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Improve dbuf_read() error reporting #16042

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Apr 3, 2024
Merged

Improve dbuf_read() error reporting #16042

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38 changes: 20 additions & 18 deletions module/zfs/dbuf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1557,17 +1557,14 @@ dbuf_read_verify_dnode_crypt(dmu_buf_impl_t *db, uint32_t flags)
* returning.
*/
static int
dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags,
dbuf_read_impl(dmu_buf_impl_t *db, dnode_t *dn, zio_t *zio, uint32_t flags,
db_lock_type_t dblt, const void *tag)
{
dnode_t *dn;
zbookmark_phys_t zb;
uint32_t aflags = ARC_FLAG_NOWAIT;
int err, zio_flags;
blkptr_t bp, *bpp;

DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
ASSERT(!zfs_refcount_is_zero(&db->db_holds));
ASSERT(MUTEX_HELD(&db->db_mtx));
ASSERT(db->db_state == DB_UNCACHED || db->db_state == DB_NOFILL);
Expand Down Expand Up @@ -1643,8 +1640,6 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags,
if (err != 0)
goto early_unlock;

DB_DNODE_EXIT(db);

db->db_state = DB_READ;
DTRACE_SET_STATE(db, "read issued");
mutex_exit(&db->db_mtx);
Expand All @@ -1669,12 +1664,11 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags,
* parent's rwlock, which would be a lock ordering violation.
*/
dmu_buf_unlock_parent(db, dblt, tag);
(void) arc_read(zio, db->db_objset->os_spa, bpp,
return (arc_read(zio, db->db_objset->os_spa, bpp,
dbuf_read_done, db, ZIO_PRIORITY_SYNC_READ, zio_flags,
&aflags, &zb);
return (err);
&aflags, &zb));

early_unlock:
DB_DNODE_EXIT(db);
mutex_exit(&db->db_mtx);
dmu_buf_unlock_parent(db, dblt, tag);
return (err);
Expand Down Expand Up @@ -1759,7 +1753,7 @@ dbuf_fix_old_data(dmu_buf_impl_t *db, uint64_t txg)
}

int
dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
dbuf_read(dmu_buf_impl_t *db, zio_t *pio, uint32_t flags)
{
int err = 0;
boolean_t prefetch;
Expand All @@ -1775,7 +1769,7 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
dn = DB_DNODE(db);

prefetch = db->db_level == 0 && db->db_blkid != DMU_BONUS_BLKID &&
(flags & DB_RF_NOPREFETCH) == 0 && dn != NULL;
(flags & DB_RF_NOPREFETCH) == 0;

mutex_enter(&db->db_mtx);
if (flags & DB_RF_PARTIAL_FIRST)
Expand Down Expand Up @@ -1822,13 +1816,13 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)

db_lock_type_t dblt = dmu_buf_lock_parent(db, RW_READER, FTAG);

if (zio == NULL && (db->db_state == DB_NOFILL ||
if (pio == NULL && (db->db_state == DB_NOFILL ||
(db->db_blkptr != NULL && !BP_IS_HOLE(db->db_blkptr)))) {
spa_t *spa = dn->dn_objset->os_spa;
zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CANFAIL);
pio = zio_root(spa, NULL, NULL, ZIO_FLAG_CANFAIL);
need_wait = B_TRUE;
}
err = dbuf_read_impl(db, zio, flags, dblt, FTAG);
err = dbuf_read_impl(db, dn, pio, flags, dblt, FTAG);
/*
* dbuf_read_impl has dropped db_mtx and our parent's rwlock
* for us
Expand All @@ -1849,9 +1843,10 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
*/
if (need_wait) {
if (err == 0)
err = zio_wait(zio);
err = zio_wait(pio);
else
VERIFY0(zio_wait(zio));
(void) zio_wait(pio);
pio = NULL;
}
} else {
/*
Expand All @@ -1878,7 +1873,7 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
ASSERT(db->db_state == DB_READ ||
(flags & DB_RF_HAVESTRUCT) == 0);
DTRACE_PROBE2(blocked__read, dmu_buf_impl_t *,
db, zio_t *, zio);
db, zio_t *, pio);
cv_wait(&db->db_changed, &db->db_mtx);
}
if (db->db_state == DB_UNCACHED)
Expand All @@ -1887,6 +1882,13 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
}
}

if (pio && err != 0) {
zio_t *zio = zio_null(pio, pio->io_spa, NULL, NULL, NULL,
ZIO_FLAG_CANFAIL);
zio->io_error = err;
zio_nowait(zio);
}

return (err);
}

Expand Down
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