diff options
Diffstat (limited to 'module/zfs/dnode.c')
| -rw-r--r-- | module/zfs/dnode.c | 565 |
1 files changed, 510 insertions, 55 deletions
diff --git a/module/zfs/dnode.c b/module/zfs/dnode.c index c16902d21..850dd5816 100644 --- a/module/zfs/dnode.c +++ b/module/zfs/dnode.c @@ -38,19 +38,33 @@ static int free_range_compar(const void *node1, const void *node2); static kmem_cache_t *dnode_cache; +/* + * Define DNODE_STATS to turn on statistic gathering. By default, it is only + * turned on when DEBUG is also defined. + */ +#ifdef DEBUG +#define DNODE_STATS +#endif /* DEBUG */ + +#ifdef DNODE_STATS +#define DNODE_STAT_ADD(stat) ((stat)++) +#else +#define DNODE_STAT_ADD(stat) /* nothing */ +#endif /* DNODE_STATS */ static dnode_phys_t dnode_phys_zero; int zfs_default_bs = SPA_MINBLOCKSHIFT; int zfs_default_ibs = DN_MAX_INDBLKSHIFT; +static kmem_cbrc_t dnode_move(void *, void *, size_t, void *); + /* ARGSUSED */ static int dnode_cons(void *arg, void *unused, int kmflag) { - int i; dnode_t *dn = arg; - bzero(dn, sizeof (dnode_t)); + int i; rw_init(&dn->dn_struct_rwlock, NULL, RW_DEFAULT, NULL); mutex_init(&dn->dn_mtx, NULL, MUTEX_DEFAULT, NULL); @@ -59,8 +73,18 @@ dnode_cons(void *arg, void *unused, int kmflag) refcount_create(&dn->dn_holds); refcount_create(&dn->dn_tx_holds); + list_link_init(&dn->dn_link); + + bzero(&dn->dn_next_nblkptr[0], sizeof (dn->dn_next_nblkptr)); + bzero(&dn->dn_next_nlevels[0], sizeof (dn->dn_next_nlevels)); + bzero(&dn->dn_next_indblkshift[0], sizeof (dn->dn_next_indblkshift)); + bzero(&dn->dn_next_bonustype[0], sizeof (dn->dn_next_bonustype)); + bzero(&dn->dn_rm_spillblk[0], sizeof (dn->dn_rm_spillblk)); + bzero(&dn->dn_next_bonuslen[0], sizeof (dn->dn_next_bonuslen)); + bzero(&dn->dn_next_blksz[0], sizeof (dn->dn_next_blksz)); for (i = 0; i < TXG_SIZE; i++) { + list_link_init(&dn->dn_dirty_link[i]); avl_create(&dn->dn_ranges[i], free_range_compar, sizeof (free_range_t), offsetof(struct free_range, fr_node)); @@ -69,9 +93,27 @@ dnode_cons(void *arg, void *unused, int kmflag) offsetof(dbuf_dirty_record_t, dr_dirty_node)); } + dn->dn_allocated_txg = 0; + dn->dn_free_txg = 0; + dn->dn_assigned_txg = 0; + dn->dn_dirtyctx = 0; + dn->dn_dirtyctx_firstset = NULL; + dn->dn_bonus = NULL; + dn->dn_have_spill = B_FALSE; + dn->dn_zio = NULL; + dn->dn_oldused = 0; + dn->dn_oldflags = 0; + dn->dn_olduid = 0; + dn->dn_oldgid = 0; + dn->dn_newuid = 0; + dn->dn_newgid = 0; + dn->dn_id_flags = 0; + + dn->dn_dbufs_count = 0; list_create(&dn->dn_dbufs, sizeof (dmu_buf_impl_t), offsetof(dmu_buf_impl_t, db_link)); + dn->dn_moved = 0; return (0); } @@ -88,27 +130,56 @@ dnode_dest(void *arg, void *unused) cv_destroy(&dn->dn_notxholds); refcount_destroy(&dn->dn_holds); refcount_destroy(&dn->dn_tx_holds); + ASSERT(!list_link_active(&dn->dn_link)); for (i = 0; i < TXG_SIZE; i++) { + ASSERT(!list_link_active(&dn->dn_dirty_link[i])); avl_destroy(&dn->dn_ranges[i]); list_destroy(&dn->dn_dirty_records[i]); + ASSERT3U(dn->dn_next_nblkptr[i], ==, 0); + ASSERT3U(dn->dn_next_nlevels[i], ==, 0); + ASSERT3U(dn->dn_next_indblkshift[i], ==, 0); + ASSERT3U(dn->dn_next_bonustype[i], ==, 0); + ASSERT3U(dn->dn_rm_spillblk[i], ==, 0); + ASSERT3U(dn->dn_next_bonuslen[i], ==, 0); + ASSERT3U(dn->dn_next_blksz[i], ==, 0); } + ASSERT3U(dn->dn_allocated_txg, ==, 0); + ASSERT3U(dn->dn_free_txg, ==, 0); + ASSERT3U(dn->dn_assigned_txg, ==, 0); + ASSERT3U(dn->dn_dirtyctx, ==, 0); + ASSERT3P(dn->dn_dirtyctx_firstset, ==, NULL); + ASSERT3P(dn->dn_bonus, ==, NULL); + ASSERT(!dn->dn_have_spill); + ASSERT3P(dn->dn_zio, ==, NULL); + ASSERT3U(dn->dn_oldused, ==, 0); + ASSERT3U(dn->dn_oldflags, ==, 0); + ASSERT3U(dn->dn_olduid, ==, 0); + ASSERT3U(dn->dn_oldgid, ==, 0); + ASSERT3U(dn->dn_newuid, ==, 0); + ASSERT3U(dn->dn_newgid, ==, 0); + ASSERT3U(dn->dn_id_flags, ==, 0); + + ASSERT3U(dn->dn_dbufs_count, ==, 0); list_destroy(&dn->dn_dbufs); } void dnode_init(void) { + ASSERT(dnode_cache == NULL); dnode_cache = kmem_cache_create("dnode_t", sizeof (dnode_t), 0, dnode_cons, dnode_dest, NULL, NULL, NULL, 0); + kmem_cache_set_move(dnode_cache, dnode_move); } void dnode_fini(void) { kmem_cache_destroy(dnode_cache); + dnode_cache = NULL; } @@ -120,6 +191,7 @@ dnode_verify(dnode_t *dn) ASSERT(dn->dn_phys); ASSERT(dn->dn_objset); + ASSERT(dn->dn_handle->dnh_dnode == dn); ASSERT(dn->dn_phys->dn_type < DMU_OT_NUMTYPES); @@ -298,18 +370,29 @@ dnode_setdblksz(dnode_t *dn, int size) static dnode_t * dnode_create(objset_t *os, dnode_phys_t *dnp, dmu_buf_impl_t *db, - uint64_t object) + uint64_t object, dnode_handle_t *dnh) { dnode_t *dn = kmem_cache_alloc(dnode_cache, KM_SLEEP); - (void) dnode_cons(dn, NULL, 0); /* XXX */ - dn->dn_objset = os; + ASSERT(!POINTER_IS_VALID(dn->dn_objset)); + dn->dn_moved = 0; + + /* + * Defer setting dn_objset until the dnode is ready to be a candidate + * for the dnode_move() callback. + */ dn->dn_object = object; dn->dn_dbuf = db; + dn->dn_handle = dnh; dn->dn_phys = dnp; - if (dnp->dn_datablkszsec) + if (dnp->dn_datablkszsec) { dnode_setdblksz(dn, dnp->dn_datablkszsec << SPA_MINBLOCKSHIFT); + } else { + dn->dn_datablksz = 0; + dn->dn_datablkszsec = 0; + dn->dn_datablkshift = 0; + } dn->dn_indblkshift = dnp->dn_indblkshift; dn->dn_nlevels = dnp->dn_nlevels; dn->dn_type = dnp->dn_type; @@ -325,45 +408,65 @@ dnode_create(objset_t *os, dnode_phys_t *dnp, dmu_buf_impl_t *db, dmu_zfetch_init(&dn->dn_zfetch, dn); ASSERT(dn->dn_phys->dn_type < DMU_OT_NUMTYPES); + mutex_enter(&os->os_lock); list_insert_head(&os->os_dnodes, dn); + membar_producer(); + /* + * Everything else must be valid before assigning dn_objset makes the + * dnode eligible for dnode_move(). + */ + dn->dn_objset = os; mutex_exit(&os->os_lock); arc_space_consume(sizeof (dnode_t), ARC_SPACE_OTHER); return (dn); } +/* + * Caller must be holding the dnode handle, which is released upon return. + */ static void dnode_destroy(dnode_t *dn) { objset_t *os = dn->dn_objset; -#ifdef ZFS_DEBUG - int i; - - for (i = 0; i < TXG_SIZE; i++) { - ASSERT(!list_link_active(&dn->dn_dirty_link[i])); - ASSERT(NULL == list_head(&dn->dn_dirty_records[i])); - ASSERT(0 == avl_numnodes(&dn->dn_ranges[i])); - } - ASSERT(NULL == list_head(&dn->dn_dbufs)); -#endif ASSERT((dn->dn_id_flags & DN_ID_NEW_EXIST) == 0); mutex_enter(&os->os_lock); + POINTER_INVALIDATE(&dn->dn_objset); list_remove(&os->os_dnodes, dn); mutex_exit(&os->os_lock); - if (dn->dn_dirtyctx_firstset) { + /* the dnode can no longer move, so we can release the handle */ + zrl_remove(&dn->dn_handle->dnh_zrlock); + + dn->dn_allocated_txg = 0; + dn->dn_free_txg = 0; + dn->dn_assigned_txg = 0; + + dn->dn_dirtyctx = 0; + if (dn->dn_dirtyctx_firstset != NULL) { kmem_free(dn->dn_dirtyctx_firstset, 1); dn->dn_dirtyctx_firstset = NULL; } - dmu_zfetch_rele(&dn->dn_zfetch); - if (dn->dn_bonus) { + if (dn->dn_bonus != NULL) { mutex_enter(&dn->dn_bonus->db_mtx); dbuf_evict(dn->dn_bonus); dn->dn_bonus = NULL; } + dn->dn_zio = NULL; + + dn->dn_have_spill = B_FALSE; + dn->dn_oldused = 0; + dn->dn_oldflags = 0; + dn->dn_olduid = 0; + dn->dn_oldgid = 0; + dn->dn_newuid = 0; + dn->dn_newgid = 0; + dn->dn_id_flags = 0; + + dmu_zfetch_rele(&dn->dn_zfetch); kmem_cache_free(dnode_cache, dn); arc_space_return(sizeof (dnode_t), ARC_SPACE_OTHER); } @@ -408,6 +511,7 @@ dnode_allocate(dnode_t *dn, dmu_object_type_t ot, int blocksize, int ibs, ASSERT3P(list_head(&dn->dn_dbufs), ==, NULL); for (i = 0; i < TXG_SIZE; i++) { + ASSERT3U(dn->dn_next_nblkptr[i], ==, 0); ASSERT3U(dn->dn_next_nlevels[i], ==, 0); ASSERT3U(dn->dn_next_indblkshift[i], ==, 0); ASSERT3U(dn->dn_next_bonuslen[i], ==, 0); @@ -522,9 +626,304 @@ dnode_reallocate(dnode_t *dn, dmu_object_type_t ot, int blocksize, mutex_exit(&dn->dn_mtx); } +#ifdef DNODE_STATS +static struct { + uint64_t dms_dnode_invalid; + uint64_t dms_dnode_recheck1; + uint64_t dms_dnode_recheck2; + uint64_t dms_dnode_special; + uint64_t dms_dnode_handle; + uint64_t dms_dnode_rwlock; + uint64_t dms_dnode_active; +} dnode_move_stats; +#endif /* DNODE_STATS */ + +static void +dnode_move_impl(dnode_t *odn, dnode_t *ndn) +{ + int i; + + ASSERT(!RW_LOCK_HELD(&odn->dn_struct_rwlock)); + ASSERT(MUTEX_NOT_HELD(&odn->dn_mtx)); + ASSERT(MUTEX_NOT_HELD(&odn->dn_dbufs_mtx)); + ASSERT(!RW_LOCK_HELD(&odn->dn_zfetch.zf_rwlock)); + + /* Copy fields. */ + ndn->dn_objset = odn->dn_objset; + ndn->dn_object = odn->dn_object; + ndn->dn_dbuf = odn->dn_dbuf; + ndn->dn_handle = odn->dn_handle; + ndn->dn_phys = odn->dn_phys; + ndn->dn_type = odn->dn_type; + ndn->dn_bonuslen = odn->dn_bonuslen; + ndn->dn_bonustype = odn->dn_bonustype; + ndn->dn_nblkptr = odn->dn_nblkptr; + ndn->dn_checksum = odn->dn_checksum; + ndn->dn_compress = odn->dn_compress; + ndn->dn_nlevels = odn->dn_nlevels; + ndn->dn_indblkshift = odn->dn_indblkshift; + ndn->dn_datablkshift = odn->dn_datablkshift; + ndn->dn_datablkszsec = odn->dn_datablkszsec; + ndn->dn_datablksz = odn->dn_datablksz; + ndn->dn_maxblkid = odn->dn_maxblkid; + bcopy(&odn->dn_next_nblkptr[0], &ndn->dn_next_nblkptr[0], + sizeof (odn->dn_next_nblkptr)); + bcopy(&odn->dn_next_nlevels[0], &ndn->dn_next_nlevels[0], + sizeof (odn->dn_next_nlevels)); + bcopy(&odn->dn_next_indblkshift[0], &ndn->dn_next_indblkshift[0], + sizeof (odn->dn_next_indblkshift)); + bcopy(&odn->dn_next_bonustype[0], &ndn->dn_next_bonustype[0], + sizeof (odn->dn_next_bonustype)); + bcopy(&odn->dn_rm_spillblk[0], &ndn->dn_rm_spillblk[0], + sizeof (odn->dn_rm_spillblk)); + bcopy(&odn->dn_next_bonuslen[0], &ndn->dn_next_bonuslen[0], + sizeof (odn->dn_next_bonuslen)); + bcopy(&odn->dn_next_blksz[0], &ndn->dn_next_blksz[0], + sizeof (odn->dn_next_blksz)); + for (i = 0; i < TXG_SIZE; i++) { + list_move_tail(&ndn->dn_dirty_records[i], + &odn->dn_dirty_records[i]); + } + bcopy(&odn->dn_ranges[0], &ndn->dn_ranges[0], sizeof (odn->dn_ranges)); + ndn->dn_allocated_txg = odn->dn_allocated_txg; + ndn->dn_free_txg = odn->dn_free_txg; + ndn->dn_assigned_txg = odn->dn_assigned_txg; + ndn->dn_dirtyctx = odn->dn_dirtyctx; + ndn->dn_dirtyctx_firstset = odn->dn_dirtyctx_firstset; + ASSERT(refcount_count(&odn->dn_tx_holds) == 0); + refcount_transfer(&ndn->dn_holds, &odn->dn_holds); + ASSERT(list_is_empty(&ndn->dn_dbufs)); + list_move_tail(&ndn->dn_dbufs, &odn->dn_dbufs); + ndn->dn_dbufs_count = odn->dn_dbufs_count; + ndn->dn_bonus = odn->dn_bonus; + ndn->dn_have_spill = odn->dn_have_spill; + ndn->dn_zio = odn->dn_zio; + ndn->dn_oldused = odn->dn_oldused; + ndn->dn_oldflags = odn->dn_oldflags; + ndn->dn_olduid = odn->dn_olduid; + ndn->dn_oldgid = odn->dn_oldgid; + ndn->dn_newuid = odn->dn_newuid; + ndn->dn_newgid = odn->dn_newgid; + ndn->dn_id_flags = odn->dn_id_flags; + dmu_zfetch_init(&ndn->dn_zfetch, NULL); + list_move_tail(&ndn->dn_zfetch.zf_stream, &odn->dn_zfetch.zf_stream); + ndn->dn_zfetch.zf_dnode = odn->dn_zfetch.zf_dnode; + ndn->dn_zfetch.zf_stream_cnt = odn->dn_zfetch.zf_stream_cnt; + ndn->dn_zfetch.zf_alloc_fail = odn->dn_zfetch.zf_alloc_fail; + + /* + * Update back pointers. Updating the handle fixes the back pointer of + * every descendant dbuf as well as the bonus dbuf. + */ + ASSERT(ndn->dn_handle->dnh_dnode == odn); + ndn->dn_handle->dnh_dnode = ndn; + if (ndn->dn_zfetch.zf_dnode == odn) { + ndn->dn_zfetch.zf_dnode = ndn; + } + + /* + * Invalidate the original dnode by clearing all of its back pointers. + */ + odn->dn_dbuf = NULL; + odn->dn_handle = NULL; + list_create(&odn->dn_dbufs, sizeof (dmu_buf_impl_t), + offsetof(dmu_buf_impl_t, db_link)); + odn->dn_dbufs_count = 0; + odn->dn_bonus = NULL; + odn->dn_zfetch.zf_dnode = NULL; + + /* + * Set the low bit of the objset pointer to ensure that dnode_move() + * recognizes the dnode as invalid in any subsequent callback. + */ + POINTER_INVALIDATE(&odn->dn_objset); + + /* + * Satisfy the destructor. + */ + for (i = 0; i < TXG_SIZE; i++) { + list_create(&odn->dn_dirty_records[i], + sizeof (dbuf_dirty_record_t), + offsetof(dbuf_dirty_record_t, dr_dirty_node)); + odn->dn_ranges[i].avl_root = NULL; + odn->dn_ranges[i].avl_numnodes = 0; + odn->dn_next_nlevels[i] = 0; + odn->dn_next_indblkshift[i] = 0; + odn->dn_next_bonustype[i] = 0; + odn->dn_rm_spillblk[i] = 0; + odn->dn_next_bonuslen[i] = 0; + odn->dn_next_blksz[i] = 0; + } + odn->dn_allocated_txg = 0; + odn->dn_free_txg = 0; + odn->dn_assigned_txg = 0; + odn->dn_dirtyctx = 0; + odn->dn_dirtyctx_firstset = NULL; + odn->dn_have_spill = B_FALSE; + odn->dn_zio = NULL; + odn->dn_oldused = 0; + odn->dn_oldflags = 0; + odn->dn_olduid = 0; + odn->dn_oldgid = 0; + odn->dn_newuid = 0; + odn->dn_newgid = 0; + odn->dn_id_flags = 0; + + /* + * Mark the dnode. + */ + ndn->dn_moved = 1; + odn->dn_moved = (uint8_t)-1; +} + +#ifdef _KERNEL +/*ARGSUSED*/ +static kmem_cbrc_t +dnode_move(void *buf, void *newbuf, size_t size, void *arg) +{ + dnode_t *odn = buf, *ndn = newbuf; + objset_t *os; + int64_t refcount; + uint32_t dbufs; + + /* + * The dnode is on the objset's list of known dnodes if the objset + * pointer is valid. We set the low bit of the objset pointer when + * freeing the dnode to invalidate it, and the memory patterns written + * by kmem (baddcafe and deadbeef) set at least one of the two low bits. + * A newly created dnode sets the objset pointer last of all to indicate + * that the dnode is known and in a valid state to be moved by this + * function. + */ + os = odn->dn_objset; + if (!POINTER_IS_VALID(os)) { + DNODE_STAT_ADD(dnode_move_stats.dms_dnode_invalid); + return (KMEM_CBRC_DONT_KNOW); + } + + /* + * Ensure that the objset does not go away during the move. + */ + rw_enter(&os_lock, RW_WRITER); + if (os != odn->dn_objset) { + rw_exit(&os_lock); + DNODE_STAT_ADD(dnode_move_stats.dms_dnode_recheck1); + return (KMEM_CBRC_DONT_KNOW); + } + + /* + * If the dnode is still valid, then so is the objset. We know that no + * valid objset can be freed while we hold os_lock, so we can safely + * ensure that the objset remains in use. + */ + mutex_enter(&os->os_lock); + + /* + * Recheck the objset pointer in case the dnode was removed just before + * acquiring the lock. + */ + if (os != odn->dn_objset) { + mutex_exit(&os->os_lock); + rw_exit(&os_lock); + DNODE_STAT_ADD(dnode_move_stats.dms_dnode_recheck2); + return (KMEM_CBRC_DONT_KNOW); + } + + /* + * At this point we know that as long as we hold os->os_lock, the dnode + * cannot be freed and fields within the dnode can be safely accessed. + * The objset listing this dnode cannot go away as long as this dnode is + * on its list. + */ + rw_exit(&os_lock); + if (DMU_OBJECT_IS_SPECIAL(odn->dn_object)) { + mutex_exit(&os->os_lock); + DNODE_STAT_ADD(dnode_move_stats.dms_dnode_special); + return (KMEM_CBRC_NO); + } + ASSERT(odn->dn_dbuf != NULL); /* only "special" dnodes have no parent */ + + /* + * Lock the dnode handle to prevent the dnode from obtaining any new + * holds. This also prevents the descendant dbufs and the bonus dbuf + * from accessing the dnode, so that we can discount their holds. The + * handle is safe to access because we know that while the dnode cannot + * go away, neither can its handle. Once we hold dnh_zrlock, we can + * safely move any dnode referenced only by dbufs. + */ + if (!zrl_tryenter(&odn->dn_handle->dnh_zrlock)) { + mutex_exit(&os->os_lock); + DNODE_STAT_ADD(dnode_move_stats.dms_dnode_handle); + return (KMEM_CBRC_LATER); + } + + /* + * Ensure a consistent view of the dnode's holds and the dnode's dbufs. + * We need to guarantee that there is a hold for every dbuf in order to + * determine whether the dnode is actively referenced. Falsely matching + * a dbuf to an active hold would lead to an unsafe move. It's possible + * that a thread already having an active dnode hold is about to add a + * dbuf, and we can't compare hold and dbuf counts while the add is in + * progress. + */ + if (!rw_tryenter(&odn->dn_struct_rwlock, RW_WRITER)) { + zrl_exit(&odn->dn_handle->dnh_zrlock); + mutex_exit(&os->os_lock); + DNODE_STAT_ADD(dnode_move_stats.dms_dnode_rwlock); + return (KMEM_CBRC_LATER); + } + + /* + * A dbuf may be removed (evicted) without an active dnode hold. In that + * case, the dbuf count is decremented under the handle lock before the + * dbuf's hold is released. This order ensures that if we count the hold + * after the dbuf is removed but before its hold is released, we will + * treat the unmatched hold as active and exit safely. If we count the + * hold before the dbuf is removed, the hold is discounted, and the + * removal is blocked until the move completes. + */ + refcount = refcount_count(&odn->dn_holds); + ASSERT(refcount >= 0); + dbufs = odn->dn_dbufs_count; + + /* We can't have more dbufs than dnode holds. */ + ASSERT3U(dbufs, <=, refcount); + DTRACE_PROBE3(dnode__move, dnode_t *, odn, int64_t, refcount, + uint32_t, dbufs); + + if (refcount > dbufs) { + rw_exit(&odn->dn_struct_rwlock); + zrl_exit(&odn->dn_handle->dnh_zrlock); + mutex_exit(&os->os_lock); + DNODE_STAT_ADD(dnode_move_stats.dms_dnode_active); + return (KMEM_CBRC_LATER); + } + + rw_exit(&odn->dn_struct_rwlock); + + /* + * At this point we know that anyone with a hold on the dnode is not + * actively referencing it. The dnode is known and in a valid state to + * move. We're holding the locks needed to execute the critical section. + */ + dnode_move_impl(odn, ndn); + + list_link_replace(&odn->dn_link, &ndn->dn_link); + /* If the dnode was safe to move, the refcount cannot have changed. */ + ASSERT(refcount == refcount_count(&ndn->dn_holds)); + ASSERT(dbufs == ndn->dn_dbufs_count); + zrl_exit(&ndn->dn_handle->dnh_zrlock); /* handle has moved */ + mutex_exit(&os->os_lock); + + return (KMEM_CBRC_YES); +} +#endif /* _KERNEL */ + void -dnode_special_close(dnode_t *dn) +dnode_special_close(dnode_handle_t *dnh) { + dnode_t *dn = dnh->dnh_dnode; + /* * Wait for final references to the dnode to clear. This can * only happen if the arc is asyncronously evicting state that @@ -533,13 +932,19 @@ dnode_special_close(dnode_t *dn) */ while (refcount_count(&dn->dn_holds) > 0) delay(1); - dnode_destroy(dn); + zrl_add(&dnh->dnh_zrlock); + dnode_destroy(dn); /* implicit zrl_remove() */ + zrl_destroy(&dnh->dnh_zrlock); + dnh->dnh_dnode = NULL; } dnode_t * -dnode_special_open(objset_t *os, dnode_phys_t *dnp, uint64_t object) +dnode_special_open(objset_t *os, dnode_phys_t *dnp, uint64_t object, + dnode_handle_t *dnh) { - dnode_t *dn = dnode_create(os, dnp, NULL, object); + dnode_t *dn = dnode_create(os, dnp, NULL, object, dnh); + dnh->dnh_dnode = dn; + zrl_init(&dnh->dnh_zrlock); DNODE_VERIFY(dn); return (dn); } @@ -547,34 +952,43 @@ dnode_special_open(objset_t *os, dnode_phys_t *dnp, uint64_t object) static void dnode_buf_pageout(dmu_buf_t *db, void *arg) { - dnode_t **children_dnodes = arg; + dnode_children_t *children_dnodes = arg; int i; int epb = db->db_size >> DNODE_SHIFT; + ASSERT(epb == children_dnodes->dnc_count); + for (i = 0; i < epb; i++) { - dnode_t *dn = children_dnodes[i]; - int n; + dnode_handle_t *dnh = &children_dnodes->dnc_children[i]; + dnode_t *dn; - if (dn == NULL) + /* + * The dnode handle lock guards against the dnode moving to + * another valid address, so there is no need here to guard + * against changes to or from NULL. + */ + if (dnh->dnh_dnode == NULL) { + zrl_destroy(&dnh->dnh_zrlock); continue; -#ifdef ZFS_DEBUG + } + + zrl_add(&dnh->dnh_zrlock); + dn = dnh->dnh_dnode; /* * If there are holds on this dnode, then there should * be holds on the dnode's containing dbuf as well; thus - * it wouldn't be eligable for eviction and this function + * it wouldn't be eligible for eviction and this function * would not have been called. */ ASSERT(refcount_is_zero(&dn->dn_holds)); - ASSERT(list_head(&dn->dn_dbufs) == NULL); ASSERT(refcount_is_zero(&dn->dn_tx_holds)); - for (n = 0; n < TXG_SIZE; n++) - ASSERT(!list_link_active(&dn->dn_dirty_link[n])); -#endif - children_dnodes[i] = NULL; - dnode_destroy(dn); + dnode_destroy(dn); /* implicit zrl_remove() */ + zrl_destroy(&dnh->dnh_zrlock); + dnh->dnh_dnode = NULL; } - kmem_free(children_dnodes, epb * sizeof (dnode_t *)); + kmem_free(children_dnodes, sizeof (dnode_children_t) + + (epb - 1) * sizeof (dnode_handle_t)); } /* @@ -593,7 +1007,8 @@ dnode_hold_impl(objset_t *os, uint64_t object, int flag, uint64_t blk; dnode_t *mdn, *dn; dmu_buf_impl_t *db; - dnode_t **children_dnodes; + dnode_children_t *children_dnodes; + dnode_handle_t *dnh; /* * If you are holding the spa config lock as writer, you shouldn't @@ -603,12 +1018,11 @@ dnode_hold_impl(objset_t *os, uint64_t object, int flag, */ ASSERT(spa_config_held(os->os_spa, SCL_ALL, RW_WRITER) == 0 || (spa_is_root(os->os_spa) && - spa_config_held(os->os_spa, SCL_STATE, RW_WRITER) && - !spa_config_held(os->os_spa, SCL_ZIO, RW_WRITER))); + spa_config_held(os->os_spa, SCL_STATE, RW_WRITER))); if (object == DMU_USERUSED_OBJECT || object == DMU_GROUPUSED_OBJECT) { dn = (object == DMU_USERUSED_OBJECT) ? - os->os_userused_dnode : os->os_groupused_dnode; + DMU_USERUSED_DNODE(os) : DMU_GROUPUSED_DNODE(os); if (dn == NULL) return (ENOENT); type = dn->dn_type; @@ -625,7 +1039,8 @@ dnode_hold_impl(objset_t *os, uint64_t object, int flag, if (object == 0 || object >= DN_MAX_OBJECT) return (EINVAL); - mdn = os->os_meta_dnode; + mdn = DMU_META_DNODE(os); + ASSERT(mdn->dn_object == DMU_META_DNODE_OBJECT); DNODE_VERIFY(mdn); @@ -652,26 +1067,39 @@ dnode_hold_impl(objset_t *os, uint64_t object, int flag, idx = object & (epb-1); + ASSERT(DB_DNODE(db)->dn_type == DMU_OT_DNODE); children_dnodes = dmu_buf_get_user(&db->db); if (children_dnodes == NULL) { - dnode_t **winner; - children_dnodes = kmem_zalloc(epb * sizeof (dnode_t *), - KM_SLEEP); + int i; + dnode_children_t *winner; + children_dnodes = kmem_alloc(sizeof (dnode_children_t) + + (epb - 1) * sizeof (dnode_handle_t), KM_SLEEP); + children_dnodes->dnc_count = epb; + dnh = &children_dnodes->dnc_children[0]; + for (i = 0; i < epb; i++) { + zrl_init(&dnh[i].dnh_zrlock); + dnh[i].dnh_dnode = NULL; + } if (winner = dmu_buf_set_user(&db->db, children_dnodes, NULL, dnode_buf_pageout)) { - kmem_free(children_dnodes, epb * sizeof (dnode_t *)); + kmem_free(children_dnodes, sizeof (dnode_children_t) + + (epb - 1) * sizeof (dnode_handle_t)); children_dnodes = winner; } } + ASSERT(children_dnodes->dnc_count == epb); - if ((dn = children_dnodes[idx]) == NULL) { - dnode_phys_t *dnp = (dnode_phys_t *)db->db.db_data+idx; + dnh = &children_dnodes->dnc_children[idx]; + zrl_add(&dnh->dnh_zrlock); + if ((dn = dnh->dnh_dnode) == NULL) { + dnode_phys_t *phys = (dnode_phys_t *)db->db.db_data+idx; dnode_t *winner; - dn = dnode_create(os, dnp, db, object); - winner = atomic_cas_ptr(&children_dnodes[idx], NULL, dn); + dn = dnode_create(os, phys, db, object, dnh); + winner = atomic_cas_ptr(&dnh->dnh_dnode, NULL, dn); if (winner != NULL) { - dnode_destroy(dn); + zrl_add(&dnh->dnh_zrlock); + dnode_destroy(dn); /* implicit zrl_remove() */ dn = winner; } } @@ -683,13 +1111,16 @@ dnode_hold_impl(objset_t *os, uint64_t object, int flag, ((flag & DNODE_MUST_BE_FREE) && (type != DMU_OT_NONE || !refcount_is_zero(&dn->dn_holds)))) { mutex_exit(&dn->dn_mtx); + zrl_remove(&dnh->dnh_zrlock); dbuf_rele(db, FTAG); return (type == DMU_OT_NONE ? ENOENT : EEXIST); } mutex_exit(&dn->dn_mtx); if (refcount_add(&dn->dn_holds, tag) == 1) - dbuf_add_ref(db, dn); + dbuf_add_ref(db, dnh); + /* Now we can rely on the hold to prevent the dnode from moving. */ + zrl_remove(&dnh->dnh_zrlock); DNODE_VERIFY(dn); ASSERT3P(dn->dn_dbuf, ==, db); @@ -731,13 +1162,37 @@ void dnode_rele(dnode_t *dn, void *tag) { uint64_t refs; + /* Get while the hold prevents the dnode from moving. */ + dmu_buf_impl_t *db = dn->dn_dbuf; + dnode_handle_t *dnh = dn->dn_handle; mutex_enter(&dn->dn_mtx); refs = refcount_remove(&dn->dn_holds, tag); mutex_exit(&dn->dn_mtx); + + /* + * It's unsafe to release the last hold on a dnode by dnode_rele() or + * indirectly by dbuf_rele() while relying on the dnode handle to + * prevent the dnode from moving, since releasing the last hold could + * result in the dnode's parent dbuf evicting its dnode handles. For + * that reason anyone calling dnode_rele() or dbuf_rele() without some + * other direct or indirect hold on the dnode must first drop the dnode + * handle. + */ + ASSERT(refs > 0 || dnh->dnh_zrlock.zr_owner != curthread); + /* NOTE: the DNODE_DNODE does not have a dn_dbuf */ - if (refs == 0 && dn->dn_dbuf) - dbuf_rele(dn->dn_dbuf, dn); + if (refs == 0 && db != NULL) { + /* + * Another thread could add a hold to the dnode handle in + * dnode_hold_impl() while holding the parent dbuf. Since the + * hold on the parent dbuf prevents the handle from being + * destroyed, the hold on the handle is OK. We can't yet assert + * that the handle has zero references, but that will be + * asserted anyway when the handle gets destroyed. + */ + dbuf_rele(db, dnh); + } } void @@ -756,7 +1211,7 @@ dnode_setdirty(dnode_t *dn, dmu_tx_t *tx) #ifdef ZFS_DEBUG mutex_enter(&dn->dn_mtx); ASSERT(dn->dn_phys->dn_type || dn->dn_allocated_txg); - /* ASSERT(dn->dn_free_txg == 0 || dn->dn_free_txg >= txg); */ + ASSERT(dn->dn_free_txg == 0 || dn->dn_free_txg >= txg); mutex_exit(&dn->dn_mtx); #endif @@ -795,7 +1250,7 @@ dnode_setdirty(dnode_t *dn, dmu_tx_t *tx) /* * The dnode maintains a hold on its containing dbuf as * long as there are holds on it. Each instantiated child - * dbuf maintaines a hold on the dnode. When the last child + * dbuf maintains a hold on the dnode. When the last child * drops its hold, the dnode will drop its hold on the * containing dbuf. We add a "dirty hold" here so that the * dnode will hang around after we finish processing its |