Exemplo n.º 1
0
/*
 * __wt_txn_commit --
 *	Commit the current transaction.
 */
int
__wt_txn_commit(WT_SESSION_IMPL *session, const char *cfg[])
{
	WT_TXN *txn;

	WT_UNUSED(cfg);

	txn = &session->txn;
	WT_ASSERT(session, !F_ISSET(txn, TXN_ERROR));

	if (!F_ISSET(txn, TXN_RUNNING))
		WT_RET_MSG(session, EINVAL, "No transaction is active");

	/*
	 * Auto-commit transactions need a new transaction snapshot so that the
	 * committed changes are visible to subsequent reads.  However, cursor
	 * keys and values will point to the data that was just modified, so
	 * the snapshot cannot be so new that updates could be freed underneath
	 * the cursor.  Get the new snapshot before releasing the ID for the
	 * commit.
	 */
	if (session->ncursors > 0)
		__wt_txn_get_snapshot(session, txn->id, WT_TXN_NONE, 1);
	__wt_txn_release(session);
	return (0);
}
Exemplo n.º 2
0
/*
 * __sync_file --
 *	Flush pages for a specific file.
 */
static int
__sync_file(WT_SESSION_IMPL *session, WT_CACHE_OP syncop)
{
	WT_BTREE *btree;
	WT_CONNECTION_IMPL *conn;
	WT_DECL_RET;
	WT_PAGE *page;
	WT_PAGE_MODIFY *mod;
	WT_REF *prev, *walk;
	WT_TXN *txn;
	uint64_t internal_bytes, internal_pages, leaf_bytes, leaf_pages;
	uint64_t oldest_id, saved_pinned_id, time_start, time_stop;
	uint32_t flags;
	bool timer, tried_eviction;

	conn = S2C(session);
	btree = S2BT(session);
	prev = walk = NULL;
	txn = &session->txn;
	tried_eviction = false;
	time_start = time_stop = 0;

	/* Only visit pages in cache and don't bump page read generations. */
	flags = WT_READ_CACHE | WT_READ_NO_GEN;

	/*
	 * Skip all deleted pages.  For a page to be marked deleted, it must
	 * have been evicted from cache and marked clean.  Checkpoint should
	 * never instantiate deleted pages: if a truncate is not visible to the
	 * checkpoint, the on-disk version is correct.  If the truncate is
	 * visible, we skip over the child page when writing its parent.  We
	 * check whether a truncate is visible in the checkpoint as part of
	 * reconciling internal pages (specifically in __rec_child_modify).
	 */
	LF_SET(WT_READ_DELETED_SKIP);

	internal_bytes = leaf_bytes = 0;
	internal_pages = leaf_pages = 0;
	saved_pinned_id = WT_SESSION_TXN_STATE(session)->pinned_id;
	timer = WT_VERBOSE_ISSET(session, WT_VERB_CHECKPOINT);
	if (timer)
		time_start = __wt_clock(session);

	switch (syncop) {
	case WT_SYNC_WRITE_LEAVES:
		/*
		 * Write all immediately available, dirty in-cache leaf pages.
		 *
		 * Writing the leaf pages is done without acquiring a high-level
		 * lock, serialize so multiple threads don't walk the tree at
		 * the same time.
		 */
		if (!btree->modified)
			return (0);
		__wt_spin_lock(session, &btree->flush_lock);
		if (!btree->modified) {
			__wt_spin_unlock(session, &btree->flush_lock);
			return (0);
		}

		/*
		 * Save the oldest transaction ID we need to keep around.
		 * Otherwise, in a busy system, we could be updating pages so
		 * fast that write leaves never catches up.  We deliberately
		 * have no transaction running at this point that would keep
		 * the oldest ID from moving forwards as we walk the tree.
		 */
		oldest_id = __wt_txn_oldest_id(session);

		LF_SET(WT_READ_NO_WAIT | WT_READ_SKIP_INTL);
		for (;;) {
			WT_ERR(__wt_tree_walk(session, &walk, flags));
			if (walk == NULL)
				break;

			/*
			 * Write dirty pages if nobody beat us to it.  Don't
			 * try to write hot pages (defined as pages that have
			 * been updated since the write phase leaves started):
			 * checkpoint will have to visit them anyway.
			 */
			page = walk->page;
			if (__wt_page_is_modified(page) &&
			    WT_TXNID_LT(page->modify->update_txn, oldest_id)) {
				if (txn->isolation == WT_ISO_READ_COMMITTED)
					__wt_txn_get_snapshot(session);
				leaf_bytes += page->memory_footprint;
				++leaf_pages;
				WT_ERR(__wt_reconcile(session,
				    walk, NULL, WT_REC_CHECKPOINT, NULL));
			}
		}
		break;
	case WT_SYNC_CHECKPOINT:
		/*
		 * If we are flushing a file at read-committed isolation, which
		 * is of particular interest for flushing the metadata to make
		 * a schema-changing operation durable, get a transactional
		 * snapshot now.
		 *
		 * All changes committed up to this point should be included.
		 * We don't update the snapshot in between pages because the
		 * metadata shouldn't have many pages.  Instead, read-committed
		 * isolation ensures that all metadata updates completed before
		 * the checkpoint are included.
		 */
		if (txn->isolation == WT_ISO_READ_COMMITTED)
			__wt_txn_get_snapshot(session);

		/*
		 * We cannot check the tree modified flag in the case of a
		 * checkpoint, the checkpoint code has already cleared it.
		 *
		 * Writing the leaf pages is done without acquiring a high-level
		 * lock, serialize so multiple threads don't walk the tree at
		 * the same time.  We're holding the schema lock, but need the
		 * lower-level lock as well.
		 */
		__wt_spin_lock(session, &btree->flush_lock);

		/*
		 * In the final checkpoint pass, child pages cannot be evicted
		 * from underneath internal pages nor can underlying blocks be
		 * freed until the checkpoint's block lists are stable. Also,
		 * we cannot split child pages into parents unless we know the
		 * final pass will write a consistent view of that namespace.
		 * Set the checkpointing flag to block such actions and wait for
		 * any problematic eviction or page splits to complete.
		 */
		WT_ASSERT(session, btree->syncing == WT_BTREE_SYNC_OFF &&
		    btree->sync_session == NULL);

		btree->sync_session = session;
		btree->syncing = WT_BTREE_SYNC_WAIT;
		(void)__wt_gen_next_drain(session, WT_GEN_EVICT);
		btree->syncing = WT_BTREE_SYNC_RUNNING;

		/* Write all dirty in-cache pages. */
		LF_SET(WT_READ_NO_EVICT);

		/* Read pages with lookaside entries and evict them asap. */
		LF_SET(WT_READ_LOOKASIDE | WT_READ_WONT_NEED);

		for (;;) {
			WT_ERR(__sync_dup_walk(session, walk, flags, &prev));
			WT_ERR(__wt_tree_walk(session, &walk, flags));

			if (walk == NULL)
				break;

			/*
			 * Skip clean pages, but need to make sure maximum
			 * transaction ID is always updated.
			 */
			if (!__wt_page_is_modified(walk->page)) {
				if (((mod = walk->page->modify) != NULL) &&
				    mod->rec_max_txn > btree->rec_max_txn)
					btree->rec_max_txn = mod->rec_max_txn;
				if (mod != NULL &&
				    btree->rec_max_timestamp <
				    mod->rec_max_timestamp)
					btree->rec_max_timestamp =
					    mod->rec_max_timestamp;
				continue;
			}

			/*
			 * Take a local reference to the page modify structure
			 * now that we know the page is dirty. It needs to be
			 * done in this order otherwise the page modify
			 * structure could have been created between taking the
			 * reference and checking modified.
			 */
			page = walk->page;

			/*
			 * Write dirty pages, if we can't skip them. If we skip
			 * a page, mark the tree dirty. The checkpoint marked it
			 * clean and we can't skip future checkpoints until this
			 * page is written.
			 */
			if (__sync_checkpoint_can_skip(session, page)) {
				__wt_tree_modify_set(session);
				continue;
			}

			if (WT_PAGE_IS_INTERNAL(page)) {
				internal_bytes += page->memory_footprint;
				++internal_pages;
			} else {
				leaf_bytes += page->memory_footprint;
				++leaf_pages;
			}

			/*
			 * If the page was pulled into cache by our read, try
			 * to evict it now.
			 *
			 * For eviction to have a chance, we first need to move
			 * the walk point to the next page checkpoint will
			 * visit.  We want to avoid this code being too special
			 * purpose, so try to reuse the ordinary eviction path.
			 *
			 * Regardless of whether eviction succeeds or fails,
			 * the walk continues from the previous location.  We
			 * remember whether we tried eviction, and don't try
			 * again.  Even if eviction fails (the page may stay in
			 * cache clean but with history that cannot be
			 * discarded), that is not wasted effort because
			 * checkpoint doesn't need to write the page again.
			 */
			if (!WT_PAGE_IS_INTERNAL(page) &&
			    page->read_gen == WT_READGEN_WONT_NEED &&
			    !tried_eviction) {
				WT_ERR_BUSY_OK(
				    __wt_page_release_evict(session, walk));
				walk = prev;
				prev = NULL;
				tried_eviction = true;
				continue;
			}
			tried_eviction = false;

			WT_ERR(__wt_reconcile(
			    session, walk, NULL, WT_REC_CHECKPOINT, NULL));

			/*
			 * Update checkpoint IO tracking data if configured
			 * to log verbose progress messages.
			 */
			if (conn->ckpt_timer_start.tv_sec > 0) {
				conn->ckpt_write_bytes +=
				    page->memory_footprint;
				++conn->ckpt_write_pages;

				/* Periodically log checkpoint progress. */
				if (conn->ckpt_write_pages % 5000 == 0)
					__wt_checkpoint_progress(
					    session, false);
			}
		}
		break;
	case WT_SYNC_CLOSE:
	case WT_SYNC_DISCARD:
		WT_ERR(__wt_illegal_value(session, syncop));
		break;
	}

	if (timer) {
		time_stop = __wt_clock(session);
		__wt_verbose(session, WT_VERB_CHECKPOINT,
		    "__sync_file WT_SYNC_%s wrote: %" PRIu64
		    " leaf pages (%" PRIu64 "B), %" PRIu64
		    " internal pages (%" PRIu64 "B), and took %" PRIu64 "ms",
		    syncop == WT_SYNC_WRITE_LEAVES ?
		    "WRITE_LEAVES" : "CHECKPOINT",
		    leaf_pages, leaf_bytes, internal_pages, internal_bytes,
		    WT_CLOCKDIFF_MS(time_stop, time_start));
	}

err:	/* On error, clear any left-over tree walk. */
	WT_TRET(__wt_page_release(session, walk, flags));
	WT_TRET(__wt_page_release(session, prev, flags));

	/*
	 * If we got a snapshot in order to write pages, and there was no
	 * snapshot active when we started, release it.
	 */
	if (txn->isolation == WT_ISO_READ_COMMITTED &&
	    saved_pinned_id == WT_TXN_NONE)
		__wt_txn_release_snapshot(session);

	/* Clear the checkpoint flag. */
	btree->syncing = WT_BTREE_SYNC_OFF;
	btree->sync_session = NULL;

	__wt_spin_unlock(session, &btree->flush_lock);

	/*
	 * Leaves are written before a checkpoint (or as part of a file close,
	 * before checkpointing the file).  Start a flush to stable storage,
	 * but don't wait for it.
	 */
	if (ret == 0 &&
	    syncop == WT_SYNC_WRITE_LEAVES && F_ISSET(conn, WT_CONN_CKPT_SYNC))
		WT_RET(btree->bm->sync(btree->bm, session, false));

	return (ret);
}
Exemplo n.º 3
0
/*
 * __sync_file --
 *	Flush pages for a specific file.
 */
static int
__sync_file(WT_SESSION_IMPL *session, int syncop)
{
	struct timespec end, start;
	WT_BTREE *btree;
	WT_DECL_RET;
	WT_PAGE *page;
	WT_PAGE_MODIFY *mod;
	WT_REF *walk;
	WT_TXN *txn;
	uint64_t internal_bytes, leaf_bytes;
	uint64_t internal_pages, leaf_pages;
	uint32_t flags;
	bool evict_reset;

	btree = S2BT(session);

	flags = WT_READ_CACHE | WT_READ_NO_GEN;
	walk = NULL;
	txn = &session->txn;

	internal_bytes = leaf_bytes = 0;
	internal_pages = leaf_pages = 0;
	if (WT_VERBOSE_ISSET(session, WT_VERB_CHECKPOINT))
		WT_RET(__wt_epoch(session, &start));

	switch (syncop) {
	case WT_SYNC_WRITE_LEAVES:
		/*
		 * Write all immediately available, dirty in-cache leaf pages.
		 *
		 * Writing the leaf pages is done without acquiring a high-level
		 * lock, serialize so multiple threads don't walk the tree at
		 * the same time.
		 */
		if (!btree->modified)
			return (0);
		__wt_spin_lock(session, &btree->flush_lock);
		if (!btree->modified) {
			__wt_spin_unlock(session, &btree->flush_lock);
			return (0);
		}

		flags |= WT_READ_NO_WAIT | WT_READ_SKIP_INTL;
		for (walk = NULL;;) {
			WT_ERR(__wt_tree_walk(session, &walk, NULL, flags));
			if (walk == NULL)
				break;

			/*
			 * Write dirty pages if nobody beat us to it.  Don't
			 * try to write the hottest pages: checkpoint will have
			 * to visit them anyway.
			 */
			page = walk->page;
			if (__wt_page_is_modified(page) &&
			    __wt_txn_visible_all(
			    session, page->modify->update_txn)) {
				if (txn->isolation == WT_ISO_READ_COMMITTED)
					__wt_txn_get_snapshot(session);
				leaf_bytes += page->memory_footprint;
				++leaf_pages;
				WT_ERR(__wt_reconcile(session, walk, NULL, 0));
			}
		}
		break;
	case WT_SYNC_CHECKPOINT:
		/*
		 * We cannot check the tree modified flag in the case of a
		 * checkpoint, the checkpoint code has already cleared it.
		 *
		 * Writing the leaf pages is done without acquiring a high-level
		 * lock, serialize so multiple threads don't walk the tree at
		 * the same time.  We're holding the schema lock, but need the
		 * lower-level lock as well.
		 */
		__wt_spin_lock(session, &btree->flush_lock);

		/*
		 * When internal pages are being reconciled by checkpoint their
		 * child pages cannot disappear from underneath them or be split
		 * into them, nor can underlying blocks be freed until the block
		 * lists for the checkpoint are stable.  Set the checkpointing
		 * flag to block eviction of dirty pages until the checkpoint's
		 * internal page pass is complete, then wait for any existing
		 * eviction to complete.
		 */
		btree->checkpointing = 1;
		WT_FULL_BARRIER();

		WT_ERR(__wt_evict_file_exclusive_on(session, &evict_reset));
		if (evict_reset)
			__wt_evict_file_exclusive_off(session);

		/* Write all dirty in-cache pages. */
		flags |= WT_READ_NO_EVICT;
		for (walk = NULL;;) {
			/*
			 * If we have a page, and it was ever modified, track
			 * the highest transaction ID in the tree.  We do this
			 * here because we want the value after reconciling
			 * dirty pages.
			 */
			if (walk != NULL && walk->page != NULL &&
			    (mod = walk->page->modify) != NULL &&
			    WT_TXNID_LT(btree->rec_max_txn, mod->rec_max_txn))
				btree->rec_max_txn = mod->rec_max_txn;

			WT_ERR(__wt_tree_walk(session, &walk, NULL, flags));
			if (walk == NULL)
				break;

			page = walk->page;
			mod = page->modify;

			/* Skip clean pages. */
			if (!__wt_page_is_modified(page))
				continue;

			/*
			 * Write dirty pages, unless we can be sure they only
			 * became dirty after the checkpoint started.
			 *
			 * We can skip dirty pages if:
			 * (1) they are leaf pages;
			 * (2) there is a snapshot transaction active (which
			 *     is the case in ordinary application checkpoints
			 *     but not all internal cases); and
			 * (3) the first dirty update on the page is
			 *     sufficiently recent that the checkpoint
			 *     transaction would skip them.
			 *
			 * Mark the tree dirty: the checkpoint marked it clean
			 * and we can't skip future checkpoints until this page
			 * is written.
			 */
			if (!WT_PAGE_IS_INTERNAL(page) &&
			    F_ISSET(txn, WT_TXN_HAS_SNAPSHOT) &&
			    WT_TXNID_LT(txn->snap_max, mod->first_dirty_txn) &&
			    mod->rec_result != WT_PM_REC_REWRITE) {
				__wt_page_modify_set(session, page);
				continue;
			}

			if (WT_PAGE_IS_INTERNAL(page)) {
				internal_bytes += page->memory_footprint;
				++internal_pages;
			} else {
				leaf_bytes += page->memory_footprint;
				++leaf_pages;
			}
			WT_ERR(__wt_reconcile(session, walk, NULL, 0));
		}
		break;
	}

	if (WT_VERBOSE_ISSET(session, WT_VERB_CHECKPOINT)) {
		WT_ERR(__wt_epoch(session, &end));
		WT_ERR(__wt_verbose(session, WT_VERB_CHECKPOINT,
		    "__sync_file WT_SYNC_%s wrote:\n\t %" PRIu64
		    " bytes, %" PRIu64 " pages of leaves\n\t %" PRIu64
		    " bytes, %" PRIu64 " pages of internal\n\t"
		    "Took: %" PRIu64 "ms",
		    syncop == WT_SYNC_WRITE_LEAVES ?
		    "WRITE_LEAVES" : "CHECKPOINT",
		    leaf_bytes, leaf_pages, internal_bytes, internal_pages,
		    WT_TIMEDIFF(end, start) / WT_MILLION));
	}

err:	/* On error, clear any left-over tree walk. */
	if (walk != NULL)
		WT_TRET(__wt_page_release(session, walk, flags));

	if (txn->isolation == WT_ISO_READ_COMMITTED && session->ncursors == 0)
		__wt_txn_release_snapshot(session);

	if (btree->checkpointing) {
		/*
		 * Update the checkpoint generation for this handle so visible
		 * updates newer than the checkpoint can be evicted.
		 *
		 * This has to be published before eviction is enabled again,
		 * so that eviction knows that the checkpoint has completed.
		 */
		WT_PUBLISH(btree->checkpoint_gen,
		    S2C(session)->txn_global.checkpoint_gen);
		WT_STAT_FAST_DATA_SET(session,
		    btree_checkpoint_generation, btree->checkpoint_gen);

		/*
		 * Clear the checkpoint flag and push the change; not required,
		 * but publishing the change means stalled eviction gets moving
		 * as soon as possible.
		 */
		btree->checkpointing = 0;
		WT_FULL_BARRIER();

		/*
		 * If this tree was being skipped by the eviction server during
		 * the checkpoint, clear the wait.
		 */
		btree->evict_walk_period = 0;

		/*
		 * Wake the eviction server, in case application threads have
		 * stalled while the eviction server decided it couldn't make
		 * progress.  Without this, application threads will be stalled
		 * until the eviction server next wakes.
		 */
		WT_TRET(__wt_evict_server_wake(session));
	}

	__wt_spin_unlock(session, &btree->flush_lock);

	/*
	 * Leaves are written before a checkpoint (or as part of a file close,
	 * before checkpointing the file).  Start a flush to stable storage,
	 * but don't wait for it.
	 */
	if (ret == 0 && syncop == WT_SYNC_WRITE_LEAVES)
		WT_RET(btree->bm->sync(btree->bm, session, true));

	return (ret);
}
Exemplo n.º 4
0
/*
 * __sync_file --
 *	Flush pages for a specific file.
 */
static int
__sync_file(WT_SESSION_IMPL *session, WT_CACHE_OP syncop)
{
	struct timespec end, start;
	WT_BTREE *btree;
	WT_CONNECTION_IMPL *conn;
	WT_DECL_RET;
	WT_PAGE *page;
	WT_PAGE_MODIFY *mod;
	WT_REF *walk;
	WT_TXN *txn;
	uint64_t internal_bytes, internal_pages, leaf_bytes, leaf_pages;
	uint64_t oldest_id, saved_snap_min;
	uint32_t flags;

	conn = S2C(session);
	btree = S2BT(session);
	walk = NULL;
	txn = &session->txn;
	saved_snap_min = WT_SESSION_TXN_STATE(session)->snap_min;
	flags = WT_READ_CACHE | WT_READ_NO_GEN;

	internal_bytes = leaf_bytes = 0;
	internal_pages = leaf_pages = 0;
	if (WT_VERBOSE_ISSET(session, WT_VERB_CHECKPOINT))
		WT_RET(__wt_epoch(session, &start));

	switch (syncop) {
	case WT_SYNC_WRITE_LEAVES:
		/*
		 * Write all immediately available, dirty in-cache leaf pages.
		 *
		 * Writing the leaf pages is done without acquiring a high-level
		 * lock, serialize so multiple threads don't walk the tree at
		 * the same time.
		 */
		if (!btree->modified)
			return (0);
		__wt_spin_lock(session, &btree->flush_lock);
		if (!btree->modified) {
			__wt_spin_unlock(session, &btree->flush_lock);
			return (0);
		}

		/*
		 * Save the oldest transaction ID we need to keep around.
		 * Otherwise, in a busy system, we could be updating pages so
		 * fast that write leaves never catches up.  We deliberately
		 * have no transaction running at this point that would keep
		 * the oldest ID from moving forwards as we walk the tree.
		 */
		oldest_id = __wt_txn_oldest_id(session);

		flags |= WT_READ_NO_WAIT | WT_READ_SKIP_INTL;
		for (walk = NULL;;) {
			WT_ERR(__wt_tree_walk(session, &walk, flags));
			if (walk == NULL)
				break;

			/*
			 * Write dirty pages if nobody beat us to it.  Don't
			 * try to write hot pages (defined as pages that have
			 * been updated since the write phase leaves started):
			 * checkpoint will have to visit them anyway.
			 */
			page = walk->page;
			if (__wt_page_is_modified(page) &&
			    WT_TXNID_LT(page->modify->update_txn, oldest_id)) {
				if (txn->isolation == WT_ISO_READ_COMMITTED)
					__wt_txn_get_snapshot(session);
				leaf_bytes += page->memory_footprint;
				++leaf_pages;
				WT_ERR(__wt_reconcile(session, walk, NULL, 0));
			}
		}
		break;
	case WT_SYNC_CHECKPOINT:
		/*
		 * If we are flushing a file at read-committed isolation, which
		 * is of particular interest for flushing the metadata to make
		 * schema-changing operation durable, get a transactional
		 * snapshot now.
		 *
		 * All changes committed up to this point should be included.
		 * We don't update the snapshot in between pages because (a)
		 * the metadata shouldn't be that big, and (b) if we do ever
		 */
		if (txn->isolation == WT_ISO_READ_COMMITTED)
			__wt_txn_get_snapshot(session);

		/*
		 * We cannot check the tree modified flag in the case of a
		 * checkpoint, the checkpoint code has already cleared it.
		 *
		 * Writing the leaf pages is done without acquiring a high-level
		 * lock, serialize so multiple threads don't walk the tree at
		 * the same time.  We're holding the schema lock, but need the
		 * lower-level lock as well.
		 */
		__wt_spin_lock(session, &btree->flush_lock);

		/*
		 * In the final checkpoint pass, child pages cannot be evicted
		 * from underneath internal pages nor can underlying blocks be
		 * freed until the checkpoint's block lists are stable. Also,
		 * we cannot split child pages into parents unless we know the
		 * final pass will write a consistent view of that namespace.
		 * Set the checkpointing flag to block such actions and wait for
		 * any problematic eviction or page splits to complete.
		 */
		WT_PUBLISH(btree->checkpointing, WT_CKPT_PREPARE);

		WT_ERR(__wt_evict_file_exclusive_on(session));
		__wt_evict_file_exclusive_off(session);

		WT_PUBLISH(btree->checkpointing, WT_CKPT_RUNNING);

		/* Write all dirty in-cache pages. */
		flags |= WT_READ_NO_EVICT;
		for (walk = NULL;;) {
			WT_ERR(__wt_tree_walk(session, &walk, flags));
			if (walk == NULL)
				break;

			/* Skip clean pages. */
			if (!__wt_page_is_modified(walk->page))
				continue;

			/*
			 * Take a local reference to the page modify structure
			 * now that we know the page is dirty. It needs to be
			 * done in this order otherwise the page modify
			 * structure could have been created between taking the
			 * reference and checking modified.
			 */
			page = walk->page;
			mod = page->modify;

			/*
			 * Write dirty pages, unless we can be sure they only
			 * became dirty after the checkpoint started.
			 *
			 * We can skip dirty pages if:
			 * (1) they are leaf pages;
			 * (2) there is a snapshot transaction active (which
			 *     is the case in ordinary application checkpoints
			 *     but not all internal cases); and
			 * (3) the first dirty update on the page is
			 *     sufficiently recent that the checkpoint
			 *     transaction would skip them.
			 *
			 * Mark the tree dirty: the checkpoint marked it clean
			 * and we can't skip future checkpoints until this page
			 * is written.
			 */
			if (!WT_PAGE_IS_INTERNAL(page) &&
			    F_ISSET(txn, WT_TXN_HAS_SNAPSHOT) &&
			    WT_TXNID_LT(txn->snap_max, mod->first_dirty_txn)) {
				__wt_page_modify_set(session, page);
				continue;
			}

			if (WT_PAGE_IS_INTERNAL(page)) {
				internal_bytes += page->memory_footprint;
				++internal_pages;
			} else {
				leaf_bytes += page->memory_footprint;
				++leaf_pages;
			}
			WT_ERR(__wt_reconcile(session, walk, NULL, 0));
		}
		break;
	case WT_SYNC_CLOSE:
	case WT_SYNC_DISCARD:
	WT_ILLEGAL_VALUE_ERR(session);
	}

	if (WT_VERBOSE_ISSET(session, WT_VERB_CHECKPOINT)) {
		WT_ERR(__wt_epoch(session, &end));
		WT_ERR(__wt_verbose(session, WT_VERB_CHECKPOINT,
		    "__sync_file WT_SYNC_%s wrote:\n\t %" PRIu64
		    " bytes, %" PRIu64 " pages of leaves\n\t %" PRIu64
		    " bytes, %" PRIu64 " pages of internal\n\t"
		    "Took: %" PRIu64 "ms",
		    syncop == WT_SYNC_WRITE_LEAVES ?
		    "WRITE_LEAVES" : "CHECKPOINT",
		    leaf_bytes, leaf_pages, internal_bytes, internal_pages,
		    WT_TIMEDIFF_MS(end, start)));
	}

err:	/* On error, clear any left-over tree walk. */
	if (walk != NULL)
		WT_TRET(__wt_page_release(session, walk, flags));

	/*
	 * If we got a snapshot in order to write pages, and there was no
	 * snapshot active when we started, release it.
	 */
	if (txn->isolation == WT_ISO_READ_COMMITTED &&
	    saved_snap_min == WT_TXN_NONE)
		__wt_txn_release_snapshot(session);

	if (btree->checkpointing != WT_CKPT_OFF) {
		/*
		 * Update the checkpoint generation for this handle so visible
		 * updates newer than the checkpoint can be evicted.
		 *
		 * This has to be published before eviction is enabled again,
		 * so that eviction knows that the checkpoint has completed.
		 */
		WT_PUBLISH(btree->checkpoint_gen,
		    conn->txn_global.checkpoint_gen);
		WT_STAT_FAST_DATA_SET(session,
		    btree_checkpoint_generation, btree->checkpoint_gen);

		/*
		 * Clear the checkpoint flag and push the change; not required,
		 * but publishing the change means stalled eviction gets moving
		 * as soon as possible.
		 */
		btree->checkpointing = WT_CKPT_OFF;
		WT_FULL_BARRIER();

		/*
		 * If this tree was being skipped by the eviction server during
		 * the checkpoint, clear the wait.
		 */
		btree->evict_walk_period = 0;

		/*
		 * Wake the eviction server, in case application threads have
		 * stalled while the eviction server decided it couldn't make
		 * progress.  Without this, application threads will be stalled
		 * until the eviction server next wakes.
		 */
		WT_TRET(__wt_evict_server_wake(session));
	}

	__wt_spin_unlock(session, &btree->flush_lock);

	/*
	 * Leaves are written before a checkpoint (or as part of a file close,
	 * before checkpointing the file).  Start a flush to stable storage,
	 * but don't wait for it.
	 */
	if (ret == 0 &&
	    syncop == WT_SYNC_WRITE_LEAVES && F_ISSET(conn, WT_CONN_CKPT_SYNC))
		WT_RET(btree->bm->sync(btree->bm, session, true));

	return (ret);
}