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Assert that a dnode's bonuslen never exceeds its recorded size

This patch introduces an assertion that can catch pitfalls in
development where there is a mismatch between the size of
reads and writes between a *_phys structure and its respective
in-core structure when bonus buffers are used.

This debugging-aid should be complementary to the verification
done by ztest in ztest_verify_dnode_bt().

A side to this patch is that we now clear out any extra bytes
past a bonus buffer's new size when the buffer is shrinking.

Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com>
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sdimitro committed Jan 24, 2019
1 parent c8242a9 commit a62f3064c66bb4ae9d8f38eb9a8a53a5a4b4e3b8
Showing with 52 additions and 0 deletions.
  1. +44 −0 module/zfs/dbuf.c
  2. +8 −0 module/zfs/dnode.c
@@ -3931,6 +3931,46 @@ dbuf_sync_indirect(dbuf_dirty_record_t *dr, dmu_tx_t *tx)
zio_nowait(zio);
}

#ifdef ZFS_DEBUG
/*
* Verify that the size of the data in our bonus buffer does not exceed
* its recorded size.
*
* The purpose of this verification is to catch any cases in development
* where the size of a phys structure (i.e space_map_phys_t) grows and,
* due to incorrect feature management, older pools expect to read more
* data even though they didn't actually write it to begin with.
*
* For a example, this would catch an error in the feature logic where we
* open an older pool and we expect to write the space map histogram of
* a space map with size SPACE_MAP_SIZE_V0.
*/
static void
dbuf_sync_leaf_verify_bonus_dnode(dbuf_dirty_record_t *dr)
{
dnode_t *dn = DB_DNODE(dr->dr_dbuf);

/*
* Encrypted bonus buffers can have data past their bonuslen.
* Skip the verification of these blocks.
*/
if (DMU_OT_IS_ENCRYPTED(dn->dn_bonustype))
return;

uint16_t bonuslen = dn->dn_phys->dn_bonuslen;
uint16_t maxbonuslen = DN_SLOTS_TO_BONUSLEN(dn->dn_num_slots);
ASSERT3U(bonuslen, <=, maxbonuslen);

arc_buf_t *datap = dr->dt.dl.dr_data;
char *datap_end = ((char *)datap) + bonuslen;
char *datap_max = ((char *)datap) + maxbonuslen;

/* ensure that everything is zero after our data */
for (; datap_end < datap_max; datap_end++)
ASSERT(*datap_end == 0);
}
#endif

/*
* dbuf_sync_leaf() is called recursively from dbuf_sync_list() so it is
* critical the we not allow the compiler to inline this function in to
@@ -4007,6 +4047,10 @@ dbuf_sync_leaf(dbuf_dirty_record_t *dr, dmu_tx_t *tx)
DN_MAX_BONUS_LEN(dn->dn_phys));
DB_DNODE_EXIT(db);

#ifdef ZFS_DEBUG
dbuf_sync_leaf_verify_bonus_dnode(dr);
#endif

if (*datap != db->db.db_data) {
int slots = DB_DNODE(db)->dn_num_slots;
int bonuslen = DN_SLOTS_TO_BONUSLEN(slots);
@@ -390,6 +390,14 @@ dnode_setbonuslen(dnode_t *dn, int newsize, dmu_tx_t *tx)
rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
ASSERT3U(newsize, <=, DN_SLOTS_TO_BONUSLEN(dn->dn_num_slots) -
(dn->dn_nblkptr-1) * sizeof (blkptr_t));

if (newsize < dn->dn_bonuslen) {
/* clear any data after the end of the new size */
size_t diff = dn->dn_bonuslen - newsize;
char *data_end = ((char *)dn->dn_bonus->db.db_data) + newsize;
bzero(data_end, diff);
}

dn->dn_bonuslen = newsize;
if (newsize == 0)
dn->dn_next_bonuslen[tx->tx_txg & TXG_MASK] = DN_ZERO_BONUSLEN;

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