Bug#12612184 Race condition after btr_cur_pessimistic_update()

btr_cur_compress_if_useful(), btr_compress(): Add the parameter ibool
adjust. If adjust=TRUE, adjust the cursor position after compressing
the page.

btr_lift_page_up(): Return a pointer to the father page.

BTR_KEEP_POS_FLAG: A new flag for btr_cur_pessimistic_update().

btr_cur_pessimistic_update(): If *big_rec != NULL and flags &
BTR_KEEP_POS_FLAG, keep the cursor positioned on the updated record.
Also, do not release the index tree x-lock if *big_rec != NULL.

btr_cur_mtr_commit_and_start(): Commits and restarts a
mini-transaction so that it will retain an x-lock on index->lock and
the page of the cursor. This is invoked when
btr_cur_pessimistic_update() returns *big_rec != NULL.

In all callers of btr_cur_pessimistic_update() that do not pass
BTR_KEEP_POS_FLAG, assert that *big_rec == NULL.

btr_cur_compress(): Unused function [in the built-in MySQL 5.1], remove.

page_rec_get_nth(): Return the nth record on the page (an inverse
function of page_rec_get_n_recs_before()). Refactored from
page_get_middle_rec().

page_get_middle_rec(): Invoke page_rec_get_nth().

page_cur_insert_rec_zip_reorg(): Make use of the page directory
shortcuts in page_rec_get_nth() instead of scanning the whole list of
records.

row_ins_clust_index_entry_by_modify(): Pass BTR_KEEP_POS_FLAG to
btr_cur_pessimistic_update().

row_ins_index_entry_low(): If row_ins_clust_index_entry_by_modify()
returns a big_rec, invoke btr_cur_mtr_commit_and_start() in order to
commit and start the mini-transaction without releasing the x-locks on
index->lock and the cursor page, and write the big_rec. Releasing the
page latch in mtr_commit() caused a race condition.

row_upd_clust_rec(): Pass BTR_KEEP_POS_FLAG to
btr_cur_pessimistic_update(). If it returns a big_rec, invoke
btr_cur_mtr_commit_and_start() in order to commit and start the
mini-transaction without releasing the x-locks on index->lock and the
cursor page, and write the big_rec. Releasing the page latch in
mtr_commit() caused a race condition.

sync_thread_add_level(): Add the parameter ibool relock. When TRUE,
bypass the latching order rules.

rw_lock_add_debug_info(): For nested X-lock requests, pass relock=TRUE
to sync_thread_add_level().

rb:678 approved by Jimmy Yang

1 files changed, 12 insertions, 19 deletions

diff --git a/storage/innobase/page/page0page.c b/storage/innobase/page/page0page.c
index 543cf9e34eb..6a89df7de22 100644
--- a/storage/innobase/page/page0page.c
+++ b/storage/innobase/page/page0page.c
@@ -1194,49 +1194,42 @@ page_dir_balance_slot(
 }
 
 /****************************************************************
-Returns the middle record of the record list. If there are an even number
-of records in the list, returns the first record of the upper half-list. */
+Returns the nth record of the record list. */
 
 rec_t*
-page_get_middle_rec(
-/*================*/
-			/* out: middle record */
-	page_t*	page)	/* in: page */
+page_rec_get_nth(
+/*=============*/
+			/* out: nth record */
+	page_t*	page,	/* in: page */
+	ulint	nth)	/* in: nth record */
 {
 	page_dir_slot_t*	slot;
-	ulint			middle;
 	ulint			i;
 	ulint			n_owned;
-	ulint			count;
 	rec_t*			rec;
 
-	/* This many records we must leave behind */
-	middle = (page_get_n_recs(page) + 2) / 2;
-
-	count = 0;
+	ut_ad(nth < UNIV_PAGE_SIZE / (REC_N_NEW_EXTRA_BYTES + 1));
 
 	for (i = 0;; i++) {
 
 		slot = page_dir_get_nth_slot(page, i);
 		n_owned = page_dir_slot_get_n_owned(slot);
 
-		if (count + n_owned > middle) {
+		if (n_owned > nth) {
 			break;
 		} else {
-			count += n_owned;
+			nth -= n_owned;
 		}
 	}
 
 	ut_ad(i > 0);
 	slot = page_dir_get_nth_slot(page, i - 1);
 	rec = page_dir_slot_get_rec(slot);
-	rec = page_rec_get_next(rec);
-
-	/* There are now count records behind rec */
 
-	for (i = 0; i < middle - count; i++) {
+	do {
 		rec = page_rec_get_next(rec);
-	}
+		ut_ad(rec);
+	} while (nth--);
 
 	return(rec);
 }