kernel/fs/zfs/dsl_synctask.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  23  * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
  24  */
  25
  26 #include <sys/dmu.h>
  27 #include <sys/dmu_tx.h>
  28 #include <sys/dsl_pool.h>
  29 #include <sys/dsl_dir.h>
  30 #include <sys/dsl_synctask.h>
  31 #include <sys/metaslab.h>
  32
  33 #define DST_AVG_BLKSHIFT 14
  34
  35 /* ARGSUSED */
  36 static int
  37 dsl_null_checkfunc(void *arg, dmu_tx_t *tx)
  38 {
  39         return (0);
  40 }
  41
  42 /*
  43  * Called from open context to perform a callback in syncing context.  Waits
  44  * for the operation to complete.
  45  *
  46  * The checkfunc will be called from open context as a preliminary check
  47  * which can quickly fail.  If it succeeds, it will be called again from
  48  * syncing context.  The checkfunc should generally be designed to work
  49  * properly in either context, but if necessary it can check
  50  * dmu_tx_is_syncing(tx).
  51  *
  52  * The synctask infrastructure enforces proper locking strategy with respect
  53  * to the dp_config_rwlock -- the lock will always be held when the callbacks
  54  * are called.  It will be held for read during the open-context (preliminary)
  55  * call to the checkfunc, and then held for write from syncing context during
  56  * the calls to the check and sync funcs.
  57  *
  58  * A dataset or pool name can be passed as the first argument.  Typically,
  59  * the check func will hold, check the return value of the hold, and then
  60  * release the dataset.  The sync func will VERIFYO(hold()) the dataset.
  61  * This is safe because no changes can be made between the check and sync funcs,
  62  * and the sync func will only be called if the check func successfully opened
  63  * the dataset.
  64  */
  65 int
  66 dsl_sync_task(const char *pool, dsl_checkfunc_t *checkfunc,
  67     dsl_syncfunc_t *syncfunc, void *arg,
  68     int blocks_modified, zfs_space_check_t space_check)
  69 {
  70         spa_t *spa;
  71         dmu_tx_t *tx;
  72         int err;
  73         dsl_sync_task_t dst = { 0 };
  74         dsl_pool_t *dp;
  75
  76         err = spa_open(pool, &spa, FTAG);
  77         if (err != 0)
  78                 return (err);
  79         dp = spa_get_dsl(spa);
  80
  81 top:
  82         tx = dmu_tx_create_dd(dp->dp_mos_dir);
  83         VERIFY0(dmu_tx_assign(tx, TXG_WAIT));
  84
  85         dst.dst_pool = dp;
  86         dst.dst_txg = dmu_tx_get_txg(tx);
  87         dst.dst_space = blocks_modified << DST_AVG_BLKSHIFT;
  88         dst.dst_space_check = space_check;
  89         dst.dst_checkfunc = checkfunc != NULL ? checkfunc : dsl_null_checkfunc;
  90         dst.dst_syncfunc = syncfunc;
  91         dst.dst_arg = arg;
  92         dst.dst_error = 0;
  93         dst.dst_nowaiter = B_FALSE;
  94
  95         dsl_pool_config_enter(dp, FTAG);
  96         err = dst.dst_checkfunc(arg, tx);
  97         dsl_pool_config_exit(dp, FTAG);
  98
  99         if (err != 0) {
 100                 dmu_tx_commit(tx);
 101                 spa_close(spa, FTAG);
 102                 return (err);
 103         }
 104
 105         VERIFY(txg_list_add_tail(&dp->dp_sync_tasks, &dst, dst.dst_txg));
 106
 107         dmu_tx_commit(tx);
 108
 109         txg_wait_synced(dp, dst.dst_txg);
 110
 111         if (dst.dst_error == EAGAIN) {
 112                 txg_wait_synced(dp, dst.dst_txg + TXG_DEFER_SIZE);
 113                 goto top;
 114         }
 115
 116         spa_close(spa, FTAG);
 117         return (dst.dst_error);
 118 }
 119
 120 void
 121 dsl_sync_task_nowait(dsl_pool_t *dp, dsl_syncfunc_t *syncfunc, void *arg,
 122     int blocks_modified, zfs_space_check_t space_check, dmu_tx_t *tx)
 123 {
 124         dsl_sync_task_t *dst = kmem_zalloc(sizeof (*dst), KM_SLEEP);
 125
 126         dst->dst_pool = dp;
 127         dst->dst_txg = dmu_tx_get_txg(tx);
 128         dst->dst_space = blocks_modified << DST_AVG_BLKSHIFT;
 129         dst->dst_space_check = space_check;
 130         dst->dst_checkfunc = dsl_null_checkfunc;
 131         dst->dst_syncfunc = syncfunc;
 132         dst->dst_arg = arg;
 133         dst->dst_error = 0;
 134         dst->dst_nowaiter = B_TRUE;
 135
 136         VERIFY(txg_list_add_tail(&dp->dp_sync_tasks, dst, dst->dst_txg));
 137 }
 138
 139 /*
 140  * Called in syncing context to execute the synctask.
 141  */
 142 void
 143 dsl_sync_task_sync(dsl_sync_task_t *dst, dmu_tx_t *tx)
 144 {
 145         dsl_pool_t *dp = dst->dst_pool;
 146
 147         ASSERT0(dst->dst_error);
 148
 149         /*
 150          * Check for sufficient space.
 151          *
 152          * When the sync task was created, the caller specified the
 153          * type of space checking required.  See the comment in
 154          * zfs_space_check_t for details on the semantics of each
 155          * type of space checking.
 156          *
 157          * We just check against what's on-disk; we don't want any
 158          * in-flight accounting to get in our way, because open context
 159          * may have already used up various in-core limits
 160          * (arc_tempreserve, dsl_pool_tempreserve).
 161          */
 162         if (dst->dst_space_check != ZFS_SPACE_CHECK_NONE) {
 163                 uint64_t quota = dsl_pool_adjustedsize(dp,
 164                     dst->dst_space_check == ZFS_SPACE_CHECK_RESERVED) -
 165                     metaslab_class_get_deferred(spa_normal_class(dp->dp_spa));
 166                 uint64_t used = dsl_dir_phys(dp->dp_root_dir)->dd_used_bytes;
 167                 /* MOS space is triple-dittoed, so we multiply by 3. */
 168                 if (dst->dst_space > 0 && used + dst->dst_space * 3 > quota) {
 169                         dst->dst_error = SET_ERROR(ENOSPC);
 170                         if (dst->dst_nowaiter)
 171                                 kmem_free(dst, sizeof (*dst));
 172                         return;
 173                 }
 174         }
 175
 176         /*
 177          * Check for errors by calling checkfunc.
 178          */
 179         rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG);
 180         dst->dst_error = dst->dst_checkfunc(dst->dst_arg, tx);
 181         if (dst->dst_error == 0)
 182                 dst->dst_syncfunc(dst->dst_arg, tx);
 183         rrw_exit(&dp->dp_config_rwlock, FTAG);
 184         if (dst->dst_nowaiter)
 185                 kmem_free(dst, sizeof (*dst));
 186 }