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mirror_zfs/module/zfs/dsl_pool.c
Serapheim Dimitropoulos 0f8ff49eb6 dmu_tx_wait() hang likely due to cv_signal() in dsl_pool_dirty_delta() 
Even though the bug's writeup (Github issue #9136) is very detailed,
we still don't know exactly how we got to that state, thus I wasn't
able to reproduce the bug. That said, we can make an educated guess
combining the information on filled issue with the code.

From the fact that `dp_dirty_total` was 0 (which is less than
`zfs_dirty_data_max`) we know that there was one thread that set it to
0 and then signaled one of the waiters of `dp_spaceavail_cv` [see
`dsl_pool_dirty_delta()` which is also the only place that
`dp_dirty_total` is changed].  Thus, the only logical explaination
then for the bug being hit is that the waiter that just got awaken
didn't go through `dsl_pool_dirty_data()`. Given that this function
is only called by `dsl_pool_dirty_space()` or `dsl_pool_undirty_space()`
I can only think of two possible ways of the above scenario happening:

[1] The waiter didn't call into any of the two functions - which I
    find highly unlikely (i.e. why wait on `dp_spaceavail_cv` to begin
    with?).
[2] The waiter did call in one of the above function but it passed 0 as
    the space/delta to be dirtied (or undirtied) and then the callee
    returned immediately (e.g both `dsl_pool_dirty_space()` and
    `dsl_pool_undirty_space()` return immediately when space is 0).

In any case and no matter how we got there, the easy fix would be to
just broadcast to all waiters whenever `dp_dirty_total` hits 0. That
said and given that we've never hit this before, it would make sense
to think more on why the above situation occured.

Attempting to mimic what Prakash was doing in the issue filed, I
created a dataset with `sync=always` and started doing contiguous
writes in a file within that dataset. I observed with DTrace that even
though we update the pool's dirty data accounting when we would dirty
stuff, the accounting wouldn't be decremented incrementally as we were
done with the ZIOs of those writes (the reason being that
`dbuf_write_physdone()` isn't be called as we go through the override
code paths, and thus `dsl_pool_undirty_space()` is never called). As a
result we'd have to wait until we get to `dsl_pool_sync()` where we
zero out all dirty data accounting for the pool and the current TXG's
metadata.

In addition, as Matt noted and I later verified, the same issue would
arise when using dedup.

In both cases (sync & dedup) we shouldn't have to wait until
`dsl_pool_sync()` zeros out the accounting data. According to the
comment in that part of the code, the reasons why we do the zeroing,
have nothing to do with what we observe:
````
/*
 * We have written all of the accounted dirty data, so our
 * dp_space_towrite should now be zero.  However, some seldom-used
 * code paths do not adhere to this (e.g. dbuf_undirty(), also
 * rounding error in dbuf_write_physdone).
 * Shore up the accounting of any dirtied space now.
 */
dsl_pool_undirty_space(dp, dp->dp_dirty_pertxg[txg & TXG_MASK], txg);
````

Ideally what we want to do is to undirty in the accounting exactly what
we dirty (I use the word ideally as we can still have rounding errors).
This would make the behavior of the system more clear and predictable.

Another interesting issue that I observed with DTrace was that we
wouldn't update any of the pool's dirty data accounting whenever we
would dirty and/or undirty MOS data. In addition, every time we would
change the size of a dbuf through `dbuf_new_size()` we wouldn't update
the accounted space dirtied in the appropriate dirty record, so when
ZIOs are done we would undirty less that we dirtied from the pool's
accounting point of view.

For the first two issues observed (sync & dedup) this patch ensures
that we still update the pool's accounting when we undirty data,
regardless of the write being physical or not.

For changes in the MOS, we first ensure to zero out the pool's dirty
data accounting in `dsl_pool_sync()` after we synced the MOS. Then we
can go ahead and enable the update of the pool's dirty data accounting
wheneve we change MOS data.

Another fix is that we now update the accounting explicitly for
counting errors in `dbuf_write_done()`.

Finally, `dbuf_new_size()` updates the accounted space of the
appropriate dirty record correctly now.

The problem is that we still don't know how the bug came up in the
issue filled. That said the issues fixed seem to be very relevant, so
instead of going with the broadcasting solution right away,
I decided to leave this patch as is.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Prakash Surya <prakash.surya@delphix.com>
Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com>
External-issue: DLPX-47285
Closes #9137
2019-08-15 17:53:53 -06:00

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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) 2011, 2019 by Delphix. All rights reserved.
* Copyright (c) 2013 Steven Hartland. All rights reserved.
* Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
* Copyright 2016 Nexenta Systems, Inc. All rights reserved.
*/
#include <sys/dsl_pool.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_prop.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_synctask.h>
#include <sys/dsl_scan.h>
#include <sys/dnode.h>
#include <sys/dmu_tx.h>
#include <sys/dmu_objset.h>
#include <sys/arc.h>
#include <sys/zap.h>
#include <sys/zio.h>
#include <sys/zfs_context.h>
#include <sys/fs/zfs.h>
#include <sys/zfs_znode.h>
#include <sys/spa_impl.h>
#include <sys/vdev_impl.h>
#include <sys/metaslab_impl.h>
#include <sys/bptree.h>
#include <sys/zfeature.h>
#include <sys/zil_impl.h>
#include <sys/dsl_userhold.h>
#include <sys/trace_txg.h>
#include <sys/mmp.h>
/*
* ZFS Write Throttle
* ------------------
*
* ZFS must limit the rate of incoming writes to the rate at which it is able
* to sync data modifications to the backend storage. Throttling by too much
* creates an artificial limit; throttling by too little can only be sustained
* for short periods and would lead to highly lumpy performance. On a per-pool
* basis, ZFS tracks the amount of modified (dirty) data. As operations change
* data, the amount of dirty data increases; as ZFS syncs out data, the amount
* of dirty data decreases. When the amount of dirty data exceeds a
* predetermined threshold further modifications are blocked until the amount
* of dirty data decreases (as data is synced out).
*
* The limit on dirty data is tunable, and should be adjusted according to
* both the IO capacity and available memory of the system. The larger the
* window, the more ZFS is able to aggregate and amortize metadata (and data)
* changes. However, memory is a limited resource, and allowing for more dirty
* data comes at the cost of keeping other useful data in memory (for example
* ZFS data cached by the ARC).
*
* Implementation
*
* As buffers are modified dsl_pool_willuse_space() increments both the per-
* txg (dp_dirty_pertxg[]) and poolwide (dp_dirty_total) accounting of
* dirty space used; dsl_pool_dirty_space() decrements those values as data
* is synced out from dsl_pool_sync(). While only the poolwide value is
* relevant, the per-txg value is useful for debugging. The tunable
* zfs_dirty_data_max determines the dirty space limit. Once that value is
* exceeded, new writes are halted until space frees up.
*
* The zfs_dirty_data_sync_percent tunable dictates the threshold at which we
* ensure that there is a txg syncing (see the comment in txg.c for a full
* description of transaction group stages).
*
* The IO scheduler uses both the dirty space limit and current amount of
* dirty data as inputs. Those values affect the number of concurrent IOs ZFS
* issues. See the comment in vdev_queue.c for details of the IO scheduler.
*
* The delay is also calculated based on the amount of dirty data. See the
* comment above dmu_tx_delay() for details.
*/
/*
* zfs_dirty_data_max will be set to zfs_dirty_data_max_percent% of all memory,
* capped at zfs_dirty_data_max_max. It can also be overridden with a module
* parameter.
*/
unsigned long zfs_dirty_data_max = 0;
unsigned long zfs_dirty_data_max_max = 0;
int zfs_dirty_data_max_percent = 10;
int zfs_dirty_data_max_max_percent = 25;
/*
* If there's at least this much dirty data (as a percentage of
* zfs_dirty_data_max), push out a txg. This should be less than
* zfs_vdev_async_write_active_min_dirty_percent.
*/
int zfs_dirty_data_sync_percent = 20;
/*
* Once there is this amount of dirty data, the dmu_tx_delay() will kick in
* and delay each transaction.
* This value should be >= zfs_vdev_async_write_active_max_dirty_percent.
*/
int zfs_delay_min_dirty_percent = 60;
/*
* This controls how quickly the delay approaches infinity.
* Larger values cause it to delay more for a given amount of dirty data.
* Therefore larger values will cause there to be less dirty data for a
* given throughput.
*
* For the smoothest delay, this value should be about 1 billion divided
* by the maximum number of operations per second. This will smoothly
* handle between 10x and 1/10th this number.
*
* Note: zfs_delay_scale * zfs_dirty_data_max must be < 2^64, due to the
* multiply in dmu_tx_delay().
*/
unsigned long zfs_delay_scale = 1000 * 1000 * 1000 / 2000;
/*
* This determines the number of threads used by the dp_sync_taskq.
*/
int zfs_sync_taskq_batch_pct = 75;
/*
* These tunables determine the behavior of how zil_itxg_clean() is
* called via zil_clean() in the context of spa_sync(). When an itxg
* list needs to be cleaned, TQ_NOSLEEP will be used when dispatching.
* If the dispatch fails, the call to zil_itxg_clean() will occur
* synchronously in the context of spa_sync(), which can negatively
* impact the performance of spa_sync() (e.g. in the case of the itxg
* list having a large number of itxs that needs to be cleaned).
*
* Thus, these tunables can be used to manipulate the behavior of the
* taskq used by zil_clean(); they determine the number of taskq entries
* that are pre-populated when the taskq is first created (via the
* "zfs_zil_clean_taskq_minalloc" tunable) and the maximum number of
* taskq entries that are cached after an on-demand allocation (via the
* "zfs_zil_clean_taskq_maxalloc").
*
* The idea being, we want to try reasonably hard to ensure there will
* already be a taskq entry pre-allocated by the time that it is needed
* by zil_clean(). This way, we can avoid the possibility of an
* on-demand allocation of a new taskq entry from failing, which would
* result in zil_itxg_clean() being called synchronously from zil_clean()
* (which can adversely affect performance of spa_sync()).
*
* Additionally, the number of threads used by the taskq can be
* configured via the "zfs_zil_clean_taskq_nthr_pct" tunable.
*/
int zfs_zil_clean_taskq_nthr_pct = 100;
int zfs_zil_clean_taskq_minalloc = 1024;
int zfs_zil_clean_taskq_maxalloc = 1024 * 1024;
int
dsl_pool_open_special_dir(dsl_pool_t *dp, const char *name, dsl_dir_t **ddp)
{
uint64_t obj;
int err;
err = zap_lookup(dp->dp_meta_objset,
dsl_dir_phys(dp->dp_root_dir)->dd_child_dir_zapobj,
name, sizeof (obj), 1, &obj);
if (err)
return (err);
return (dsl_dir_hold_obj(dp, obj, name, dp, ddp));
}
static dsl_pool_t *
dsl_pool_open_impl(spa_t *spa, uint64_t txg)
{
dsl_pool_t *dp;
blkptr_t *bp = spa_get_rootblkptr(spa);
dp = kmem_zalloc(sizeof (dsl_pool_t), KM_SLEEP);
dp->dp_spa = spa;
dp->dp_meta_rootbp = *bp;
rrw_init(&dp->dp_config_rwlock, B_TRUE);
txg_init(dp, txg);
mmp_init(spa);
txg_list_create(&dp->dp_dirty_datasets, spa,
offsetof(dsl_dataset_t, ds_dirty_link));
txg_list_create(&dp->dp_dirty_zilogs, spa,
offsetof(zilog_t, zl_dirty_link));
txg_list_create(&dp->dp_dirty_dirs, spa,
offsetof(dsl_dir_t, dd_dirty_link));
txg_list_create(&dp->dp_sync_tasks, spa,
offsetof(dsl_sync_task_t, dst_node));
txg_list_create(&dp->dp_early_sync_tasks, spa,
offsetof(dsl_sync_task_t, dst_node));
dp->dp_sync_taskq = taskq_create("dp_sync_taskq",
zfs_sync_taskq_batch_pct, minclsyspri, 1, INT_MAX,
TASKQ_THREADS_CPU_PCT);
dp->dp_zil_clean_taskq = taskq_create("dp_zil_clean_taskq",
zfs_zil_clean_taskq_nthr_pct, minclsyspri,
zfs_zil_clean_taskq_minalloc,
zfs_zil_clean_taskq_maxalloc,
TASKQ_PREPOPULATE | TASKQ_THREADS_CPU_PCT);
mutex_init(&dp->dp_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&dp->dp_spaceavail_cv, NULL, CV_DEFAULT, NULL);
dp->dp_iput_taskq = taskq_create("z_iput", max_ncpus, defclsyspri,
max_ncpus * 8, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
dp->dp_unlinked_drain_taskq = taskq_create("z_unlinked_drain",
max_ncpus, defclsyspri, max_ncpus, INT_MAX,
TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
return (dp);
}
int
dsl_pool_init(spa_t *spa, uint64_t txg, dsl_pool_t **dpp)
{
int err;
dsl_pool_t *dp = dsl_pool_open_impl(spa, txg);
/*
* Initialize the caller's dsl_pool_t structure before we actually open
* the meta objset. This is done because a self-healing write zio may
* be issued as part of dmu_objset_open_impl() and the spa needs its
* dsl_pool_t initialized in order to handle the write.
*/
*dpp = dp;
err = dmu_objset_open_impl(spa, NULL, &dp->dp_meta_rootbp,
&dp->dp_meta_objset);
if (err != 0) {
dsl_pool_close(dp);
*dpp = NULL;
}
return (err);
}
int
dsl_pool_open(dsl_pool_t *dp)
{
int err;
dsl_dir_t *dd;
dsl_dataset_t *ds;
uint64_t obj;
rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG);
err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_ROOT_DATASET, sizeof (uint64_t), 1,
&dp->dp_root_dir_obj);
if (err)
goto out;
err = dsl_dir_hold_obj(dp, dp->dp_root_dir_obj,
NULL, dp, &dp->dp_root_dir);
if (err)
goto out;
err = dsl_pool_open_special_dir(dp, MOS_DIR_NAME, &dp->dp_mos_dir);
if (err)
goto out;
if (spa_version(dp->dp_spa) >= SPA_VERSION_ORIGIN) {
err = dsl_pool_open_special_dir(dp, ORIGIN_DIR_NAME, &dd);
if (err)
goto out;
err = dsl_dataset_hold_obj(dp,
dsl_dir_phys(dd)->dd_head_dataset_obj, FTAG, &ds);
if (err == 0) {
err = dsl_dataset_hold_obj(dp,
dsl_dataset_phys(ds)->ds_prev_snap_obj, dp,
&dp->dp_origin_snap);
dsl_dataset_rele(ds, FTAG);
}
dsl_dir_rele(dd, dp);
if (err)
goto out;
}
if (spa_version(dp->dp_spa) >= SPA_VERSION_DEADLISTS) {
err = dsl_pool_open_special_dir(dp, FREE_DIR_NAME,
&dp->dp_free_dir);
if (err)
goto out;
err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj);
if (err)
goto out;
VERIFY0(bpobj_open(&dp->dp_free_bpobj,
dp->dp_meta_objset, obj));
}
if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_OBSOLETE_COUNTS)) {
err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_OBSOLETE_BPOBJ, sizeof (uint64_t), 1, &obj);
if (err == 0) {
VERIFY0(bpobj_open(&dp->dp_obsolete_bpobj,
dp->dp_meta_objset, obj));
} else if (err == ENOENT) {
/*
* We might not have created the remap bpobj yet.
*/
err = 0;
} else {
goto out;
}
}
/*
* Note: errors ignored, because the these special dirs, used for
* space accounting, are only created on demand.
*/
(void) dsl_pool_open_special_dir(dp, LEAK_DIR_NAME,
&dp->dp_leak_dir);
if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_ASYNC_DESTROY)) {
err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_BPTREE_OBJ, sizeof (uint64_t), 1,
&dp->dp_bptree_obj);
if (err != 0)
goto out;
}
if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_EMPTY_BPOBJ)) {
err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_EMPTY_BPOBJ, sizeof (uint64_t), 1,
&dp->dp_empty_bpobj);
if (err != 0)
goto out;
}
err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_TMP_USERREFS, sizeof (uint64_t), 1,
&dp->dp_tmp_userrefs_obj);
if (err == ENOENT)
err = 0;
if (err)
goto out;
err = dsl_scan_init(dp, dp->dp_tx.tx_open_txg);
out:
rrw_exit(&dp->dp_config_rwlock, FTAG);
return (err);
}
void
dsl_pool_close(dsl_pool_t *dp)
{
/*
* Drop our references from dsl_pool_open().
*
* Since we held the origin_snap from "syncing" context (which
* includes pool-opening context), it actually only got a "ref"
* and not a hold, so just drop that here.
*/
if (dp->dp_origin_snap != NULL)
dsl_dataset_rele(dp->dp_origin_snap, dp);
if (dp->dp_mos_dir != NULL)
dsl_dir_rele(dp->dp_mos_dir, dp);
if (dp->dp_free_dir != NULL)
dsl_dir_rele(dp->dp_free_dir, dp);
if (dp->dp_leak_dir != NULL)
dsl_dir_rele(dp->dp_leak_dir, dp);
if (dp->dp_root_dir != NULL)
dsl_dir_rele(dp->dp_root_dir, dp);
bpobj_close(&dp->dp_free_bpobj);
bpobj_close(&dp->dp_obsolete_bpobj);
/* undo the dmu_objset_open_impl(mos) from dsl_pool_open() */
if (dp->dp_meta_objset != NULL)
dmu_objset_evict(dp->dp_meta_objset);
txg_list_destroy(&dp->dp_dirty_datasets);
txg_list_destroy(&dp->dp_dirty_zilogs);
txg_list_destroy(&dp->dp_sync_tasks);
txg_list_destroy(&dp->dp_early_sync_tasks);
txg_list_destroy(&dp->dp_dirty_dirs);
taskq_destroy(dp->dp_zil_clean_taskq);
taskq_destroy(dp->dp_sync_taskq);
/*
* We can't set retry to TRUE since we're explicitly specifying
* a spa to flush. This is good enough; any missed buffers for
* this spa won't cause trouble, and they'll eventually fall
* out of the ARC just like any other unused buffer.
*/
arc_flush(dp->dp_spa, FALSE);
mmp_fini(dp->dp_spa);
txg_fini(dp);
dsl_scan_fini(dp);
dmu_buf_user_evict_wait();
rrw_destroy(&dp->dp_config_rwlock);
mutex_destroy(&dp->dp_lock);
cv_destroy(&dp->dp_spaceavail_cv);
taskq_destroy(dp->dp_unlinked_drain_taskq);
taskq_destroy(dp->dp_iput_taskq);
if (dp->dp_blkstats != NULL) {
mutex_destroy(&dp->dp_blkstats->zab_lock);
vmem_free(dp->dp_blkstats, sizeof (zfs_all_blkstats_t));
}
kmem_free(dp, sizeof (dsl_pool_t));
}
void
dsl_pool_create_obsolete_bpobj(dsl_pool_t *dp, dmu_tx_t *tx)
{
uint64_t obj;
/*
* Currently, we only create the obsolete_bpobj where there are
* indirect vdevs with referenced mappings.
*/
ASSERT(spa_feature_is_active(dp->dp_spa, SPA_FEATURE_DEVICE_REMOVAL));
/* create and open the obsolete_bpobj */
obj = bpobj_alloc(dp->dp_meta_objset, SPA_OLD_MAXBLOCKSIZE, tx);
VERIFY0(bpobj_open(&dp->dp_obsolete_bpobj, dp->dp_meta_objset, obj));
VERIFY0(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_OBSOLETE_BPOBJ, sizeof (uint64_t), 1, &obj, tx));
spa_feature_incr(dp->dp_spa, SPA_FEATURE_OBSOLETE_COUNTS, tx);
}
void
dsl_pool_destroy_obsolete_bpobj(dsl_pool_t *dp, dmu_tx_t *tx)
{
spa_feature_decr(dp->dp_spa, SPA_FEATURE_OBSOLETE_COUNTS, tx);
VERIFY0(zap_remove(dp->dp_meta_objset,
DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_OBSOLETE_BPOBJ, tx));
bpobj_free(dp->dp_meta_objset,
dp->dp_obsolete_bpobj.bpo_object, tx);
bpobj_close(&dp->dp_obsolete_bpobj);
}
dsl_pool_t *
dsl_pool_create(spa_t *spa, nvlist_t *zplprops, dsl_crypto_params_t *dcp,
uint64_t txg)
{
int err;
dsl_pool_t *dp = dsl_pool_open_impl(spa, txg);
dmu_tx_t *tx = dmu_tx_create_assigned(dp, txg);
#ifdef _KERNEL
objset_t *os;
#else
objset_t *os __attribute__((unused));
#endif
dsl_dataset_t *ds;
uint64_t obj;
rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG);
/* create and open the MOS (meta-objset) */
dp->dp_meta_objset = dmu_objset_create_impl(spa,
NULL, &dp->dp_meta_rootbp, DMU_OST_META, tx);
spa->spa_meta_objset = dp->dp_meta_objset;
/* create the pool directory */
err = zap_create_claim(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_OT_OBJECT_DIRECTORY, DMU_OT_NONE, 0, tx);
ASSERT0(err);
/* Initialize scan structures */
VERIFY0(dsl_scan_init(dp, txg));
/* create and open the root dir */
dp->dp_root_dir_obj = dsl_dir_create_sync(dp, NULL, NULL, tx);
VERIFY0(dsl_dir_hold_obj(dp, dp->dp_root_dir_obj,
NULL, dp, &dp->dp_root_dir));
/* create and open the meta-objset dir */
(void) dsl_dir_create_sync(dp, dp->dp_root_dir, MOS_DIR_NAME, tx);
VERIFY0(dsl_pool_open_special_dir(dp,
MOS_DIR_NAME, &dp->dp_mos_dir));
if (spa_version(spa) >= SPA_VERSION_DEADLISTS) {
/* create and open the free dir */
(void) dsl_dir_create_sync(dp, dp->dp_root_dir,
FREE_DIR_NAME, tx);
VERIFY0(dsl_pool_open_special_dir(dp,
FREE_DIR_NAME, &dp->dp_free_dir));
/* create and open the free_bplist */
obj = bpobj_alloc(dp->dp_meta_objset, SPA_OLD_MAXBLOCKSIZE, tx);
VERIFY(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj, tx) == 0);
VERIFY0(bpobj_open(&dp->dp_free_bpobj,
dp->dp_meta_objset, obj));
}
if (spa_version(spa) >= SPA_VERSION_DSL_SCRUB)
dsl_pool_create_origin(dp, tx);
/*
* Some features may be needed when creating the root dataset, so we
* create the feature objects here.
*/
if (spa_version(spa) >= SPA_VERSION_FEATURES)
spa_feature_create_zap_objects(spa, tx);
if (dcp != NULL && dcp->cp_crypt != ZIO_CRYPT_OFF &&
dcp->cp_crypt != ZIO_CRYPT_INHERIT)
spa_feature_enable(spa, SPA_FEATURE_ENCRYPTION, tx);
/* create the root dataset */
obj = dsl_dataset_create_sync_dd(dp->dp_root_dir, NULL, dcp, 0, tx);
/* create the root objset */
VERIFY0(dsl_dataset_hold_obj_flags(dp, obj,
DS_HOLD_FLAG_DECRYPT, FTAG, &ds));
rrw_enter(&ds->ds_bp_rwlock, RW_READER, FTAG);
os = dmu_objset_create_impl(dp->dp_spa, ds,
dsl_dataset_get_blkptr(ds), DMU_OST_ZFS, tx);
rrw_exit(&ds->ds_bp_rwlock, FTAG);
#ifdef _KERNEL
zfs_create_fs(os, kcred, zplprops, tx);
#endif
dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
dmu_tx_commit(tx);
rrw_exit(&dp->dp_config_rwlock, FTAG);
return (dp);
}
/*
* Account for the meta-objset space in its placeholder dsl_dir.
*/
void
dsl_pool_mos_diduse_space(dsl_pool_t *dp,
int64_t used, int64_t comp, int64_t uncomp)
{
ASSERT3U(comp, ==, uncomp); /* it's all metadata */
mutex_enter(&dp->dp_lock);
dp->dp_mos_used_delta += used;
dp->dp_mos_compressed_delta += comp;
dp->dp_mos_uncompressed_delta += uncomp;
mutex_exit(&dp->dp_lock);
}
static void
dsl_pool_sync_mos(dsl_pool_t *dp, dmu_tx_t *tx)
{
zio_t *zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
dmu_objset_sync(dp->dp_meta_objset, zio, tx);
VERIFY0(zio_wait(zio));
dprintf_bp(&dp->dp_meta_rootbp, "meta objset rootbp is %s", "");
spa_set_rootblkptr(dp->dp_spa, &dp->dp_meta_rootbp);
}
static void
dsl_pool_dirty_delta(dsl_pool_t *dp, int64_t delta)
{
ASSERT(MUTEX_HELD(&dp->dp_lock));
if (delta < 0)
ASSERT3U(-delta, <=, dp->dp_dirty_total);
dp->dp_dirty_total += delta;
/*
* Note: we signal even when increasing dp_dirty_total.
* This ensures forward progress -- each thread wakes the next waiter.
*/
if (dp->dp_dirty_total < zfs_dirty_data_max)
cv_signal(&dp->dp_spaceavail_cv);
}
#ifdef ZFS_DEBUG
static boolean_t
dsl_early_sync_task_verify(dsl_pool_t *dp, uint64_t txg)
{
spa_t *spa = dp->dp_spa;
vdev_t *rvd = spa->spa_root_vdev;
for (uint64_t c = 0; c < rvd->vdev_children; c++) {
vdev_t *vd = rvd->vdev_child[c];
txg_list_t *tl = &vd->vdev_ms_list;
metaslab_t *ms;
for (ms = txg_list_head(tl, TXG_CLEAN(txg)); ms;
ms = txg_list_next(tl, ms, TXG_CLEAN(txg))) {
VERIFY(range_tree_is_empty(ms->ms_freeing));
VERIFY(range_tree_is_empty(ms->ms_checkpointing));
}
}
return (B_TRUE);
}
#endif
void
dsl_pool_sync(dsl_pool_t *dp, uint64_t txg)
{
zio_t *zio;
dmu_tx_t *tx;
dsl_dir_t *dd;
dsl_dataset_t *ds;
objset_t *mos = dp->dp_meta_objset;
list_t synced_datasets;
list_create(&synced_datasets, sizeof (dsl_dataset_t),
offsetof(dsl_dataset_t, ds_synced_link));
tx = dmu_tx_create_assigned(dp, txg);
/*
* Run all early sync tasks before writing out any dirty blocks.
* For more info on early sync tasks see block comment in
* dsl_early_sync_task().
*/
if (!txg_list_empty(&dp->dp_early_sync_tasks, txg)) {
dsl_sync_task_t *dst;
ASSERT3U(spa_sync_pass(dp->dp_spa), ==, 1);
while ((dst =
txg_list_remove(&dp->dp_early_sync_tasks, txg)) != NULL) {
ASSERT(dsl_early_sync_task_verify(dp, txg));
dsl_sync_task_sync(dst, tx);
}
ASSERT(dsl_early_sync_task_verify(dp, txg));
}
/*
* Write out all dirty blocks of dirty datasets.
*/
zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
while ((ds = txg_list_remove(&dp->dp_dirty_datasets, txg)) != NULL) {
/*
* We must not sync any non-MOS datasets twice, because
* we may have taken a snapshot of them. However, we
* may sync newly-created datasets on pass 2.
*/
ASSERT(!list_link_active(&ds->ds_synced_link));
list_insert_tail(&synced_datasets, ds);
dsl_dataset_sync(ds, zio, tx);
}
VERIFY0(zio_wait(zio));
/*
* Update the long range free counter after
* we're done syncing user data
*/
mutex_enter(&dp->dp_lock);
ASSERT(spa_sync_pass(dp->dp_spa) == 1 ||
dp->dp_long_free_dirty_pertxg[txg & TXG_MASK] == 0);
dp->dp_long_free_dirty_pertxg[txg & TXG_MASK] = 0;
mutex_exit(&dp->dp_lock);
/*
* After the data blocks have been written (ensured by the zio_wait()
* above), update the user/group/project space accounting. This happens
* in tasks dispatched to dp_sync_taskq, so wait for them before
* continuing.
*/
for (ds = list_head(&synced_datasets); ds != NULL;
ds = list_next(&synced_datasets, ds)) {
dmu_objset_do_userquota_updates(ds->ds_objset, tx);
}
taskq_wait(dp->dp_sync_taskq);
/*
* Sync the datasets again to push out the changes due to
* userspace updates. This must be done before we process the
* sync tasks, so that any snapshots will have the correct
* user accounting information (and we won't get confused
* about which blocks are part of the snapshot).
*/
zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
while ((ds = txg_list_remove(&dp->dp_dirty_datasets, txg)) != NULL) {
objset_t *os = ds->ds_objset;
ASSERT(list_link_active(&ds->ds_synced_link));
dmu_buf_rele(ds->ds_dbuf, ds);
dsl_dataset_sync(ds, zio, tx);
/*
* Release any key mappings created by calls to
* dsl_dataset_dirty() from the userquota accounting
* code paths.
*/
if (os->os_encrypted && !os->os_raw_receive &&
!os->os_next_write_raw[txg & TXG_MASK]) {
ASSERT3P(ds->ds_key_mapping, !=, NULL);
key_mapping_rele(dp->dp_spa, ds->ds_key_mapping, ds);
}
}
VERIFY0(zio_wait(zio));
/*
* Now that the datasets have been completely synced, we can
* clean up our in-memory structures accumulated while syncing:
*
* - move dead blocks from the pending deadlist and livelists
* to the on-disk versions
* - release hold from dsl_dataset_dirty()
* - release key mapping hold from dsl_dataset_dirty()
*/
while ((ds = list_remove_head(&synced_datasets)) != NULL) {
objset_t *os = ds->ds_objset;
if (os->os_encrypted && !os->os_raw_receive &&
!os->os_next_write_raw[txg & TXG_MASK]) {
ASSERT3P(ds->ds_key_mapping, !=, NULL);
key_mapping_rele(dp->dp_spa, ds->ds_key_mapping, ds);
}
dsl_dataset_sync_done(ds, tx);
}
while ((dd = txg_list_remove(&dp->dp_dirty_dirs, txg)) != NULL) {
dsl_dir_sync(dd, tx);
}
/*
* The MOS's space is accounted for in the pool/$MOS
* (dp_mos_dir). We can't modify the mos while we're syncing
* it, so we remember the deltas and apply them here.
*/
if (dp->dp_mos_used_delta != 0 || dp->dp_mos_compressed_delta != 0 ||
dp->dp_mos_uncompressed_delta != 0) {
dsl_dir_diduse_space(dp->dp_mos_dir, DD_USED_HEAD,
dp->dp_mos_used_delta,
dp->dp_mos_compressed_delta,
dp->dp_mos_uncompressed_delta, tx);
dp->dp_mos_used_delta = 0;
dp->dp_mos_compressed_delta = 0;
dp->dp_mos_uncompressed_delta = 0;
}
if (dmu_objset_is_dirty(mos, txg)) {
dsl_pool_sync_mos(dp, tx);
}
/*
* We have written all of the accounted dirty data, so our
* dp_space_towrite should now be zero. However, some seldom-used
* code paths do not adhere to this (e.g. dbuf_undirty()). Shore up
* the accounting of any dirtied space now.
*
* Note that, besides any dirty data from datasets, the amount of
* dirty data in the MOS is also accounted by the pool. Therefore,
* we want to do this cleanup after dsl_pool_sync_mos() so we don't
* attempt to update the accounting for the same dirty data twice.
* (i.e. at this point we only update the accounting for the space
* that we know that we "leaked").
*/
dsl_pool_undirty_space(dp, dp->dp_dirty_pertxg[txg & TXG_MASK], txg);
/*
* If we modify a dataset in the same txg that we want to destroy it,
* its dsl_dir's dd_dbuf will be dirty, and thus have a hold on it.
* dsl_dir_destroy_check() will fail if there are unexpected holds.
* Therefore, we want to sync the MOS (thus syncing the dd_dbuf
* and clearing the hold on it) before we process the sync_tasks.
* The MOS data dirtied by the sync_tasks will be synced on the next
* pass.
*/
if (!txg_list_empty(&dp->dp_sync_tasks, txg)) {
dsl_sync_task_t *dst;
/*
* No more sync tasks should have been added while we
* were syncing.
*/
ASSERT3U(spa_sync_pass(dp->dp_spa), ==, 1);
while ((dst = txg_list_remove(&dp->dp_sync_tasks, txg)) != NULL)
dsl_sync_task_sync(dst, tx);
}
dmu_tx_commit(tx);
DTRACE_PROBE2(dsl_pool_sync__done, dsl_pool_t *dp, dp, uint64_t, txg);
}
void
dsl_pool_sync_done(dsl_pool_t *dp, uint64_t txg)
{
zilog_t *zilog;
while ((zilog = txg_list_head(&dp->dp_dirty_zilogs, txg))) {
dsl_dataset_t *ds = dmu_objset_ds(zilog->zl_os);
/*
* We don't remove the zilog from the dp_dirty_zilogs
* list until after we've cleaned it. This ensures that
* callers of zilog_is_dirty() receive an accurate
* answer when they are racing with the spa sync thread.
*/
zil_clean(zilog, txg);
(void) txg_list_remove_this(&dp->dp_dirty_zilogs, zilog, txg);
ASSERT(!dmu_objset_is_dirty(zilog->zl_os, txg));
dmu_buf_rele(ds->ds_dbuf, zilog);
}
ASSERT(!dmu_objset_is_dirty(dp->dp_meta_objset, txg));
}
/*
* TRUE if the current thread is the tx_sync_thread or if we
* are being called from SPA context during pool initialization.
*/
int
dsl_pool_sync_context(dsl_pool_t *dp)
{
return (curthread == dp->dp_tx.tx_sync_thread ||
spa_is_initializing(dp->dp_spa) ||
taskq_member(dp->dp_sync_taskq, curthread));
}
/*
* This function returns the amount of allocatable space in the pool
* minus whatever space is currently reserved by ZFS for specific
* purposes. Specifically:
*
* 1] Any reserved SLOP space
* 2] Any space used by the checkpoint
* 3] Any space used for deferred frees
*
* The latter 2 are especially important because they are needed to
* rectify the SPA's and DMU's different understanding of how much space
* is used. Now the DMU is aware of that extra space tracked by the SPA
* without having to maintain a separate special dir (e.g similar to
* $MOS, $FREEING, and $LEAKED).
*
* Note: By deferred frees here, we mean the frees that were deferred
* in spa_sync() after sync pass 1 (spa_deferred_bpobj), and not the
* segments placed in ms_defer trees during metaslab_sync_done().
*/
uint64_t
dsl_pool_adjustedsize(dsl_pool_t *dp, zfs_space_check_t slop_policy)
{
spa_t *spa = dp->dp_spa;
uint64_t space, resv, adjustedsize;
uint64_t spa_deferred_frees =
spa->spa_deferred_bpobj.bpo_phys->bpo_bytes;
space = spa_get_dspace(spa)
- spa_get_checkpoint_space(spa) - spa_deferred_frees;
resv = spa_get_slop_space(spa);
switch (slop_policy) {
case ZFS_SPACE_CHECK_NORMAL:
break;
case ZFS_SPACE_CHECK_RESERVED:
resv >>= 1;
break;
case ZFS_SPACE_CHECK_EXTRA_RESERVED:
resv >>= 2;
break;
case ZFS_SPACE_CHECK_NONE:
resv = 0;
break;
default:
panic("invalid slop policy value: %d", slop_policy);
break;
}
adjustedsize = (space >= resv) ? (space - resv) : 0;
return (adjustedsize);
}
uint64_t
dsl_pool_unreserved_space(dsl_pool_t *dp, zfs_space_check_t slop_policy)
{
uint64_t poolsize = dsl_pool_adjustedsize(dp, slop_policy);
uint64_t deferred =
metaslab_class_get_deferred(spa_normal_class(dp->dp_spa));
uint64_t quota = (poolsize >= deferred) ? (poolsize - deferred) : 0;
return (quota);
}
boolean_t
dsl_pool_need_dirty_delay(dsl_pool_t *dp)
{
uint64_t delay_min_bytes =
zfs_dirty_data_max * zfs_delay_min_dirty_percent / 100;
uint64_t dirty_min_bytes =
zfs_dirty_data_max * zfs_dirty_data_sync_percent / 100;
uint64_t dirty;
mutex_enter(&dp->dp_lock);
dirty = dp->dp_dirty_total;
mutex_exit(&dp->dp_lock);
if (dirty > dirty_min_bytes)
txg_kick(dp);
return (dirty > delay_min_bytes);
}
void
dsl_pool_dirty_space(dsl_pool_t *dp, int64_t space, dmu_tx_t *tx)
{
if (space > 0) {
mutex_enter(&dp->dp_lock);
dp->dp_dirty_pertxg[tx->tx_txg & TXG_MASK] += space;
dsl_pool_dirty_delta(dp, space);
mutex_exit(&dp->dp_lock);
}
}
void
dsl_pool_undirty_space(dsl_pool_t *dp, int64_t space, uint64_t txg)
{
ASSERT3S(space, >=, 0);
if (space == 0)
return;
mutex_enter(&dp->dp_lock);
if (dp->dp_dirty_pertxg[txg & TXG_MASK] < space) {
/* XXX writing something we didn't dirty? */
space = dp->dp_dirty_pertxg[txg & TXG_MASK];
}
ASSERT3U(dp->dp_dirty_pertxg[txg & TXG_MASK], >=, space);
dp->dp_dirty_pertxg[txg & TXG_MASK] -= space;
ASSERT3U(dp->dp_dirty_total, >=, space);
dsl_pool_dirty_delta(dp, -space);
mutex_exit(&dp->dp_lock);
}
/* ARGSUSED */
static int
upgrade_clones_cb(dsl_pool_t *dp, dsl_dataset_t *hds, void *arg)
{
dmu_tx_t *tx = arg;
dsl_dataset_t *ds, *prev = NULL;
int err;
err = dsl_dataset_hold_obj(dp, hds->ds_object, FTAG, &ds);
if (err)
return (err);
while (dsl_dataset_phys(ds)->ds_prev_snap_obj != 0) {
err = dsl_dataset_hold_obj(dp,
dsl_dataset_phys(ds)->ds_prev_snap_obj, FTAG, &prev);
if (err) {
dsl_dataset_rele(ds, FTAG);
return (err);
}
if (dsl_dataset_phys(prev)->ds_next_snap_obj != ds->ds_object)
break;
dsl_dataset_rele(ds, FTAG);
ds = prev;
prev = NULL;
}
if (prev == NULL) {
prev = dp->dp_origin_snap;
/*
* The $ORIGIN can't have any data, or the accounting
* will be wrong.
*/
rrw_enter(&ds->ds_bp_rwlock, RW_READER, FTAG);
ASSERT0(dsl_dataset_phys(prev)->ds_bp.blk_birth);
rrw_exit(&ds->ds_bp_rwlock, FTAG);
/* The origin doesn't get attached to itself */
if (ds->ds_object == prev->ds_object) {
dsl_dataset_rele(ds, FTAG);
return (0);
}
dmu_buf_will_dirty(ds->ds_dbuf, tx);
dsl_dataset_phys(ds)->ds_prev_snap_obj = prev->ds_object;
dsl_dataset_phys(ds)->ds_prev_snap_txg =
dsl_dataset_phys(prev)->ds_creation_txg;
dmu_buf_will_dirty(ds->ds_dir->dd_dbuf, tx);
dsl_dir_phys(ds->ds_dir)->dd_origin_obj = prev->ds_object;
dmu_buf_will_dirty(prev->ds_dbuf, tx);
dsl_dataset_phys(prev)->ds_num_children++;
if (dsl_dataset_phys(ds)->ds_next_snap_obj == 0) {
ASSERT(ds->ds_prev == NULL);
VERIFY0(dsl_dataset_hold_obj(dp,
dsl_dataset_phys(ds)->ds_prev_snap_obj,
ds, &ds->ds_prev));
}
}
ASSERT3U(dsl_dir_phys(ds->ds_dir)->dd_origin_obj, ==, prev->ds_object);
ASSERT3U(dsl_dataset_phys(ds)->ds_prev_snap_obj, ==, prev->ds_object);
if (dsl_dataset_phys(prev)->ds_next_clones_obj == 0) {
dmu_buf_will_dirty(prev->ds_dbuf, tx);
dsl_dataset_phys(prev)->ds_next_clones_obj =
zap_create(dp->dp_meta_objset,
DMU_OT_NEXT_CLONES, DMU_OT_NONE, 0, tx);
}
VERIFY0(zap_add_int(dp->dp_meta_objset,
dsl_dataset_phys(prev)->ds_next_clones_obj, ds->ds_object, tx));
dsl_dataset_rele(ds, FTAG);
if (prev != dp->dp_origin_snap)
dsl_dataset_rele(prev, FTAG);
return (0);
}
void
dsl_pool_upgrade_clones(dsl_pool_t *dp, dmu_tx_t *tx)
{
ASSERT(dmu_tx_is_syncing(tx));
ASSERT(dp->dp_origin_snap != NULL);
VERIFY0(dmu_objset_find_dp(dp, dp->dp_root_dir_obj, upgrade_clones_cb,
tx, DS_FIND_CHILDREN | DS_FIND_SERIALIZE));
}
/* ARGSUSED */
static int
upgrade_dir_clones_cb(dsl_pool_t *dp, dsl_dataset_t *ds, void *arg)
{
dmu_tx_t *tx = arg;
objset_t *mos = dp->dp_meta_objset;
if (dsl_dir_phys(ds->ds_dir)->dd_origin_obj != 0) {
dsl_dataset_t *origin;
VERIFY0(dsl_dataset_hold_obj(dp,
dsl_dir_phys(ds->ds_dir)->dd_origin_obj, FTAG, &origin));
if (dsl_dir_phys(origin->ds_dir)->dd_clones == 0) {
dmu_buf_will_dirty(origin->ds_dir->dd_dbuf, tx);
dsl_dir_phys(origin->ds_dir)->dd_clones =
zap_create(mos, DMU_OT_DSL_CLONES, DMU_OT_NONE,
0, tx);
}
VERIFY0(zap_add_int(dp->dp_meta_objset,
dsl_dir_phys(origin->ds_dir)->dd_clones,
ds->ds_object, tx));
dsl_dataset_rele(origin, FTAG);
}
return (0);
}
void
dsl_pool_upgrade_dir_clones(dsl_pool_t *dp, dmu_tx_t *tx)
{
uint64_t obj;
ASSERT(dmu_tx_is_syncing(tx));
(void) dsl_dir_create_sync(dp, dp->dp_root_dir, FREE_DIR_NAME, tx);
VERIFY0(dsl_pool_open_special_dir(dp,
FREE_DIR_NAME, &dp->dp_free_dir));
/*
* We can't use bpobj_alloc(), because spa_version() still
* returns the old version, and we need a new-version bpobj with
* subobj support. So call dmu_object_alloc() directly.
*/
obj = dmu_object_alloc(dp->dp_meta_objset, DMU_OT_BPOBJ,
SPA_OLD_MAXBLOCKSIZE, DMU_OT_BPOBJ_HDR, sizeof (bpobj_phys_t), tx);
VERIFY0(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj, tx));
VERIFY0(bpobj_open(&dp->dp_free_bpobj, dp->dp_meta_objset, obj));
VERIFY0(dmu_objset_find_dp(dp, dp->dp_root_dir_obj,
upgrade_dir_clones_cb, tx, DS_FIND_CHILDREN | DS_FIND_SERIALIZE));
}
void
dsl_pool_create_origin(dsl_pool_t *dp, dmu_tx_t *tx)
{
uint64_t dsobj;
dsl_dataset_t *ds;
ASSERT(dmu_tx_is_syncing(tx));
ASSERT(dp->dp_origin_snap == NULL);
ASSERT(rrw_held(&dp->dp_config_rwlock, RW_WRITER));
/* create the origin dir, ds, & snap-ds */
dsobj = dsl_dataset_create_sync(dp->dp_root_dir, ORIGIN_DIR_NAME,
NULL, 0, kcred, NULL, tx);
VERIFY0(dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds));
dsl_dataset_snapshot_sync_impl(ds, ORIGIN_DIR_NAME, tx);
VERIFY0(dsl_dataset_hold_obj(dp, dsl_dataset_phys(ds)->ds_prev_snap_obj,
dp, &dp->dp_origin_snap));
dsl_dataset_rele(ds, FTAG);
}
taskq_t *
dsl_pool_iput_taskq(dsl_pool_t *dp)
{
return (dp->dp_iput_taskq);
}
taskq_t *
dsl_pool_unlinked_drain_taskq(dsl_pool_t *dp)
{
return (dp->dp_unlinked_drain_taskq);
}
/*
* Walk through the pool-wide zap object of temporary snapshot user holds
* and release them.
*/
void
dsl_pool_clean_tmp_userrefs(dsl_pool_t *dp)
{
zap_attribute_t za;
zap_cursor_t zc;
objset_t *mos = dp->dp_meta_objset;
uint64_t zapobj = dp->dp_tmp_userrefs_obj;
nvlist_t *holds;
if (zapobj == 0)
return;
ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS);
holds = fnvlist_alloc();
for (zap_cursor_init(&zc, mos, zapobj);
zap_cursor_retrieve(&zc, &za) == 0;
zap_cursor_advance(&zc)) {
char *htag;
nvlist_t *tags;
htag = strchr(za.za_name, '-');
*htag = '\0';
++htag;
if (nvlist_lookup_nvlist(holds, za.za_name, &tags) != 0) {
tags = fnvlist_alloc();
fnvlist_add_boolean(tags, htag);
fnvlist_add_nvlist(holds, za.za_name, tags);
fnvlist_free(tags);
} else {
fnvlist_add_boolean(tags, htag);
}
}
dsl_dataset_user_release_tmp(dp, holds);
fnvlist_free(holds);
zap_cursor_fini(&zc);
}
/*
* Create the pool-wide zap object for storing temporary snapshot holds.
*/
void
dsl_pool_user_hold_create_obj(dsl_pool_t *dp, dmu_tx_t *tx)
{
objset_t *mos = dp->dp_meta_objset;
ASSERT(dp->dp_tmp_userrefs_obj == 0);
ASSERT(dmu_tx_is_syncing(tx));
dp->dp_tmp_userrefs_obj = zap_create_link(mos, DMU_OT_USERREFS,
DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_TMP_USERREFS, tx);
}
static int
dsl_pool_user_hold_rele_impl(dsl_pool_t *dp, uint64_t dsobj,
const char *tag, uint64_t now, dmu_tx_t *tx, boolean_t holding)
{
objset_t *mos = dp->dp_meta_objset;
uint64_t zapobj = dp->dp_tmp_userrefs_obj;
char *name;
int error;
ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS);
ASSERT(dmu_tx_is_syncing(tx));
/*
* If the pool was created prior to SPA_VERSION_USERREFS, the
* zap object for temporary holds might not exist yet.
*/
if (zapobj == 0) {
if (holding) {
dsl_pool_user_hold_create_obj(dp, tx);
zapobj = dp->dp_tmp_userrefs_obj;
} else {
return (SET_ERROR(ENOENT));
}
}
name = kmem_asprintf("%llx-%s", (u_longlong_t)dsobj, tag);
if (holding)
error = zap_add(mos, zapobj, name, 8, 1, &now, tx);
else
error = zap_remove(mos, zapobj, name, tx);
strfree(name);
return (error);
}
/*
* Add a temporary hold for the given dataset object and tag.
*/
int
dsl_pool_user_hold(dsl_pool_t *dp, uint64_t dsobj, const char *tag,
uint64_t now, dmu_tx_t *tx)
{
return (dsl_pool_user_hold_rele_impl(dp, dsobj, tag, now, tx, B_TRUE));
}
/*
* Release a temporary hold for the given dataset object and tag.
*/
int
dsl_pool_user_release(dsl_pool_t *dp, uint64_t dsobj, const char *tag,
dmu_tx_t *tx)
{
return (dsl_pool_user_hold_rele_impl(dp, dsobj, tag, 0,
tx, B_FALSE));
}
/*
* DSL Pool Configuration Lock
*
* The dp_config_rwlock protects against changes to DSL state (e.g. dataset
* creation / destruction / rename / property setting). It must be held for
* read to hold a dataset or dsl_dir. I.e. you must call
* dsl_pool_config_enter() or dsl_pool_hold() before calling
* dsl_{dataset,dir}_hold{_obj}. In most circumstances, the dp_config_rwlock
* must be held continuously until all datasets and dsl_dirs are released.
*
* The only exception to this rule is that if a "long hold" is placed on
* a dataset, then the dp_config_rwlock may be dropped while the dataset
* is still held. The long hold will prevent the dataset from being
* destroyed -- the destroy will fail with EBUSY. A long hold can be
* obtained by calling dsl_dataset_long_hold(), or by "owning" a dataset
* (by calling dsl_{dataset,objset}_{try}own{_obj}).
*
* Legitimate long-holders (including owners) should be long-running, cancelable
* tasks that should cause "zfs destroy" to fail. This includes DMU
* consumers (i.e. a ZPL filesystem being mounted or ZVOL being open),
* "zfs send", and "zfs diff". There are several other long-holders whose
* uses are suboptimal (e.g. "zfs promote", and zil_suspend()).
*
* The usual formula for long-holding would be:
* dsl_pool_hold()
* dsl_dataset_hold()
* ... perform checks ...
* dsl_dataset_long_hold()
* dsl_pool_rele()
* ... perform long-running task ...
* dsl_dataset_long_rele()
* dsl_dataset_rele()
*
* Note that when the long hold is released, the dataset is still held but
* the pool is not held. The dataset may change arbitrarily during this time
* (e.g. it could be destroyed). Therefore you shouldn't do anything to the
* dataset except release it.
*
* User-initiated operations (e.g. ioctls, zfs_ioc_*()) are either read-only
* or modifying operations.
*
* Modifying operations should generally use dsl_sync_task(). The synctask
* infrastructure enforces proper locking strategy with respect to the
* dp_config_rwlock. See the comment above dsl_sync_task() for details.
*
* Read-only operations will manually hold the pool, then the dataset, obtain
* information from the dataset, then release the pool and dataset.
* dmu_objset_{hold,rele}() are convenience routines that also do the pool
* hold/rele.
*/
int
dsl_pool_hold(const char *name, void *tag, dsl_pool_t **dp)
{
spa_t *spa;
int error;
error = spa_open(name, &spa, tag);
if (error == 0) {
*dp = spa_get_dsl(spa);
dsl_pool_config_enter(*dp, tag);
}
return (error);
}
void
dsl_pool_rele(dsl_pool_t *dp, void *tag)
{
dsl_pool_config_exit(dp, tag);
spa_close(dp->dp_spa, tag);
}
void
dsl_pool_config_enter(dsl_pool_t *dp, void *tag)
{
/*
* We use a "reentrant" reader-writer lock, but not reentrantly.
*
* The rrwlock can (with the track_all flag) track all reading threads,
* which is very useful for debugging which code path failed to release
* the lock, and for verifying that the *current* thread does hold
* the lock.
*
* (Unlike a rwlock, which knows that N threads hold it for
* read, but not *which* threads, so rw_held(RW_READER) returns TRUE
* if any thread holds it for read, even if this thread doesn't).
*/
ASSERT(!rrw_held(&dp->dp_config_rwlock, RW_READER));
rrw_enter(&dp->dp_config_rwlock, RW_READER, tag);
}
void
dsl_pool_config_enter_prio(dsl_pool_t *dp, void *tag)
{
ASSERT(!rrw_held(&dp->dp_config_rwlock, RW_READER));
rrw_enter_read_prio(&dp->dp_config_rwlock, tag);
}
void
dsl_pool_config_exit(dsl_pool_t *dp, void *tag)
{
rrw_exit(&dp->dp_config_rwlock, tag);
}
boolean_t
dsl_pool_config_held(dsl_pool_t *dp)
{
return (RRW_LOCK_HELD(&dp->dp_config_rwlock));
}
boolean_t
dsl_pool_config_held_writer(dsl_pool_t *dp)
{
return (RRW_WRITE_HELD(&dp->dp_config_rwlock));
}
#if defined(_KERNEL)
EXPORT_SYMBOL(dsl_pool_config_enter);
EXPORT_SYMBOL(dsl_pool_config_exit);
/* BEGIN CSTYLED */
/* zfs_dirty_data_max_percent only applied at module load in arc_init(). */
module_param(zfs_dirty_data_max_percent, int, 0444);
MODULE_PARM_DESC(zfs_dirty_data_max_percent, "percent of ram can be dirty");
/* zfs_dirty_data_max_max_percent only applied at module load in arc_init(). */
module_param(zfs_dirty_data_max_max_percent, int, 0444);
MODULE_PARM_DESC(zfs_dirty_data_max_max_percent,
"zfs_dirty_data_max upper bound as % of RAM");
module_param(zfs_delay_min_dirty_percent, int, 0644);
MODULE_PARM_DESC(zfs_delay_min_dirty_percent, "transaction delay threshold");
module_param(zfs_dirty_data_max, ulong, 0644);
MODULE_PARM_DESC(zfs_dirty_data_max, "determines the dirty space limit");
/* zfs_dirty_data_max_max only applied at module load in arc_init(). */
module_param(zfs_dirty_data_max_max, ulong, 0444);
MODULE_PARM_DESC(zfs_dirty_data_max_max,
"zfs_dirty_data_max upper bound in bytes");
module_param(zfs_dirty_data_sync_percent, int, 0644);
MODULE_PARM_DESC(zfs_dirty_data_sync_percent,
"dirty data txg sync threshold as a percentage of zfs_dirty_data_max");
module_param(zfs_delay_scale, ulong, 0644);
MODULE_PARM_DESC(zfs_delay_scale, "how quickly delay approaches infinity");
module_param(zfs_sync_taskq_batch_pct, int, 0644);
MODULE_PARM_DESC(zfs_sync_taskq_batch_pct,
"max percent of CPUs that are used to sync dirty data");
module_param(zfs_zil_clean_taskq_nthr_pct, int, 0644);
MODULE_PARM_DESC(zfs_zil_clean_taskq_nthr_pct,
"max percent of CPUs that are used per dp_sync_taskq");
module_param(zfs_zil_clean_taskq_minalloc, int, 0644);
MODULE_PARM_DESC(zfs_zil_clean_taskq_minalloc,
"number of taskq entries that are pre-populated");
module_param(zfs_zil_clean_taskq_maxalloc, int, 0644);
MODULE_PARM_DESC(zfs_zil_clean_taskq_maxalloc,
"max number of taskq entries that are cached");
/* END CSTYLED */
#endif
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