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freebsd-dev/module/zfs/dmu.c
Matthew Ahrens e8b96c6007 Illumos #4045 write throttle & i/o scheduler performance work 
4045 zfs write throttle & i/o scheduler performance work

1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync
read, sync write, async read, async write, and scrub/resilver.  The scheduler
issues a number of concurrent i/os from each class to the device.  Once a class
has been selected, an i/o is selected from this class using either an elevator
algorithem (async, scrub classes) or FIFO (sync classes).  The number of
concurrent async write i/os is tuned dynamically based on i/o load, to achieve
good sync i/o latency when there is not a high load of writes, and good write
throughput when there is.  See the block comment in vdev_queue.c (reproduced
below) for more details.

2. The write throttle (dsl_pool_tempreserve_space() and
txg_constrain_throughput()) is rewritten to produce much more consistent delays
when under constant load.  The new write throttle is based on the amount of
dirty data, rather than guesses about future performance of the system.  When
there is a lot of dirty data, each transaction (e.g. write() syscall) will be
delayed by the same small amount.  This eliminates the "brick wall of wait"
that the old write throttle could hit, causing all transactions to wait several
seconds until the next txg opens.  One of the keys to the new write throttle is
decrementing the amount of dirty data as i/o completes, rather than at the end
of spa_sync().  Note that the write throttle is only applied once the i/o
scheduler is issuing the maximum number of outstanding async writes.  See the
block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for
more details.

This diff has several other effects, including:

 * the commonly-tuned global variable zfs_vdev_max_pending has been removed;
use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead.

 * the size of each txg (meaning the amount of dirty data written, and thus the
time it takes to write out) is now controlled differently.  There is no longer
an explicit time goal; the primary determinant is amount of dirty data.
Systems that are under light or medium load will now often see that a txg is
always syncing, but the impact to performance (e.g. read latency) is minimal.
Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this.

 * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression,
checksum, etc.  This improves latency by not allowing these CPU-intensive tasks
to consume all CPU (on machines with at least 4 CPU's; the percentage is
rounded up).

--matt

APPENDIX: problems with the current i/o scheduler

The current ZFS i/o scheduler (vdev_queue.c) is deadline based.  The problem
with this is that if there are always i/os pending, then certain classes of
i/os can see very long delays.

For example, if there are always synchronous reads outstanding, then no async
writes will be serviced until they become "past due".  One symptom of this
situation is that each pass of the txg sync takes at least several seconds
(typically 3 seconds).

If many i/os become "past due" (their deadline is in the past), then we must
service all of these overdue i/os before any new i/os.  This happens when we
enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in
the future.  If we can't complete all the i/os in 2.5 seconds (e.g. because
there were always reads pending), then these i/os will become past due.  Now we
must service all the "async" writes (which could be hundreds of megabytes)
before we service any reads, introducing considerable latency to synchronous
i/os (reads or ZIL writes).

Notes on porting to ZFS on Linux:

- zio_t gained new members io_physdone and io_phys_children.  Because
  object caches in the Linux port call the constructor only once at
  allocation time, objects may contain residual data when retrieved
  from the cache. Therefore zio_create() was updated to zero out the two
  new fields.

- vdev_mirror_pending() relied on the depth of the per-vdev pending queue
  (vq->vq_pending_tree) to select the least-busy leaf vdev to read from.
  This tree has been replaced by vq->vq_active_tree which is now used
  for the same purpose.

- vdev_queue_init() used the value of zfs_vdev_max_pending to determine
  the number of vdev I/O buffers to pre-allocate.  That global no longer
  exists, so we instead use the sum of the *_max_active values for each of
  the five I/O classes described above.

- The Illumos implementation of dmu_tx_delay() delays a transaction by
  sleeping in condition variable embedded in the thread
  (curthread->t_delay_cv).  We do not have an equivalent CV to use in
  Linux, so this change replaced the delay logic with a wrapper called
  zfs_sleep_until(). This wrapper could be adopted upstream and in other
  downstream ports to abstract away operating system-specific delay logic.

- These tunables are added as module parameters, and descriptions added
  to the zfs-module-parameters.5 man page.

  spa_asize_inflation
  zfs_deadman_synctime_ms
  zfs_vdev_max_active
  zfs_vdev_async_write_active_min_dirty_percent
  zfs_vdev_async_write_active_max_dirty_percent
  zfs_vdev_async_read_max_active
  zfs_vdev_async_read_min_active
  zfs_vdev_async_write_max_active
  zfs_vdev_async_write_min_active
  zfs_vdev_scrub_max_active
  zfs_vdev_scrub_min_active
  zfs_vdev_sync_read_max_active
  zfs_vdev_sync_read_min_active
  zfs_vdev_sync_write_max_active
  zfs_vdev_sync_write_min_active
  zfs_dirty_data_max_percent
  zfs_delay_min_dirty_percent
  zfs_dirty_data_max_max_percent
  zfs_dirty_data_max
  zfs_dirty_data_max_max
  zfs_dirty_data_sync
  zfs_delay_scale

  The latter four have type unsigned long, whereas they are uint64_t in
  Illumos.  This accommodates Linux's module_param() supported types, but
  means they may overflow on 32-bit architectures.

  The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most
  likely to overflow on 32-bit systems, since they express physical RAM
  sizes in bytes.  In fact, Illumos initializes zfs_dirty_data_max_max to
  2^32 which does overflow. To resolve that, this port instead initializes
  it in arc_init() to 25% of physical RAM, and adds the tunable
  zfs_dirty_data_max_max_percent to override that percentage.  While this
  solution doesn't completely avoid the overflow issue, it should be a
  reasonable default for most systems, and the minority of affected
  systems can work around the issue by overriding the defaults.

- Fixed reversed logic in comment above zfs_delay_scale declaration.

- Clarified comments in vdev_queue.c regarding when per-queue minimums take
  effect.

- Replaced dmu_tx_write_limit in the dmu_tx kstat file
  with dmu_tx_dirty_delay and dmu_tx_dirty_over_max.  The first counts
  how many times a transaction has been delayed because the pool dirty
  data has exceeded zfs_delay_min_dirty_percent.  The latter counts how
  many times the pool dirty data has exceeded zfs_dirty_data_max (which
  we expect to never happen).

- The original patch would have regressed the bug fixed in
  zfsonlinux/zfs@c418410, which prevented users from setting the
  zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE.
  A similar fix is added to vdev_queue_aggregate().

- In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the
  heap instead of the stack.  In Linux we can't afford such large
  structures on the stack.

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Ned Bass <bass6@llnl.gov>
Reviewed by: Brendan Gregg <brendan.gregg@joyent.com>
Approved by: Robert Mustacchi <rm@joyent.com>

References:
  http://www.illumos.org/issues/4045
  illumos/illumos-gate@69962b5647

Ported-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1913
2013-12-06 09:32:43 -08:00

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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2013 by Delphix. All rights reserved.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
*/
#include <sys/dmu.h>
#include <sys/dmu_impl.h>
#include <sys/dmu_tx.h>
#include <sys/dbuf.h>
#include <sys/dnode.h>
#include <sys/zfs_context.h>
#include <sys/dmu_objset.h>
#include <sys/dmu_traverse.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_pool.h>
#include <sys/dsl_synctask.h>
#include <sys/dsl_prop.h>
#include <sys/dmu_zfetch.h>
#include <sys/zfs_ioctl.h>
#include <sys/zap.h>
#include <sys/zio_checksum.h>
#include <sys/zio_compress.h>
#include <sys/sa.h>
#ifdef _KERNEL
#include <sys/vmsystm.h>
#include <sys/zfs_znode.h>
#endif
/*
* Enable/disable nopwrite feature.
*/
int zfs_nopwrite_enabled = 1;
const dmu_object_type_info_t dmu_ot[DMU_OT_NUMTYPES] = {
{ DMU_BSWAP_UINT8, TRUE, "unallocated" },
{ DMU_BSWAP_ZAP, TRUE, "object directory" },
{ DMU_BSWAP_UINT64, TRUE, "object array" },
{ DMU_BSWAP_UINT8, TRUE, "packed nvlist" },
{ DMU_BSWAP_UINT64, TRUE, "packed nvlist size" },
{ DMU_BSWAP_UINT64, TRUE, "bpobj" },
{ DMU_BSWAP_UINT64, TRUE, "bpobj header" },
{ DMU_BSWAP_UINT64, TRUE, "SPA space map header" },
{ DMU_BSWAP_UINT64, TRUE, "SPA space map" },
{ DMU_BSWAP_UINT64, TRUE, "ZIL intent log" },
{ DMU_BSWAP_DNODE, TRUE, "DMU dnode" },
{ DMU_BSWAP_OBJSET, TRUE, "DMU objset" },
{ DMU_BSWAP_UINT64, TRUE, "DSL directory" },
{ DMU_BSWAP_ZAP, TRUE, "DSL directory child map"},
{ DMU_BSWAP_ZAP, TRUE, "DSL dataset snap map" },
{ DMU_BSWAP_ZAP, TRUE, "DSL props" },
{ DMU_BSWAP_UINT64, TRUE, "DSL dataset" },
{ DMU_BSWAP_ZNODE, TRUE, "ZFS znode" },
{ DMU_BSWAP_OLDACL, TRUE, "ZFS V0 ACL" },
{ DMU_BSWAP_UINT8, FALSE, "ZFS plain file" },
{ DMU_BSWAP_ZAP, TRUE, "ZFS directory" },
{ DMU_BSWAP_ZAP, TRUE, "ZFS master node" },
{ DMU_BSWAP_ZAP, TRUE, "ZFS delete queue" },
{ DMU_BSWAP_UINT8, FALSE, "zvol object" },
{ DMU_BSWAP_ZAP, TRUE, "zvol prop" },
{ DMU_BSWAP_UINT8, FALSE, "other uint8[]" },
{ DMU_BSWAP_UINT64, FALSE, "other uint64[]" },
{ DMU_BSWAP_ZAP, TRUE, "other ZAP" },
{ DMU_BSWAP_ZAP, TRUE, "persistent error log" },
{ DMU_BSWAP_UINT8, TRUE, "SPA history" },
{ DMU_BSWAP_UINT64, TRUE, "SPA history offsets" },
{ DMU_BSWAP_ZAP, TRUE, "Pool properties" },
{ DMU_BSWAP_ZAP, TRUE, "DSL permissions" },
{ DMU_BSWAP_ACL, TRUE, "ZFS ACL" },
{ DMU_BSWAP_UINT8, TRUE, "ZFS SYSACL" },
{ DMU_BSWAP_UINT8, TRUE, "FUID table" },
{ DMU_BSWAP_UINT64, TRUE, "FUID table size" },
{ DMU_BSWAP_ZAP, TRUE, "DSL dataset next clones"},
{ DMU_BSWAP_ZAP, TRUE, "scan work queue" },
{ DMU_BSWAP_ZAP, TRUE, "ZFS user/group used" },
{ DMU_BSWAP_ZAP, TRUE, "ZFS user/group quota" },
{ DMU_BSWAP_ZAP, TRUE, "snapshot refcount tags"},
{ DMU_BSWAP_ZAP, TRUE, "DDT ZAP algorithm" },
{ DMU_BSWAP_ZAP, TRUE, "DDT statistics" },
{ DMU_BSWAP_UINT8, TRUE, "System attributes" },
{ DMU_BSWAP_ZAP, TRUE, "SA master node" },
{ DMU_BSWAP_ZAP, TRUE, "SA attr registration" },
{ DMU_BSWAP_ZAP, TRUE, "SA attr layouts" },
{ DMU_BSWAP_ZAP, TRUE, "scan translations" },
{ DMU_BSWAP_UINT8, FALSE, "deduplicated block" },
{ DMU_BSWAP_ZAP, TRUE, "DSL deadlist map" },
{ DMU_BSWAP_UINT64, TRUE, "DSL deadlist map hdr" },
{ DMU_BSWAP_ZAP, TRUE, "DSL dir clones" },
{ DMU_BSWAP_UINT64, TRUE, "bpobj subobj" }
};
const dmu_object_byteswap_info_t dmu_ot_byteswap[DMU_BSWAP_NUMFUNCS] = {
{ byteswap_uint8_array, "uint8" },
{ byteswap_uint16_array, "uint16" },
{ byteswap_uint32_array, "uint32" },
{ byteswap_uint64_array, "uint64" },
{ zap_byteswap, "zap" },
{ dnode_buf_byteswap, "dnode" },
{ dmu_objset_byteswap, "objset" },
{ zfs_znode_byteswap, "znode" },
{ zfs_oldacl_byteswap, "oldacl" },
{ zfs_acl_byteswap, "acl" }
};
int
dmu_buf_hold(objset_t *os, uint64_t object, uint64_t offset,
void *tag, dmu_buf_t **dbp, int flags)
{
dnode_t *dn;
uint64_t blkid;
dmu_buf_impl_t *db;
int err;
int db_flags = DB_RF_CANFAIL;
if (flags & DMU_READ_NO_PREFETCH)
db_flags |= DB_RF_NOPREFETCH;
err = dnode_hold(os, object, FTAG, &dn);
if (err)
return (err);
blkid = dbuf_whichblock(dn, offset);
rw_enter(&dn->dn_struct_rwlock, RW_READER);
db = dbuf_hold(dn, blkid, tag);
rw_exit(&dn->dn_struct_rwlock);
if (db == NULL) {
err = SET_ERROR(EIO);
} else {
err = dbuf_read(db, NULL, db_flags);
if (err) {
dbuf_rele(db, tag);
db = NULL;
}
}
dnode_rele(dn, FTAG);
*dbp = &db->db; /* NULL db plus first field offset is NULL */
return (err);
}
int
dmu_bonus_max(void)
{
return (DN_MAX_BONUSLEN);
}
int
dmu_set_bonus(dmu_buf_t *db_fake, int newsize, dmu_tx_t *tx)
{
dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
dnode_t *dn;
int error;
DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
if (dn->dn_bonus != db) {
error = SET_ERROR(EINVAL);
} else if (newsize < 0 || newsize > db_fake->db_size) {
error = SET_ERROR(EINVAL);
} else {
dnode_setbonuslen(dn, newsize, tx);
error = 0;
}
DB_DNODE_EXIT(db);
return (error);
}
int
dmu_set_bonustype(dmu_buf_t *db_fake, dmu_object_type_t type, dmu_tx_t *tx)
{
dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
dnode_t *dn;
int error;
DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
if (!DMU_OT_IS_VALID(type)) {
error = SET_ERROR(EINVAL);
} else if (dn->dn_bonus != db) {
error = SET_ERROR(EINVAL);
} else {
dnode_setbonus_type(dn, type, tx);
error = 0;
}
DB_DNODE_EXIT(db);
return (error);
}
dmu_object_type_t
dmu_get_bonustype(dmu_buf_t *db_fake)
{
dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
dnode_t *dn;
dmu_object_type_t type;
DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
type = dn->dn_bonustype;
DB_DNODE_EXIT(db);
return (type);
}
int
dmu_rm_spill(objset_t *os, uint64_t object, dmu_tx_t *tx)
{
dnode_t *dn;
int error;
error = dnode_hold(os, object, FTAG, &dn);
dbuf_rm_spill(dn, tx);
rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
dnode_rm_spill(dn, tx);
rw_exit(&dn->dn_struct_rwlock);
dnode_rele(dn, FTAG);
return (error);
}
/*
* returns ENOENT, EIO, or 0.
*/
int
dmu_bonus_hold(objset_t *os, uint64_t object, void *tag, dmu_buf_t **dbp)
{
dnode_t *dn;
dmu_buf_impl_t *db;
int error;
error = dnode_hold(os, object, FTAG, &dn);
if (error)
return (error);
rw_enter(&dn->dn_struct_rwlock, RW_READER);
if (dn->dn_bonus == NULL) {
rw_exit(&dn->dn_struct_rwlock);
rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
if (dn->dn_bonus == NULL)
dbuf_create_bonus(dn);
}
db = dn->dn_bonus;
/* as long as the bonus buf is held, the dnode will be held */
if (refcount_add(&db->db_holds, tag) == 1) {
VERIFY(dnode_add_ref(dn, db));
(void) atomic_inc_32_nv(&dn->dn_dbufs_count);
}
/*
* Wait to drop dn_struct_rwlock until after adding the bonus dbuf's
* hold and incrementing the dbuf count to ensure that dnode_move() sees
* a dnode hold for every dbuf.
*/
rw_exit(&dn->dn_struct_rwlock);
dnode_rele(dn, FTAG);
VERIFY(0 == dbuf_read(db, NULL, DB_RF_MUST_SUCCEED | DB_RF_NOPREFETCH));
*dbp = &db->db;
return (0);
}
/*
* returns ENOENT, EIO, or 0.
*
* This interface will allocate a blank spill dbuf when a spill blk
* doesn't already exist on the dnode.
*
* if you only want to find an already existing spill db, then
* dmu_spill_hold_existing() should be used.
*/
int
dmu_spill_hold_by_dnode(dnode_t *dn, uint32_t flags, void *tag, dmu_buf_t **dbp)
{
dmu_buf_impl_t *db = NULL;
int err;
if ((flags & DB_RF_HAVESTRUCT) == 0)
rw_enter(&dn->dn_struct_rwlock, RW_READER);
db = dbuf_hold(dn, DMU_SPILL_BLKID, tag);
if ((flags & DB_RF_HAVESTRUCT) == 0)
rw_exit(&dn->dn_struct_rwlock);
ASSERT(db != NULL);
err = dbuf_read(db, NULL, flags);
if (err == 0)
*dbp = &db->db;
else
dbuf_rele(db, tag);
return (err);
}
int
dmu_spill_hold_existing(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp)
{
dmu_buf_impl_t *db = (dmu_buf_impl_t *)bonus;
dnode_t *dn;
int err;
DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
if (spa_version(dn->dn_objset->os_spa) < SPA_VERSION_SA) {
err = SET_ERROR(EINVAL);
} else {
rw_enter(&dn->dn_struct_rwlock, RW_READER);
if (!dn->dn_have_spill) {
err = SET_ERROR(ENOENT);
} else {
err = dmu_spill_hold_by_dnode(dn,
DB_RF_HAVESTRUCT | DB_RF_CANFAIL, tag, dbp);
}
rw_exit(&dn->dn_struct_rwlock);
}
DB_DNODE_EXIT(db);
return (err);
}
int
dmu_spill_hold_by_bonus(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp)
{
dmu_buf_impl_t *db = (dmu_buf_impl_t *)bonus;
dnode_t *dn;
int err;
DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
err = dmu_spill_hold_by_dnode(dn, DB_RF_CANFAIL, tag, dbp);
DB_DNODE_EXIT(db);
return (err);
}
/*
* Note: longer-term, we should modify all of the dmu_buf_*() interfaces
* to take a held dnode rather than <os, object> -- the lookup is wasteful,
* and can induce severe lock contention when writing to several files
* whose dnodes are in the same block.
*/
static int
dmu_buf_hold_array_by_dnode(dnode_t *dn, uint64_t offset, uint64_t length,
int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp, uint32_t flags)
{
dmu_buf_t **dbp;
uint64_t blkid, nblks, i;
uint32_t dbuf_flags;
int err;
zio_t *zio;
ASSERT(length <= DMU_MAX_ACCESS);
dbuf_flags = DB_RF_CANFAIL | DB_RF_NEVERWAIT | DB_RF_HAVESTRUCT;
if (flags & DMU_READ_NO_PREFETCH || length > zfetch_array_rd_sz)
dbuf_flags |= DB_RF_NOPREFETCH;
rw_enter(&dn->dn_struct_rwlock, RW_READER);
if (dn->dn_datablkshift) {
int blkshift = dn->dn_datablkshift;
nblks = (P2ROUNDUP(offset+length, 1ULL<<blkshift) -
P2ALIGN(offset, 1ULL<<blkshift)) >> blkshift;
} else {
if (offset + length > dn->dn_datablksz) {
zfs_panic_recover("zfs: accessing past end of object "
"%llx/%llx (size=%u access=%llu+%llu)",
(longlong_t)dn->dn_objset->
os_dsl_dataset->ds_object,
(longlong_t)dn->dn_object, dn->dn_datablksz,
(longlong_t)offset, (longlong_t)length);
rw_exit(&dn->dn_struct_rwlock);
return (SET_ERROR(EIO));
}
nblks = 1;
}
dbp = kmem_zalloc(sizeof (dmu_buf_t *) * nblks, KM_PUSHPAGE | KM_NODEBUG);
zio = zio_root(dn->dn_objset->os_spa, NULL, NULL, ZIO_FLAG_CANFAIL);
blkid = dbuf_whichblock(dn, offset);
for (i = 0; i < nblks; i++) {
dmu_buf_impl_t *db = dbuf_hold(dn, blkid+i, tag);
if (db == NULL) {
rw_exit(&dn->dn_struct_rwlock);
dmu_buf_rele_array(dbp, nblks, tag);
zio_nowait(zio);
return (SET_ERROR(EIO));
}
/* initiate async i/o */
if (read) {
(void) dbuf_read(db, zio, dbuf_flags);
}
dbp[i] = &db->db;
}
rw_exit(&dn->dn_struct_rwlock);
/* wait for async i/o */
err = zio_wait(zio);
if (err) {
dmu_buf_rele_array(dbp, nblks, tag);
return (err);
}
/* wait for other io to complete */
if (read) {
for (i = 0; i < nblks; i++) {
dmu_buf_impl_t *db = (dmu_buf_impl_t *)dbp[i];
mutex_enter(&db->db_mtx);
while (db->db_state == DB_READ ||
db->db_state == DB_FILL)
cv_wait(&db->db_changed, &db->db_mtx);
if (db->db_state == DB_UNCACHED)
err = SET_ERROR(EIO);
mutex_exit(&db->db_mtx);
if (err) {
dmu_buf_rele_array(dbp, nblks, tag);
return (err);
}
}
}
*numbufsp = nblks;
*dbpp = dbp;
return (0);
}
static int
dmu_buf_hold_array(objset_t *os, uint64_t object, uint64_t offset,
uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
{
dnode_t *dn;
int err;
err = dnode_hold(os, object, FTAG, &dn);
if (err)
return (err);
err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
numbufsp, dbpp, DMU_READ_PREFETCH);
dnode_rele(dn, FTAG);
return (err);
}
int
dmu_buf_hold_array_by_bonus(dmu_buf_t *db_fake, uint64_t offset,
uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
{
dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
dnode_t *dn;
int err;
DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
numbufsp, dbpp, DMU_READ_PREFETCH);
DB_DNODE_EXIT(db);
return (err);
}
void
dmu_buf_rele_array(dmu_buf_t **dbp_fake, int numbufs, void *tag)
{
int i;
dmu_buf_impl_t **dbp = (dmu_buf_impl_t **)dbp_fake;
if (numbufs == 0)
return;
for (i = 0; i < numbufs; i++) {
if (dbp[i])
dbuf_rele(dbp[i], tag);
}
kmem_free(dbp, sizeof (dmu_buf_t *) * numbufs);
}
/*
* Issue prefetch i/os for the given blocks.
*
* Note: The assumption is that we *know* these blocks will be needed
* almost immediately. Therefore, the prefetch i/os will be issued at
* ZIO_PRIORITY_SYNC_READ
*
* Note: indirect blocks and other metadata will be read synchronously,
* causing this function to block if they are not already cached.
*/
void
dmu_prefetch(objset_t *os, uint64_t object, uint64_t offset, uint64_t len)
{
dnode_t *dn;
uint64_t blkid;
int nblks, err;
if (zfs_prefetch_disable)
return;
if (len == 0) { /* they're interested in the bonus buffer */
dn = DMU_META_DNODE(os);
if (object == 0 || object >= DN_MAX_OBJECT)
return;
rw_enter(&dn->dn_struct_rwlock, RW_READER);
blkid = dbuf_whichblock(dn, object * sizeof (dnode_phys_t));
dbuf_prefetch(dn, blkid, ZIO_PRIORITY_SYNC_READ);
rw_exit(&dn->dn_struct_rwlock);
return;
}
/*
* XXX - Note, if the dnode for the requested object is not
* already cached, we will do a *synchronous* read in the
* dnode_hold() call. The same is true for any indirects.
*/
err = dnode_hold(os, object, FTAG, &dn);
if (err != 0)
return;
rw_enter(&dn->dn_struct_rwlock, RW_READER);
if (dn->dn_datablkshift) {
int blkshift = dn->dn_datablkshift;
nblks = (P2ROUNDUP(offset + len, 1 << blkshift) -
P2ALIGN(offset, 1 << blkshift)) >> blkshift;
} else {
nblks = (offset < dn->dn_datablksz);
}
if (nblks != 0) {
int i;
blkid = dbuf_whichblock(dn, offset);
for (i = 0; i < nblks; i++)
dbuf_prefetch(dn, blkid + i, ZIO_PRIORITY_SYNC_READ);
}
rw_exit(&dn->dn_struct_rwlock);
dnode_rele(dn, FTAG);
}
/*
* Get the next "chunk" of file data to free. We traverse the file from
* the end so that the file gets shorter over time (if we crashes in the
* middle, this will leave us in a better state). We find allocated file
* data by simply searching the allocated level 1 indirects.
*
* On input, *start should be the first offset that does not need to be
* freed (e.g. "offset + length"). On return, *start will be the first
* offset that should be freed.
*/
static int
get_next_chunk(dnode_t *dn, uint64_t *start, uint64_t minimum)
{
uint64_t maxblks = DMU_MAX_ACCESS >> (dn->dn_indblkshift + 1);
/* bytes of data covered by a level-1 indirect block */
uint64_t iblkrange =
dn->dn_datablksz * EPB(dn->dn_indblkshift, SPA_BLKPTRSHIFT);
uint64_t blks;
ASSERT3U(minimum, <=, *start);
if (*start - minimum <= iblkrange * maxblks) {
*start = minimum;
return (0);
}
ASSERT(ISP2(iblkrange));
for (blks = 0; *start > minimum && blks < maxblks; blks++) {
int err;
/*
* dnode_next_offset(BACKWARDS) will find an allocated L1
* indirect block at or before the input offset. We must
* decrement *start so that it is at the end of the region
* to search.
*/
(*start)--;
err = dnode_next_offset(dn,
DNODE_FIND_BACKWARDS, start, 2, 1, 0);
/* if there are no indirect blocks before start, we are done */
if (err == ESRCH) {
*start = minimum;
break;
} else if (err != 0) {
return (err);
}
/* set start to the beginning of this L1 indirect */
*start = P2ALIGN(*start, iblkrange);
}
if (*start < minimum)
*start = minimum;
return (0);
}
static int
dmu_free_long_range_impl(objset_t *os, dnode_t *dn, uint64_t offset,
uint64_t length)
{
uint64_t object_size = (dn->dn_maxblkid + 1) * dn->dn_datablksz;
int err;
if (offset >= object_size)
return (0);
if (length == DMU_OBJECT_END || offset + length > object_size)
length = object_size - offset;
while (length != 0) {
uint64_t chunk_end, chunk_begin;
dmu_tx_t *tx;
chunk_end = chunk_begin = offset + length;
/* move chunk_begin backwards to the beginning of this chunk */
err = get_next_chunk(dn, &chunk_begin, offset);
if (err)
return (err);
ASSERT3U(chunk_begin, >=, offset);
ASSERT3U(chunk_begin, <=, chunk_end);
tx = dmu_tx_create(os);
dmu_tx_hold_free(tx, dn->dn_object,
chunk_begin, chunk_end - chunk_begin);
err = dmu_tx_assign(tx, TXG_WAIT);
if (err) {
dmu_tx_abort(tx);
return (err);
}
dnode_free_range(dn, chunk_begin, chunk_end - chunk_begin, tx);
dmu_tx_commit(tx);
length -= chunk_end - chunk_begin;
}
return (0);
}
int
dmu_free_long_range(objset_t *os, uint64_t object,
uint64_t offset, uint64_t length)
{
dnode_t *dn;
int err;
err = dnode_hold(os, object, FTAG, &dn);
if (err != 0)
return (err);
err = dmu_free_long_range_impl(os, dn, offset, length);
/*
* It is important to zero out the maxblkid when freeing the entire
* file, so that (a) subsequent calls to dmu_free_long_range_impl()
* will take the fast path, and (b) dnode_reallocate() can verify
* that the entire file has been freed.
*/
if (offset == 0 && length == DMU_OBJECT_END)
dn->dn_maxblkid = 0;
dnode_rele(dn, FTAG);
return (err);
}
int
dmu_free_long_object(objset_t *os, uint64_t object)
{
dmu_tx_t *tx;
int err;
err = dmu_free_long_range(os, object, 0, DMU_OBJECT_END);
if (err != 0)
return (err);
tx = dmu_tx_create(os);
dmu_tx_hold_bonus(tx, object);
dmu_tx_hold_free(tx, object, 0, DMU_OBJECT_END);
err = dmu_tx_assign(tx, TXG_WAIT);
if (err == 0) {
err = dmu_object_free(os, object, tx);
dmu_tx_commit(tx);
} else {
dmu_tx_abort(tx);
}
return (err);
}
int
dmu_free_range(objset_t *os, uint64_t object, uint64_t offset,
uint64_t size, dmu_tx_t *tx)
{
dnode_t *dn;
int err = dnode_hold(os, object, FTAG, &dn);
if (err)
return (err);
ASSERT(offset < UINT64_MAX);
ASSERT(size == -1ULL || size <= UINT64_MAX - offset);
dnode_free_range(dn, offset, size, tx);
dnode_rele(dn, FTAG);
return (0);
}
int
dmu_read(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
void *buf, uint32_t flags)
{
dnode_t *dn;
dmu_buf_t **dbp;
int numbufs, err;
err = dnode_hold(os, object, FTAG, &dn);
if (err)
return (err);
/*
* Deal with odd block sizes, where there can't be data past the first
* block. If we ever do the tail block optimization, we will need to
* handle that here as well.
*/
if (dn->dn_maxblkid == 0) {
int newsz = offset > dn->dn_datablksz ? 0 :
MIN(size, dn->dn_datablksz - offset);
bzero((char *)buf + newsz, size - newsz);
size = newsz;
}
while (size > 0) {
uint64_t mylen = MIN(size, DMU_MAX_ACCESS / 2);
int i;
/*
* NB: we could do this block-at-a-time, but it's nice
* to be reading in parallel.
*/
err = dmu_buf_hold_array_by_dnode(dn, offset, mylen,
TRUE, FTAG, &numbufs, &dbp, flags);
if (err)
break;
for (i = 0; i < numbufs; i++) {
int tocpy;
int bufoff;
dmu_buf_t *db = dbp[i];
ASSERT(size > 0);
bufoff = offset - db->db_offset;
tocpy = (int)MIN(db->db_size - bufoff, size);
bcopy((char *)db->db_data + bufoff, buf, tocpy);
offset += tocpy;
size -= tocpy;
buf = (char *)buf + tocpy;
}
dmu_buf_rele_array(dbp, numbufs, FTAG);
}
dnode_rele(dn, FTAG);
return (err);
}
void
dmu_write(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
const void *buf, dmu_tx_t *tx)
{
dmu_buf_t **dbp;
int numbufs, i;
if (size == 0)
return;
VERIFY(0 == dmu_buf_hold_array(os, object, offset, size,
FALSE, FTAG, &numbufs, &dbp));
for (i = 0; i < numbufs; i++) {
int tocpy;
int bufoff;
dmu_buf_t *db = dbp[i];
ASSERT(size > 0);
bufoff = offset - db->db_offset;
tocpy = (int)MIN(db->db_size - bufoff, size);
ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
if (tocpy == db->db_size)
dmu_buf_will_fill(db, tx);
else
dmu_buf_will_dirty(db, tx);
(void) memcpy((char *)db->db_data + bufoff, buf, tocpy);
if (tocpy == db->db_size)
dmu_buf_fill_done(db, tx);
offset += tocpy;
size -= tocpy;
buf = (char *)buf + tocpy;
}
dmu_buf_rele_array(dbp, numbufs, FTAG);
}
void
dmu_prealloc(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
dmu_tx_t *tx)
{
dmu_buf_t **dbp;
int numbufs, i;
if (size == 0)
return;
VERIFY(0 == dmu_buf_hold_array(os, object, offset, size,
FALSE, FTAG, &numbufs, &dbp));
for (i = 0; i < numbufs; i++) {
dmu_buf_t *db = dbp[i];
dmu_buf_will_not_fill(db, tx);
}
dmu_buf_rele_array(dbp, numbufs, FTAG);
}
/*
* DMU support for xuio
*/
kstat_t *xuio_ksp = NULL;
typedef struct xuio_stats {
/* loaned yet not returned arc_buf */
kstat_named_t xuiostat_onloan_rbuf;
kstat_named_t xuiostat_onloan_wbuf;
/* whether a copy is made when loaning out a read buffer */
kstat_named_t xuiostat_rbuf_copied;
kstat_named_t xuiostat_rbuf_nocopy;
/* whether a copy is made when assigning a write buffer */
kstat_named_t xuiostat_wbuf_copied;
kstat_named_t xuiostat_wbuf_nocopy;
} xuio_stats_t;
static xuio_stats_t xuio_stats = {
{ "onloan_read_buf", KSTAT_DATA_UINT64 },
{ "onloan_write_buf", KSTAT_DATA_UINT64 },
{ "read_buf_copied", KSTAT_DATA_UINT64 },
{ "read_buf_nocopy", KSTAT_DATA_UINT64 },
{ "write_buf_copied", KSTAT_DATA_UINT64 },
{ "write_buf_nocopy", KSTAT_DATA_UINT64 }
};
#define XUIOSTAT_INCR(stat, val) \
atomic_add_64(&xuio_stats.stat.value.ui64, (val))
#define XUIOSTAT_BUMP(stat) XUIOSTAT_INCR(stat, 1)
int
dmu_xuio_init(xuio_t *xuio, int nblk)
{
dmu_xuio_t *priv;
uio_t *uio = &xuio->xu_uio;
uio->uio_iovcnt = nblk;
uio->uio_iov = kmem_zalloc(nblk * sizeof (iovec_t), KM_PUSHPAGE);
priv = kmem_zalloc(sizeof (dmu_xuio_t), KM_PUSHPAGE);
priv->cnt = nblk;
priv->bufs = kmem_zalloc(nblk * sizeof (arc_buf_t *), KM_PUSHPAGE);
priv->iovp = uio->uio_iov;
XUIO_XUZC_PRIV(xuio) = priv;
if (XUIO_XUZC_RW(xuio) == UIO_READ)
XUIOSTAT_INCR(xuiostat_onloan_rbuf, nblk);
else
XUIOSTAT_INCR(xuiostat_onloan_wbuf, nblk);
return (0);
}
void
dmu_xuio_fini(xuio_t *xuio)
{
dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
int nblk = priv->cnt;
kmem_free(priv->iovp, nblk * sizeof (iovec_t));
kmem_free(priv->bufs, nblk * sizeof (arc_buf_t *));
kmem_free(priv, sizeof (dmu_xuio_t));
if (XUIO_XUZC_RW(xuio) == UIO_READ)
XUIOSTAT_INCR(xuiostat_onloan_rbuf, -nblk);
else
XUIOSTAT_INCR(xuiostat_onloan_wbuf, -nblk);
}
/*
* Initialize iov[priv->next] and priv->bufs[priv->next] with { off, n, abuf }
* and increase priv->next by 1.
*/
int
dmu_xuio_add(xuio_t *xuio, arc_buf_t *abuf, offset_t off, size_t n)
{
struct iovec *iov;
uio_t *uio = &xuio->xu_uio;
dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
int i = priv->next++;
ASSERT(i < priv->cnt);
ASSERT(off + n <= arc_buf_size(abuf));
iov = uio->uio_iov + i;
iov->iov_base = (char *)abuf->b_data + off;
iov->iov_len = n;
priv->bufs[i] = abuf;
return (0);
}
int
dmu_xuio_cnt(xuio_t *xuio)
{
dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
return (priv->cnt);
}
arc_buf_t *
dmu_xuio_arcbuf(xuio_t *xuio, int i)
{
dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
ASSERT(i < priv->cnt);
return (priv->bufs[i]);
}
void
dmu_xuio_clear(xuio_t *xuio, int i)
{
dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
ASSERT(i < priv->cnt);
priv->bufs[i] = NULL;
}
static void
xuio_stat_init(void)
{
xuio_ksp = kstat_create("zfs", 0, "xuio_stats", "misc",
KSTAT_TYPE_NAMED, sizeof (xuio_stats) / sizeof (kstat_named_t),
KSTAT_FLAG_VIRTUAL);
if (xuio_ksp != NULL) {
xuio_ksp->ks_data = &xuio_stats;
kstat_install(xuio_ksp);
}
}
static void
xuio_stat_fini(void)
{
if (xuio_ksp != NULL) {
kstat_delete(xuio_ksp);
xuio_ksp = NULL;
}
}
void
xuio_stat_wbuf_copied()
{
XUIOSTAT_BUMP(xuiostat_wbuf_copied);
}
void
xuio_stat_wbuf_nocopy()
{
XUIOSTAT_BUMP(xuiostat_wbuf_nocopy);
}
#ifdef _KERNEL
/*
* Copy up to size bytes between arg_buf and req based on the data direction
* described by the req. If an entire req's data cannot be transfered the
* req's is updated such that it's current index and bv offsets correctly
* reference any residual data which could not be copied. The return value
* is the number of bytes successfully copied to arg_buf.
*/
static int
dmu_req_copy(void *arg_buf, int size, int *offset, struct request *req)
{
struct bio_vec *bv;
struct req_iterator iter;
char *bv_buf;
int tocpy;
*offset = 0;
rq_for_each_segment(bv, req, iter) {
/* Fully consumed the passed arg_buf */
ASSERT3S(*offset, <=, size);
if (size == *offset)
break;
/* Skip fully consumed bv's */
if (bv->bv_len == 0)
continue;
tocpy = MIN(bv->bv_len, size - *offset);
ASSERT3S(tocpy, >=, 0);
bv_buf = page_address(bv->bv_page) + bv->bv_offset;
ASSERT3P(bv_buf, !=, NULL);
if (rq_data_dir(req) == WRITE)
memcpy(arg_buf + *offset, bv_buf, tocpy);
else
memcpy(bv_buf, arg_buf + *offset, tocpy);
*offset += tocpy;
bv->bv_offset += tocpy;
bv->bv_len -= tocpy;
}
return 0;
}
static void
dmu_bio_put(struct bio *bio)
{
struct bio *bio_next;
while (bio) {
bio_next = bio->bi_next;
bio_put(bio);
bio = bio_next;
}
}
static int
dmu_bio_clone(struct bio *bio, struct bio **bio_copy)
{
struct bio *bio_root = NULL;
struct bio *bio_last = NULL;
struct bio *bio_new;
if (bio == NULL)
return EINVAL;
while (bio) {
bio_new = bio_clone(bio, GFP_NOIO);
if (bio_new == NULL) {
dmu_bio_put(bio_root);
return ENOMEM;
}
if (bio_last) {
bio_last->bi_next = bio_new;
bio_last = bio_new;
} else {
bio_root = bio_new;
bio_last = bio_new;
}
bio = bio->bi_next;
}
*bio_copy = bio_root;
return 0;
}
int
dmu_read_req(objset_t *os, uint64_t object, struct request *req)
{
uint64_t size = blk_rq_bytes(req);
uint64_t offset = blk_rq_pos(req) << 9;
struct bio *bio_saved = req->bio;
dmu_buf_t **dbp;
int numbufs, i, err;
/*
* NB: we could do this block-at-a-time, but it's nice
* to be reading in parallel.
*/
err = dmu_buf_hold_array(os, object, offset, size, TRUE, FTAG,
&numbufs, &dbp);
if (err)
return (err);
/*
* Clone the bio list so the bv->bv_offset and bv->bv_len members
* can be safely modified. The original bio list is relinked in to
* the request when the function exits. This is required because
* some file systems blindly assume that these values will remain
* constant between bio_submit() and the IO completion callback.
*/
err = dmu_bio_clone(bio_saved, &req->bio);
if (err)
goto error;
for (i = 0; i < numbufs; i++) {
int tocpy, didcpy, bufoff;
dmu_buf_t *db = dbp[i];
bufoff = offset - db->db_offset;
ASSERT3S(bufoff, >=, 0);
tocpy = (int)MIN(db->db_size - bufoff, size);
if (tocpy == 0)
break;
err = dmu_req_copy(db->db_data + bufoff, tocpy, &didcpy, req);
if (didcpy < tocpy)
err = EIO;
if (err)
break;
size -= tocpy;
offset += didcpy;
err = 0;
}
dmu_bio_put(req->bio);
req->bio = bio_saved;
error:
dmu_buf_rele_array(dbp, numbufs, FTAG);
return (err);
}
int
dmu_write_req(objset_t *os, uint64_t object, struct request *req, dmu_tx_t *tx)
{
uint64_t size = blk_rq_bytes(req);
uint64_t offset = blk_rq_pos(req) << 9;
struct bio *bio_saved = req->bio;
dmu_buf_t **dbp;
int numbufs;
int err = 0;
int i;
if (size == 0)
return (0);
err = dmu_buf_hold_array(os, object, offset, size, FALSE, FTAG,
&numbufs, &dbp);
if (err)
return (err);
/*
* Clone the bio list so the bv->bv_offset and bv->bv_len members
* can be safely modified. The original bio list is relinked in to
* the request when the function exits. This is required because
* some file systems blindly assume that these values will remain
* constant between bio_submit() and the IO completion callback.
*/
err = dmu_bio_clone(bio_saved, &req->bio);
if (err)
goto error;
for (i = 0; i < numbufs; i++) {
int tocpy, didcpy, bufoff;
dmu_buf_t *db = dbp[i];
bufoff = offset - db->db_offset;
ASSERT3S(bufoff, >=, 0);
tocpy = (int)MIN(db->db_size - bufoff, size);
if (tocpy == 0)
break;
ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
if (tocpy == db->db_size)
dmu_buf_will_fill(db, tx);
else
dmu_buf_will_dirty(db, tx);
err = dmu_req_copy(db->db_data + bufoff, tocpy, &didcpy, req);
if (tocpy == db->db_size)
dmu_buf_fill_done(db, tx);
if (didcpy < tocpy)
err = EIO;
if (err)
break;
size -= tocpy;
offset += didcpy;
err = 0;
}
dmu_bio_put(req->bio);
req->bio = bio_saved;
error:
dmu_buf_rele_array(dbp, numbufs, FTAG);
return (err);
}
int
dmu_read_uio(objset_t *os, uint64_t object, uio_t *uio, uint64_t size)
{
dmu_buf_t **dbp;
int numbufs, i, err;
xuio_t *xuio = NULL;
/*
* NB: we could do this block-at-a-time, but it's nice
* to be reading in parallel.
*/
err = dmu_buf_hold_array(os, object, uio->uio_loffset, size, TRUE, FTAG,
&numbufs, &dbp);
if (err)
return (err);
for (i = 0; i < numbufs; i++) {
int tocpy;
int bufoff;
dmu_buf_t *db = dbp[i];
ASSERT(size > 0);
bufoff = uio->uio_loffset - db->db_offset;
tocpy = (int)MIN(db->db_size - bufoff, size);
if (xuio) {
dmu_buf_impl_t *dbi = (dmu_buf_impl_t *)db;
arc_buf_t *dbuf_abuf = dbi->db_buf;
arc_buf_t *abuf = dbuf_loan_arcbuf(dbi);
err = dmu_xuio_add(xuio, abuf, bufoff, tocpy);
if (!err) {
uio->uio_resid -= tocpy;
uio->uio_loffset += tocpy;
}
if (abuf == dbuf_abuf)
XUIOSTAT_BUMP(xuiostat_rbuf_nocopy);
else
XUIOSTAT_BUMP(xuiostat_rbuf_copied);
} else {
err = uiomove((char *)db->db_data + bufoff, tocpy,
UIO_READ, uio);
}
if (err)
break;
size -= tocpy;
}
dmu_buf_rele_array(dbp, numbufs, FTAG);
return (err);
}
static int
dmu_write_uio_dnode(dnode_t *dn, uio_t *uio, uint64_t size, dmu_tx_t *tx)
{
dmu_buf_t **dbp;
int numbufs;
int err = 0;
int i;
err = dmu_buf_hold_array_by_dnode(dn, uio->uio_loffset, size,
FALSE, FTAG, &numbufs, &dbp, DMU_READ_PREFETCH);
if (err)
return (err);
for (i = 0; i < numbufs; i++) {
int tocpy;
int bufoff;
dmu_buf_t *db = dbp[i];
ASSERT(size > 0);
bufoff = uio->uio_loffset - db->db_offset;
tocpy = (int)MIN(db->db_size - bufoff, size);
ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
if (tocpy == db->db_size)
dmu_buf_will_fill(db, tx);
else
dmu_buf_will_dirty(db, tx);
/*
* XXX uiomove could block forever (eg.nfs-backed
* pages). There needs to be a uiolockdown() function
* to lock the pages in memory, so that uiomove won't
* block.
*/
err = uiomove((char *)db->db_data + bufoff, tocpy,
UIO_WRITE, uio);
if (tocpy == db->db_size)
dmu_buf_fill_done(db, tx);
if (err)
break;
size -= tocpy;
}
dmu_buf_rele_array(dbp, numbufs, FTAG);
return (err);
}
int
dmu_write_uio_dbuf(dmu_buf_t *zdb, uio_t *uio, uint64_t size,
dmu_tx_t *tx)
{
dmu_buf_impl_t *db = (dmu_buf_impl_t *)zdb;
dnode_t *dn;
int err;
if (size == 0)
return (0);
DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
err = dmu_write_uio_dnode(dn, uio, size, tx);
DB_DNODE_EXIT(db);
return (err);
}
int
dmu_write_uio(objset_t *os, uint64_t object, uio_t *uio, uint64_t size,
dmu_tx_t *tx)
{
dnode_t *dn;
int err;
if (size == 0)
return (0);
err = dnode_hold(os, object, FTAG, &dn);
if (err)
return (err);
err = dmu_write_uio_dnode(dn, uio, size, tx);
dnode_rele(dn, FTAG);
return (err);
}
#endif /* _KERNEL */
/*
* Allocate a loaned anonymous arc buffer.
*/
arc_buf_t *
dmu_request_arcbuf(dmu_buf_t *handle, int size)
{
dmu_buf_impl_t *db = (dmu_buf_impl_t *)handle;
spa_t *spa;
DB_GET_SPA(&spa, db);
return (arc_loan_buf(spa, size));
}
/*
* Free a loaned arc buffer.
*/
void
dmu_return_arcbuf(arc_buf_t *buf)
{
arc_return_buf(buf, FTAG);
VERIFY(arc_buf_remove_ref(buf, FTAG));
}
/*
* When possible directly assign passed loaned arc buffer to a dbuf.
* If this is not possible copy the contents of passed arc buf via
* dmu_write().
*/
void
dmu_assign_arcbuf(dmu_buf_t *handle, uint64_t offset, arc_buf_t *buf,
dmu_tx_t *tx)
{
dmu_buf_impl_t *dbuf = (dmu_buf_impl_t *)handle;
dnode_t *dn;
dmu_buf_impl_t *db;
uint32_t blksz = (uint32_t)arc_buf_size(buf);
uint64_t blkid;
DB_DNODE_ENTER(dbuf);
dn = DB_DNODE(dbuf);
rw_enter(&dn->dn_struct_rwlock, RW_READER);
blkid = dbuf_whichblock(dn, offset);
VERIFY((db = dbuf_hold(dn, blkid, FTAG)) != NULL);
rw_exit(&dn->dn_struct_rwlock);
DB_DNODE_EXIT(dbuf);
if (offset == db->db.db_offset && blksz == db->db.db_size) {
dbuf_assign_arcbuf(db, buf, tx);
dbuf_rele(db, FTAG);
} else {
objset_t *os;
uint64_t object;
DB_DNODE_ENTER(dbuf);
dn = DB_DNODE(dbuf);
os = dn->dn_objset;
object = dn->dn_object;
DB_DNODE_EXIT(dbuf);
dbuf_rele(db, FTAG);
dmu_write(os, object, offset, blksz, buf->b_data, tx);
dmu_return_arcbuf(buf);
XUIOSTAT_BUMP(xuiostat_wbuf_copied);
}
}
typedef struct {
dbuf_dirty_record_t *dsa_dr;
dmu_sync_cb_t *dsa_done;
zgd_t *dsa_zgd;
dmu_tx_t *dsa_tx;
} dmu_sync_arg_t;
/* ARGSUSED */
static void
dmu_sync_ready(zio_t *zio, arc_buf_t *buf, void *varg)
{
dmu_sync_arg_t *dsa = varg;
dmu_buf_t *db = dsa->dsa_zgd->zgd_db;
blkptr_t *bp = zio->io_bp;
if (zio->io_error == 0) {
if (BP_IS_HOLE(bp)) {
/*
* A block of zeros may compress to a hole, but the
* block size still needs to be known for replay.
*/
BP_SET_LSIZE(bp, db->db_size);
} else {
ASSERT(BP_GET_LEVEL(bp) == 0);
bp->blk_fill = 1;
}
}
}
static void
dmu_sync_late_arrival_ready(zio_t *zio)
{
dmu_sync_ready(zio, NULL, zio->io_private);
}
/* ARGSUSED */
static void
dmu_sync_done(zio_t *zio, arc_buf_t *buf, void *varg)
{
dmu_sync_arg_t *dsa = varg;
dbuf_dirty_record_t *dr = dsa->dsa_dr;
dmu_buf_impl_t *db = dr->dr_dbuf;
mutex_enter(&db->db_mtx);
ASSERT(dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC);
if (zio->io_error == 0) {
dr->dt.dl.dr_nopwrite = !!(zio->io_flags & ZIO_FLAG_NOPWRITE);
if (dr->dt.dl.dr_nopwrite) {
ASSERTV(blkptr_t *bp = zio->io_bp);
ASSERTV(blkptr_t *bp_orig = &zio->io_bp_orig);
ASSERTV(uint8_t chksum = BP_GET_CHECKSUM(bp_orig));
ASSERT(BP_EQUAL(bp, bp_orig));
ASSERT(zio->io_prop.zp_compress != ZIO_COMPRESS_OFF);
ASSERT(zio_checksum_table[chksum].ci_dedup);
}
dr->dt.dl.dr_overridden_by = *zio->io_bp;
dr->dt.dl.dr_override_state = DR_OVERRIDDEN;
dr->dt.dl.dr_copies = zio->io_prop.zp_copies;
if (BP_IS_HOLE(&dr->dt.dl.dr_overridden_by))
BP_ZERO(&dr->dt.dl.dr_overridden_by);
} else {
dr->dt.dl.dr_override_state = DR_NOT_OVERRIDDEN;
}
cv_broadcast(&db->db_changed);
mutex_exit(&db->db_mtx);
dsa->dsa_done(dsa->dsa_zgd, zio->io_error);
kmem_free(dsa, sizeof (*dsa));
}
static void
dmu_sync_late_arrival_done(zio_t *zio)
{
blkptr_t *bp = zio->io_bp;
dmu_sync_arg_t *dsa = zio->io_private;
ASSERTV(blkptr_t *bp_orig = &zio->io_bp_orig);
if (zio->io_error == 0 && !BP_IS_HOLE(bp)) {
/*
* If we didn't allocate a new block (i.e. ZIO_FLAG_NOPWRITE)
* then there is nothing to do here. Otherwise, free the
* newly allocated block in this txg.
*/
if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
ASSERT(BP_EQUAL(bp, bp_orig));
} else {
ASSERT(BP_IS_HOLE(bp_orig) || !BP_EQUAL(bp, bp_orig));
ASSERT(zio->io_bp->blk_birth == zio->io_txg);
ASSERT(zio->io_txg > spa_syncing_txg(zio->io_spa));
zio_free(zio->io_spa, zio->io_txg, zio->io_bp);
}
}
dmu_tx_commit(dsa->dsa_tx);
dsa->dsa_done(dsa->dsa_zgd, zio->io_error);
kmem_free(dsa, sizeof (*dsa));
}
static int
dmu_sync_late_arrival(zio_t *pio, objset_t *os, dmu_sync_cb_t *done, zgd_t *zgd,
zio_prop_t *zp, zbookmark_t *zb)
{
dmu_sync_arg_t *dsa;
dmu_tx_t *tx;
tx = dmu_tx_create(os);
dmu_tx_hold_space(tx, zgd->zgd_db->db_size);
if (dmu_tx_assign(tx, TXG_WAIT) != 0) {
dmu_tx_abort(tx);
/* Make zl_get_data do txg_waited_synced() */
return (SET_ERROR(EIO));
}
dsa = kmem_alloc(sizeof (dmu_sync_arg_t), KM_PUSHPAGE);
dsa->dsa_dr = NULL;
dsa->dsa_done = done;
dsa->dsa_zgd = zgd;
dsa->dsa_tx = tx;
zio_nowait(zio_write(pio, os->os_spa, dmu_tx_get_txg(tx), zgd->zgd_bp,
zgd->zgd_db->db_data, zgd->zgd_db->db_size, zp,
dmu_sync_late_arrival_ready, NULL, dmu_sync_late_arrival_done, dsa,
ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL | ZIO_FLAG_FASTWRITE, zb));
return (0);
}
/*
* Intent log support: sync the block associated with db to disk.
* N.B. and XXX: the caller is responsible for making sure that the
* data isn't changing while dmu_sync() is writing it.
*
* Return values:
*
* EEXIST: this txg has already been synced, so there's nothing to do.
* The caller should not log the write.
*
* ENOENT: the block was dbuf_free_range()'d, so there's nothing to do.
* The caller should not log the write.
*
* EALREADY: this block is already in the process of being synced.
* The caller should track its progress (somehow).
*
* EIO: could not do the I/O.
* The caller should do a txg_wait_synced().
*
* 0: the I/O has been initiated.
* The caller should log this blkptr in the done callback.
* It is possible that the I/O will fail, in which case
* the error will be reported to the done callback and
* propagated to pio from zio_done().
*/
int
dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd)
{
blkptr_t *bp = zgd->zgd_bp;
dmu_buf_impl_t *db = (dmu_buf_impl_t *)zgd->zgd_db;
objset_t *os = db->db_objset;
dsl_dataset_t *ds = os->os_dsl_dataset;
dbuf_dirty_record_t *dr;
dmu_sync_arg_t *dsa;
zbookmark_t zb;
zio_prop_t zp;
dnode_t *dn;
ASSERT(pio != NULL);
ASSERT(txg != 0);
SET_BOOKMARK(&zb, ds->ds_object,
db->db.db_object, db->db_level, db->db_blkid);
DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
dmu_write_policy(os, dn, db->db_level, WP_DMU_SYNC, &zp);
DB_DNODE_EXIT(db);
/*
* If we're frozen (running ziltest), we always need to generate a bp.
*/
if (txg > spa_freeze_txg(os->os_spa))
return (dmu_sync_late_arrival(pio, os, done, zgd, &zp, &zb));
/*
* Grabbing db_mtx now provides a barrier between dbuf_sync_leaf()
* and us. If we determine that this txg is not yet syncing,
* but it begins to sync a moment later, that's OK because the
* sync thread will block in dbuf_sync_leaf() until we drop db_mtx.
*/
mutex_enter(&db->db_mtx);
if (txg <= spa_last_synced_txg(os->os_spa)) {
/*
* This txg has already synced. There's nothing to do.
*/
mutex_exit(&db->db_mtx);
return (SET_ERROR(EEXIST));
}
if (txg <= spa_syncing_txg(os->os_spa)) {
/*
* This txg is currently syncing, so we can't mess with
* the dirty record anymore; just write a new log block.
*/
mutex_exit(&db->db_mtx);
return (dmu_sync_late_arrival(pio, os, done, zgd, &zp, &zb));
}
dr = db->db_last_dirty;
while (dr && dr->dr_txg != txg)
dr = dr->dr_next;
if (dr == NULL) {
/*
* There's no dr for this dbuf, so it must have been freed.
* There's no need to log writes to freed blocks, so we're done.
*/
mutex_exit(&db->db_mtx);
return (SET_ERROR(ENOENT));
}
ASSERT(dr->dr_next == NULL || dr->dr_next->dr_txg < txg);
/*
* Assume the on-disk data is X, the current syncing data is Y,
* and the current in-memory data is Z (currently in dmu_sync).
* X and Z are identical but Y is has been modified. Normally,
* when X and Z are the same we will perform a nopwrite but if Y
* is different we must disable nopwrite since the resulting write
* of Y to disk can free the block containing X. If we allowed a
* nopwrite to occur the block pointing to Z would reference a freed
* block. Since this is a rare case we simplify this by disabling
* nopwrite if the current dmu_sync-ing dbuf has been modified in
* a previous transaction.
*/
if (dr->dr_next)
zp.zp_nopwrite = B_FALSE;
ASSERT(dr->dr_txg == txg);
if (dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC ||
dr->dt.dl.dr_override_state == DR_OVERRIDDEN) {
/*
* We have already issued a sync write for this buffer,
* or this buffer has already been synced. It could not
* have been dirtied since, or we would have cleared the state.
*/
mutex_exit(&db->db_mtx);
return (SET_ERROR(EALREADY));
}
ASSERT(dr->dt.dl.dr_override_state == DR_NOT_OVERRIDDEN);
dr->dt.dl.dr_override_state = DR_IN_DMU_SYNC;
mutex_exit(&db->db_mtx);
dsa = kmem_alloc(sizeof (dmu_sync_arg_t), KM_PUSHPAGE);
dsa->dsa_dr = dr;
dsa->dsa_done = done;
dsa->dsa_zgd = zgd;
dsa->dsa_tx = NULL;
zio_nowait(arc_write(pio, os->os_spa, txg,
bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db),
DBUF_IS_L2COMPRESSIBLE(db), &zp, dmu_sync_ready,
NULL, dmu_sync_done, dsa, ZIO_PRIORITY_SYNC_WRITE,
ZIO_FLAG_CANFAIL, &zb));
return (0);
}
int
dmu_object_set_blocksize(objset_t *os, uint64_t object, uint64_t size, int ibs,
dmu_tx_t *tx)
{
dnode_t *dn;
int err;
err = dnode_hold(os, object, FTAG, &dn);
if (err)
return (err);
err = dnode_set_blksz(dn, size, ibs, tx);
dnode_rele(dn, FTAG);
return (err);
}
void
dmu_object_set_checksum(objset_t *os, uint64_t object, uint8_t checksum,
dmu_tx_t *tx)
{
dnode_t *dn;
/* XXX assumes dnode_hold will not get an i/o error */
(void) dnode_hold(os, object, FTAG, &dn);
ASSERT(checksum < ZIO_CHECKSUM_FUNCTIONS);
dn->dn_checksum = checksum;
dnode_setdirty(dn, tx);
dnode_rele(dn, FTAG);
}
void
dmu_object_set_compress(objset_t *os, uint64_t object, uint8_t compress,
dmu_tx_t *tx)
{
dnode_t *dn;
/* XXX assumes dnode_hold will not get an i/o error */
(void) dnode_hold(os, object, FTAG, &dn);
ASSERT(compress < ZIO_COMPRESS_FUNCTIONS);
dn->dn_compress = compress;
dnode_setdirty(dn, tx);
dnode_rele(dn, FTAG);
}
int zfs_mdcomp_disable = 0;
void
dmu_write_policy(objset_t *os, dnode_t *dn, int level, int wp, zio_prop_t *zp)
{
dmu_object_type_t type = dn ? dn->dn_type : DMU_OT_OBJSET;
boolean_t ismd = (level > 0 || DMU_OT_IS_METADATA(type) ||
(wp & WP_SPILL));
enum zio_checksum checksum = os->os_checksum;
enum zio_compress compress = os->os_compress;
enum zio_checksum dedup_checksum = os->os_dedup_checksum;
boolean_t dedup = B_FALSE;
boolean_t nopwrite = B_FALSE;
boolean_t dedup_verify = os->os_dedup_verify;
int copies = os->os_copies;
/*
* We maintain different write policies for each of the following
* types of data:
* 1. metadata
* 2. preallocated blocks (i.e. level-0 blocks of a dump device)
* 3. all other level 0 blocks
*/
if (ismd) {
/*
* XXX -- we should design a compression algorithm
* that specializes in arrays of bps.
*/
compress = zfs_mdcomp_disable ? ZIO_COMPRESS_EMPTY :
ZIO_COMPRESS_LZJB;
/*
* Metadata always gets checksummed. If the data
* checksum is multi-bit correctable, and it's not a
* ZBT-style checksum, then it's suitable for metadata
* as well. Otherwise, the metadata checksum defaults
* to fletcher4.
*/
if (zio_checksum_table[checksum].ci_correctable < 1 ||
zio_checksum_table[checksum].ci_eck)
checksum = ZIO_CHECKSUM_FLETCHER_4;
} else if (wp & WP_NOFILL) {
ASSERT(level == 0);
/*
* If we're writing preallocated blocks, we aren't actually
* writing them so don't set any policy properties. These
* blocks are currently only used by an external subsystem
* outside of zfs (i.e. dump) and not written by the zio
* pipeline.
*/
compress = ZIO_COMPRESS_OFF;
checksum = ZIO_CHECKSUM_OFF;
} else {
compress = zio_compress_select(dn->dn_compress, compress);
checksum = (dedup_checksum == ZIO_CHECKSUM_OFF) ?
zio_checksum_select(dn->dn_checksum, checksum) :
dedup_checksum;
/*
* Determine dedup setting. If we are in dmu_sync(),
* we won't actually dedup now because that's all
* done in syncing context; but we do want to use the
* dedup checkum. If the checksum is not strong
* enough to ensure unique signatures, force
* dedup_verify.
*/
if (dedup_checksum != ZIO_CHECKSUM_OFF) {
dedup = (wp & WP_DMU_SYNC) ? B_FALSE : B_TRUE;
if (!zio_checksum_table[checksum].ci_dedup)
dedup_verify = B_TRUE;
}
/*
* Enable nopwrite if we have a cryptographically secure
* checksum that has no known collisions (i.e. SHA-256)
* and compression is enabled. We don't enable nopwrite if
* dedup is enabled as the two features are mutually exclusive.
*/
nopwrite = (!dedup && zio_checksum_table[checksum].ci_dedup &&
compress != ZIO_COMPRESS_OFF && zfs_nopwrite_enabled);
}
zp->zp_checksum = checksum;
zp->zp_compress = compress;
zp->zp_type = (wp & WP_SPILL) ? dn->dn_bonustype : type;
zp->zp_level = level;
zp->zp_copies = MIN(copies + ismd, spa_max_replication(os->os_spa));
zp->zp_dedup = dedup;
zp->zp_dedup_verify = dedup && dedup_verify;
zp->zp_nopwrite = nopwrite;
}
int
dmu_offset_next(objset_t *os, uint64_t object, boolean_t hole, uint64_t *off)
{
dnode_t *dn;
int i, err;
err = dnode_hold(os, object, FTAG, &dn);
if (err)
return (err);
/*
* Sync any current changes before
* we go trundling through the block pointers.
*/
for (i = 0; i < TXG_SIZE; i++) {
if (list_link_active(&dn->dn_dirty_link[i]))
break;
}
if (i != TXG_SIZE) {
dnode_rele(dn, FTAG);
txg_wait_synced(dmu_objset_pool(os), 0);
err = dnode_hold(os, object, FTAG, &dn);
if (err)
return (err);
}
err = dnode_next_offset(dn, (hole ? DNODE_FIND_HOLE : 0), off, 1, 1, 0);
dnode_rele(dn, FTAG);
return (err);
}
void
__dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi)
{
dnode_phys_t *dnp = dn->dn_phys;
int i;
doi->doi_data_block_size = dn->dn_datablksz;
doi->doi_metadata_block_size = dn->dn_indblkshift ?
1ULL << dn->dn_indblkshift : 0;
doi->doi_type = dn->dn_type;
doi->doi_bonus_type = dn->dn_bonustype;
doi->doi_bonus_size = dn->dn_bonuslen;
doi->doi_indirection = dn->dn_nlevels;
doi->doi_checksum = dn->dn_checksum;
doi->doi_compress = dn->dn_compress;
doi->doi_physical_blocks_512 = (DN_USED_BYTES(dnp) + 256) >> 9;
doi->doi_max_offset = (dn->dn_maxblkid + 1) * dn->dn_datablksz;
doi->doi_fill_count = 0;
for (i = 0; i < dnp->dn_nblkptr; i++)
doi->doi_fill_count += dnp->dn_blkptr[i].blk_fill;
}
void
dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi)
{
rw_enter(&dn->dn_struct_rwlock, RW_READER);
mutex_enter(&dn->dn_mtx);
__dmu_object_info_from_dnode(dn, doi);
mutex_exit(&dn->dn_mtx);
rw_exit(&dn->dn_struct_rwlock);
}
/*
* Get information on a DMU object.
* If doi is NULL, just indicates whether the object exists.
*/
int
dmu_object_info(objset_t *os, uint64_t object, dmu_object_info_t *doi)
{
dnode_t *dn;
int err = dnode_hold(os, object, FTAG, &dn);
if (err)
return (err);
if (doi != NULL)
dmu_object_info_from_dnode(dn, doi);
dnode_rele(dn, FTAG);
return (0);
}
/*
* As above, but faster; can be used when you have a held dbuf in hand.
*/
void
dmu_object_info_from_db(dmu_buf_t *db_fake, dmu_object_info_t *doi)
{
dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
DB_DNODE_ENTER(db);
dmu_object_info_from_dnode(DB_DNODE(db), doi);
DB_DNODE_EXIT(db);
}
/*
* Faster still when you only care about the size.
* This is specifically optimized for zfs_getattr().
*/
void
dmu_object_size_from_db(dmu_buf_t *db_fake, uint32_t *blksize,
u_longlong_t *nblk512)
{
dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
dnode_t *dn;
DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
*blksize = dn->dn_datablksz;
/* add 1 for dnode space */
*nblk512 = ((DN_USED_BYTES(dn->dn_phys) + SPA_MINBLOCKSIZE/2) >>
SPA_MINBLOCKSHIFT) + 1;
DB_DNODE_EXIT(db);
}
void
byteswap_uint64_array(void *vbuf, size_t size)
{
uint64_t *buf = vbuf;
size_t count = size >> 3;
int i;
ASSERT((size & 7) == 0);
for (i = 0; i < count; i++)
buf[i] = BSWAP_64(buf[i]);
}
void
byteswap_uint32_array(void *vbuf, size_t size)
{
uint32_t *buf = vbuf;
size_t count = size >> 2;
int i;
ASSERT((size & 3) == 0);
for (i = 0; i < count; i++)
buf[i] = BSWAP_32(buf[i]);
}
void
byteswap_uint16_array(void *vbuf, size_t size)
{
uint16_t *buf = vbuf;
size_t count = size >> 1;
int i;
ASSERT((size & 1) == 0);
for (i = 0; i < count; i++)
buf[i] = BSWAP_16(buf[i]);
}
/* ARGSUSED */
void
byteswap_uint8_array(void *vbuf, size_t size)
{
}
void
dmu_init(void)
{
zfs_dbgmsg_init();
sa_cache_init();
xuio_stat_init();
dmu_objset_init();
dnode_init();
dbuf_init();
zfetch_init();
dmu_tx_init();
l2arc_init();
arc_init();
}
void
dmu_fini(void)
{
arc_fini(); /* arc depends on l2arc, so arc must go first */
l2arc_fini();
dmu_tx_fini();
zfetch_fini();
dbuf_fini();
dnode_fini();
dmu_objset_fini();
xuio_stat_fini();
sa_cache_fini();
zfs_dbgmsg_fini();
}
#if defined(_KERNEL) && defined(HAVE_SPL)
EXPORT_SYMBOL(dmu_bonus_hold);
EXPORT_SYMBOL(dmu_buf_hold_array_by_bonus);
EXPORT_SYMBOL(dmu_buf_rele_array);
EXPORT_SYMBOL(dmu_prefetch);
EXPORT_SYMBOL(dmu_free_range);
EXPORT_SYMBOL(dmu_free_long_range);
EXPORT_SYMBOL(dmu_free_long_object);
EXPORT_SYMBOL(dmu_read);
EXPORT_SYMBOL(dmu_write);
EXPORT_SYMBOL(dmu_prealloc);
EXPORT_SYMBOL(dmu_object_info);
EXPORT_SYMBOL(dmu_object_info_from_dnode);
EXPORT_SYMBOL(dmu_object_info_from_db);
EXPORT_SYMBOL(dmu_object_size_from_db);
EXPORT_SYMBOL(dmu_object_set_blocksize);
EXPORT_SYMBOL(dmu_object_set_checksum);
EXPORT_SYMBOL(dmu_object_set_compress);
EXPORT_SYMBOL(dmu_write_policy);
EXPORT_SYMBOL(dmu_sync);
EXPORT_SYMBOL(dmu_request_arcbuf);
EXPORT_SYMBOL(dmu_return_arcbuf);
EXPORT_SYMBOL(dmu_assign_arcbuf);
EXPORT_SYMBOL(dmu_buf_hold);
EXPORT_SYMBOL(dmu_ot);
module_param(zfs_mdcomp_disable, int, 0644);
MODULE_PARM_DESC(zfs_mdcomp_disable, "Disable meta data compression");
module_param(zfs_nopwrite_enabled, int, 0644);
MODULE_PARM_DESC(zfs_nopwrite_enabled, "Enable NOP writes");
#endif
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