/*
* __ovfl_read --
* Read an overflow item from the disk.
*/
static int
__ovfl_read(WT_SESSION_IMPL *session,
const uint8_t *addr, size_t addr_size, WT_ITEM *store)
{
WT_BTREE *btree;
const WT_PAGE_HEADER *dsk;
btree = S2BT(session);
/*
* Read the overflow item from the block manager, then reference the
* start of the data and set the data's length.
*
* Overflow reads are synchronous. That may bite me at some point, but
* WiredTiger supports large page sizes, overflow items should be rare.
*/
WT_RET(__wt_bt_read(session, store, addr, addr_size));
dsk = store->data;
store->data = WT_PAGE_HEADER_BYTE(btree, dsk);
store->size = dsk->u.datalen;
WT_STAT_FAST_DATA_INCR(session, cache_read_overflow);
return (0);
}
/*
* __wt_debug_offset --
* Read and dump a disk page in debugging mode, using a file
* offset/size/checksum triplet.
*/
int
__wt_debug_offset(WT_SESSION_IMPL *session,
wt_off_t offset, uint32_t size, uint32_t cksum, const char *ofile)
{
WT_DECL_ITEM(buf);
WT_DECL_RET;
uint8_t addr[WT_BTREE_MAX_ADDR_COOKIE], *endp;
WT_ASSERT(session, S2BT_SAFE(session) != NULL);
/*
* This routine depends on the default block manager's view of files,
* where an address consists of a file offset, length, and checksum.
* This is for debugging only: other block managers might not see a
* file or address the same way, that's why there's no block manager
* method.
*
* Convert the triplet into an address structure.
*/
endp = addr;
WT_RET(__wt_block_addr_to_buffer(
S2BT(session)->bm->block, &endp, offset, size, cksum));
/*
* Read the address through the btree I/O functions (so the block is
* decompressed as necessary).
*/
WT_RET(__wt_scr_alloc(session, 0, &buf));
WT_ERR(__wt_bt_read(session, buf, addr, WT_PTRDIFF(endp, addr)));
ret = __wt_debug_disk(session, buf->mem, ofile);
err: __wt_scr_free(session, &buf);
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_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);
}
