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ztest fails assertion in zio_write_gang_member_ready()

Description

ztest fails assertion in zio_write_gang_member_ready()

Encrypted blocks can have up to 2 DVA's, as the third DVA is reserved
for the salt+IV. However, dmu_write_policy() allows non-encrypted
blocks (e.g. DMU_OT_OBJSET) inside encrypted datasets to request and
allocate 3 DVA's, since they don't need a salt+IV (they are merely
authenicated).

However, if such a block becomes a gang block, the gang code incorrectly
limits the gang block header to 2 DVA's. This leads to a "NDVAs
inversion", where a parent block (the gang block header) has less DVA's
than its children (the gang members), causing an assertion failure in
zio_write_gang_member_ready().

This commit addresses the problem by only restricting the gang block
header to 2 DVA's if the block is actually encrypted (and thus its gang
block members can have at most 2 DVA's).

Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes #14250
Closes #14356

Details

Provenance
mahrensAuthored on Jan 10 2023, 12:43 AM
Brian Behlendorf <behlendorf1@llnl.gov>Committed on Jan 10 2023, 4:44 PM
Parents
rG3e0962a236d9: Introduce ZFS_LINUX_REQUIRE_API autoconf macro
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Reverted By
rG11bdc5c8e8fb: Revert "ztest fails assertion in zio_write_gang_member_ready()"