MFV r303078:
7086 ztest attempts dva_get_dsize_sync on an embedded blockpointer illumos/illumos-gate@926549256b https://github.com/illumos/illumos-gate/commit/926549256b71acd595f69b236779ff6b7 8fa08ef https://www.illumos.org/issues/7086 In dbuf_dirty(), we need to grab the dn_struct_rwlock before looking at the db_blkptr, to prevent it from being changed by syncing context. Otherwise we may see that ztest got a segfault from this stack: libzpool.so.1`dva_get_dsize_sync+0x98(872f000,b32b240
, fed7811b, 0, b4cda20, 0) libzpool.so.1`bp_get_dsize+0x60(872f000,b32b240
, 0, 97cb780, 9d4c1a8, 0) libzpool.so.1`dbuf_dirty+0x9b3(ce0a100, 97cb780, 9, fecd2530) libzpool.so.1`dmu_buf_will_dirty+0xc3(ce0a100, 97cb780, ea293d6c, 1) libzpool.so.1`zap_lockdir+0x1a0(8aaa3c0, 1, 0, 97cb780, 1, 1) libzpool.so.1`zap_remove_norm+0x30(8aaa3c0, 1, 0, 8728b10, 0, 97cb780) libzpool.so.1`zap_remove+0x29(8aaa3c0, 1, 0, 8728b10, 97cb780, a) ztest_replay_remove+0x225(ea294588, 8728ae8, 0, 38010000, 0, 0) ztest_remove+0x9f(ea294588, ea293f50, 4, 3) ztest_object_init+0x78(ea294588, ea293f50, 4e0, 1) ztest_dmu_object_alloc_free+0x71(ea294588, 13) ztest_dmu_objset_create_destroy+0x224(80cef08, 13, 0, 805d36c, 9017ad44, 0) ztest_execute+0x89(a, 807c720, 13, 0) ztest_thread+0xea(13, 0, 0, 0) libc.so.1`_thrp_setup+0x88(f0983240) libc.so.1`_lwp_start(f0983240, 0, 0, 0, 0, 0) Looking into it a bit, we see that this is an embedded blockpointer, so BP_GET_NDVAS should have returned 0: b32b240::blkptr EMBEDDED [L0 ZAP_OTHER] et=0 LZ4 size=200L/4aP birth=80L Instead, it looks like another thread is modifying this blockpointer: b32b240::ugrep | ::whatis f47a0e0c is in [ stack tid=0x19f ] ebd6ec40 is in [ stack tid=0x226 ] ea293bd0 is in [ stack tid=0x244 ] ea293be4 is in [ stack tid=0x244 ] Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Author: Matthew Ahrens <mahrens@delphix.com>
This commit is contained in:
commit
0b51a59fc7
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=305325
@ -1662,7 +1662,20 @@ dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
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dnode_setdirty(dn, tx);
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DB_DNODE_EXIT(db);
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return (dr);
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} else if (do_free_accounting) {
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}
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/*
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* The dn_struct_rwlock prevents db_blkptr from changing
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* due to a write from syncing context completing
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* while we are running, so we want to acquire it before
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* looking at db_blkptr.
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*/
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if (!RW_WRITE_HELD(&dn->dn_struct_rwlock)) {
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rw_enter(&dn->dn_struct_rwlock, RW_READER);
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drop_struct_lock = TRUE;
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}
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if (do_free_accounting) {
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blkptr_t *bp = db->db_blkptr;
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int64_t willfree = (bp && !BP_IS_HOLE(bp)) ?
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bp_get_dsize(os->os_spa, bp) : db->db.db_size;
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@ -1678,11 +1691,6 @@ dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
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dnode_willuse_space(dn, -willfree, tx);
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}
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if (!RW_WRITE_HELD(&dn->dn_struct_rwlock)) {
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rw_enter(&dn->dn_struct_rwlock, RW_READER);
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drop_struct_lock = TRUE;
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}
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if (db->db_level == 0) {
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dnode_new_blkid(dn, db->db_blkid, tx, drop_struct_lock);
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ASSERT(dn->dn_maxblkid >= db->db_blkid);
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