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Wait for txg sync if the last DRR_FREEOBJECTS might result in a hole

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If we receive a DRR_FREEOBJECTS as the first entry in an object range,
this might end up producing a hole if the freed objects were the
only existing objects in the block.

If the txg starts syncing before we've processed any following
DRR_OBJECT records, this leads to a possible race where the backing
arc_buf_t gets its psize set to 0 in the arc_write_ready() callback
while still being referenced from a dirty record in the open txg.

To prevent this, we insert a txg_wait_synced call if the first
record in the range was a DRR_FREEOBJECTS that actually
resulted in one or more freed objects.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: David Hedberg <david.hedberg@findity.com>
Sponsored by: Findity AB
Closes #11893
Closes #14358
This commit is contained in:
David Hedberg
2023-01-23 22:19:43 +01:00
committed by GitHub
parent 73968defdd
commit 37a27b4306
5 changed files with 116 additions and 1 deletions
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module/zfs/dmu_recv.c
+26
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@@ -76,6 +76,12 @@ static int zfs_recv_best_effort_corrective = 0;
static const void *const dmu_recv_tag = "dmu_recv_tag";
const char *const recv_clone_name = "%recv";
typedef enum {
ORNS_NO,
ORNS_YES,
ORNS_MAYBE
} or_need_sync_t;
static int receive_read_payload_and_next_header(dmu_recv_cookie_t *ra, int len,
void *buf);
@@ -129,6 +135,9 @@ struct receive_writer_arg {
uint8_t or_mac[ZIO_DATA_MAC_LEN];
boolean_t or_byteorder;
zio_t *heal_pio;
/* Keep track of DRR_FREEOBJECTS right after DRR_OBJECT_RANGE */
or_need_sync_t or_need_sync;
};
typedef struct dmu_recv_begin_arg {
@@ -1914,10 +1923,22 @@ receive_object(struct receive_writer_arg *rwa, struct drr_object *drro,
/* object was freed and we are about to allocate a new one */
object_to_hold = DMU_NEW_OBJECT;
} else {
/*
* If the only record in this range so far was DRR_FREEOBJECTS
* with at least one actually freed object, it's possible that
* the block will now be converted to a hole. We need to wait
* for the txg to sync to prevent races.
*/
if (rwa->or_need_sync == ORNS_YES)
txg_wait_synced(dmu_objset_pool(rwa->os), 0);
/* object is free and we are about to allocate a new one */
object_to_hold = DMU_NEW_OBJECT;
}
/* Only relevant for the first object in the range */
rwa->or_need_sync = ORNS_NO;
/*
* If this is a multi-slot dnode there is a chance that this
* object will expand into a slot that is already used by
@@ -2111,6 +2132,9 @@ receive_freeobjects(struct receive_writer_arg *rwa,
if (err != 0)
return (err);
if (rwa->or_need_sync == ORNS_MAYBE)
rwa->or_need_sync = ORNS_YES;
}
if (next_err != ESRCH)
return (next_err);
@@ -2604,6 +2628,8 @@ receive_object_range(struct receive_writer_arg *rwa,
memcpy(rwa->or_mac, drror->drr_mac, ZIO_DATA_MAC_LEN);
rwa->or_byteorder = byteorder;
rwa->or_need_sync = ORNS_MAYBE;
return (0);
}