diff options
Diffstat (limited to 'module/zfs/dmu_tx.c')
| -rw-r--r-- | module/zfs/dmu_tx.c | 1404 |
1 files changed, 1404 insertions, 0 deletions
diff --git a/module/zfs/dmu_tx.c b/module/zfs/dmu_tx.c new file mode 100644 index 000000000000..09ef2be94944 --- /dev/null +++ b/module/zfs/dmu_tx.c @@ -0,0 +1,1404 @@ +/* + * 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 2011 Nexenta Systems, Inc. All rights reserved. + * Copyright (c) 2012, 2017 by Delphix. All rights reserved. + */ + +#include <sys/dmu.h> +#include <sys/dmu_impl.h> +#include <sys/dbuf.h> +#include <sys/dmu_tx.h> +#include <sys/dmu_objset.h> +#include <sys/dsl_dataset.h> +#include <sys/dsl_dir.h> +#include <sys/dsl_pool.h> +#include <sys/zap_impl.h> +#include <sys/spa.h> +#include <sys/sa.h> +#include <sys/sa_impl.h> +#include <sys/zfs_context.h> +#include <sys/trace_zfs.h> + +typedef void (*dmu_tx_hold_func_t)(dmu_tx_t *tx, struct dnode *dn, + uint64_t arg1, uint64_t arg2); + +dmu_tx_stats_t dmu_tx_stats = { + { "dmu_tx_assigned", KSTAT_DATA_UINT64 }, + { "dmu_tx_delay", KSTAT_DATA_UINT64 }, + { "dmu_tx_error", KSTAT_DATA_UINT64 }, + { "dmu_tx_suspended", KSTAT_DATA_UINT64 }, + { "dmu_tx_group", KSTAT_DATA_UINT64 }, + { "dmu_tx_memory_reserve", KSTAT_DATA_UINT64 }, + { "dmu_tx_memory_reclaim", KSTAT_DATA_UINT64 }, + { "dmu_tx_dirty_throttle", KSTAT_DATA_UINT64 }, + { "dmu_tx_dirty_delay", KSTAT_DATA_UINT64 }, + { "dmu_tx_dirty_over_max", KSTAT_DATA_UINT64 }, + { "dmu_tx_dirty_frees_delay", KSTAT_DATA_UINT64 }, + { "dmu_tx_quota", KSTAT_DATA_UINT64 }, +}; + +static kstat_t *dmu_tx_ksp; + +dmu_tx_t * +dmu_tx_create_dd(dsl_dir_t *dd) +{ + dmu_tx_t *tx = kmem_zalloc(sizeof (dmu_tx_t), KM_SLEEP); + tx->tx_dir = dd; + if (dd != NULL) + tx->tx_pool = dd->dd_pool; + list_create(&tx->tx_holds, sizeof (dmu_tx_hold_t), + offsetof(dmu_tx_hold_t, txh_node)); + list_create(&tx->tx_callbacks, sizeof (dmu_tx_callback_t), + offsetof(dmu_tx_callback_t, dcb_node)); + tx->tx_start = gethrtime(); + return (tx); +} + +dmu_tx_t * +dmu_tx_create(objset_t *os) +{ + dmu_tx_t *tx = dmu_tx_create_dd(os->os_dsl_dataset->ds_dir); + tx->tx_objset = os; + return (tx); +} + +dmu_tx_t * +dmu_tx_create_assigned(struct dsl_pool *dp, uint64_t txg) +{ + dmu_tx_t *tx = dmu_tx_create_dd(NULL); + + TXG_VERIFY(dp->dp_spa, txg); + tx->tx_pool = dp; + tx->tx_txg = txg; + tx->tx_anyobj = TRUE; + + return (tx); +} + +int +dmu_tx_is_syncing(dmu_tx_t *tx) +{ + return (tx->tx_anyobj); +} + +int +dmu_tx_private_ok(dmu_tx_t *tx) +{ + return (tx->tx_anyobj); +} + +static dmu_tx_hold_t * +dmu_tx_hold_dnode_impl(dmu_tx_t *tx, dnode_t *dn, enum dmu_tx_hold_type type, + uint64_t arg1, uint64_t arg2) +{ + dmu_tx_hold_t *txh; + + if (dn != NULL) { + (void) zfs_refcount_add(&dn->dn_holds, tx); + if (tx->tx_txg != 0) { + mutex_enter(&dn->dn_mtx); + /* + * dn->dn_assigned_txg == tx->tx_txg doesn't pose a + * problem, but there's no way for it to happen (for + * now, at least). + */ + ASSERT(dn->dn_assigned_txg == 0); + dn->dn_assigned_txg = tx->tx_txg; + (void) zfs_refcount_add(&dn->dn_tx_holds, tx); + mutex_exit(&dn->dn_mtx); + } + } + + txh = kmem_zalloc(sizeof (dmu_tx_hold_t), KM_SLEEP); + txh->txh_tx = tx; + txh->txh_dnode = dn; + zfs_refcount_create(&txh->txh_space_towrite); + zfs_refcount_create(&txh->txh_memory_tohold); + txh->txh_type = type; + txh->txh_arg1 = arg1; + txh->txh_arg2 = arg2; + list_insert_tail(&tx->tx_holds, txh); + + return (txh); +} + +static dmu_tx_hold_t * +dmu_tx_hold_object_impl(dmu_tx_t *tx, objset_t *os, uint64_t object, + enum dmu_tx_hold_type type, uint64_t arg1, uint64_t arg2) +{ + dnode_t *dn = NULL; + dmu_tx_hold_t *txh; + int err; + + if (object != DMU_NEW_OBJECT) { + err = dnode_hold(os, object, FTAG, &dn); + if (err != 0) { + tx->tx_err = err; + return (NULL); + } + } + txh = dmu_tx_hold_dnode_impl(tx, dn, type, arg1, arg2); + if (dn != NULL) + dnode_rele(dn, FTAG); + return (txh); +} + +void +dmu_tx_add_new_object(dmu_tx_t *tx, dnode_t *dn) +{ + /* + * If we're syncing, they can manipulate any object anyhow, and + * the hold on the dnode_t can cause problems. + */ + if (!dmu_tx_is_syncing(tx)) + (void) dmu_tx_hold_dnode_impl(tx, dn, THT_NEWOBJECT, 0, 0); +} + +/* + * This function reads specified data from disk. The specified data will + * be needed to perform the transaction -- i.e, it will be read after + * we do dmu_tx_assign(). There are two reasons that we read the data now + * (before dmu_tx_assign()): + * + * 1. Reading it now has potentially better performance. The transaction + * has not yet been assigned, so the TXG is not held open, and also the + * caller typically has less locks held when calling dmu_tx_hold_*() than + * after the transaction has been assigned. This reduces the lock (and txg) + * hold times, thus reducing lock contention. + * + * 2. It is easier for callers (primarily the ZPL) to handle i/o errors + * that are detected before they start making changes to the DMU state + * (i.e. now). Once the transaction has been assigned, and some DMU + * state has been changed, it can be difficult to recover from an i/o + * error (e.g. to undo the changes already made in memory at the DMU + * layer). Typically code to do so does not exist in the caller -- it + * assumes that the data has already been cached and thus i/o errors are + * not possible. + * + * It has been observed that the i/o initiated here can be a performance + * problem, and it appears to be optional, because we don't look at the + * data which is read. However, removing this read would only serve to + * move the work elsewhere (after the dmu_tx_assign()), where it may + * have a greater impact on performance (in addition to the impact on + * fault tolerance noted above). + */ +static int +dmu_tx_check_ioerr(zio_t *zio, dnode_t *dn, int level, uint64_t blkid) +{ + int err; + dmu_buf_impl_t *db; + + rw_enter(&dn->dn_struct_rwlock, RW_READER); + db = dbuf_hold_level(dn, level, blkid, FTAG); + rw_exit(&dn->dn_struct_rwlock); + if (db == NULL) + return (SET_ERROR(EIO)); + err = dbuf_read(db, zio, DB_RF_CANFAIL | DB_RF_NOPREFETCH); + dbuf_rele(db, FTAG); + return (err); +} + +/* ARGSUSED */ +static void +dmu_tx_count_write(dmu_tx_hold_t *txh, uint64_t off, uint64_t len) +{ + dnode_t *dn = txh->txh_dnode; + int err = 0; + + if (len == 0) + return; + + (void) zfs_refcount_add_many(&txh->txh_space_towrite, len, FTAG); + + if (zfs_refcount_count(&txh->txh_space_towrite) > 2 * DMU_MAX_ACCESS) + err = SET_ERROR(EFBIG); + + if (dn == NULL) + return; + + /* + * For i/o error checking, read the blocks that will be needed + * to perform the write: the first and last level-0 blocks (if + * they are not aligned, i.e. if they are partial-block writes), + * and all the level-1 blocks. + */ + if (dn->dn_maxblkid == 0) { + if (off < dn->dn_datablksz && + (off > 0 || len < dn->dn_datablksz)) { + err = dmu_tx_check_ioerr(NULL, dn, 0, 0); + if (err != 0) { + txh->txh_tx->tx_err = err; + } + } + } else { + zio_t *zio = zio_root(dn->dn_objset->os_spa, + NULL, NULL, ZIO_FLAG_CANFAIL); + + /* first level-0 block */ + uint64_t start = off >> dn->dn_datablkshift; + if (P2PHASE(off, dn->dn_datablksz) || len < dn->dn_datablksz) { + err = dmu_tx_check_ioerr(zio, dn, 0, start); + if (err != 0) { + txh->txh_tx->tx_err = err; + } + } + + /* last level-0 block */ + uint64_t end = (off + len - 1) >> dn->dn_datablkshift; + if (end != start && end <= dn->dn_maxblkid && + P2PHASE(off + len, dn->dn_datablksz)) { + err = dmu_tx_check_ioerr(zio, dn, 0, end); + if (err != 0) { + txh->txh_tx->tx_err = err; + } + } + + /* level-1 blocks */ + if (dn->dn_nlevels > 1) { + int shft = dn->dn_indblkshift - SPA_BLKPTRSHIFT; + for (uint64_t i = (start >> shft) + 1; + i < end >> shft; i++) { + err = dmu_tx_check_ioerr(zio, dn, 1, i); + if (err != 0) { + txh->txh_tx->tx_err = err; + } + } + } + + err = zio_wait(zio); + if (err != 0) { + txh->txh_tx->tx_err = err; + } + } +} + +static void +dmu_tx_count_dnode(dmu_tx_hold_t *txh) +{ + (void) zfs_refcount_add_many(&txh->txh_space_towrite, + DNODE_MIN_SIZE, FTAG); +} + +void +dmu_tx_hold_write(dmu_tx_t *tx, uint64_t object, uint64_t off, int len) +{ + dmu_tx_hold_t *txh; + + ASSERT0(tx->tx_txg); + ASSERT3U(len, <=, DMU_MAX_ACCESS); + ASSERT(len == 0 || UINT64_MAX - off >= len - 1); + + txh = dmu_tx_hold_object_impl(tx, tx->tx_objset, + object, THT_WRITE, off, len); + if (txh != NULL) { + dmu_tx_count_write(txh, off, len); + dmu_tx_count_dnode(txh); + } +} + +void +dmu_tx_hold_write_by_dnode(dmu_tx_t *tx, dnode_t *dn, uint64_t off, int len) +{ + dmu_tx_hold_t *txh; + + ASSERT0(tx->tx_txg); + ASSERT3U(len, <=, DMU_MAX_ACCESS); + ASSERT(len == 0 || UINT64_MAX - off >= len - 1); + + txh = dmu_tx_hold_dnode_impl(tx, dn, THT_WRITE, off, len); + if (txh != NULL) { + dmu_tx_count_write(txh, off, len); + dmu_tx_count_dnode(txh); + } +} + +/* + * This function marks the transaction as being a "net free". The end + * result is that refquotas will be disabled for this transaction, and + * this transaction will be able to use half of the pool space overhead + * (see dsl_pool_adjustedsize()). Therefore this function should only + * be called for transactions that we expect will not cause a net increase + * in the amount of space used (but it's OK if that is occasionally not true). + */ +void +dmu_tx_mark_netfree(dmu_tx_t *tx) +{ + tx->tx_netfree = B_TRUE; +} + +static void +dmu_tx_hold_free_impl(dmu_tx_hold_t *txh, uint64_t off, uint64_t len) +{ + dmu_tx_t *tx = txh->txh_tx; + dnode_t *dn = txh->txh_dnode; + int err; + + ASSERT(tx->tx_txg == 0); + + dmu_tx_count_dnode(txh); + + if (off >= (dn->dn_maxblkid + 1) * dn->dn_datablksz) + return; + if (len == DMU_OBJECT_END) + len = (dn->dn_maxblkid + 1) * dn->dn_datablksz - off; + + dmu_tx_count_dnode(txh); + + /* + * For i/o error checking, we read the first and last level-0 + * blocks if they are not aligned, and all the level-1 blocks. + * + * Note: dbuf_free_range() assumes that we have not instantiated + * any level-0 dbufs that will be completely freed. Therefore we must + * exercise care to not read or count the first and last blocks + * if they are blocksize-aligned. + */ + if (dn->dn_datablkshift == 0) { + if (off != 0 || len < dn->dn_datablksz) + dmu_tx_count_write(txh, 0, dn->dn_datablksz); + } else { + /* first block will be modified if it is not aligned */ + if (!IS_P2ALIGNED(off, 1 << dn->dn_datablkshift)) + dmu_tx_count_write(txh, off, 1); + /* last block will be modified if it is not aligned */ + if (!IS_P2ALIGNED(off + len, 1 << dn->dn_datablkshift)) + dmu_tx_count_write(txh, off + len, 1); + } + + /* + * Check level-1 blocks. + */ + if (dn->dn_nlevels > 1) { + int shift = dn->dn_datablkshift + dn->dn_indblkshift - + SPA_BLKPTRSHIFT; + uint64_t start = off >> shift; + uint64_t end = (off + len) >> shift; + + ASSERT(dn->dn_indblkshift != 0); + + /* + * dnode_reallocate() can result in an object with indirect + * blocks having an odd data block size. In this case, + * just check the single block. + */ + if (dn->dn_datablkshift == 0) + start = end = 0; + + zio_t *zio = zio_root(tx->tx_pool->dp_spa, + NULL, NULL, ZIO_FLAG_CANFAIL); + for (uint64_t i = start; i <= end; i++) { + uint64_t ibyte = i << shift; + err = dnode_next_offset(dn, 0, &ibyte, 2, 1, 0); + i = ibyte >> shift; + if (err == ESRCH || i > end) + break; + if (err != 0) { + tx->tx_err = err; + (void) zio_wait(zio); + return; + } + + (void) zfs_refcount_add_many(&txh->txh_memory_tohold, + 1 << dn->dn_indblkshift, FTAG); + + err = dmu_tx_check_ioerr(zio, dn, 1, i); + if (err != 0) { + tx->tx_err = err; + (void) zio_wait(zio); + return; + } + } + err = zio_wait(zio); + if (err != 0) { + tx->tx_err = err; + return; + } + } +} + +void +dmu_tx_hold_free(dmu_tx_t *tx, uint64_t object, uint64_t off, uint64_t len) +{ + dmu_tx_hold_t *txh; + + txh = dmu_tx_hold_object_impl(tx, tx->tx_objset, + object, THT_FREE, off, len); + if (txh != NULL) + (void) dmu_tx_hold_free_impl(txh, off, len); +} + +void +dmu_tx_hold_free_by_dnode(dmu_tx_t *tx, dnode_t *dn, uint64_t off, uint64_t len) +{ + dmu_tx_hold_t *txh; + + txh = dmu_tx_hold_dnode_impl(tx, dn, THT_FREE, off, len); + if (txh != NULL) + (void) dmu_tx_hold_free_impl(txh, off, len); +} + +static void +dmu_tx_hold_zap_impl(dmu_tx_hold_t *txh, const char *name) +{ + dmu_tx_t *tx = txh->txh_tx; + dnode_t *dn = txh->txh_dnode; + int err; + + ASSERT(tx->tx_txg == 0); + + dmu_tx_count_dnode(txh); + + /* + * Modifying a almost-full microzap is around the worst case (128KB) + * + * If it is a fat zap, the worst case would be 7*16KB=112KB: + * - 3 blocks overwritten: target leaf, ptrtbl block, header block + * - 4 new blocks written if adding: + * - 2 blocks for possibly split leaves, + * - 2 grown ptrtbl blocks + */ + (void) zfs_refcount_add_many(&txh->txh_space_towrite, + MZAP_MAX_BLKSZ, FTAG); + + if (dn == NULL) + return; + + ASSERT3U(DMU_OT_BYTESWAP(dn->dn_type), ==, DMU_BSWAP_ZAP); + + if (dn->dn_maxblkid == 0 || name == NULL) { + /* + * This is a microzap (only one block), or we don't know + * the name. Check the first block for i/o errors. + */ + err = dmu_tx_check_ioerr(NULL, dn, 0, 0); + if (err != 0) { + tx->tx_err = err; + } + } else { + /* + * Access the name so that we'll check for i/o errors to + * the leaf blocks, etc. We ignore ENOENT, as this name + * may not yet exist. + */ + err = zap_lookup_by_dnode(dn, name, 8, 0, NULL); + if (err == EIO || err == ECKSUM || err == ENXIO) { + tx->tx_err = err; + } + } +} + +void +dmu_tx_hold_zap(dmu_tx_t *tx, uint64_t object, int add, const char *name) +{ + dmu_tx_hold_t *txh; + + ASSERT0(tx->tx_txg); + + txh = dmu_tx_hold_object_impl(tx, tx->tx_objset, + object, THT_ZAP, add, (uintptr_t)name); + if (txh != NULL) + dmu_tx_hold_zap_impl(txh, name); +} + +void +dmu_tx_hold_zap_by_dnode(dmu_tx_t *tx, dnode_t *dn, int add, const char *name) +{ + dmu_tx_hold_t *txh; + + ASSERT0(tx->tx_txg); + ASSERT(dn != NULL); + + txh = dmu_tx_hold_dnode_impl(tx, dn, THT_ZAP, add, (uintptr_t)name); + if (txh != NULL) + dmu_tx_hold_zap_impl(txh, name); +} + +void +dmu_tx_hold_bonus(dmu_tx_t *tx, uint64_t object) +{ + dmu_tx_hold_t *txh; + + ASSERT(tx->tx_txg == 0); + + txh = dmu_tx_hold_object_impl(tx, tx->tx_objset, + object, THT_BONUS, 0, 0); + if (txh) + dmu_tx_count_dnode(txh); +} + +void +dmu_tx_hold_bonus_by_dnode(dmu_tx_t *tx, dnode_t *dn) +{ + dmu_tx_hold_t *txh; + + ASSERT0(tx->tx_txg); + + txh = dmu_tx_hold_dnode_impl(tx, dn, THT_BONUS, 0, 0); + if (txh) + dmu_tx_count_dnode(txh); +} + +void +dmu_tx_hold_space(dmu_tx_t *tx, uint64_t space) +{ + dmu_tx_hold_t *txh; + + ASSERT(tx->tx_txg == 0); + + txh = dmu_tx_hold_object_impl(tx, tx->tx_objset, + DMU_NEW_OBJECT, THT_SPACE, space, 0); + if (txh) { + (void) zfs_refcount_add_many( + &txh->txh_space_towrite, space, FTAG); + } +} + +#ifdef ZFS_DEBUG +void +dmu_tx_dirty_buf(dmu_tx_t *tx, dmu_buf_impl_t *db) +{ + boolean_t match_object = B_FALSE; + boolean_t match_offset = B_FALSE; + + DB_DNODE_ENTER(db); + dnode_t *dn = DB_DNODE(db); + ASSERT(tx->tx_txg != 0); + ASSERT(tx->tx_objset == NULL || dn->dn_objset == tx->tx_objset); + ASSERT3U(dn->dn_object, ==, db->db.db_object); + + if (tx->tx_anyobj) { + DB_DNODE_EXIT(db); + return; + } + + /* XXX No checking on the meta dnode for now */ + if (db->db.db_object == DMU_META_DNODE_OBJECT) { + DB_DNODE_EXIT(db); + return; + } + + for (dmu_tx_hold_t *txh = list_head(&tx->tx_holds); txh != NULL; + txh = list_next(&tx->tx_holds, txh)) { + ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg); + if (txh->txh_dnode == dn && txh->txh_type != THT_NEWOBJECT) + match_object = TRUE; + if (txh->txh_dnode == NULL || txh->txh_dnode == dn) { + int datablkshift = dn->dn_datablkshift ? + dn->dn_datablkshift : SPA_MAXBLOCKSHIFT; + int epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT; + int shift = datablkshift + epbs * db->db_level; + uint64_t beginblk = shift >= 64 ? 0 : + (txh->txh_arg1 >> shift); + uint64_t endblk = shift >= 64 ? 0 : + ((txh->txh_arg1 + txh->txh_arg2 - 1) >> shift); + uint64_t blkid = db->db_blkid; + + /* XXX txh_arg2 better not be zero... */ + + dprintf("found txh type %x beginblk=%llx endblk=%llx\n", + txh->txh_type, beginblk, endblk); + + switch (txh->txh_type) { + case THT_WRITE: + if (blkid >= beginblk && blkid <= endblk) + match_offset = TRUE; + /* + * We will let this hold work for the bonus + * or spill buffer so that we don't need to + * hold it when creating a new object. + */ + if (blkid == DMU_BONUS_BLKID || + blkid == DMU_SPILL_BLKID) + match_offset = TRUE; + /* + * They might have to increase nlevels, + * thus dirtying the new TLIBs. Or the + * might have to change the block size, + * thus dirying the new lvl=0 blk=0. + */ + if (blkid == 0) + match_offset = TRUE; + break; + case THT_FREE: + /* + * We will dirty all the level 1 blocks in + * the free range and perhaps the first and + * last level 0 block. + */ + if (blkid >= beginblk && (blkid <= endblk || + txh->txh_arg2 == DMU_OBJECT_END)) + match_offset = TRUE; + break; + case THT_SPILL: + if (blkid == DMU_SPILL_BLKID) + match_offset = TRUE; + break; + case THT_BONUS: + if (blkid == DMU_BONUS_BLKID) + match_offset = TRUE; + break; + case THT_ZAP: + match_offset = TRUE; + break; + case THT_NEWOBJECT: + match_object = TRUE; + break; + default: + cmn_err(CE_PANIC, "bad txh_type %d", + txh->txh_type); + } + } + if (match_object && match_offset) { + DB_DNODE_EXIT(db); + return; + } + } + DB_DNODE_EXIT(db); + panic("dirtying dbuf obj=%llx lvl=%u blkid=%llx but not tx_held\n", + (u_longlong_t)db->db.db_object, db->db_level, + (u_longlong_t)db->db_blkid); +} +#endif + +/* + * If we can't do 10 iops, something is wrong. Let us go ahead + * and hit zfs_dirty_data_max. + */ +hrtime_t zfs_delay_max_ns = 100 * MICROSEC; /* 100 milliseconds */ +int zfs_delay_resolution_ns = 100 * 1000; /* 100 microseconds */ + +/* + * We delay transactions when we've determined that the backend storage + * isn't able to accommodate the rate of incoming writes. + * + * If there is already a transaction waiting, we delay relative to when + * that transaction finishes waiting. This way the calculated min_time + * is independent of the number of threads concurrently executing + * transactions. + * + * If we are the only waiter, wait relative to when the transaction + * started, rather than the current time. This credits the transaction for + * "time already served", e.g. reading indirect blocks. + * + * The minimum time for a transaction to take is calculated as: + * min_time = scale * (dirty - min) / (max - dirty) + * min_time is then capped at zfs_delay_max_ns. + * + * The delay has two degrees of freedom that can be adjusted via tunables. + * The percentage of dirty data at which we start to delay is defined by + * zfs_delay_min_dirty_percent. This should typically be at or above + * zfs_vdev_async_write_active_max_dirty_percent so that we only start to + * delay after writing at full speed has failed to keep up with the incoming + * write rate. The scale of the curve is defined by zfs_delay_scale. Roughly + * speaking, this variable determines the amount of delay at the midpoint of + * the curve. + * + * delay + * 10ms +-------------------------------------------------------------*+ + * | *| + * 9ms + *+ + * | *| + * 8ms + *+ + * | * | + * 7ms + * + + * | * | + * 6ms + * + + * | * | + * 5ms + * + + * | * | + * 4ms + * + + * | * | + * 3ms + * + + * | * | + * 2ms + (midpoint) * + + * | | ** | + * 1ms + v *** + + * | zfs_delay_scale ----------> ******** | + * 0 +-------------------------------------*********----------------+ + * 0% <- zfs_dirty_data_max -> 100% + * + * Note that since the delay is added to the outstanding time remaining on the + * most recent transaction, the delay is effectively the inverse of IOPS. + * Here the midpoint of 500us translates to 2000 IOPS. The shape of the curve + * was chosen such that small changes in the amount of accumulated dirty data + * in the first 3/4 of the curve yield relatively small differences in the + * amount of delay. + * + * The effects can be easier to understand when the amount of delay is + * represented on a log scale: + * + * delay + * 100ms +-------------------------------------------------------------++ + * + + + * | | + * + *+ + * 10ms + *+ + * + ** + + * | (midpoint) ** | + * + | ** + + * 1ms + v **** + + * + zfs_delay_scale ----------> ***** + + * | **** | + * + **** + + * 100us + ** + + * + * + + * | * | + * + * + + * 10us + * + + * + + + * | | + * + + + * +--------------------------------------------------------------+ + * 0% <- zfs_dirty_data_max -> 100% + * + * Note here that only as the amount of dirty data approaches its limit does + * the delay start to increase rapidly. The goal of a properly tuned system + * should be to keep the amount of dirty data out of that range by first + * ensuring that the appropriate limits are set for the I/O scheduler to reach + * optimal throughput on the backend storage, and then by changing the value + * of zfs_delay_scale to increase the steepness of the curve. + */ +static void +dmu_tx_delay(dmu_tx_t *tx, uint64_t dirty) +{ + dsl_pool_t *dp = tx->tx_pool; + uint64_t delay_min_bytes = + zfs_dirty_data_max * zfs_delay_min_dirty_percent / 100; + hrtime_t wakeup, min_tx_time, now; + + if (dirty <= delay_min_bytes) + return; + + /* + * The caller has already waited until we are under the max. + * We make them pass us the amount of dirty data so we don't + * have to handle the case of it being >= the max, which could + * cause a divide-by-zero if it's == the max. + */ + ASSERT3U(dirty, <, zfs_dirty_data_max); + + now = gethrtime(); + min_tx_time = zfs_delay_scale * + (dirty - delay_min_bytes) / (zfs_dirty_data_max - dirty); + min_tx_time = MIN(min_tx_time, zfs_delay_max_ns); + if (now > tx->tx_start + min_tx_time) + return; + + DTRACE_PROBE3(delay__mintime, dmu_tx_t *, tx, uint64_t, dirty, + uint64_t, min_tx_time); + + mutex_enter(&dp->dp_lock); + wakeup = MAX(tx->tx_start + min_tx_time, + dp->dp_last_wakeup + min_tx_time); + dp->dp_last_wakeup = wakeup; + mutex_exit(&dp->dp_lock); + + zfs_sleep_until(wakeup); +} + +/* + * This routine attempts to assign the transaction to a transaction group. + * To do so, we must determine if there is sufficient free space on disk. + * + * If this is a "netfree" transaction (i.e. we called dmu_tx_mark_netfree() + * on it), then it is assumed that there is sufficient free space, + * unless there's insufficient slop space in the pool (see the comment + * above spa_slop_shift in spa_misc.c). + * + * If it is not a "netfree" transaction, then if the data already on disk + * is over the allowed usage (e.g. quota), this will fail with EDQUOT or + * ENOSPC. Otherwise, if the current rough estimate of pending changes, + * plus the rough estimate of this transaction's changes, may exceed the + * allowed usage, then this will fail with ERESTART, which will cause the + * caller to wait for the pending changes to be written to disk (by waiting + * for the next TXG to open), and then check the space usage again. + * + * The rough estimate of pending changes is comprised of the sum of: + * + * - this transaction's holds' txh_space_towrite + * + * - dd_tempreserved[], which is the sum of in-flight transactions' + * holds' txh_space_towrite (i.e. those transactions that have called + * dmu_tx_assign() but not yet called dmu_tx_commit()). + * + * - dd_space_towrite[], which is the amount of dirtied dbufs. + * + * Note that all of these values are inflated by spa_get_worst_case_asize(), + * which means that we may get ERESTART well before we are actually in danger + * of running out of space, but this also mitigates any small inaccuracies + * in the rough estimate (e.g. txh_space_towrite doesn't take into account + * indirect blocks, and dd_space_towrite[] doesn't take into account changes + * to the MOS). + * + * Note that due to this algorithm, it is possible to exceed the allowed + * usage by one transaction. Also, as we approach the allowed usage, + * we will allow a very limited amount of changes into each TXG, thus + * decreasing performance. + */ +static int +dmu_tx_try_assign(dmu_tx_t *tx, uint64_t txg_how) +{ + spa_t *spa = tx->tx_pool->dp_spa; + + ASSERT0(tx->tx_txg); + + if (tx->tx_err) { + DMU_TX_STAT_BUMP(dmu_tx_error); + return (tx->tx_err); + } + + if (spa_suspended(spa)) { + DMU_TX_STAT_BUMP(dmu_tx_suspended); + + /* + * If the user has indicated a blocking failure mode + * then return ERESTART which will block in dmu_tx_wait(). + * Otherwise, return EIO so that an error can get + * propagated back to the VOP calls. + * + * Note that we always honor the txg_how flag regardless + * of the failuremode setting. + */ + if (spa_get_failmode(spa) == ZIO_FAILURE_MODE_CONTINUE && + !(txg_how & TXG_WAIT)) + return (SET_ERROR(EIO)); + + return (SET_ERROR(ERESTART)); + } + + if (!tx->tx_dirty_delayed && + dsl_pool_need_dirty_delay(tx->tx_pool)) { + tx->tx_wait_dirty = B_TRUE; + DMU_TX_STAT_BUMP(dmu_tx_dirty_delay); + return (SET_ERROR(ERESTART)); + } + + tx->tx_txg = txg_hold_open(tx->tx_pool, &tx->tx_txgh); + tx->tx_needassign_txh = NULL; + + /* + * NB: No error returns are allowed after txg_hold_open, but + * before processing the dnode holds, due to the + * dmu_tx_unassign() logic. + */ + + uint64_t towrite = 0; + uint64_t tohold = 0; + for (dmu_tx_hold_t *txh = list_head(&tx->tx_holds); txh != NULL; + txh = list_next(&tx->tx_holds, txh)) { + dnode_t *dn = txh->txh_dnode; + if (dn != NULL) { + /* + * This thread can't hold the dn_struct_rwlock + * while assigning the tx, because this can lead to + * deadlock. Specifically, if this dnode is already + * assigned to an earlier txg, this thread may need + * to wait for that txg to sync (the ERESTART case + * below). The other thread that has assigned this + * dnode to an earlier txg prevents this txg from + * syncing until its tx can complete (calling + * dmu_tx_commit()), but it may need to acquire the + * dn_struct_rwlock to do so (e.g. via + * dmu_buf_hold*()). + * + * Note that this thread can't hold the lock for + * read either, but the rwlock doesn't record + * enough information to make that assertion. + */ + ASSERT(!RW_WRITE_HELD(&dn->dn_struct_rwlock)); + + mutex_enter(&dn->dn_mtx); + if (dn->dn_assigned_txg == tx->tx_txg - 1) { + mutex_exit(&dn->dn_mtx); + tx->tx_needassign_txh = txh; + DMU_TX_STAT_BUMP(dmu_tx_group); + return (SET_ERROR(ERESTART)); + } + if (dn->dn_assigned_txg == 0) + dn->dn_assigned_txg = tx->tx_txg; + ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg); + (void) zfs_refcount_add(&dn->dn_tx_holds, tx); + mutex_exit(&dn->dn_mtx); + } + towrite += zfs_refcount_count(&txh->txh_space_towrite); + tohold += zfs_refcount_count(&txh->txh_memory_tohold); + } + + /* needed allocation: worst-case estimate of write space */ + uint64_t asize = spa_get_worst_case_asize(tx->tx_pool->dp_spa, towrite); + /* calculate memory footprint estimate */ + uint64_t memory = towrite + tohold; + + if (tx->tx_dir != NULL && asize != 0) { + int err = dsl_dir_tempreserve_space(tx->tx_dir, memory, + asize, tx->tx_netfree, &tx->tx_tempreserve_cookie, tx); + if (err != 0) + return (err); + } + + DMU_TX_STAT_BUMP(dmu_tx_assigned); + + return (0); +} + +static void +dmu_tx_unassign(dmu_tx_t *tx) +{ + if (tx->tx_txg == 0) + return; + + txg_rele_to_quiesce(&tx->tx_txgh); + + /* + * Walk the transaction's hold list, removing the hold on the + * associated dnode, and notifying waiters if the refcount drops to 0. + */ + for (dmu_tx_hold_t *txh = list_head(&tx->tx_holds); + txh && txh != tx->tx_needassign_txh; + txh = list_next(&tx->tx_holds, txh)) { + dnode_t *dn = txh->txh_dnode; + + if (dn == NULL) + continue; + mutex_enter(&dn->dn_mtx); + ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg); + + if (zfs_refcount_remove(&dn->dn_tx_holds, tx) == 0) { + dn->dn_assigned_txg = 0; + cv_broadcast(&dn->dn_notxholds); + } + mutex_exit(&dn->dn_mtx); + } + + txg_rele_to_sync(&tx->tx_txgh); + + tx->tx_lasttried_txg = tx->tx_txg; + tx->tx_txg = 0; +} + +/* + * Assign tx to a transaction group; txg_how is a bitmask: + * + * If TXG_WAIT is set and the currently open txg is full, this function + * will wait until there's a new txg. This should be used when no locks + * are being held. With this bit set, this function will only fail if + * we're truly out of space (or over quota). + * + * If TXG_WAIT is *not* set and we can't assign into the currently open + * txg without blocking, this function will return immediately with + * ERESTART. This should be used whenever locks are being held. On an + * ERESTART error, the caller should drop all locks, call dmu_tx_wait(), + * and try again. + * + * If TXG_NOTHROTTLE is set, this indicates that this tx should not be + * delayed due on the ZFS Write Throttle (see comments in dsl_pool.c for + * details on the throttle). This is used by the VFS operations, after + * they have already called dmu_tx_wait() (though most likely on a + * different tx). + */ +int +dmu_tx_assign(dmu_tx_t *tx, uint64_t txg_how) +{ + int err; + + ASSERT(tx->tx_txg == 0); + ASSERT0(txg_how & ~(TXG_WAIT | TXG_NOTHROTTLE)); + ASSERT(!dsl_pool_sync_context(tx->tx_pool)); + + /* If we might wait, we must not hold the config lock. */ + IMPLY((txg_how & TXG_WAIT), !dsl_pool_config_held(tx->tx_pool)); + + if ((txg_how & TXG_NOTHROTTLE)) + tx->tx_dirty_delayed = B_TRUE; + + while ((err = dmu_tx_try_assign(tx, txg_how)) != 0) { + dmu_tx_unassign(tx); + + if (err != ERESTART || !(txg_how & TXG_WAIT)) + return (err); + + dmu_tx_wait(tx); + } + + txg_rele_to_quiesce(&tx->tx_txgh); + + return (0); +} + +void +dmu_tx_wait(dmu_tx_t *tx) +{ + spa_t *spa = tx->tx_pool->dp_spa; + dsl_pool_t *dp = tx->tx_pool; + hrtime_t before; + + ASSERT(tx->tx_txg == 0); + ASSERT(!dsl_pool_config_held(tx->tx_pool)); + + before = gethrtime(); + + if (tx->tx_wait_dirty) { + uint64_t dirty; + + /* + * dmu_tx_try_assign() has determined that we need to wait + * because we've consumed much or all of the dirty buffer + * space. + */ + mutex_enter(&dp->dp_lock); + if (dp->dp_dirty_total >= zfs_dirty_data_max) + DMU_TX_STAT_BUMP(dmu_tx_dirty_over_max); + while (dp->dp_dirty_total >= zfs_dirty_data_max) + cv_wait(&dp->dp_spaceavail_cv, &dp->dp_lock); + dirty = dp->dp_dirty_total; + mutex_exit(&dp->dp_lock); + + dmu_tx_delay(tx, dirty); + + tx->tx_wait_dirty = B_FALSE; + + /* + * Note: setting tx_dirty_delayed only has effect if the + * caller used TX_WAIT. Otherwise they are going to + * destroy this tx and try again. The common case, + * zfs_write(), uses TX_WAIT. + */ + tx->tx_dirty_delayed = B_TRUE; + } else if (spa_suspended(spa) || tx->tx_lasttried_txg == 0) { + /* + * If the pool is suspended we need to wait until it + * is resumed. Note that it's possible that the pool + * has become active after this thread has tried to + * obtain a tx. If that's the case then tx_lasttried_txg + * would not have been set. + */ + txg_wait_synced(dp, spa_last_synced_txg(spa) + 1); + } else if (tx->tx_needassign_txh) { + dnode_t *dn = tx->tx_needassign_txh->txh_dnode; + + mutex_enter(&dn->dn_mtx); + while (dn->dn_assigned_txg == tx->tx_lasttried_txg - 1) + cv_wait(&dn->dn_notxholds, &dn->dn_mtx); + mutex_exit(&dn->dn_mtx); + tx->tx_needassign_txh = NULL; + } else { + /* + * If we have a lot of dirty data just wait until we sync + * out a TXG at which point we'll hopefully have synced + * a portion of the changes. + */ + txg_wait_synced(dp, spa_last_synced_txg(spa) + 1); + } + + spa_tx_assign_add_nsecs(spa, gethrtime() - before); +} + +static void +dmu_tx_destroy(dmu_tx_t *tx) +{ + dmu_tx_hold_t *txh; + + while ((txh = list_head(&tx->tx_holds)) != NULL) { + dnode_t *dn = txh->txh_dnode; + + list_remove(&tx->tx_holds, txh); + zfs_refcount_destroy_many(&txh->txh_space_towrite, + zfs_refcount_count(&txh->txh_space_towrite)); + zfs_refcount_destroy_many(&txh->txh_memory_tohold, + zfs_refcount_count(&txh->txh_memory_tohold)); + kmem_free(txh, sizeof (dmu_tx_hold_t)); + if (dn != NULL) + dnode_rele(dn, tx); + } + + list_destroy(&tx->tx_callbacks); + list_destroy(&tx->tx_holds); + kmem_free(tx, sizeof (dmu_tx_t)); +} + +void +dmu_tx_commit(dmu_tx_t *tx) +{ + ASSERT(tx->tx_txg != 0); + + /* + * Go through the transaction's hold list and remove holds on + * associated dnodes, notifying waiters if no holds remain. + */ + for (dmu_tx_hold_t *txh = list_head(&tx->tx_holds); txh != NULL; + txh = list_next(&tx->tx_holds, txh)) { + dnode_t *dn = txh->txh_dnode; + + if (dn == NULL) + continue; + + mutex_enter(&dn->dn_mtx); + ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg); + + if (zfs_refcount_remove(&dn->dn_tx_holds, tx) == 0) { + dn->dn_assigned_txg = 0; + cv_broadcast(&dn->dn_notxholds); + } + mutex_exit(&dn->dn_mtx); + } + + if (tx->tx_tempreserve_cookie) + dsl_dir_tempreserve_clear(tx->tx_tempreserve_cookie, tx); + + if (!list_is_empty(&tx->tx_callbacks)) + txg_register_callbacks(&tx->tx_txgh, &tx->tx_callbacks); + + if (tx->tx_anyobj == FALSE) + txg_rele_to_sync(&tx->tx_txgh); + + dmu_tx_destroy(tx); +} + +void +dmu_tx_abort(dmu_tx_t *tx) +{ + ASSERT(tx->tx_txg == 0); + + /* + * Call any registered callbacks with an error code. + */ + if (!list_is_empty(&tx->tx_callbacks)) + dmu_tx_do_callbacks(&tx->tx_callbacks, SET_ERROR(ECANCELED)); + + dmu_tx_destroy(tx); +} + +uint64_t +dmu_tx_get_txg(dmu_tx_t *tx) +{ + ASSERT(tx->tx_txg != 0); + return (tx->tx_txg); +} + +dsl_pool_t * +dmu_tx_pool(dmu_tx_t *tx) +{ + ASSERT(tx->tx_pool != NULL); + return (tx->tx_pool); +} + +void +dmu_tx_callback_register(dmu_tx_t *tx, dmu_tx_callback_func_t *func, void *data) +{ + dmu_tx_callback_t *dcb; + + dcb = kmem_alloc(sizeof (dmu_tx_callback_t), KM_SLEEP); + + dcb->dcb_func = func; + dcb->dcb_data = data; + + list_insert_tail(&tx->tx_callbacks, dcb); +} + +/* + * Call all the commit callbacks on a list, with a given error code. + */ +void +dmu_tx_do_callbacks(list_t *cb_list, int error) +{ + dmu_tx_callback_t *dcb; + + while ((dcb = list_tail(cb_list)) != NULL) { + list_remove(cb_list, dcb); + dcb->dcb_func(dcb->dcb_data, error); + kmem_free(dcb, sizeof (dmu_tx_callback_t)); + } +} + +/* + * Interface to hold a bunch of attributes. + * used for creating new files. + * attrsize is the total size of all attributes + * to be added during object creation + * + * For updating/adding a single attribute dmu_tx_hold_sa() should be used. + */ + +/* + * hold necessary attribute name for attribute registration. + * should be a very rare case where this is needed. If it does + * happen it would only happen on the first write to the file system. + */ +static void +dmu_tx_sa_registration_hold(sa_os_t *sa, dmu_tx_t *tx) +{ + if (!sa->sa_need_attr_registration) + return; + + for (int i = 0; i != sa->sa_num_attrs; i++) { + if (!sa->sa_attr_table[i].sa_registered) { + if (sa->sa_reg_attr_obj) + dmu_tx_hold_zap(tx, sa->sa_reg_attr_obj, + B_TRUE, sa->sa_attr_table[i].sa_name); + else + dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, + B_TRUE, sa->sa_attr_table[i].sa_name); + } + } +} + +void +dmu_tx_hold_spill(dmu_tx_t *tx, uint64_t object) +{ + dmu_tx_hold_t *txh; + + txh = dmu_tx_hold_object_impl(tx, tx->tx_objset, object, + THT_SPILL, 0, 0); + if (txh != NULL) + (void) zfs_refcount_add_many(&txh->txh_space_towrite, + SPA_OLD_MAXBLOCKSIZE, FTAG); +} + +void +dmu_tx_hold_sa_create(dmu_tx_t *tx, int attrsize) +{ + sa_os_t *sa = tx->tx_objset->os_sa; + + dmu_tx_hold_bonus(tx, DMU_NEW_OBJECT); + + if (tx->tx_objset->os_sa->sa_master_obj == 0) + return; + + if (tx->tx_objset->os_sa->sa_layout_attr_obj) { + dmu_tx_hold_zap(tx, sa->sa_layout_attr_obj, B_TRUE, NULL); + } else { + dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_LAYOUTS); + dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_REGISTRY); + dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL); + dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL); + } + + dmu_tx_sa_registration_hold(sa, tx); + + if (attrsize <= DN_OLD_MAX_BONUSLEN && !sa->sa_force_spill) + return; + + (void) dmu_tx_hold_object_impl(tx, tx->tx_objset, DMU_NEW_OBJECT, + THT_SPILL, 0, 0); +} + +/* + * Hold SA attribute + * + * dmu_tx_hold_sa(dmu_tx_t *tx, sa_handle_t *, attribute, add, size) + * + * variable_size is the total size of all variable sized attributes + * passed to this function. It is not the total size of all + * variable size attributes that *may* exist on this object. + */ +void +dmu_tx_hold_sa(dmu_tx_t *tx, sa_handle_t *hdl, boolean_t may_grow) +{ + uint64_t object; + sa_os_t *sa = tx->tx_objset->os_sa; + + ASSERT(hdl != NULL); + + object = sa_handle_object(hdl); + + dmu_buf_impl_t *db = (dmu_buf_impl_t *)hdl->sa_bonus; + DB_DNODE_ENTER(db); + dmu_tx_hold_bonus_by_dnode(tx, DB_DNODE(db)); + DB_DNODE_EXIT(db); + + if (tx->tx_objset->os_sa->sa_master_obj == 0) + return; + + if (tx->tx_objset->os_sa->sa_reg_attr_obj == 0 || + tx->tx_objset->os_sa->sa_layout_attr_obj == 0) { + dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_LAYOUTS); + dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_REGISTRY); + dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL); + dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL); + } + + dmu_tx_sa_registration_hold(sa, tx); + + if (may_grow && tx->tx_objset->os_sa->sa_layout_attr_obj) + dmu_tx_hold_zap(tx, sa->sa_layout_attr_obj, B_TRUE, NULL); + + if (sa->sa_force_spill || may_grow || hdl->sa_spill) { + ASSERT(tx->tx_txg == 0); + dmu_tx_hold_spill(tx, object); + } else { + dnode_t *dn; + + DB_DNODE_ENTER(db); + dn = DB_DNODE(db); + if (dn->dn_have_spill) { + ASSERT(tx->tx_txg == 0); + dmu_tx_hold_spill(tx, object); + } + DB_DNODE_EXIT(db); + } +} + +void +dmu_tx_init(void) +{ + dmu_tx_ksp = kstat_create("zfs", 0, "dmu_tx", "misc", + KSTAT_TYPE_NAMED, sizeof (dmu_tx_stats) / sizeof (kstat_named_t), + KSTAT_FLAG_VIRTUAL); + + if (dmu_tx_ksp != NULL) { + dmu_tx_ksp->ks_data = &dmu_tx_stats; + kstat_install(dmu_tx_ksp); + } +} + +void +dmu_tx_fini(void) +{ + if (dmu_tx_ksp != NULL) { + kstat_delete(dmu_tx_ksp); + dmu_tx_ksp = NULL; + } +} + +#if defined(_KERNEL) +EXPORT_SYMBOL(dmu_tx_create); +EXPORT_SYMBOL(dmu_tx_hold_write); +EXPORT_SYMBOL(dmu_tx_hold_write_by_dnode); +EXPORT_SYMBOL(dmu_tx_hold_free); +EXPORT_SYMBOL(dmu_tx_hold_free_by_dnode); +EXPORT_SYMBOL(dmu_tx_hold_zap); +EXPORT_SYMBOL(dmu_tx_hold_zap_by_dnode); +EXPORT_SYMBOL(dmu_tx_hold_bonus); +EXPORT_SYMBOL(dmu_tx_hold_bonus_by_dnode); +EXPORT_SYMBOL(dmu_tx_abort); +EXPORT_SYMBOL(dmu_tx_assign); +EXPORT_SYMBOL(dmu_tx_wait); +EXPORT_SYMBOL(dmu_tx_commit); +EXPORT_SYMBOL(dmu_tx_mark_netfree); +EXPORT_SYMBOL(dmu_tx_get_txg); +EXPORT_SYMBOL(dmu_tx_callback_register); +EXPORT_SYMBOL(dmu_tx_do_callbacks); +EXPORT_SYMBOL(dmu_tx_hold_spill); +EXPORT_SYMBOL(dmu_tx_hold_sa_create); +EXPORT_SYMBOL(dmu_tx_hold_sa); +#endif |