/*-
 * Copyright (c) 2014-2015 MongoDB, Inc.
 * Copyright (c) 2008-2014 WiredTiger, Inc.
 *	All rights reserved.
 *
 * See the file LICENSE for redistribution information.
 */

#include "wt_internal.h"

/*
 * __wt_cache_read --
 *	Read a page from the file.
 */
int
__wt_cache_read(WT_SESSION_IMPL *session, WT_REF *ref)
{
	WT_DECL_RET;
	WT_ITEM tmp;
	WT_PAGE *page;
	size_t addr_size;
	uint32_t previous_state;
	const uint8_t *addr;

	page = NULL;

	/*
	 * Don't pass an allocated buffer to the underlying block read function,
	 * force allocation of new memory of the appropriate size.
	 */
	WT_CLEAR(tmp);

	/*
	 * Attempt to set the state to WT_REF_READING for normal reads, or
	 * WT_REF_LOCKED, for deleted pages.  If successful, we've won the
	 * race, read the page.
	 */
	if (__wt_atomic_casv32(&ref->state, WT_REF_DISK, WT_REF_READING))
		previous_state = WT_REF_DISK;
	else if (__wt_atomic_casv32(&ref->state, WT_REF_DELETED, WT_REF_LOCKED))
		previous_state = WT_REF_DELETED;
	else
		return (0);

	/*
	 * Get the address: if there is no address, the page was deleted, but a
	 * subsequent search or insert is forcing re-creation of the name space.
	 * Otherwise, there's an address, read the backing disk page and build
	 * an in-memory version of the page.
	 */
	WT_ERR(__wt_ref_info(session, ref, &addr, &addr_size, NULL));
	if (addr == NULL) {
		WT_ASSERT(session, previous_state == WT_REF_DELETED);

		WT_ERR(__wt_btree_new_leaf_page(session, &page));
		ref->page = page;
	} else {
		/*
		 * Read the page, then build the in-memory version of the page.
		 * Clear any local reference to an allocated copy of the disk
		 * image on return, the page steals it.
		 */
		WT_ERR(__wt_bt_read(session, &tmp, addr, addr_size));
		WT_ERR(__wt_page_inmem(session, ref, tmp.data, tmp.memsize,
		    WT_DATA_IN_ITEM(&tmp) ?
		    WT_PAGE_DISK_ALLOC : WT_PAGE_DISK_MAPPED, &page));
		tmp.mem = NULL;

		/* If the page was deleted, instantiate that information. */
		if (previous_state == WT_REF_DELETED)
			WT_ERR(__wt_delete_page_instantiate(session, ref));
	}

	WT_ERR(__wt_verbose(session, WT_VERB_READ,
	    "page %p: %s", page, __wt_page_type_string(page->type)));

	WT_PUBLISH(ref->state, WT_REF_MEM);
	return (0);

err:	/*
	 * If the function building an in-memory version of the page failed,
	 * it discarded the page, but not the disk image.  Discard the page
	 * and separately discard the disk image in all cases.
	 */
	if (ref->page != NULL)
		__wt_ref_out(session, ref);
	WT_PUBLISH(ref->state, previous_state);

	__wt_buf_free(session, &tmp);

	return (ret);
}