Related to commit 4859fe796, when directly using the kernel's
refcount functions in kernel compatibility code do not map
refcount_t to zfs_refcount_t. This leads to a type mismatch.
Longer term we should consider renaming refcount_t to
zfs_refcount_t in the zfs code base.
Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Chunwei Chen <david.chen@nutanix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#7148
A new interface was added to manipulate the version field of an
inode. Add a inode_set_iversion() wrapper for older kernels and
use the new interface when available.
The i_version field was dropped from the trace point due to the
switch to an atomic64_t i_version type.
Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Chunwei Chen <david.chen@nutanix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#7148
generic_start_io_acct/generic_end_io_acct in the master
branch of the linux kernel requires that the request_queue
be provided.
Move the logic from freemem in the spl to arc_free_memory
in arc.c. Do this so we can take advantage of global_page_state
interface checks in zfs.
Upstream kernel replaced struct block_device with
struct gendisk in struct bio. Determine if the
function bio_set_dev exists during configure
and have zfs use that if it exists.
bio_set_dev https://github.com/torvalds/linux/commit/74d4699
global_node_page_state https://github.com/torvalds/linux/commit/75ef718
io acct https://github.com/torvalds/linux/commit/d62e26b
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Closes#6635
Commit torvalds/linux@4e4cbee9. The bio->bi_error field was
replaced with bio->bi_status which is an enum that describes
all possible error types.
Reviewed-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#6351
Provide a format parameter to super_setup_bdi_name() so we don't
create duplicate names in '/devices/virtual/bdi' sysfs namespace which
would prevent us from mounting more than one ZFS filesystem at a time.
Reviewed-by: Chunwei Chen <david.chen@osnexus.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes#6147
Linux 4.9 added current_time() as the preferred interface to get
the filesystem time. CURRENT_TIME was retired in Linux 4.12.
Reviewed-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#6114
Linux has read-ahead logic designed to accelerate sequential workloads.
ZFS has its own read-ahead logic called zprefetch that operates on both
ZVOLs and datasets. Having two prefetchers active at the same time can
cause overprefetching, which unnecessarily reduces IOPS performance on
CoW filesystems like ZFS.
Testing shows that entirely disabling the Linux prefetch results in
a significant performance penalty for reads while commensurate benefits
are seen in random writes. It appears that read-ahead benefits are
inversely proportional to random write benefits, and so a single page
of Linux-layer read-ahead appears to offer the middle ground for both
workloads.
Reviewed-by: Chunwei Chen <david.chen@osnexus.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Issue #5902
All filesystems were converted to dynamically allocated BDIs. The
destruction of backing_dev_info structures is handled as part of
super block destruction. Refactor the code to abstract away the
details of creating and destroying a BDI.
Reviewed-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#6089
Commit 37f9dac removed the zvol_taskq for processing zvol requests.
This was removed as part of switching to make_request_fn and was
motivated by a concern at the time over dispatch latency.
However, this also made all bio request synchronous, and caused
serious performance issues as the bio submitter would wait for
every bio it submitted, effectively making the IO depth 1.
This patch reinstate zvol_taskq, and to make sure overlapped I/Os
are ordered properly, we take range lock in zvol_request, and pass
it along with bio to the I/O functions zvol_{write,discard,read}.
In order to facilitate benchmarks a zvol_request_sync module
option was added to switch between sync and async request handling.
For the moment, the default behavior is synchronous but this is
likely to change pending additional testing.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#5824
In torvalds/linux@a528d35, there are changes to the getattr family of functions,
struct kstat, and the interface of inode_operations .getattr.
The inode_operations .getattr and simple_getattr() interface changed to:
int (*getattr) (const struct path *, struct dentry *, struct kstat *,
u32 request_mask, unsigned int query_flags)
The request_mask argument indicates which field(s) the caller intends to use.
Fields the caller has not specified via request_mask may be set in the returned
struct anyway, but their values may be approximate.
The query_flags argument indicates whether the filesystem must update
the attributes from the backing store.
Currently both fields are ignored. It is possible that getattr-related
functions within zfs could be optimized based on the request_mask.
struct kstat includes new fields:
u32 result_mask; /* What fields the user got */
u64 attributes; /* See STATX_ATTR_* flags */
struct timespec btime; /* File creation time */
Fields attribute and btime are cleared; the result_mask reflects this. These
appear to be optional based on simple_getattr() and vfs_getattr() within the
kernel, which take the same approach.
Reviewed-by: Chunwei Chen <david.chen@osnexus.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Closes#5875
A one time warning after module load that "BARRIER is deprecated" was seen
on the heavily patched 2.6.32-642.13.1.el6.x86_64 Centos 6.8 kernel. It seems
that kernel had both the old BARRIER and the newer FLUSH/FUA interfaces
defined. This fixes the warning by prefering the newer FLUSH/FUA interface
if it's available.
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes#5739Closes#5828
Fix multi-line error messages in blkdev_compat.h by changing
error-generating multi-line error messages to single line errors.
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: bunder2015 <omfgbunder@gmail.com>
Closes#5860
[bio] The req_op enum was changed to req_opf. Update the "Linux 4.8 API"
autotools checks to use an int to determine whether the various REQ_OP
values are defined. This should work properly on kernels >= 4.8.
[bio] bio_set_op_attrs() is now an inline function and can't be detected
with #ifdef. Add a configure check to determine whether bio_set_op_attrs()
is defined. Move the local definition of it from vdev_disk.c to
blkdev_compat.h for consistency with other related compability shims.
[bio] The read/write flags and their modifiers, including WRITE_FLUSH,
WRITE_FUA and WRITE_FLUSH_FUA have been removed from fs.h. Add the new
bio_set_flush() compatibility wrapper to replace VDEV_WRITE_FLUSH_FUA
and set the flags appropriately for each supported kernel version.
[vfs] The generic_readlink() function has been made static. If .readlink
in inode_operations is NULL, generic_readlink() is used.
[zol typo] Completely unrelated to 4.10 compat, fix a typo in the check
for REQ_OP_SECURE_ERASE so that the proper macro is defined:
s/HAVE_REQ_OP_SECURE_DISCARD/HAVE_REQ_OP_SECURE_ERASE/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes#5499
Enable picky cstyle checks and resolve the new warnings. The vast
majority of the changes needed were to handle minor issues with
whitespace formatting. This patch contains no functional changes.
Non-whitespace changes are as follows:
* 8 times ; to { } in for/while loop
* fix missing ; in cmd/zed/agents/zfs_diagnosis.c
* comment (confim -> confirm)
* change endline , to ; in cmd/zpool/zpool_main.c
* a number of /* BEGIN CSTYLED */ /* END CSTYLED */ blocks
* /* CSTYLED */ markers
* change == 0 to !
* ulong to unsigned long in module/zfs/dsl_scan.c
* rearrangement of module_param lines in module/zfs/metaslab.c
* add { } block around statement after for_each_online_node
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Håkan Johansson <f96hajo@chalmers.se>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#5465
Originally, these two function are inline, so their usability is tied to
posix_acl_release. However, since Linux 3.14, they became EXPORT_SYMBOL, so we
can always use them. In this patch, we create an independent test for these
two functions so we can use them when possible.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Currently every calls to zpl_posix_acl_release will schedule a delayed task,
and each delayed task will add a timer. This used to be fine except for
possibly bad performance impact.
However, in Linux 4.8, a new timer wheel implementation[1] is introduced. In
this new implementation, the larger the delay, the less accuracy the timer is.
So when we have a flood of timer from zpl_posix_acl_release, they will expire
at the same time. Couple with the fact that task_expire will do linear search
with lock held. This causes an extreme amount of contention inside interrupt
and would actually lockup the system.
We fix this by doing batch free to prevent a flood of delayed task. Every call
to zpl_posix_acl_release will put the posix_acl to be freed on a lockless
list. Every batch window, 1 sec, the zpl_posix_acl_free will fire up and free
every posix_acl that passed the grace period on the list. This way, we only
have one delayed task every second.
[1] https://lwn.net/Articles/646950/
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Ubuntu added support for checking inode permissions to lookup_bdev() in kernel
commit 193fb6a2c94fab8eb8ce70a5da4d21c7d4023bee (merged in 4.4.0-6.21).
Upstream bug: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1636517
This patch adds a test for Ubuntu's variant of lookup_bdev() to configure and
calls the function in the correct way.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Hajo Möller <dasjoe@gmail.com>
Closes#5336
In torvalds/linux@31051c8 the inode_change_ok() function was
renamed setattr_prepare() and updated to take a dentry ratheri
than an inode. Update the code to call the setattr_prepare()
and add a wrapper function which call inode_change_ok() for
older kernels.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Requires-spl: refs/pull/581/head
This re-use the framework established for SSE2, SSSE3 and
AVX2. However, GCC is using FP registers on Aarch64, so
unlike SSE/AVX2 we can't rely on the registers being left alone
between ASM statements. So instead, the NEON code uses
C variables and GCC extended ASM syntax. Note that since
the kernel explicitly disable vector registers, they
have to be locally re-enabled explicitly.
As we use the variable's number to define the symbolic
name, and GCC won't allow duplicate symbolic names,
numbers have to be unique. Even when the code is not
going to be used (e.g. the case for 4 registers when
using the macro with only 2). Only the actually used
variables should be declared, otherwise the build
will fails in debug mode.
This requires the replacement of the XOR(X,X) syntax
by a new ZERO(X) macro, which does the same thing but
without repeating the argument. And perhaps someday
there will be a machine where there is a more efficient
way to zero a register than XOR with itself. This affects
scalar, SSE2, SSSE3 and AVX2 as they need the new macro.
It's possible to write faster implementations (different
scheduling, different unrolling, interleaving NEON and
scalar, ...) for various cores, but this one has the
advantage of fitting in the current state of the code,
and thus is likely easier to review/check/merge.
The only difference between aarch64-neon and aarch64-neonx2
is that aarch64-neonx2 unroll some functions some more.
Reviewed-by: Gvozden Neskovic <neskovic@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Romain Dolbeau <romain.dolbeau@atos.net>
Closes#4801
API Change: Module parameter set/get methods take const parameter in
Grsecurity kernel v4.7.1
Signed-off-by: Gvozden Neskovic <neskovic@gmail.com>
Signed-off-by: Jason Zaman <jason@perfinion.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#4997Closes#5001
This patch adds compiler and runtime tests (user and kernel) for following
instruction sets: avx512f, avx512cd, avx512er, avx512pf, avx512bw, avx512dq,
avx512vl, avx512ifma, avx512vbmi.
note: Linux support for AVX-512F (Foundation) instruction set started with
linux v3.15
Signed-off-by: Gvozden Neskovic <neskovic@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4952
The HAVE_BIO_RW_* #ifdef's must appear before REQ_* #ifdef's
in the bio_is_flush() and bio_is_discard() macros. Linux 2.6.32
era kernels defined both of values and the HAVE_BIO_RW_* must be
used in this case. This resulted in a panic in zconfig test 5.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#4951Closes#4959
Fix bugs due to kernel change in torvalds/linux@4bacc9c923 ("overlayfs:
Make f_path always point to the overlay and f_inode to the underlay").
This problem crashes system when use zfs as a layer of overlayfs.
Signed-off-by: Chen Haiquan <oc@yunify.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#4914Closes#4935
All users of bio->bi_rw have been replaced with compatibility wrappers.
This allows the kernel specific logic to be abstracted away, and for
each of the supported cases to be documented with the wrapper. The
updated interfaces are as follows:
* void blk_queue_set_write_cache(struct request_queue *, bool, bool)
* boolean_t bio_is_flush(struct bio *)
* boolean_t bio_is_fua(struct bio *)
* boolean_t bio_is_discard(struct bio *)
* boolean_t bio_is_secure_erase(struct bio *)
* VDEV_WRITE_FLUSH_FUA
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#4951
The posix_acl_valid() function has been updated to require a
user namespace. Filesystem callers should normally provide the
user_ns from the super block associcated with the ACL; the
zpl_posix_acl_valid() wrapper has been added for this purpose.
See https://github.com/torvalds/linux/commit/0d4d717f for
complete details.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Nikolay Borisov <n.borisov.lkml@gmail.com>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#4922
Remove ZFS_AC_KERNEL_CURRENT_UMASK and ZFS_AC_KERNEL_POSIX_ACL_CACHING
configure checks, all supported kernel provide this functionality.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Nikolay Borisov <n.borisov.lkml@gmail.com>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#4922
Kernel 4.8 paved the way to enabling mounting a file system inside a
non-init user namespace. To facilitate this a s_user_ns member was
added holding the userns in which the filesystem's instance was
mounted. This enables doing the uid/gid translation relative to
this particular username space and not the default init_user_ns.
Signed-off-by: Nikolay Borisov <n.borisov.lkml@gmail.com>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#4928
New REQ_OP_* definitions have been introduced to separate the
WRITE, READ, and DISCARD operations from the flags. This included
changing the encoding of bi_rw. It places REQ_OP_* in high order
bits and other stuff in low order bits. This encoding is done
through the new helper function bio_set_op_attrs. For complete
details refer to:
https://github.com/torvalds/linux/commit/f215082https://github.com/torvalds/linux/commit/4e1b2d5
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#4892Closes#4899
The REQ_FLUSH flag was renamed REQ_PREFLUSH to avoid confusion with
REQ_OP_FLUSH. See https://github.com/torvalds/linux/commit/28a8f0d3
for complete details.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4892
Issue #4899
Since the concept of a kuid and the need to translate from it to
ordinary integer type was added in kernel version 3.5 implement necessary
plumbing to be able to detect this condition during compile time. If
the kernel doesn't support the kuid then just fall back to directly
accessing the respective struct inode's members
Signed-off-by: Nikolay Borisov <n.borisov.lkml@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4685
Issue #227
Counterpart to fd4c7b7, the same approach was taken to resolve
the compatibility issue.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes#4717
Issue #4665
As described in torvalds/linux@5f3a4a2 the &init_user_ns, and
not the current user_ns, should be passed to posix_acl_from_xattr()
and posix_acl_to_xattr(). Conveniently the init_user_ns is
available through the init credential (kcred).
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Massimo Maggi <me@massimo-maggi.eu>
Closes#4177
This is initial support for x86 vectorized implementations of ZFS parity
and checksum algorithms.
For the compilation phase, configure step checks if toolchain supports relevant
instruction sets. Each implementation must ensure that the code is not passed
to compiler if relevant instruction set is not supported. For this purpose,
following new defines are provided if instruction set is supported:
- HAVE_SSE,
- HAVE_SSE2,
- HAVE_SSE3,
- HAVE_SSSE3,
- HAVE_SSE4_1,
- HAVE_SSE4_2,
- HAVE_AVX,
- HAVE_AVX2.
For detecting if an instruction set can be used in runtime, following functions
are provided in (include/linux/simd_x86.h):
- zfs_sse_available()
- zfs_sse2_available()
- zfs_sse3_available()
- zfs_ssse3_available()
- zfs_sse4_1_available()
- zfs_sse4_2_available()
- zfs_avx_available()
- zfs_avx2_available()
- zfs_bmi1_available()
- zfs_bmi2_available()
These function should be called once, on module load, or initialization.
They are safe to use from user and kernel space.
If an implementation is using more than single instruction set, both compiler
and runtime support for all relevant instruction sets should be checked.
Kernel fpu methods:
- kfpu_begin()
- kfpu_end()
Use __get_cpuid_max and __cpuid_count from <cpuid.h>
Both gcc and clang have support for these. They also handle ebx register
in case it is used for PIC code.
Signed-off-by: Gvozden Neskovic <neskovic@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Closes#4381
The registered xattr .list handler was simplified in the 4.5 kernel
to only perform a permission check. Given a dentry for the file it
must return a boolean indicating if the name is visible. This
differs slightly from the previous APIs which also required the
function to copy the name in to the provided list and return its
size. That is now all the responsibility of the caller.
This should be straight forward change to make to ZoL since we've
always required the caller to make the copy. However, this was
slightly complicated by the need to support 3 older APIs. Yes,
between 2.6.32 and 4.5 there are 4 versions of this interface!
Therefore, while the functional change in this patch is small it
includes significant cleanup to make the code understandable and
maintainable. These changes include:
- Improved configure checks for .list, .get, and .set interfaces.
- Interfaces checked from newest to oldest.
- Strict checking for each possible known interface.
- Configure fails when no known interface is available.
- HAVE_*_XATTR_LIST renamed HAVE_XATTR_LIST_* for consistency
with similar iops and fops configure checks.
- POSIX_ACL_XATTR_{DEFAULT|ACCESS} were removed forcing callers to
move to their replacements, XATTR_NAME_POSIX_ACL_{DEFAULT|ACCESS}.
Compatibility wrapper were added for old kernels.
- ZPL_XATTR_LIST_WRAPPER added which behaves the same as the existing
ZPL_XATTR_{GET|SET} WRAPPERs. Only the inode is guaranteed to be
a valid pointer, passing NULL for the 'list' and 'name' variables
is allowed and must be checked for. All .list functions were
updated to use the wrapper to aid readability.
- zpl_xattr_filldir() updated to use the .list function for its
permission check which is consistent with the updated Linux 4.5
interface. If a .list function is registered it should return 0
to indicate a name should be skipped, if there is no registered
function the name will be added.
- Additional documentation from xattr(7) describing the correct
behavior for each namespace was added before the relevant handlers.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Issue #4228
Since uio now supports bvec, we can convert bio into uio and reuse
dmu_{read,write}_uio. This way, we can remove some duplicate code.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#4078
The xattr_hander->{list,get,set} were changed to take a xattr_handler,
and handler_flags argument was removed and should be accessed by
handler->flags.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4021
Commit torvalds/linux@4246a0b63b
("block: add a bi_error field to struct bio") dropped the error
argument from bio_endio in favor of newly introduced bio->bi_error.
This also replaces bio->bi_flags value BIO_UPTODATE.
bio_endio was a 3 argument function until Linux 2.6.24, which made it
a 2 argument function, and now the prototype has changed yet again to
a 1 argument function. Support for pre 2.6.24 kernels was already
dropped with 37f9dac592 ("zvol processing should use struct bio")
which assumed the 2 argument version in zvol_request(). Remaining code
to support the 3 argument version is hereby removed.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Issue #3799
zfsonlinux/zfs@e20cd6f7a8 caused us to
lose IO accounting on zvols. When I originally wrote that last year, the
symbols we needed to maintain IO accounting were GPL exported, but
torvalds/linux@394ffa503b provided
suitable symbols for restoring this functionality 4 months later. We
can call them to restore the IO accounting on Linux 3.19 and later as
well as any older kernels where that patch is backported.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3741
Internally, zvols are files exposed through the block device API. This
is intended to reduce overhead when things require block devices.
However, the ZoL zvol code emulates a traditional block device in that
it has a top half and a bottom half. This is an unnecessary source of
overhead that does not exist on any other OpenZFS platform does this.
This patch removes it. Early users of this patch reported double digit
performance gains in IOPS on zvols in the range of 50% to 80%.
Comments in the code suggest that the current implementation was done to
obtain IO merging from Linux's IO elevator. However, the DMU already
does write merging while arc_read() should implicitly merge read IOs
because only 1 thread is permitted to fetch the buffer into ARC. In
addition, commercial ZFSOnLinux distributions report that regular files
are more performant than zvols under the current implementation, and the
main consumers of zvols are VMs and iSCSI targets, which have their own
elevators to merge IOs.
Some minor refactoring allows us to register zfs_request() as our
->make_request() handler in place of the generic_make_request()
function. This eliminates the layer of code that broke IO requests on
zvols into a top half and a bottom half. This has several benefits:
1. No per zvol spinlocks.
2. No redundant IO elevator processing.
3. Interrupts are disabled only when actually necessary.
4. No redispatching of IOs when all taskq threads are busy.
5. Linux's page out routines will properly block.
6. Many autotools checks become obsolete.
An unfortunate consequence of eliminating the layer that
generic_make_request() is that we no longer calls the instrumentation
hooks for block IO accounting. Those hooks are GPL-exported, so we
cannot call them ourselves and consequently, we lose the ability to do
IO monitoring via iostat. Since zvols are internally files mapped as
block devices, this should be okay. Anyone who is willing to accept the
performance penalty for the block IO layer's accounting could use the
loop device in between the zvol and its consumer. Alternatively, perf
and ftrace likely could be used. Also, tools like latencytop will still
work. Tools such as latencytop sometimes provide a better view of
performance bottlenecks than the traditional block IO accounting tools
do.
Lastly, if direct reclaim occurs during spacemap loading and swap is on
a zvol, this code will deadlock. That deadlock could already occur with
sync=always on zvols. Given that swap on zvols is not yet production
ready, this is not a blocker.
Signed-off-by: Richard Yao <ryao@gentoo.org>
Pre-2.6.37 kernels support REQ_FUA in request flags, but not in BIO
flags. zvols are the only consumer of VDEV_REQ_FUA and since they are
passed requests, they should be obey the REQ_FUA flag like later
kernels. This optimization will only matter on 2.6.36 and 2.6.37 because
the zvol rework changes things to use bio, where we no longer are able
to distinguish on earlier kernels
Signed-off-by: Richard Yao <ryao@gentoo.org>
