/*
* __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);
}
/*
* __page_read --
* Read a page from the file.
*/
static int
__page_read(WT_SESSION_IMPL *session, WT_REF *ref)
{
const WT_PAGE_HEADER *dsk;
WT_BTREE *btree;
WT_DECL_RET;
WT_ITEM tmp;
WT_PAGE *page;
size_t addr_size;
uint32_t previous_state;
const uint8_t *addr;
btree = S2BT(session);
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.
*/
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;
goto done;
}
/*
* There's an address, read or map the backing disk page and build an
* in-memory version of the page.
*/
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));
/*
* Clear the local reference to an allocated copy of the disk image on
* return; the page steals it, errors in this code should not free it.
*/
tmp.mem = NULL;
/*
* If reading for a checkpoint, there's no additional work to do, the
* page on disk is correct as written.
*/
if (session->dhandle->checkpoint != NULL)
goto done;
/* If the page was deleted, instantiate that information. */
if (previous_state == WT_REF_DELETED)
WT_ERR(__wt_delete_page_instantiate(session, ref));
/*
* Instantiate updates from the database's lookaside table. The page
* flag was set when the page was written, potentially a long time ago.
* We only care if the lookaside table is currently active, check that
* before doing any work.
*/
dsk = tmp.data;
if (F_ISSET(dsk, WT_PAGE_LAS_UPDATE) && __wt_las_is_written(session)) {
WT_STAT_FAST_CONN_INCR(session, cache_read_lookaside);
WT_STAT_FAST_DATA_INCR(session, cache_read_lookaside);
WT_ERR(__las_page_instantiate(
session, ref, btree->id, addr, addr_size));
}
done: 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);
}
/*
* __wt_evict_file --
* Discard pages for a specific file.
*/
int
__wt_evict_file(WT_SESSION_IMPL *session, WT_CACHE_OP syncop)
{
WT_DECL_RET;
WT_PAGE *page;
WT_REF *next_ref, *ref;
/*
* We need exclusive access to the file -- disable ordinary eviction
* and drain any blocks already queued.
*/
WT_RET(__wt_evict_file_exclusive_on(session));
/* Make sure the oldest transaction ID is up-to-date. */
__wt_txn_update_oldest(session, true);
/* Walk the tree, discarding pages. */
next_ref = NULL;
WT_ERR(__wt_tree_walk(
session, &next_ref, WT_READ_CACHE | WT_READ_NO_EVICT));
while ((ref = next_ref) != NULL) {
page = ref->page;
/*
* Eviction can fail when a page in the evicted page's subtree
* switches state. For example, if we don't evict a page marked
* empty, because we expect it to be merged into its parent, it
* might no longer be empty after it's reconciled, in which case
* eviction of its parent would fail. We can either walk the
* tree multiple times (until it's finally empty), or reconcile
* each page to get it to its final state before considering if
* it's an eviction target or will be merged into its parent.
*
* Don't limit this test to any particular page type, that tends
* to introduce bugs when the reconciliation of other page types
* changes, and there's no advantage to doing so.
*
* Eviction can also fail because an update cannot be written.
* If sessions have disjoint sets of files open, updates in a
* no-longer-referenced file may not yet be globally visible,
* and the write will fail with EBUSY. Our caller handles that
* error, retrying later.
*/
if (syncop == WT_SYNC_CLOSE && __wt_page_is_modified(page))
WT_ERR(__wt_reconcile(session, ref, NULL, WT_EVICTING));
/*
* We can't evict the page just returned to us (it marks our
* place in the tree), so move the walk to one page ahead of
* the page being evicted. Note, we reconciled the returned
* page first: if reconciliation of that page were to change
* the shape of the tree, and we did the next walk call before
* the reconciliation, the next walk call could miss a page in
* the tree.
*/
WT_ERR(__wt_tree_walk(session,
&next_ref, WT_READ_CACHE | WT_READ_NO_EVICT));
switch (syncop) {
case WT_SYNC_CLOSE:
/*
* Evict the page.
*/
WT_ERR(__wt_evict(session, ref, true));
break;
case WT_SYNC_DISCARD:
/*
* Discard the page regardless of whether it is dirty.
*/
WT_ASSERT(session,
F_ISSET(session->dhandle, WT_DHANDLE_DEAD) ||
__wt_page_can_evict(session, ref, NULL));
__wt_ref_out(session, ref);
break;
WT_ILLEGAL_VALUE_ERR(session);
}
}
if (0) {
err: /* On error, clear any left-over tree walk. */
if (next_ref != NULL)
WT_TRET(__wt_page_release(
session, next_ref, WT_READ_NO_EVICT));
}
__wt_evict_file_exclusive_off(session);
return (ret);
}
