/* * __curds_txn_leave -- * Do transactional cleanup when ending an operation. */ static void __curds_txn_leave(WT_SESSION_IMPL *session) { if (--session->ncursors == 0) /* XXX */ __wt_txn_read_last(session); }
/* * __rec_review -- * Get exclusive access to the page and review the page and its subtree * for conditions that would block its eviction. * * The ref and page arguments may appear to be redundant, because usually * ref->page == page and page->ref == ref. However, we need both because * (a) there are cases where ref == NULL (e.g., for root page or during * salvage), and (b) we can't safely look at page->ref until we have a * hazard reference. */ static int __rec_review(WT_SESSION_IMPL *session, WT_REF *ref, WT_PAGE *page, uint32_t flags, int top) { WT_DECL_RET; WT_PAGE_MODIFY *mod; WT_TXN *txn; uint32_t i; txn = &session->txn; /* * Get exclusive access to the page if our caller doesn't have the tree * locked down. */ if (!LF_ISSET(WT_REC_SINGLE)) WT_RET(__hazard_exclusive(session, ref, top)); /* * Recurse through the page's subtree: this happens first because we * have to write pages in depth-first order, otherwise we'll dirty * pages after we've written them. */ if (page->type == WT_PAGE_COL_INT || page->type == WT_PAGE_ROW_INT) WT_REF_FOREACH(page, ref, i) switch (ref->state) { case WT_REF_DISK: /* On-disk */ case WT_REF_DELETED: /* On-disk, deleted */ break; case WT_REF_MEM: /* In-memory */ WT_RET(__rec_review( session, ref, ref->page, flags, 0)); break; case WT_REF_EVICT_WALK: /* Walk point */ case WT_REF_LOCKED: /* Being evicted */ case WT_REF_READING: /* Being read */ return (EBUSY); } /* * Check if this page can be evicted: * * Fail if the top-level page is a page expected to be removed from the * tree as part of eviction (an empty page or a split-merge page). Note * "split" pages are NOT included in this test, because a split page can * be separately evicted, at which point it's replaced in its parent by * a reference to a split-merge page. That's a normal part of the leaf * page life-cycle if it grows too large and must be pushed out of the * cache. There is also an exception for empty pages, the root page may * be empty when evicted, but that only happens when the tree is closed. * * Fail if any page in the top-level page's subtree can't be merged into * its parent. You can't evict a page that references such in-memory * pages, they must be evicted first. The test is necessary but should * not fire much: the LRU-based eviction code is biased for leaf pages, * an internal page shouldn't be selected for LRU-based eviction until * its children have been evicted. Empty, split and split-merge pages * are all included in this test, they can all be merged into a parent. * * We have to write dirty pages to know their final state, a page marked * empty may have had records added since reconciliation, a page marked * split may have had records deleted and no longer need to split. * Split-merge pages are the exception: they can never be change into * anything other than a split-merge page and are merged regardless of * being clean or dirty. * * Writing the page is expensive, do a cheap test first: if it doesn't * appear a subtree page can be merged, quit. It's possible the page * has been emptied since it was last reconciled, and writing it before * testing might be worthwhile, but it's more probable we're attempting * to evict an internal page with live children, and that's a waste of * time. * * We don't do a cheap test for the top-level page: we're not called * to evict split-merge pages, which means the only interesting case * is an empty page. If the eviction thread picked an "empty" page * for eviction, it must have had reason, probably the empty page got * really, really full. */ mod = page->modify; if (!top && (mod == NULL || !F_ISSET(mod, WT_PM_REC_EMPTY | WT_PM_REC_SPLIT | WT_PM_REC_SPLIT_MERGE))) return (EBUSY); /* If the page is dirty, write it so we know the final state. */ if (__wt_page_is_modified(page) && !F_ISSET(mod, WT_PM_REC_SPLIT_MERGE)) { ret = __wt_rec_write(session, page, NULL, flags); /* If there are unwritten changes on the page, give up. */ if (ret == 0 && !LF_ISSET(WT_REC_SINGLE) && __wt_page_is_modified(page)) ret = EBUSY; if (ret == EBUSY) { WT_VERBOSE_RET(session, evict, "page %p written but not clean", page); if (F_ISSET(txn, TXN_RUNNING) && ++txn->eviction_fails >= 100) { txn->eviction_fails = 0; ret = WT_DEADLOCK; WT_STAT_INCR( S2C(session)->stats, txn_fail_cache); } /* * If there aren't multiple cursors active, there * are no consistency issues: try to bump our snapshot. */ if (session->ncursors <= 1) { __wt_txn_read_last(session); __wt_txn_read_first(session); } switch (page->type) { case WT_PAGE_COL_FIX: case WT_PAGE_COL_VAR: __wt_col_leaf_obsolete(session, page); break; case WT_PAGE_ROW_LEAF: __wt_row_leaf_obsolete(session, page); break; } } WT_RET(ret); txn->eviction_fails = 0; } /* * Repeat the eviction tests. * * Fail if the top-level page should be merged into its parent, and it's * not the root page. * * Fail if a page in the top-level page's subtree can't be merged into * its parent. */ if (top) { /* * We never get a top-level split-merge page to evict, they are * ignored by the eviction thread. Check out of sheer paranoia. */ if (mod != NULL) { if (F_ISSET(mod, WT_PM_REC_SPLIT_MERGE)) return (EBUSY); if (F_ISSET(mod, WT_PM_REC_EMPTY) && !WT_PAGE_IS_ROOT(page)) return (EBUSY); } } else if (mod == NULL || !F_ISSET(mod, WT_PM_REC_EMPTY | WT_PM_REC_SPLIT | WT_PM_REC_SPLIT_MERGE)) return (EBUSY); return (0); }