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MFV r275914:

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As of r270383, the dbuf_compare comparator compares the dbuf
attributes in the following order:

	db_level (indirect level)
	db_blkid (block number)
	db_state (current state)
	the address of the element

Because db_state is being considered before the element's state,
changing of db_state would affect balancedness of the AVL tree,
even when the address of element compares differently.  For
instance, in dbuf_create, db_state may be altered after the
node is inserted into the AVL tree and may break AVL tree
balancedness.

Instead of using db_state as a comparision critera (introduced
in r270383), consider it only when we are doing a lookup, that
is one of the two dbuf pointers contains DB_SEARCH.

Illumos issue:
    5422 preserve AVL invariants in dn_dbufs

MFC after:	2 weeks
This commit is contained in:
Xin LI 2014-12-18 23:45:26 +00:00
commit 7d073f8411
1 changed files with 4 additions and 6 deletions
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10
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dnode.c
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@ -81,16 +81,14 @@ dbuf_compare(const void *x1, const void *x2)
return (1);
}
if (d1->db_state < d2->db_state) {
if (d1->db_state == DB_SEARCH) {
ASSERT3S(d2->db_state, !=, DB_SEARCH);
return (-1);
}
if (d1->db_state > d2->db_state) {
} else if (d2->db_state == DB_SEARCH) {
ASSERT3S(d1->db_state, !=, DB_SEARCH);
return (1);
}
ASSERT3S(d1->db_state, !=, DB_SEARCH);
ASSERT3S(d2->db_state, !=, DB_SEARCH);
if ((uintptr_t)d1 < (uintptr_t)d2) {
return (-1);
}