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5820 verify failed in zio_done(): BP_EQUAL(bp, io_bp_orig)

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Reviewed by: Alex Reece <alex@delphix.com>
Reviewed by: George Wilson <george@delphix.com>
Reviewed by: Steven Hartland <killing@multiplay.co.uk>
Approved by: Garrett D'Amore <garrett@damore.org>
Author: Matthew Ahrens <mahrens@delphix.com>

illumod/illumos-gate@34e8acef00
This commit is contained in:
Alexander Motin 2015-08-10 19:37:43 +00:00
parent 283af7ea31
commit 21bb89cfda
1 changed files with 24 additions and 11 deletions
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35
uts/common/fs/zfs/dmu.c
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@ -1596,19 +1596,32 @@ dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd)
ASSERT(dr->dr_next == NULL || dr->dr_next->dr_txg < txg);
/*
* Assume the on-disk data is X, the current syncing data is Y,
* and the current in-memory data is Z (currently in dmu_sync).
* X and Z are identical but Y is has been modified. Normally,
* when X and Z are the same we will perform a nopwrite but if Y
* is different we must disable nopwrite since the resulting write
* of Y to disk can free the block containing X. If we allowed a
* nopwrite to occur the block pointing to Z would reference a freed
* block. Since this is a rare case we simplify this by disabling
* nopwrite if the current dmu_sync-ing dbuf has been modified in
* a previous transaction.
* Assume the on-disk data is X, the current syncing data (in
* txg - 1) is Y, and the current in-memory data is Z (currently
* in dmu_sync).
*
* We usually want to perform a nopwrite if X and Z are the
* same. However, if Y is different (i.e. the BP is going to
* change before this write takes effect), then a nopwrite will
* be incorrect - we would override with X, which could have
* been freed when Y was written.
*
* (Note that this is not a concern when we are nop-writing from
* syncing context, because X and Y must be identical, because
* all previous txgs have been synced.)
*
* Therefore, we disable nopwrite if the current BP could change
* before this TXG. There are two ways it could change: by
* being dirty (dr_next is non-NULL), or by being freed
* (dnode_block_freed()). This behavior is verified by
* zio_done(), which VERIFYs that the override BP is identical
* to the on-disk BP.
*/
if (dr->dr_next)
DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
if (dr->dr_next != NULL || dnode_block_freed(dn, db->db_blkid))
zp.zp_nopwrite = B_FALSE;
DB_DNODE_EXIT(db);
ASSERT(dr->dr_txg == txg);
if (dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC ||