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ddt: simplify entry load and flags 

Only a single bit is needed to track entry state, and definitely not two
whole bytes. Some light refactoring in ddt_lookup() is needed to support
this, but it reads a lot better now.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Sponsored-by: Klara, Inc.
Sponsored-by: iXsystems, Inc.
Closes #15887
This commit is contained in:
Rob Norris 2023-12-05 14:28:39 +11:00 committed by Brian Behlendorf
parent 2cffddd405
commit 406562c563
2 changed files with 33 additions and 21 deletions
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7
include/sys/ddt.h
View File

@ -117,6 +117,10 @@ enum ddt_phys_type {
/*
* In-core ddt entry
*/
/* State flags for dde_flags */
#define DDE_FLAG_LOADED (1 << 0) /* entry ready for use */
typedef struct {
/* key must be first for ddt_key_compare */
ddt_key_t dde_key;
@ -125,8 +129,7 @@ typedef struct {
struct abd *dde_repair_abd;
ddt_type_t dde_type;
ddt_class_t dde_class;
uint8_t dde_loading;
uint8_t dde_loaded;
uint8_t dde_flags;
kcondvar_t dde_cv;
avl_node_t dde_node;
} ddt_entry_t;

47
module/zfs/ddt.c
View File

@ -448,7 +448,7 @@ ddt_alloc(const ddt_key_t *ddk)
static void
ddt_free(ddt_entry_t *dde)
{
ASSERT(!dde->dde_loading);
ASSERT(dde->dde_flags & DDE_FLAG_LOADED);
for (int p = 0; p < DDT_PHYS_TYPES; p++)
ASSERT3P(dde->dde_lead_zio[p], ==, NULL);
@ -483,26 +483,37 @@ ddt_lookup(ddt_t *ddt, const blkptr_t *bp, boolean_t add)
ddt_key_fill(&search, bp);
/* Find an existing live entry */
dde = avl_find(&ddt->ddt_tree, &search, &where);
if (dde == NULL) {
if (!add)
return (NULL);
dde = ddt_alloc(&search);
avl_insert(&ddt->ddt_tree, dde, where);
if (dde != NULL) {
/* Found it. If it's already loaded, we can just return it. */
if (dde->dde_flags & DDE_FLAG_LOADED)
return (dde);
/* Someone else is loading it, wait for it. */
while (!(dde->dde_flags & DDE_FLAG_LOADED))
cv_wait(&dde->dde_cv, &ddt->ddt_lock);
return (dde);
}
while (dde->dde_loading)
cv_wait(&dde->dde_cv, &ddt->ddt_lock);
/* Not found. */
if (!add)
return (NULL);
if (dde->dde_loaded)
return (dde);
dde->dde_loading = B_TRUE;
/* Time to make a new entry. */
dde = ddt_alloc(&search);
avl_insert(&ddt->ddt_tree, dde, where);
/*
* ddt_tree is now stable, so unlock and let everyone else keep moving.
* Anyone landing on this entry will find it without DDE_FLAG_LOADED,
* and go to sleep waiting for it above.
*/
ddt_exit(ddt);
/* Search all store objects for the entry. */
error = ENOENT;
for (type = 0; type < DDT_TYPES; type++) {
for (class = 0; class < DDT_CLASSES; class++) {
error = ddt_object_lookup(ddt, type, class, dde);
@ -517,17 +528,16 @@ ddt_lookup(ddt_t *ddt, const blkptr_t *bp, boolean_t add)
ddt_enter(ddt);
ASSERT(!dde->dde_loaded);
ASSERT(dde->dde_loading);
ASSERT(!(dde->dde_flags & DDE_FLAG_LOADED));
dde->dde_type = type; /* will be DDT_TYPES if no entry found */
dde->dde_class = class; /* will be DDT_CLASSES if no entry found */
dde->dde_loaded = B_TRUE;
dde->dde_loading = B_FALSE;
if (error == 0)
ddt_stat_update(ddt, dde, -1ULL);
/* Entry loaded, everyone can proceed now */
dde->dde_flags |= DDE_FLAG_LOADED;
cv_broadcast(&dde->dde_cv);
return (dde);
@ -812,8 +822,7 @@ ddt_sync_entry(ddt_t *ddt, ddt_entry_t *dde, dmu_tx_t *tx, uint64_t txg)
ddt_class_t nclass;
uint64_t total_refcnt = 0;
ASSERT(dde->dde_loaded);
ASSERT(!dde->dde_loading);
ASSERT(dde->dde_flags & DDE_FLAG_LOADED);
for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
ASSERT3P(dde->dde_lead_zio[p], ==, NULL);