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Fix deduplication of overridden blocks

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Implementation of DDT pruning introduced verification of DVAs in
a block pointer during ddt_lookup() to not by mistake free previous
pruned incarnation of the entry.  But when writing a new block in
zio_ddt_write() we might have the DVAs only from override pointer,
which may never have "D" flag to be confused with pruned DDT entry,
and we'll abandon those DVAs if we find a matching entry in DDT.

This fixes deduplication for blocks written via dmu_sync() for
purposes of indirect ZIL write records, that I have tested.  And
I suspect it might actually allow deduplication for Direct I/O,
even though in an odd way -- first write block directly and then
delete it later during TXG commit if found duplicate, which part
I haven't tested.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #17120
This commit is contained in:
Alexander Motin
2025-03-13 13:27:57 -04:00
committed by GitHub
parent 09f4dd06c3
commit 0ea44e576b
4 changed files with 19 additions and 11 deletions
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include/sys/ddt.h
+2 -1
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@@ -378,7 +378,8 @@ extern void ddt_enter(ddt_t *ddt);
extern void ddt_exit(ddt_t *ddt);
extern void ddt_init(void);
extern void ddt_fini(void);
extern ddt_entry_t *ddt_lookup(ddt_t *ddt, const blkptr_t *bp);
extern ddt_entry_t *ddt_lookup(ddt_t *ddt, const blkptr_t *bp,
boolean_t verify);
extern void ddt_remove(ddt_t *ddt, ddt_entry_t *dde);
extern void ddt_prefetch(spa_t *spa, const blkptr_t *bp);
extern void ddt_prefetch_all(spa_t *spa);