示例#1
0
/*
 * __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, size_t addr_size)
{
	WT_BLOCK *block;
	WT_DECL_RET;
	WT_FILE_HANDLE *handle;
	wt_off_t offset;
	uint32_t checksum, size;
	bool mapped;

	WT_UNUSED(addr_size);
	block = bm->block;

	/* Crack the cookie. */
	WT_RET(
	    __wt_block_buffer_to_addr(block, addr, &offset, &size, &checksum));

	/*
	 * Map the block if it's possible.
	 */
	handle = block->fh->handle;
	mapped = bm->map != NULL && offset + size <= (wt_off_t)bm->maplen;
	if (mapped && handle->fh_map_preload != NULL) {
		buf->data = (uint8_t *)bm->map + offset;
		buf->size = size;
		ret = handle->fh_map_preload(handle, (WT_SESSION *)session,
		    buf->data, buf->size,bm->mapped_cookie);

		WT_STAT_CONN_INCR(session, block_map_read);
		WT_STAT_CONN_INCRV(session, block_byte_map_read, size);
		return (ret);
	}

#ifdef HAVE_DIAGNOSTIC
	/*
	 * In diagnostic mode, verify the block we're about to read isn't on
	 * the available list, or for live systems, the discard list.
	 */
	WT_RET(__wt_block_misplaced(session,
	    block, "read", offset, size, bm->is_live, __func__, __LINE__));
#endif
	/* Read the block. */
	__wt_capacity_throttle(session, size, WT_THROTTLE_READ);
	WT_RET(
	    __wt_block_read_off(session, block, buf, offset, size, checksum));

	/* Optionally discard blocks from the system's buffer cache. */
	WT_RET(__wt_block_discard(session, block, (size_t)size));

	return (0);
}
示例#2
0
/*
 * __block_write_off --
 *	Write a buffer into a block, returning the block's offset, size and
 * checksum.
 */
static int
__block_write_off(WT_SESSION_IMPL *session, WT_BLOCK *block,
    WT_ITEM *buf, wt_off_t *offsetp, uint32_t *sizep, uint32_t *checksump,
    bool data_checksum, bool checkpoint_io, bool caller_locked)
{
	WT_BLOCK_HEADER *blk;
	WT_DECL_RET;
	WT_FH *fh;
	wt_off_t offset;
	size_t align_size;
	uint32_t checksum;
	bool local_locked;

	*offsetp = 0;			/* -Werror=maybe-uninitialized */
	*sizep = 0;			/* -Werror=maybe-uninitialized */
	*checksump = 0;			/* -Werror=maybe-uninitialized */

	fh = block->fh;

	/*
	 * Clear the block header to ensure all of it is initialized, even the
	 * unused fields.
	 */
	blk = WT_BLOCK_HEADER_REF(buf->mem);
	memset(blk, 0, sizeof(*blk));

	/* Buffers should be aligned for writing. */
	if (!F_ISSET(buf, WT_ITEM_ALIGNED)) {
		WT_ASSERT(session, F_ISSET(buf, WT_ITEM_ALIGNED));
		WT_RET_MSG(session, EINVAL,
		    "direct I/O check: write buffer incorrectly allocated");
	}

	/*
	 * Align the size to an allocation unit.
	 *
	 * The buffer must be big enough for us to zero to the next allocsize
	 * boundary, this is one of the reasons the btree layer must find out
	 * from the block-manager layer the maximum size of the eventual write.
	 */
	align_size = WT_ALIGN(buf->size, block->allocsize);
	if (align_size > buf->memsize) {
		WT_ASSERT(session, align_size <= buf->memsize);
		WT_RET_MSG(session, EINVAL,
		    "buffer size check: write buffer incorrectly allocated");
	}
	if (align_size > UINT32_MAX) {
		WT_ASSERT(session, align_size <= UINT32_MAX);
		WT_RET_MSG(session, EINVAL,
		    "buffer size check: write buffer too large to write");
	}

	/* Zero out any unused bytes at the end of the buffer. */
	memset((uint8_t *)buf->mem + buf->size, 0, align_size - buf->size);

	/*
	 * Set the disk size so we don't have to incrementally read blocks
	 * during salvage.
	 */
	blk->disk_size = WT_STORE_SIZE(align_size);

	/*
	 * Update the block's checksum: if our caller specifies, checksum the
	 * complete data, otherwise checksum the leading WT_BLOCK_COMPRESS_SKIP
	 * bytes.  The assumption is applications with good compression support
	 * turn off checksums and assume corrupted blocks won't decompress
	 * correctly.  However, if compression failed to shrink the block, the
	 * block wasn't compressed, in which case our caller will tell us to
	 * checksum the data to detect corruption. If compression succeeded,
	 * we still need to checksum the first WT_BLOCK_COMPRESS_SKIP bytes
	 * because they're not compressed, both to give salvage a quick test
	 * of whether a block is useful and to give us a test so we don't lose
	 * the first WT_BLOCK_COMPRESS_SKIP bytes without noticing.
	 *
	 * Checksum a little-endian version of the header, and write everything
	 * in little-endian format. The checksum is (potentially) returned in a
	 * big-endian format, swap it into place in a separate step.
	 */
	blk->flags = 0;
	if (data_checksum)
		F_SET(blk, WT_BLOCK_DATA_CKSUM);
	blk->checksum = 0;
	__wt_block_header_byteswap(blk);
	blk->checksum = checksum = __wt_checksum(
	    buf->mem, data_checksum ? align_size : WT_BLOCK_COMPRESS_SKIP);
#ifdef WORDS_BIGENDIAN
	blk->checksum = __wt_bswap32(blk->checksum);
#endif

	/* Pre-allocate some number of extension structures. */
	WT_RET(__wt_block_ext_prealloc(session, 5));

	/*
	 * Acquire a lock, if we don't already hold one.
	 * Allocate space for the write, and optionally extend the file (note
	 * the block-extend function may release the lock).
	 * Release any locally acquired lock.
	 */
	local_locked = false;
	if (!caller_locked) {
		__wt_spin_lock(session, &block->live_lock);
		local_locked = true;
	}
	ret = __wt_block_alloc(session, block, &offset, (wt_off_t)align_size);
	if (ret == 0)
		ret = __wt_block_extend(
		    session, block, fh, offset, align_size, &local_locked);
	if (local_locked)
		__wt_spin_unlock(session, &block->live_lock);
	WT_RET(ret);

	/* Write the block. */
	if ((ret =
	    __wt_write(session, fh, offset, align_size, buf->mem)) != 0) {
		if (!caller_locked)
			__wt_spin_lock(session, &block->live_lock);
		WT_TRET(__wt_block_off_free(
		    session, block, offset, (wt_off_t)align_size));
		if (!caller_locked)
			__wt_spin_unlock(session, &block->live_lock);
		WT_RET(ret);
	}

	/*
	 * Optionally schedule writes for dirty pages in the system buffer
	 * cache, but only if the current session can wait.
	 */
	if (block->os_cache_dirty_max != 0 &&
	    fh->written > block->os_cache_dirty_max &&
	    __wt_session_can_wait(session)) {
		fh->written = 0;
		if ((ret = __wt_fsync(session, fh, false)) != 0) {
			 /*
			  * Ignore ENOTSUP, but don't try again.
			  */
			if (ret != ENOTSUP)
				return (ret);
			block->os_cache_dirty_max = 0;
		}
	}

	/* Optionally discard blocks from the buffer cache. */
	WT_RET(__wt_block_discard(session, block, align_size));

	WT_STAT_CONN_INCR(session, block_write);
	WT_STAT_CONN_INCRV(session, block_byte_write, align_size);
	if (checkpoint_io)
		WT_STAT_CONN_INCRV(
		    session, block_byte_write_checkpoint, align_size);

	__wt_verbose(session, WT_VERB_WRITE,
	    "off %" PRIuMAX ", size %" PRIuMAX ", checksum %#" PRIx32,
	    (uintmax_t)offset, (uintmax_t)align_size, checksum);

	*offsetp = offset;
	*sizep = WT_STORE_SIZE(align_size);
	*checksump = checksum;

	return (0);
}