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dbuf: Handle arcbuf assignment after block cloning 

In some cases dbuf_assign_arcbuf() may be called on a block that
was recently cloned.  If it happened in current TXG we must undo
the block cloning first, since the only one dirty record per TXG
can't and shouldn't mean both cloning and overwrite same time.

Reviewed-by: Kay Pedersen <mail@mkwg.de>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #15653
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Alexander Motin 2023-12-12 15:53:59 -05:00 committed by GitHub
parent f4b97c1e00
commit 86063d9031
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1 changed files with 11 additions and 1 deletions
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12
module/zfs/dbuf.c
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@ -2945,7 +2945,8 @@ dbuf_assign_arcbuf(dmu_buf_impl_t *db, arc_buf_t *buf, dmu_tx_t *tx)
while (db->db_state == DB_READ || db->db_state == DB_FILL)
cv_wait(&db->db_changed, &db->db_mtx);
ASSERT(db->db_state == DB_CACHED || db->db_state == DB_UNCACHED);
ASSERT(db->db_state == DB_CACHED || db->db_state == DB_UNCACHED ||
db->db_state == DB_NOFILL);
if (db->db_state == DB_CACHED &&
zfs_refcount_count(&db->db_holds) - 1 > db->db_dirtycnt) {
@ -2982,6 +2983,15 @@ dbuf_assign_arcbuf(dmu_buf_impl_t *db, arc_buf_t *buf, dmu_tx_t *tx)
arc_buf_destroy(db->db_buf, db);
}
db->db_buf = NULL;
} else if (db->db_state == DB_NOFILL) {
/*
* We will be completely replacing the cloned block. In case
* it was cloned in this transaction group, let's undirty the
* pending clone and mark the block as uncached. This will be
* as if the clone was never done.
*/
VERIFY(!dbuf_undirty(db, tx));
db->db_state = DB_UNCACHED;
}
ASSERT(db->db_buf == NULL);
dbuf_set_data(db, buf);