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/*-
* Copyright (c) 2008-2013 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
#include "wt_internal.h"
/*
* __wt_bm_read --
* Map or read address cookie referenced block into a buffer.
*/
int
__wt_bm_read(WT_BM *bm, WT_SESSION_IMPL *session,
WT_ITEM *buf, const uint8_t *addr, uint32_t addr_size)
{
WT_BLOCK *block;
off_t offset;
uint32_t size, cksum;
int mapped;
WT_UNUSED(addr_size);
block = bm->block;
/* Crack the cookie. */
WT_RET(__wt_block_buffer_to_addr(block, addr, &offset, &size, &cksum));
/*
* Clear buffers previously used for mapped memory, we may be forced
* to read into this buffer.
*/
if (F_ISSET(buf, WT_ITEM_MAPPED))
__wt_buf_free(session, buf);
/*
* If we're going to be able to return mapped memory and the buffer
* has allocated memory, discard it.
*/
mapped = bm->map != NULL && offset + size <= (off_t)bm->maplen;
if (buf->mem != NULL && mapped)
__wt_buf_free(session, buf);
/* Map the block if it's possible. */
if (mapped) {
buf->mem = (uint8_t *)bm->map + offset;
buf->memsize = size;
buf->data = buf->mem;
buf->size = size;
F_SET(buf, WT_ITEM_MAPPED);
WT_CSTAT_INCR(session, block_map_read);
WT_CSTAT_INCRV(session, block_byte_map_read, size);
return (0);
}
/* Read the block. */
WT_RET(__wt_block_read_off(session, block, buf, offset, size, cksum));
#ifdef HAVE_POSIX_FADVISE
/* Optionally discard blocks from the system's buffer cache. */
if (block->os_cache_max != 0 &&
(block->os_cache += offset) > block->os_cache_max) {
WT_DECL_RET;
block->os_cache = 0;
if ((ret = posix_fadvise(block->fh->fd,
(off_t)0, (off_t)0, POSIX_FADV_DONTNEED)) != 0)
WT_RET_MSG(
session, ret, "%s: posix_fadvise", block->name);
}
#endif
return (0);
}
/*
* __wt_block_read_off --
* Read an addr/size pair referenced block into a buffer.
*/
int
__wt_block_read_off(WT_SESSION_IMPL *session,
WT_BLOCK *block, WT_ITEM *buf, off_t offset, uint32_t size, uint32_t cksum)
{
WT_BLOCK_HEADER *blk;
uint32_t alloc_size, page_cksum;
WT_VERBOSE_RET(session, read,
"off %" PRIuMAX ", size %" PRIu32 ", cksum %" PRIu32,
(uintmax_t)offset, size, cksum);
#ifdef HAVE_DIAGNOSTIC
/*
* In diagnostic mode, verify the block we're about to read isn't on
* either the available or discard lists.
*
* Don't check during salvage, it's possible we're reading an already
* freed overflow page.
*/
if (!F_ISSET(session, WT_SESSION_SALVAGE_QUIET_ERR))
WT_RET(
__wt_block_misplaced(session, block, "read", offset, size));
#endif
/*
* Grow the buffer as necessary and read the block. Buffers should be
* aligned for reading, but there are lots of buffers (for example, file
* cursors have two buffers each, key and value), and it's difficult to
* be sure we've found all of them. If the buffer isn't aligned, it's
* an easy fix: set the flag and guarantee we reallocate it. (Most of
* the time on reads, the buffer memory has not yet been allocated, so
* we're not adding any additional processing time.)
*/
if (F_ISSET(buf, WT_ITEM_ALIGNED))
alloc_size = size;
else {
F_SET(buf, WT_ITEM_ALIGNED);
alloc_size = (uint32_t)WT_MAX(size, buf->memsize + 10);
}
WT_RET(__wt_buf_init(session, buf, alloc_size));
WT_RET(__wt_read(session, block->fh, offset, size, buf->mem));
buf->size = size;
blk = WT_BLOCK_HEADER_REF(buf->mem);
blk->cksum = 0;
page_cksum = __wt_cksum(buf->mem,
F_ISSET(blk, WT_BLOCK_DATA_CKSUM) ? size : WT_BLOCK_COMPRESS_SKIP);
if (cksum != page_cksum) {
if (!F_ISSET(session, WT_SESSION_SALVAGE_QUIET_ERR))
__wt_errx(session,
"read checksum error [%"
PRIu32 "B @ %" PRIuMAX ", %"
PRIu32 " != %" PRIu32 "]",
size, (uintmax_t)offset, cksum, page_cksum);
return (WT_ERROR);
}
WT_CSTAT_INCR(session, block_read);
WT_CSTAT_INCRV(session, block_byte_read, size);
return (0);
}
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