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ITS#7515 Fix mdb_txn_commit(nested txn).

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Don't modify the parent txn until the current txn cannot fail.
Don't assume new dirty child pgnos > dirty parent pgnos.

Page alloc/touch: Fail if child+parent dirty pages would exceed
dirty_list's maxsize. Avoids an error situation in commit.
This commit is contained in:
Hallvard Furuseth 2013-02-19 22:03:41 +01:00 committed by Howard Chu
parent f43ae20be7
commit 208e5c614d
1 changed files with 42 additions and 24 deletions
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66
libraries/liblmdb/mdb.c
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@ -844,6 +844,8 @@ struct MDB_txn {
#define MDB_TXN_DIRTY 0x04 /**< must write, even if dirty list is empty */
/** @} */
unsigned int mt_flags; /**< @ref mdb_txn */
/** dirty_list maxsize - #allocated pages including in parent txns */
unsigned int mt_dirty_room;
/** Tracks which of the two meta pages was used at the start
* of this transaction.
*/
@ -1285,7 +1287,7 @@ mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
*mp = NULL;
/* If our dirty list is already full, we can't do anything */
if (txn->mt_u.dirty_list[0].mid >= MDB_IDL_UM_MAX)
if (txn->mt_dirty_room == 0)
return MDB_TXN_FULL;
/* The free list won't have any content at all until txn 2 has
@ -1524,6 +1526,7 @@ none:
} else {
mdb_mid2l_insert(txn->mt_u.dirty_list, &mid);
}
txn->mt_dirty_room--;
*mp = np;
return MDB_SUCCESS;
@ -1628,8 +1631,6 @@ finish:
return 0;
}
}
if (mc->mc_txn->mt_u.dirty_list[0].mid >= MDB_IDL_UM_MAX)
return MDB_TXN_FULL;
/* No - copy it */
np = mdb_page_malloc(mc);
if (!np)
@ -1821,6 +1822,7 @@ mdb_txn_renew0(MDB_txn *txn)
if (txn->mt_txnid == mdb_debug_start)
mdb_debug = 1;
#endif
txn->mt_dirty_room = MDB_IDL_UM_MAX;
txn->mt_u.dirty_list = env->me_dirty_list;
txn->mt_u.dirty_list[0].mid = 0;
txn->mt_free_pgs = env->me_free_pgs;
@ -1921,6 +1923,7 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
}
txn->mt_txnid = parent->mt_txnid;
txn->mt_toggle = parent->mt_toggle;
txn->mt_dirty_room = parent->mt_dirty_room;
txn->mt_u.dirty_list[0].mid = 0;
txn->mt_free_pgs[0] = 0;
txn->mt_next_pgno = parent->mt_next_pgno;
@ -2099,9 +2102,16 @@ mdb_txn_commit(MDB_txn *txn)
if (txn->mt_parent) {
MDB_txn *parent = txn->mt_parent;
unsigned x, y;
unsigned x, y, len;
MDB_ID2L dst, src;
/* Append our free list to parent's */
if (mdb_midl_append_list(&parent->mt_free_pgs, txn->mt_free_pgs)) {
mdb_txn_abort(txn);
return ENOMEM;
}
mdb_midl_free(txn->mt_free_pgs);
parent->mt_next_pgno = txn->mt_next_pgno;
parent->mt_flags = txn->mt_flags;
@ -2113,32 +2123,40 @@ mdb_txn_commit(MDB_txn *txn)
memcpy(parent->mt_dbflags, txn->mt_dbflags, txn->mt_numdbs);
txn->mt_parent->mt_numdbs = txn->mt_numdbs;
/* Append our free list to parent's */
mdb_midl_append_list(&txn->mt_parent->mt_free_pgs,
txn->mt_free_pgs);
mdb_midl_free(txn->mt_free_pgs);
/* Merge our dirty list with parent's */
dst = txn->mt_parent->mt_u.dirty_list;
src = txn->mt_u.dirty_list;
x = mdb_mid2l_search(dst, src[1].mid);
for (y=1; y<=src[0].mid; y++) {
while (x <= dst[0].mid && dst[x].mid != src[y].mid) x++;
if (x > dst[0].mid)
break;
free(dst[x].mptr);
dst[x].mptr = src[y].mptr;
}
/* Find len = length of merging our dirty list with parent's */
x = dst[0].mid;
for (; y<=src[0].mid; y++) {
if (++x >= MDB_IDL_UM_MAX) {
mdb_txn_abort(txn);
return MDB_TXN_FULL;
dst[0].mid = 0; /* simplify loops */
if (parent->mt_parent) {
len = x + src[0].mid;
y = mdb_mid2l_search(src, dst[x].mid + 1) - 1;
for (i = x; y && i; y--) {
pgno_t yp = src[y].mid;
while (yp < dst[i].mid)
i--;
if (yp == dst[i].mid) {
i--;
len--;
}
}
dst[x] = src[y];
} else { /* Simplify the above for single-ancestor case */
len = MDB_IDL_UM_MAX - txn->mt_dirty_room;
}
dst[0].mid = x;
/* Merge our dirty list with parent's */
y = src[0].mid;
for (i = len; y; dst[i--] = src[y--]) {
pgno_t yp = src[y].mid;
while (yp < dst[x].mid)
dst[i--] = dst[x--];
if (yp == dst[x].mid)
free(dst[x--].mptr);
}
assert(i == x);
dst[0].mid = len;
free(txn->mt_u.dirty_list);
parent->mt_dirty_room = txn->mt_dirty_room;
txn->mt_parent->mt_child = NULL;
free(((MDB_ntxn *)txn)->mnt_pgstate.mf_pgfree);
free(txn);