/* * 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 2006 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ #pragma ident "%Z%%M% %I% %E% SMI" /* * Virtual Device Labels * --------------------- * * The vdev label serves several distinct purposes: * * 1. Uniquely identify this device as part of a ZFS pool and confirm its * identity within the pool. * * 2. Verify that all the devices given in a configuration are present * within the pool. * * 3. Determine the uberblock for the pool. * * 4. In case of an import operation, determine the configuration of the * toplevel vdev of which it is a part. * * 5. If an import operation cannot find all the devices in the pool, * provide enough information to the administrator to determine which * devices are missing. * * It is important to note that while the kernel is responsible for writing the * label, it only consumes the information in the first three cases. The * latter information is only consumed in userland when determining the * configuration to import a pool. * * * Label Organization * ------------------ * * Before describing the contents of the label, it's important to understand how * the labels are written and updated with respect to the uberblock. * * When the pool configuration is altered, either because it was newly created * or a device was added, we want to update all the labels such that we can deal * with fatal failure at any point. To this end, each disk has two labels which * are updated before and after the uberblock is synced. Assuming we have * labels and an uberblock with the following transacation groups: * * L1 UB L2 * +------+ +------+ +------+ * | | | | | | * | t10 | | t10 | | t10 | * | | | | | | * +------+ +------+ +------+ * * In this stable state, the labels and the uberblock were all updated within * the same transaction group (10). Each label is mirrored and checksummed, so * that we can detect when we fail partway through writing the label. * * In order to identify which labels are valid, the labels are written in the * following manner: * * 1. For each vdev, update 'L1' to the new label * 2. Update the uberblock * 3. For each vdev, update 'L2' to the new label * * Given arbitrary failure, we can determine the correct label to use based on * the transaction group. If we fail after updating L1 but before updating the * UB, we will notice that L1's transaction group is greater than the uberblock, * so L2 must be valid. If we fail after writing the uberblock but before * writing L2, we will notice that L2's transaction group is less than L1, and * therefore L1 is valid. * * Another added complexity is that not every label is updated when the config * is synced. If we add a single device, we do not want to have to re-write * every label for every device in the pool. This means that both L1 and L2 may * be older than the pool uberblock, because the necessary information is stored * on another vdev. * * * On-disk Format * -------------- * * The vdev label consists of two distinct parts, and is wrapped within the * vdev_label_t structure. The label includes 8k of padding to permit legacy * VTOC disk labels, but is otherwise ignored. * * The first half of the label is a packed nvlist which contains pool wide * properties, per-vdev properties, and configuration information. It is * described in more detail below. * * The latter half of the label consists of a redundant array of uberblocks. * These uberblocks are updated whenever a transaction group is committed, * or when the configuration is updated. When a pool is loaded, we scan each * vdev for the 'best' uberblock. * * * Configuration Information * ------------------------- * * The nvlist describing the pool and vdev contains the following elements: * * version ZFS on-disk version * name Pool name * state Pool state * txg Transaction group in which this label was written * pool_guid Unique identifier for this pool * vdev_tree An nvlist describing vdev tree. * * Each leaf device label also contains the following: * * top_guid Unique ID for top-level vdev in which this is contained * guid Unique ID for the leaf vdev * * The 'vs' configuration follows the format described in 'spa_config.c'. */ #include #include #include #include #include #include #include #include #include #include #include /* * Basic routines to read and write from a vdev label. * Used throughout the rest of this file. */ uint64_t vdev_label_offset(uint64_t psize, int l, uint64_t offset) { return (offset + l * sizeof (vdev_label_t) + (l < VDEV_LABELS / 2 ? 0 : psize - VDEV_LABELS * sizeof (vdev_label_t))); } static void vdev_label_read(zio_t *zio, vdev_t *vd, int l, void *buf, uint64_t offset, uint64_t size, zio_done_func_t *done, void *private) { ASSERT(vd->vdev_children == 0); zio_nowait(zio_read_phys(zio, vd, vdev_label_offset(vd->vdev_psize, l, offset), size, buf, ZIO_CHECKSUM_LABEL, done, private, ZIO_PRIORITY_SYNC_READ, ZIO_FLAG_CONFIG_HELD | ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE)); } static void vdev_label_write(zio_t *zio, vdev_t *vd, int l, void *buf, uint64_t offset, uint64_t size, zio_done_func_t *done, void *private) { ASSERT(vd->vdev_children == 0); zio_nowait(zio_write_phys(zio, vd, vdev_label_offset(vd->vdev_psize, l, offset), size, buf, ZIO_CHECKSUM_LABEL, done, private, ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CONFIG_HELD | ZIO_FLAG_CANFAIL)); } /* * Generate the nvlist representing this vdev's config. */ nvlist_t * vdev_config_generate(vdev_t *vd, int getstats) { nvlist_t *nv = NULL; VERIFY(nvlist_alloc(&nv, NV_UNIQUE_NAME, KM_SLEEP) == 0); VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_TYPE, vd->vdev_ops->vdev_op_type) == 0); VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_ID, vd->vdev_id) == 0); VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_GUID, vd->vdev_guid) == 0); if (vd->vdev_path != NULL) VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_PATH, vd->vdev_path) == 0); if (vd->vdev_devid != NULL) VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_DEVID, vd->vdev_devid) == 0); if (vd->vdev_wholedisk != -1ULL) VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_WHOLE_DISK, vd->vdev_wholedisk) == 0); if (vd->vdev_not_present) VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_NOT_PRESENT, 1) == 0); if (vd == vd->vdev_top) { VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_METASLAB_ARRAY, vd->vdev_ms_array) == 0); VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_METASLAB_SHIFT, vd->vdev_ms_shift) == 0); VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_ASHIFT, vd->vdev_ashift) == 0); VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_ASIZE, vd->vdev_asize) == 0); } if (vd->vdev_dtl.smo_object != 0) VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_DTL, vd->vdev_dtl.smo_object) == 0); if (getstats) { vdev_stat_t vs; vdev_get_stats(vd, &vs); VERIFY(nvlist_add_uint64_array(nv, ZPOOL_CONFIG_STATS, (uint64_t *)&vs, sizeof (vs) / sizeof (uint64_t)) == 0); } if (!vd->vdev_ops->vdev_op_leaf) { nvlist_t **child; int c; child = kmem_alloc(vd->vdev_children * sizeof (nvlist_t *), KM_SLEEP); for (c = 0; c < vd->vdev_children; c++) child[c] = vdev_config_generate(vd->vdev_child[c], getstats); VERIFY(nvlist_add_nvlist_array(nv, ZPOOL_CONFIG_CHILDREN, child, vd->vdev_children) == 0); for (c = 0; c < vd->vdev_children; c++) nvlist_free(child[c]); kmem_free(child, vd->vdev_children * sizeof (nvlist_t *)); } else { if (!vd->vdev_tmpoffline) { if (vd->vdev_offline) VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_OFFLINE, B_TRUE) == 0); else (void) nvlist_remove(nv, ZPOOL_CONFIG_OFFLINE, DATA_TYPE_UINT64); } } return (nv); } nvlist_t * vdev_label_read_config(vdev_t *vd) { spa_t *spa = vd->vdev_spa; nvlist_t *config = NULL; vdev_phys_t *vp; zio_t *zio; int l; ASSERT(spa_config_held(spa, RW_READER)); if (vdev_is_dead(vd)) return (NULL); vp = zio_buf_alloc(sizeof (vdev_phys_t)); for (l = 0; l < VDEV_LABELS; l++) { zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE | ZIO_FLAG_CONFIG_HELD); vdev_label_read(zio, vd, l, vp, offsetof(vdev_label_t, vl_vdev_phys), sizeof (vdev_phys_t), NULL, NULL); if (zio_wait(zio) == 0 && nvlist_unpack(vp->vp_nvlist, sizeof (vp->vp_nvlist), &config, 0) == 0) break; if (config != NULL) { nvlist_free(config); config = NULL; } } zio_buf_free(vp, sizeof (vdev_phys_t)); return (config); } int vdev_label_init(vdev_t *vd, uint64_t crtxg) { spa_t *spa = vd->vdev_spa; nvlist_t *label; vdev_phys_t *vp; vdev_boot_header_t *vb; uberblock_phys_t *ubphys; zio_t *zio; int l, c, n; char *buf; size_t buflen; int error; ASSERT(spa_config_held(spa, RW_WRITER)); for (c = 0; c < vd->vdev_children; c++) if ((error = vdev_label_init(vd->vdev_child[c], crtxg)) != 0) return (error); if (!vd->vdev_ops->vdev_op_leaf) return (0); /* * Make sure each leaf device is writable, and zero its initial content. * Along the way, also make sure that no leaf is already in use. * Note that it's important to do this sequentially, not in parallel, * so that we catch cases of multiple use of the same leaf vdev in * the vdev we're creating -- e.g. mirroring a disk with itself. */ if (vdev_is_dead(vd)) return (EIO); /* * Check whether this device is already in use. * Ignore the check if crtxg == 0, which we use for device removal. */ if (crtxg != 0 && (label = vdev_label_read_config(vd)) != NULL) { uint64_t state, pool_guid, device_guid, txg; uint64_t mycrtxg = 0; (void) nvlist_lookup_uint64(label, ZPOOL_CONFIG_CREATE_TXG, &mycrtxg); if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_STATE, &state) == 0 && state == POOL_STATE_ACTIVE && nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID, &pool_guid) == 0 && nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID, &device_guid) == 0 && spa_guid_exists(pool_guid, device_guid) && nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_TXG, &txg) == 0 && (txg != 0 || mycrtxg == crtxg)) { dprintf("vdev %s in use, pool_state %d\n", vdev_description(vd), state); nvlist_free(label); return (EBUSY); } nvlist_free(label); } /* * The device isn't in use, so initialize its label. */ vp = zio_buf_alloc(sizeof (vdev_phys_t)); bzero(vp, sizeof (vdev_phys_t)); /* * Generate a label describing the pool and our top-level vdev. * We mark it as being from txg 0 to indicate that it's not * really part of an active pool just yet. The labels will * be written again with a meaningful txg by spa_sync(). */ label = spa_config_generate(spa, vd, 0ULL, B_FALSE); /* * Add our creation time. This allows us to detect multiple vdev * uses as described above, and automatically expires if we fail. */ VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_CREATE_TXG, crtxg) == 0); buf = vp->vp_nvlist; buflen = sizeof (vp->vp_nvlist); if (nvlist_pack(label, &buf, &buflen, NV_ENCODE_XDR, KM_SLEEP) != 0) { nvlist_free(label); zio_buf_free(vp, sizeof (vdev_phys_t)); return (EINVAL); } /* * Initialize boot block header. */ vb = zio_buf_alloc(sizeof (vdev_boot_header_t)); bzero(vb, sizeof (vdev_boot_header_t)); vb->vb_magic = VDEV_BOOT_MAGIC; vb->vb_version = VDEV_BOOT_VERSION; vb->vb_offset = VDEV_BOOT_OFFSET; vb->vb_size = VDEV_BOOT_SIZE; /* * Initialize uberblock template. */ ubphys = zio_buf_alloc(sizeof (uberblock_phys_t)); bzero(ubphys, sizeof (uberblock_phys_t)); ubphys->ubp_uberblock = spa->spa_uberblock; ubphys->ubp_uberblock.ub_txg = 0; /* * Write everything in parallel. */ zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CONFIG_HELD | ZIO_FLAG_CANFAIL); for (l = 0; l < VDEV_LABELS; l++) { vdev_label_write(zio, vd, l, vp, offsetof(vdev_label_t, vl_vdev_phys), sizeof (vdev_phys_t), NULL, NULL); vdev_label_write(zio, vd, l, vb, offsetof(vdev_label_t, vl_boot_header), sizeof (vdev_boot_header_t), NULL, NULL); for (n = 0; n < VDEV_UBERBLOCKS; n++) { vdev_label_write(zio, vd, l, ubphys, offsetof(vdev_label_t, vl_uberblock[n]), sizeof (uberblock_phys_t), NULL, NULL); } } error = zio_wait(zio); nvlist_free(label); zio_buf_free(ubphys, sizeof (uberblock_phys_t)); zio_buf_free(vb, sizeof (vdev_boot_header_t)); zio_buf_free(vp, sizeof (vdev_phys_t)); return (error); } /* * ========================================================================== * uberblock load/sync * ========================================================================== */ /* * Consider the following situation: txg is safely synced to disk. We've * written the first uberblock for txg + 1, and then we lose power. When we * come back up, we fail to see the uberblock for txg + 1 because, say, * it was on a mirrored device and the replica to which we wrote txg + 1 * is now offline. If we then make some changes and sync txg + 1, and then * the missing replica comes back, then for a new seconds we'll have two * conflicting uberblocks on disk with the same txg. The solution is simple: * among uberblocks with equal txg, choose the one with the latest timestamp. */ static int vdev_uberblock_compare(uberblock_t *ub1, uberblock_t *ub2) { if (ub1->ub_txg < ub2->ub_txg) return (-1); if (ub1->ub_txg > ub2->ub_txg) return (1); if (ub1->ub_timestamp < ub2->ub_timestamp) return (-1); if (ub1->ub_timestamp > ub2->ub_timestamp) return (1); return (0); } static void vdev_uberblock_load_done(zio_t *zio) { uberblock_phys_t *ubphys = zio->io_data; uberblock_t *ub = &ubphys->ubp_uberblock; uberblock_t *ubbest = zio->io_private; spa_t *spa = zio->io_spa; ASSERT3U(zio->io_size, ==, sizeof (uberblock_phys_t)); if (zio->io_error == 0 && uberblock_verify(ub) == 0) { mutex_enter(&spa->spa_uberblock_lock); if (vdev_uberblock_compare(ub, ubbest) > 0) *ubbest = *ub; mutex_exit(&spa->spa_uberblock_lock); } zio_buf_free(zio->io_data, zio->io_size); } void vdev_uberblock_load(zio_t *zio, vdev_t *vd, uberblock_t *ubbest) { int l, c, n; for (c = 0; c < vd->vdev_children; c++) vdev_uberblock_load(zio, vd->vdev_child[c], ubbest); if (!vd->vdev_ops->vdev_op_leaf) return; if (vdev_is_dead(vd)) return; for (l = 0; l < VDEV_LABELS; l++) { for (n = 0; n < VDEV_UBERBLOCKS; n++) { vdev_label_read(zio, vd, l, zio_buf_alloc(sizeof (uberblock_phys_t)), offsetof(vdev_label_t, vl_uberblock[n]), sizeof (uberblock_phys_t), vdev_uberblock_load_done, ubbest); } } } /* * Write the uberblock to both labels of all leaves of the specified vdev. * We only get credit for writes to known-visible vdevs; see spa_vdev_add(). */ static void vdev_uberblock_sync_done(zio_t *zio) { uint64_t *good_writes = zio->io_root->io_private; if (zio->io_error == 0 && zio->io_vd->vdev_top->vdev_ms_array != 0) atomic_add_64(good_writes, 1); } static void vdev_uberblock_sync(zio_t *zio, uberblock_phys_t *ubphys, vdev_t *vd, uint64_t txg) { int l, c, n; for (c = 0; c < vd->vdev_children; c++) vdev_uberblock_sync(zio, ubphys, vd->vdev_child[c], txg); if (!vd->vdev_ops->vdev_op_leaf) return; if (vdev_is_dead(vd)) return; n = txg & (VDEV_UBERBLOCKS - 1); ASSERT(ubphys->ubp_uberblock.ub_txg == txg); for (l = 0; l < VDEV_LABELS; l++) vdev_label_write(zio, vd, l, ubphys, offsetof(vdev_label_t, vl_uberblock[n]), sizeof (uberblock_phys_t), vdev_uberblock_sync_done, NULL); dprintf("vdev %s in txg %llu\n", vdev_description(vd), txg); } static int vdev_uberblock_sync_tree(spa_t *spa, uberblock_t *ub, vdev_t *uvd, uint64_t txg) { uberblock_phys_t *ubphys; uint64_t *good_writes; zio_t *zio; int error; ubphys = zio_buf_alloc(sizeof (uberblock_phys_t)); bzero(ubphys, sizeof (uberblock_phys_t)); ubphys->ubp_uberblock = *ub; good_writes = kmem_zalloc(sizeof (uint64_t), KM_SLEEP); zio = zio_root(spa, NULL, good_writes, ZIO_FLAG_CONFIG_HELD | ZIO_FLAG_CANFAIL); vdev_uberblock_sync(zio, ubphys, uvd, txg); error = zio_wait(zio); if (error && *good_writes != 0) { dprintf("partial success: good_writes = %llu\n", *good_writes); error = 0; } /* * It's possible to have no good writes and no error if every vdev is in * the CANT_OPEN state. */ if (*good_writes == 0 && error == 0) error = EIO; kmem_free(good_writes, sizeof (uint64_t)); zio_buf_free(ubphys, sizeof (uberblock_phys_t)); return (error); } /* * Sync out an individual vdev. */ static void vdev_sync_label_done(zio_t *zio) { uint64_t *good_writes = zio->io_root->io_private; if (zio->io_error == 0) atomic_add_64(good_writes, 1); } static void vdev_sync_label(zio_t *zio, vdev_t *vd, int l, uint64_t txg) { nvlist_t *label; vdev_phys_t *vp; char *buf; size_t buflen; int c; for (c = 0; c < vd->vdev_children; c++) vdev_sync_label(zio, vd->vdev_child[c], l, txg); if (!vd->vdev_ops->vdev_op_leaf) return; if (vdev_is_dead(vd)) return; /* * Generate a label describing the top-level config to which we belong. */ label = spa_config_generate(vd->vdev_spa, vd, txg, B_FALSE); vp = zio_buf_alloc(sizeof (vdev_phys_t)); bzero(vp, sizeof (vdev_phys_t)); buf = vp->vp_nvlist; buflen = sizeof (vp->vp_nvlist); if (nvlist_pack(label, &buf, &buflen, NV_ENCODE_XDR, KM_SLEEP) == 0) vdev_label_write(zio, vd, l, vp, offsetof(vdev_label_t, vl_vdev_phys), sizeof (vdev_phys_t), vdev_sync_label_done, NULL); zio_buf_free(vp, sizeof (vdev_phys_t)); nvlist_free(label); dprintf("%s label %d txg %llu\n", vdev_description(vd), l, txg); } static int vdev_sync_labels(vdev_t *vd, int l, uint64_t txg) { uint64_t *good_writes; zio_t *zio; int error; ASSERT(vd == vd->vdev_top); good_writes = kmem_zalloc(sizeof (uint64_t), KM_SLEEP); zio = zio_root(vd->vdev_spa, NULL, good_writes, ZIO_FLAG_CONFIG_HELD | ZIO_FLAG_CANFAIL); /* * Recursively kick off writes to all labels. */ vdev_sync_label(zio, vd, l, txg); error = zio_wait(zio); if (error && *good_writes != 0) { dprintf("partial success: good_writes = %llu\n", *good_writes); error = 0; } if (*good_writes == 0 && error == 0) error = ENODEV; kmem_free(good_writes, sizeof (uint64_t)); return (error); } /* * Sync the entire vdev configuration. * * The order of operations is carefully crafted to ensure that * if the system panics or loses power at any time, the state on disk * is still transactionally consistent. The in-line comments below * describe the failure semantics at each stage. * * Moreover, it is designed to be idempotent: if spa_sync_labels() fails * at any time, you can just call it again, and it will resume its work. */ int vdev_config_sync(vdev_t *uvd, uint64_t txg) { spa_t *spa = uvd->vdev_spa; uberblock_t *ub = &spa->spa_uberblock; vdev_t *rvd = spa->spa_root_vdev; vdev_t *vd; zio_t *zio; int l, error; ASSERT(ub->ub_txg <= txg); /* * If this isn't a resync due to I/O errors, and nothing changed * in this transaction group, and the vdev configuration hasn't changed, * then there's nothing to do. */ if (ub->ub_txg < txg && uberblock_update(ub, rvd, txg) == B_FALSE && list_is_empty(&spa->spa_dirty_list)) { dprintf("nothing to sync in %s in txg %llu\n", spa_name(spa), txg); return (0); } if (txg > spa_freeze_txg(spa)) return (0); ASSERT(txg <= spa->spa_final_txg); dprintf("syncing %s txg %llu\n", spa_name(spa), txg); /* * Flush the write cache of every disk that's been written to * in this transaction group. This ensures that all blocks * written in this txg will be committed to stable storage * before any uberblock that references them. */ zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CONFIG_HELD | ZIO_FLAG_CANFAIL); for (vd = txg_list_head(&spa->spa_vdev_txg_list, TXG_CLEAN(txg)); vd; vd = txg_list_next(&spa->spa_vdev_txg_list, vd, TXG_CLEAN(txg))) { zio_nowait(zio_ioctl(zio, spa, vd, DKIOCFLUSHWRITECACHE, NULL, NULL, ZIO_PRIORITY_NOW, ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_RETRY)); } (void) zio_wait(zio); /* * Sync out the even labels (L0, L2) for every dirty vdev. If the * system dies in the middle of this process, that's OK: all of the * even labels that made it to disk will be newer than any uberblock, * and will therefore be considered invalid. The odd labels (L1, L3), * which have not yet been touched, will still be valid. */ for (vd = list_head(&spa->spa_dirty_list); vd != NULL; vd = list_next(&spa->spa_dirty_list, vd)) { for (l = 0; l < VDEV_LABELS; l++) { if (l & 1) continue; if ((error = vdev_sync_labels(vd, l, txg)) != 0) return (error); } } /* * Flush the new labels to disk. This ensures that all even-label * updates are committed to stable storage before the uberblock update. */ zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CONFIG_HELD | ZIO_FLAG_CANFAIL); for (vd = list_head(&spa->spa_dirty_list); vd != NULL; vd = list_next(&spa->spa_dirty_list, vd)) { zio_nowait(zio_ioctl(zio, spa, vd, DKIOCFLUSHWRITECACHE, NULL, NULL, ZIO_PRIORITY_NOW, ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_RETRY)); } (void) zio_wait(zio); /* * Sync the uberblocks to all vdevs in the tree specified by uvd. * If the system dies in the middle of this step, there are two cases * to consider, and the on-disk state is consistent either way: * * (1) If none of the new uberblocks made it to disk, then the * previous uberblock will be the newest, and the odd labels * (which had not yet been touched) will be valid with respect * to that uberblock. * * (2) If one or more new uberblocks made it to disk, then they * will be the newest, and the even labels (which had all * been successfully committed) will be valid with respect * to the new uberblocks. */ if ((error = vdev_uberblock_sync_tree(spa, ub, uvd, txg)) != 0) return (error); /* * Flush the uberblocks to disk. This ensures that the odd labels * are no longer needed (because the new uberblocks and the even * labels are safely on disk), so it is safe to overwrite them. */ (void) zio_wait(zio_ioctl(NULL, spa, uvd, DKIOCFLUSHWRITECACHE, NULL, NULL, ZIO_PRIORITY_NOW, ZIO_FLAG_CONFIG_HELD | ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_RETRY)); /* * Sync out odd labels for every dirty vdev. If the system dies * in the middle of this process, the even labels and the new * uberblocks will suffice to open the pool. The next time * the pool is opened, the first thing we'll do -- before any * user data is modified -- is mark every vdev dirty so that * all labels will be brought up to date. */ for (vd = list_head(&spa->spa_dirty_list); vd != NULL; vd = list_next(&spa->spa_dirty_list, vd)) { for (l = 0; l < VDEV_LABELS; l++) { if ((l & 1) == 0) continue; if ((error = vdev_sync_labels(vd, l, txg)) != 0) return (error); } } /* * Flush the new labels to disk. This ensures that all odd-label * updates are committed to stable storage before the next * transaction group begins. */ zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CONFIG_HELD | ZIO_FLAG_CANFAIL); for (vd = list_head(&spa->spa_dirty_list); vd != NULL; vd = list_next(&spa->spa_dirty_list, vd)) { zio_nowait(zio_ioctl(zio, spa, vd, DKIOCFLUSHWRITECACHE, NULL, NULL, ZIO_PRIORITY_NOW, ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_RETRY)); } (void) zio_wait(zio); return (0); }