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/*-
* 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;
WT_PAGE_STATE previous_state;
size_t addr_size;
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_CAS4(ref->state, WT_REF_DISK, WT_REF_READING))
previous_state = WT_REF_DISK;
else if (WT_ATOMIC_CAS4(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 backing disk page. */
WT_ERR(__wt_bt_read(session, &tmp, addr, addr_size));
/* Build the in-memory version of the page. */
WT_ERR(__wt_page_inmem(session, ref, tmp.data,
WT_DATA_IN_ITEM(&tmp) ?
WT_PAGE_DISK_ALLOC : WT_PAGE_DISK_MAPPED, &page));
/* 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);
}
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