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Handle interaction between gang blocks, copies, and FDT.

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With the advent of fast dedup, there are no longer separate dedup tables
for different copies values. There is now logic that will add DVAs to
the dedup table entry if more copies are needed for new writes. However,
this interacts poorly with ganging. There are two different cases that
can result in mixed gang/non-gang BPs, which are illegal in ZFS.

This change modifies updates of existing FDT; if there are already gang
DVAs in the FDT, we prevent the new write from extending the DDT
entry. We cannot safely mix different gang trees in one block
pointer. if there are non-gang DVAs in the FDT, then this allocation may
not be gangs. If it would gang, we have to redo the whole write as a
non-dedup write.

This change also fixes a refcount leak that could occur if the lead DDT
write failed.

Sponsored by: iXsystems, Inc.
Sponsored-by: Klara, Inc.
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>
Closes: #17123
This commit is contained in:
Paul Dagnelie
2025-04-21 08:26:30 -07:00
committed by GitHub
parent 1d8f625233
commit 5f5321effa
6 changed files with 156 additions and 14 deletions
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include/sys/ddt.h
+2
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@@ -352,6 +352,8 @@ extern ddt_phys_variant_t ddt_phys_select(const ddt_t *ddt,
const ddt_entry_t *dde, const blkptr_t *bp);
extern uint64_t ddt_phys_birth(const ddt_univ_phys_t *ddp,
ddt_phys_variant_t v);
extern int ddt_phys_is_gang(const ddt_univ_phys_t *ddp,
ddt_phys_variant_t v);
extern int ddt_phys_dva_count(const ddt_univ_phys_t *ddp, ddt_phys_variant_t v,
boolean_t encrypted);