From b12738182cff269456e7737241415356c08b5d2e Mon Sep 17 00:00:00 2001 From: Alexander Motin Date: Wed, 3 Apr 2024 18:04:26 -0400 Subject: [PATCH] Improve dbuf_read() error reporting Previous code reported non-ZIO errors only via return value, but not via parent ZIO. It could cause NULL-dereference panics due to dmu_buf_hold_array_by_dnode() ignoring the return value, relying solely on parent ZIO status. Reviewed-by: Brian Behlendorf Reviewed-by: Ameer Hamza Reported by: Ameer Hamza Signed-off-by: Alexander Motin Sponsored by: iXsystems, Inc. Closes #16042 --- module/zfs/dbuf.c | 38 ++++++++++++++++++++------------------ 1 file changed, 20 insertions(+), 18 deletions(-) diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c index 4e190c131e1d..0ab143bd089f 100644 --- a/module/zfs/dbuf.c +++ b/module/zfs/dbuf.c @@ -1557,17 +1557,14 @@ dbuf_read_verify_dnode_crypt(dmu_buf_impl_t *db, uint32_t flags) * returning. */ static int -dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags, +dbuf_read_impl(dmu_buf_impl_t *db, dnode_t *dn, zio_t *zio, uint32_t flags, db_lock_type_t dblt, const void *tag) { - dnode_t *dn; zbookmark_phys_t zb; uint32_t aflags = ARC_FLAG_NOWAIT; int err, zio_flags; blkptr_t bp, *bpp; - DB_DNODE_ENTER(db); - dn = DB_DNODE(db); ASSERT(!zfs_refcount_is_zero(&db->db_holds)); ASSERT(MUTEX_HELD(&db->db_mtx)); ASSERT(db->db_state == DB_UNCACHED || db->db_state == DB_NOFILL); @@ -1643,8 +1640,6 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags, if (err != 0) goto early_unlock; - DB_DNODE_EXIT(db); - db->db_state = DB_READ; DTRACE_SET_STATE(db, "read issued"); mutex_exit(&db->db_mtx); @@ -1669,12 +1664,11 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags, * parent's rwlock, which would be a lock ordering violation. */ dmu_buf_unlock_parent(db, dblt, tag); - (void) arc_read(zio, db->db_objset->os_spa, bpp, + return (arc_read(zio, db->db_objset->os_spa, bpp, dbuf_read_done, db, ZIO_PRIORITY_SYNC_READ, zio_flags, - &aflags, &zb); - return (err); + &aflags, &zb)); + early_unlock: - DB_DNODE_EXIT(db); mutex_exit(&db->db_mtx); dmu_buf_unlock_parent(db, dblt, tag); return (err); @@ -1759,7 +1753,7 @@ dbuf_fix_old_data(dmu_buf_impl_t *db, uint64_t txg) } int -dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags) +dbuf_read(dmu_buf_impl_t *db, zio_t *pio, uint32_t flags) { int err = 0; boolean_t prefetch; @@ -1775,7 +1769,7 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags) dn = DB_DNODE(db); prefetch = db->db_level == 0 && db->db_blkid != DMU_BONUS_BLKID && - (flags & DB_RF_NOPREFETCH) == 0 && dn != NULL; + (flags & DB_RF_NOPREFETCH) == 0; mutex_enter(&db->db_mtx); if (flags & DB_RF_PARTIAL_FIRST) @@ -1822,13 +1816,13 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags) db_lock_type_t dblt = dmu_buf_lock_parent(db, RW_READER, FTAG); - if (zio == NULL && (db->db_state == DB_NOFILL || + if (pio == NULL && (db->db_state == DB_NOFILL || (db->db_blkptr != NULL && !BP_IS_HOLE(db->db_blkptr)))) { spa_t *spa = dn->dn_objset->os_spa; - zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CANFAIL); + pio = zio_root(spa, NULL, NULL, ZIO_FLAG_CANFAIL); need_wait = B_TRUE; } - err = dbuf_read_impl(db, zio, flags, dblt, FTAG); + err = dbuf_read_impl(db, dn, pio, flags, dblt, FTAG); /* * dbuf_read_impl has dropped db_mtx and our parent's rwlock * for us @@ -1849,9 +1843,10 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags) */ if (need_wait) { if (err == 0) - err = zio_wait(zio); + err = zio_wait(pio); else - VERIFY0(zio_wait(zio)); + (void) zio_wait(pio); + pio = NULL; } } else { /* @@ -1878,7 +1873,7 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags) ASSERT(db->db_state == DB_READ || (flags & DB_RF_HAVESTRUCT) == 0); DTRACE_PROBE2(blocked__read, dmu_buf_impl_t *, - db, zio_t *, zio); + db, zio_t *, pio); cv_wait(&db->db_changed, &db->db_mtx); } if (db->db_state == DB_UNCACHED) @@ -1887,6 +1882,13 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags) } } + if (pio && err != 0) { + zio_t *zio = zio_null(pio, pio->io_spa, NULL, NULL, NULL, + ZIO_FLAG_CANFAIL); + zio->io_error = err; + zio_nowait(zio); + } + return (err); }