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Optimize creation and removal of temporary "user holds" placed on
snapshots by a zfs send, by ensuring all the required holds and
releases are done in a single dsl_sync_task.
Creation now collates the required holds during a dry run and
then uses a single lzc_hold call via zfs_hold_apply instead of
processing each snapshot in turn.
Defered (on exit) cleanup by the kernel is also now done in
dsl_sync_task by reusing dsl_dataset_user_release.
On a test with 11 volumes in a tree each with 8 snapshots on a
single HDD zpool this reduces the time required to perform a full
send from 20 seconds to under 0.8 seconds.
For reference eliminating the hold entirely reduces this 0.15
seconds.
While I'm here:-
* Remove some unused structures
* Fix nvlist_t leak in zfs_release_one
*** 145,155 ****
VERIFY0(zap_add(mos, zapobj, htag, 8, 1, &now, tx));
if (minor != 0) {
VERIFY0(dsl_pool_user_hold(dp, ds->ds_object,
htag, now, tx));
- dsl_register_onexit_hold_cleanup(ds, htag, minor);
}
spa_history_log_internal_ds(ds, "hold", tx,
"tag=%s temp=%d refs=%llu",
htag, minor != 0, ds->ds_userrefs);
--- 145,154 ----
*** 164,173 ****
--- 163,173 ----
uint64_t now = gethrestime_sec();
for (pair = nvlist_next_nvpair(dduha->dduha_holds, NULL); pair != NULL;
pair = nvlist_next_nvpair(dduha->dduha_holds, pair)) {
dsl_dataset_t *ds;
+
VERIFY0(dsl_dataset_hold(dp, nvpair_name(pair), FTAG, &ds));
dsl_dataset_user_hold_sync_one(ds, fnvpair_value_string(pair),
dduha->dduha_minor, now, tx);
dsl_dataset_rele(ds, FTAG);
}
*** 184,204 ****
int
dsl_dataset_user_hold(nvlist_t *holds, minor_t cleanup_minor, nvlist_t *errlist)
{
dsl_dataset_user_hold_arg_t dduha;
nvpair_t *pair;
pair = nvlist_next_nvpair(holds, NULL);
if (pair == NULL)
return (0);
dduha.dduha_holds = holds;
dduha.dduha_errlist = errlist;
dduha.dduha_minor = cleanup_minor;
! return (dsl_sync_task(nvpair_name(pair), dsl_dataset_user_hold_check,
! dsl_dataset_user_hold_sync, &dduha, fnvlist_num_pairs(holds)));
}
typedef struct dsl_dataset_user_release_arg {
nvlist_t *ddura_holds;
nvlist_t *ddura_todelete;
--- 184,209 ----
int
dsl_dataset_user_hold(nvlist_t *holds, minor_t cleanup_minor, nvlist_t *errlist)
{
dsl_dataset_user_hold_arg_t dduha;
nvpair_t *pair;
+ int ret;
pair = nvlist_next_nvpair(holds, NULL);
if (pair == NULL)
return (0);
dduha.dduha_holds = holds;
dduha.dduha_errlist = errlist;
dduha.dduha_minor = cleanup_minor;
! ret = dsl_sync_task(nvpair_name(pair), dsl_dataset_user_hold_check,
! dsl_dataset_user_hold_sync, &dduha, fnvlist_num_pairs(holds));
! if (ret == 0)
! dsl_register_onexit_hold_cleanup(holds, cleanup_minor);
!
! return (ret);
}
typedef struct dsl_dataset_user_release_arg {
nvlist_t *ddura_holds;
nvlist_t *ddura_todelete;
*** 349,502 ****
*/
int
dsl_dataset_user_release(nvlist_t *holds, nvlist_t *errlist)
{
dsl_dataset_user_release_arg_t ddura;
! nvpair_t *pair;
int error;
pair = nvlist_next_nvpair(holds, NULL);
if (pair == NULL)
return (0);
ddura.ddura_holds = holds;
ddura.ddura_errlist = errlist;
ddura.ddura_todelete = fnvlist_alloc();
error = dsl_sync_task(nvpair_name(pair), dsl_dataset_user_release_check,
dsl_dataset_user_release_sync, &ddura, fnvlist_num_pairs(holds));
fnvlist_free(ddura.ddura_todelete);
return (error);
}
- typedef struct dsl_dataset_user_release_tmp_arg {
- uint64_t ddurta_dsobj;
- nvlist_t *ddurta_holds;
- boolean_t ddurta_deleteme;
- } dsl_dataset_user_release_tmp_arg_t;
-
- static int
- dsl_dataset_user_release_tmp_check(void *arg, dmu_tx_t *tx)
- {
- dsl_dataset_user_release_tmp_arg_t *ddurta = arg;
- dsl_pool_t *dp = dmu_tx_pool(tx);
- dsl_dataset_t *ds;
- int error;
-
- if (!dmu_tx_is_syncing(tx))
- return (0);
-
- error = dsl_dataset_hold_obj(dp, ddurta->ddurta_dsobj, FTAG, &ds);
- if (error)
- return (error);
-
- error = dsl_dataset_user_release_check_one(ds,
- ddurta->ddurta_holds, &ddurta->ddurta_deleteme);
- dsl_dataset_rele(ds, FTAG);
- return (error);
- }
-
static void
! dsl_dataset_user_release_tmp_sync(void *arg, dmu_tx_t *tx)
{
! dsl_dataset_user_release_tmp_arg_t *ddurta = arg;
! dsl_pool_t *dp = dmu_tx_pool(tx);
! dsl_dataset_t *ds;
! VERIFY0(dsl_dataset_hold_obj(dp, ddurta->ddurta_dsobj, FTAG, &ds));
! dsl_dataset_user_release_sync_one(ds, ddurta->ddurta_holds, tx);
! if (ddurta->ddurta_deleteme) {
! ASSERT(ds->ds_userrefs == 0 &&
! ds->ds_phys->ds_num_children == 1 &&
! DS_IS_DEFER_DESTROY(ds));
! dsl_destroy_snapshot_sync_impl(ds, B_FALSE, tx);
! }
! dsl_dataset_rele(ds, FTAG);
}
- /*
- * Called at spa_load time to release a stale temporary user hold.
- * Also called by the onexit code.
- */
void
! dsl_dataset_user_release_tmp(dsl_pool_t *dp, uint64_t dsobj, const char *htag)
! {
! dsl_dataset_user_release_tmp_arg_t ddurta;
! dsl_dataset_t *ds;
! int error;
!
! #ifdef _KERNEL
! /* Make sure it is not mounted. */
! dsl_pool_config_enter(dp, FTAG);
! error = dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds);
! if (error == 0) {
! char name[MAXNAMELEN];
! dsl_dataset_name(ds, name);
! dsl_dataset_rele(ds, FTAG);
! dsl_pool_config_exit(dp, FTAG);
! zfs_unmount_snap(name);
! } else {
! dsl_pool_config_exit(dp, FTAG);
! }
! #endif
!
! ddurta.ddurta_dsobj = dsobj;
! ddurta.ddurta_holds = fnvlist_alloc();
! fnvlist_add_boolean(ddurta.ddurta_holds, htag);
!
! (void) dsl_sync_task(spa_name(dp->dp_spa),
! dsl_dataset_user_release_tmp_check,
! dsl_dataset_user_release_tmp_sync, &ddurta, 1);
! fnvlist_free(ddurta.ddurta_holds);
! }
!
! typedef struct zfs_hold_cleanup_arg {
! char zhca_spaname[MAXNAMELEN];
! uint64_t zhca_spa_load_guid;
! uint64_t zhca_dsobj;
! char zhca_htag[MAXNAMELEN];
! } zfs_hold_cleanup_arg_t;
!
! static void
! dsl_dataset_user_release_onexit(void *arg)
{
! zfs_hold_cleanup_arg_t *ca = arg;
! spa_t *spa;
! int error;
! error = spa_open(ca->zhca_spaname, &spa, FTAG);
! if (error != 0) {
! zfs_dbgmsg("couldn't release hold on pool=%s ds=%llu tag=%s "
! "because pool is no longer loaded",
! ca->zhca_spaname, ca->zhca_dsobj, ca->zhca_htag);
! return;
! }
! if (spa_load_guid(spa) != ca->zhca_spa_load_guid) {
! zfs_dbgmsg("couldn't release hold on pool=%s ds=%llu tag=%s "
! "because pool is no longer loaded (guid doesn't match)",
! ca->zhca_spaname, ca->zhca_dsobj, ca->zhca_htag);
! spa_close(spa, FTAG);
! return;
! }
!
! dsl_dataset_user_release_tmp(spa_get_dsl(spa),
! ca->zhca_dsobj, ca->zhca_htag);
! kmem_free(ca, sizeof (zfs_hold_cleanup_arg_t));
! spa_close(spa, FTAG);
! }
! void
! dsl_register_onexit_hold_cleanup(dsl_dataset_t *ds, const char *htag,
! minor_t minor)
! {
! zfs_hold_cleanup_arg_t *ca = kmem_alloc(sizeof (*ca), KM_SLEEP);
! spa_t *spa = dsl_dataset_get_spa(ds);
! (void) strlcpy(ca->zhca_spaname, spa_name(spa),
! sizeof (ca->zhca_spaname));
! ca->zhca_spa_load_guid = spa_load_guid(spa);
! ca->zhca_dsobj = ds->ds_object;
! (void) strlcpy(ca->zhca_htag, htag, sizeof (ca->zhca_htag));
VERIFY0(zfs_onexit_add_cb(minor,
dsl_dataset_user_release_onexit, ca, NULL));
}
int
--- 354,423 ----
*/
int
dsl_dataset_user_release(nvlist_t *holds, nvlist_t *errlist)
{
dsl_dataset_user_release_arg_t ddura;
! nvpair_t *pair, *pair2;
int error;
pair = nvlist_next_nvpair(holds, NULL);
if (pair == NULL)
return (0);
+ #ifdef _KERNEL
+ /*
+ * The release may cause the snapshot to be destroyed; make sure it
+ * is not mounted.
+ */
+ for (pair2 = pair; pair2 != NULL;
+ pair2 = nvlist_next_nvpair(holds, pair2)) {
+ zfs_unmount_snap(nvpair_name(pair2));
+ }
+ #endif
+
ddura.ddura_holds = holds;
ddura.ddura_errlist = errlist;
ddura.ddura_todelete = fnvlist_alloc();
error = dsl_sync_task(nvpair_name(pair), dsl_dataset_user_release_check,
dsl_dataset_user_release_sync, &ddura, fnvlist_num_pairs(holds));
fnvlist_free(ddura.ddura_todelete);
return (error);
}
static void
! dsl_dataset_user_release_onexit(void *arg)
{
! nvlist_t *holds = arg;
! (void) dsl_dataset_user_release(holds, NULL);
! fnvlist_free(holds);
}
void
! dsl_register_onexit_hold_cleanup(nvlist_t *holds, minor_t minor)
{
! nvlist_t *ca;
! nvpair_t *pair;
! char *htag;
! ca = fnvlist_alloc();
! /*
! * Convert from hold format: nvl of snapname -> holdname
! * to release format: nvl of snapname -> { holdname, ... }
! */
! for (pair = nvlist_next_nvpair(holds, NULL); pair != NULL;
! pair = nvlist_next_nvpair(holds, pair)) {
! if (nvpair_value_string(pair, &htag) == 0) {
! nvlist_t *tags;
! tags = fnvlist_alloc();
! fnvlist_add_boolean(tags, htag);
! fnvlist_add_nvlist(ca, nvpair_name(pair), tags);
! fnvlist_free(tags);
! }
! }
VERIFY0(zfs_onexit_add_cb(minor,
dsl_dataset_user_release_onexit, ca, NULL));
}
int