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OpenZFS 7086 - ztest attempts dva_get_dsize_sync on an embedded blockpointer

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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.

Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

OpenZFS-issue: https://www.illumos.org/issues/7086
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/98fa317
Closes #5039
This commit is contained in:
Matthew Ahrens 2016-08-29 11:40:16 -07:00 committed by Brian Behlendorf
parent c40db193a5
commit 98ace739bd
1 changed files with 14 additions and 6 deletions
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20
module/zfs/dbuf.c
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@ -1468,7 +1468,20 @@ dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
dnode_setdirty(dn, tx);
DB_DNODE_EXIT(db);
return (dr);
} else if (do_free_accounting) {
}
/*
* The dn_struct_rwlock prevents db_blkptr from changing
* due to a write from syncing context completing
* while we are running, so we want to acquire it before
* looking at db_blkptr.
*/
if (!RW_WRITE_HELD(&dn->dn_struct_rwlock)) {
rw_enter(&dn->dn_struct_rwlock, RW_READER);
drop_struct_lock = TRUE;
}
if (do_free_accounting) {
blkptr_t *bp = db->db_blkptr;
int64_t willfree = (bp && !BP_IS_HOLE(bp)) ?
bp_get_dsize(os->os_spa, bp) : db->db.db_size;
@ -1484,11 +1497,6 @@ dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
dnode_willuse_space(dn, -willfree, tx);
}
if (!RW_WRITE_HELD(&dn->dn_struct_rwlock)) {
rw_enter(&dn->dn_struct_rwlock, RW_READER);
drop_struct_lock = TRUE;
}
if (db->db_level == 0) {
dnode_new_blkid(dn, db->db_blkid, tx, drop_struct_lock);
ASSERT(dn->dn_maxblkid >= db->db_blkid);