (buffered) write path. In the event that
request is block aligned and a cached copy of the buffer in the ARC,
then it will be discarded from the ARC forcing all further reads to
retrieve the data from disk.

For O_DIRECT reads:
The only alignment restrictions are PAGE_SIZE alignment. In the event
that the requested data is in buffered (in the ARC) it will just be
copied from the ARC into the user buffer.

For both O_DIRECT writes and reads the O_DIRECT flag will be ignored in
the event that file contents are mmap'ed. In this case, all requests
that are at least PAGE_SIZE aligned will just fall back to the buffered
paths. If the request however is not PAGE_SIZE aligned, EINVAL will
be returned as always regardless if the file's contents are mmap'ed.

Since O_DIRECT writes go through the normal ZIO pipeline, the
following operations are supported just as with normal buffered writes:
Checksum
Compression
Encryption
Erasure Coding
There is one caveat for the data integrity of O_DIRECT writes that is
distinct for each of the OS's supported by ZFS.
FreeBSD - FreeBSD is able to place user pages under write protection so
          any data in the user buffers and written directly down to the
	  VDEV disks is guaranteed to not change. There is no concern
	  with data integrity and O_DIRECT writes.
Linux - Linux is not able to place anonymous user pages under write
        protection. Because of this, if the user decides to manipulate
	the page contents while the write operation is occurring, data
	integrity can not be guaranteed. However, there is a module
	parameter `zfs_vdev_direct_write_verify` that controls the
	if a O_DIRECT writes that can occur to a top-level VDEV before
	a checksum verify is run before the contents of the I/O buffer
        are committed to disk. In the event of a checksum verification
	failure the write will return EIO. The number of O_DIRECT write
	checksum verification errors can be observed by doing
	`zpool status -d`, which will list all verification errors that
	have occurred on a top-level VDEV. Along with `zpool status`, a
	ZED event will be issues as `dio_verify` when a checksum
	verification error occurs.

ZVOLs and dedup is not currently supported with Direct I/O.

A new dataset property `direct` has been added with the following 3
allowable values:
disabled - Accepts O_DIRECT flag, but silently ignores it and treats
	   the request as a buffered IO request.
standard - Follows the alignment restrictions  outlined above for
	   write/read IO requests when the O_DIRECT flag is used.
always   - Treats every write/read IO request as though it passed
           O_DIRECT and will do O_DIRECT if the alignment restrictions
	   are met otherwise will redirect through the ARC. This
	   property will not allow a request to fail.

There is also a module parameter zfs_dio_enabled that can be used to
force all reads and writes through the ARC. By setting this module
parameter to 0, it mimics as if the  direct dataset property is set to
disabled.

Reviewed-by: Brian Behlendorf <behlendorf@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Co-authored-by: Mark Maybee <mark.maybee@delphix.com>
Co-authored-by: Matt Macy <mmacy@FreeBSD.org>
Co-authored-by: Brian Behlendorf <behlendorf@llnl.gov>
Closes #10018
2024-09-14 13:47:59 -07:00
Coleman Kane
36261c8238
Linux 6.5 compat: replace generic_file_splice_read with filemap_splice_read
The generic_file_splice_read function was removed in Linux 6.5 in favor
of filemap_splice_read. Add an autoconf test for filemap_splice_read and
use it if it is found as the handler for .splice_read in the
file_operations struct. Additionally, ITER_PIPE was removed in 6.5. This
change removes the ITER_* macros that OpenZFS doesn't use from being
tested in config/kernel-vfs-iov_iter.m4. The removal of ITER_PIPE was
causing the test to fail, which also affected the code responsible for
setting the .splice_read handler, above. That behavior caused run-time
panics on Linux 6.5.

Reviewed-by: Brian Atkinson <batkinson@lanl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes #15155
2023-08-07 15:47:46 -07:00
Coleman Kane
325505e5c4 Linux 6.4 compat: iter_iov() function now used to get old iov member
The iov_iter->iov member is now iov_iter->__iov and must be accessed via
the accessor function iter_iov(). Create a wrapper that is conditionally
compiled to use the access method appropriate for the target kernel
version.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Brian Atkinson <batkinson@lanl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes #15100
2023-08-01 08:42:26 -07:00
Brian Behlendorf
5e4aedaca7 Linux 5.19 compat: bdev_max_discard_sectors()
Linux 5.19 commit torvalds/linux@70200574cc removed the
blk_queue_discard() helper function.  The preferred interface
is to now use the bdev_max_discard_sectors() function to check
for discard support.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #13515
2022-05-31 12:04:17 -07:00
Rich Ercolani
299fbf75ec Linux 5.16 compat: Added mapping for iov_iter_fault_in_readable
Linux decided to rename this for some reason. At some point, we
should probably invert this mapping, but for now...

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Coleman Kane <ckane@colemankane.org>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes #12975
2022-01-24 12:59:09 -08:00
Coleman Kane
f6e22561d2 Linux 5.16: type member of iov_iter renamed iter_type
The iov_iter->type member was renamed iov_iter->iter_type. However,
while looking into this, realized that in 2018 a iov_iter_type(*iov)
accessor function was introduced. So if that is present, use it,
otherwise fall back to trying the existing behavior of directly
accessing type from iov_iter.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes #12819
2021-12-07 12:27:49 -08:00
Brian Behlendorf
96a6629872
Remove unused iov_iter_init_compat() wrapper
This compatibility code is no longer needed.  For it a while
iov_iter_init_compat() was used by zfs_uio_prefaultpages() but
this code should have been dropped as part of commit 83b91ae1.
Take care of that oversight and remove it.

Reviewed-by: Brian Atkinson <batkinson@lanl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #11543
2021-01-30 10:06:14 -08:00
Brian Behlendorf
1c2358c12a
Linux 5.10 compat: use iov_iter in uio structure
As of the 5.10 kernel the generic splice compatibility code has been
removed.  All filesystems are now responsible for registering a
->splice_read and ->splice_write callback to support this operation.

The good news is the VFS provided generic_file_splice_read() and
iter_file_splice_write() callbacks can be used provided the ->iter_read
and ->iter_write callback support pipes.  However, this is currently
not the case and only iovecs and bvecs (not pipes) are ever attached
to the uio structure.

This commit changes that by allowing full iov_iter structures to be
attached to uios.  Ever since the 4.9 kernel the iov_iter structure
has supported iovecs, kvecs, bvevs, and pipes so it's desirable to
pass the entire thing when possible.  In conjunction with this the
uio helper functions (i.e uiomove(), uiocopy(), etc) have been
updated to understand the new UIO_ITER type.

Note that using the kernel provided uio_iter interfaces allowed the
existing Linux specific uio handling code to be simplified.  When
there's no longer a need to support kernel's older than 4.9, then
it will be possible to remove the iovec and bvec members from the
uio structure and always use a uio_iter.  Until then we need to
maintain all of the existing types for older kernels.

Some additional refactoring and cleanup was included in this change:

- Added checks to configure to detect available iov_iter interfaces.
  Some are available all the way back to the 3.10 kernel and are used
  when available.  In particular, uio_prefaultpages() now always uses
  iov_iter_fault_in_readable() which is available for all supported
  kernels.

- The unused UIO_USERISPACE type has been removed.  It is no longer
  needed now that the uio_seg enum is platform specific.

- Moved zfs_uio.c from the zcommon.ko module to the Linux specific
  platform code for the zfs.ko module.  This gets it out of libzfs
  where it was never needed and keeps this Linux specific code out
  of the common sources.

- Removed unnecessary O_APPEND handling from zfs_iter_write(), this
  is redundant and O_APPEND is already handled in zfs_write();

Reviewed-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #11351
2020-12-18 08:48:26 -08:00