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OpenZFS 9439 - ZFS double-free due to failure to dirty indirect block

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Follow up commit for OpenZFS 9438.  See the OpenZFS-issue link below
for a complete analysis.

Authored by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>

OpenZFS-issue: https://illumos.org/issues/9439
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/779220d
External-issue: DLPX-46861
Closes #7746
This commit is contained in:
Matthew Ahrens
2016-10-31 10:42:37 -07:00
committed by Brian Behlendorf
parent 21d48b5eac
commit 1897bc0d48
2 changed files with 20 additions and 4 deletions
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module/zfs/dnode_sync.c
+18
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@@ -264,6 +264,24 @@ free_children(dmu_buf_impl_t *db, uint64_t blkid, uint64_t nblks,
if (db->db_state != DB_CACHED)
(void) dbuf_read(db, NULL, DB_RF_MUST_SUCCEED);
/*
* If we modify this indirect block, and we are not freeing the
* dnode (!free_indirects), then this indirect block needs to get
* written to disk by dbuf_write(). If it is dirty, we know it will
* be written (otherwise, we would have incorrect on-disk state
* because the space would be freed but still referenced by the BP
* in this indirect block). Therefore we VERIFY that it is
* dirty.
*
* Our VERIFY covers some cases that do not actually have to be
* dirty, but the open-context code happens to dirty. E.g. if the
* blocks we are freeing are all holes, because in that case, we
* are only freeing part of this indirect block, so it is an
* ancestor of the first or last block to be freed. The first and
* last L1 indirect blocks are always dirtied by dnode_free_range().
*/
VERIFY(BP_GET_FILL(db->db_blkptr) == 0 || db->db_dirtycnt > 0);
dbuf_release_bp(db);
bp = db->db.db_data;