fis-gtm/sr_unix/gtmsource_readpool.c

/****************************************************************
 *								*
 *	Copyright 2006, 2012 Fidelity Information Services, Inc	*
 *								*
 *	This source code contains the intellectual property	*
 *	of its copyright holder(s), and is made available	*
 *	under a license.  If you do not know the terms of	*
 *	the license, please stop and do not read further.	*
 *								*
 ****************************************************************/

#include "mdef.h"

#include "gtm_string.h"
#include "gtm_socket.h"
#include "gtm_inet.h"
#include "gtm_fcntl.h"
#include "gtm_unistd.h"
#include "gtm_stat.h"

#include <sys/time.h>
#include <errno.h>
#ifdef VMS
#include <descrip.h> /* Required for gtmsource.h */
#endif

#include "gdsroot.h"
#include "gdsblk.h"
#include "gtm_facility.h"
#include "fileinfo.h"
#include "gdsbt.h"
#include "gdsfhead.h"
#include "filestruct.h"
#include "repl_msg.h"
#include "gtmsource.h"
#include "jnl.h"
#include "buddy_list.h"
#include "hashtab_mname.h"	/* needed for muprec.h */
#include "hashtab_int4.h"	/* needed for muprec.h */
#include "hashtab_int8.h"	/* needed for muprec.h */
#include "muprec.h"
#include "repl_ctl.h"
#include "repl_errno.h"
#include "repl_dbg.h"
#include "memcoherency.h"
#include "repl_tr_good.h"
#include "min_max.h"
#include "repl_instance.h"

GBLREF	jnlpool_addrs		jnlpool;
GBLREF	gtmsource_state_t	gtmsource_state;

int gtmsource_readpool(uchar_ptr_t buff, int *data_len, int maxbufflen, boolean_t read_multiple, qw_num stop_read_at)
{
	uint4 			jnldata_len, read_size, read, jnlpool_size, avail_data;
	uint4			first_tr_len, num_tr_read, tr_len;
	int4			wrap_size;
	uchar_ptr_t		buf_top, tr_p;
	jnlpool_ctl_ptr_t	jctl;
	gtmsource_local_ptr_t	gtmsource_local;
	sm_uc_ptr_t		jnldata_base;
	jnldata_hdr_ptr_t	jnl_header;
	qw_num			read_addr, avail_data_qw;
	seq_num			read_jnl_seqno, jnl_seqno, next_read_seqno, next_histinfo_seqno;

	jctl = jnlpool.jnlpool_ctl;
	jnlpool_size = jctl->jnlpool_size;
	DEBUG_ONLY(jnl_seqno = jctl->jnl_seqno;) /* jnl_seqno is used in an assert below. jnl_seqno is a local variable for
						  * debugging purposes since shared memory can change from the time the assert
						  * fails to the time the core gets created
						  */
	jnldata_base = jnlpool.jnldata_base;
	gtmsource_local = jnlpool.gtmsource_local;
	do
	{
		read = gtmsource_local->read;
		read_addr = gtmsource_local->read_addr;
		assert(stop_read_at > read_addr); /* there should be data to be read, if not how did we end up here? */
		read_jnl_seqno = gtmsource_local->read_jnl_seqno;
		assert(read_jnl_seqno <= gtmsource_local->next_histinfo_seqno);
		if (read_jnl_seqno == gtmsource_local->next_histinfo_seqno)
		{	/* Request a REPL_HISTREC message be sent first before sending any more seqnos across */
			gtmsource_state = gtmsource_local->gtmsource_state = GTMSOURCE_SEND_NEW_HISTINFO;
			return 0;
		}
		next_histinfo_seqno = gtmsource_local->next_histinfo_seqno;
		next_read_seqno = read_jnl_seqno;
		if (jnlpool_hasnt_overflowed(jctl, jnlpool_size, read_addr))
		{	/* No overflow yet. Before we read the content (including the jnldata_len read below), we have to ensure
			 * we read up-to-date content. We rely on the memory barrier done in jnlpool_hasnt_overflowed for this.
			 */
			assert(read + SIZEOF(jnldata_hdr_struct) <= jnlpool_size);
			jnl_header = (jnldata_hdr_ptr_t)(jnldata_base + read);
			first_tr_len = jnldata_len = jnl_header->jnldata_len;
			if (read_multiple)
			{
				assert(stop_read_at >= read_addr);
				avail_data_qw = stop_read_at - read_addr;
				assert(maxbufflen <= MAXPOSINT4); /* to catch the case of change in type of maxbufflen */
				avail_data = (uint4)MIN(avail_data_qw, (qw_num)maxbufflen);
				read_multiple = (first_tr_len < avail_data);
				if (read_multiple)
					jnldata_len = avail_data;
			}
			if (SIZEOF(jnldata_hdr_struct) < jnldata_len && jnldata_len <= jnlpool_size)
			{
				read_size = jnldata_len - SIZEOF(jnldata_hdr_struct);
				if (0 < read_size && read_size <= maxbufflen)
				{
					if (0 < (wrap_size = (int4)(read - (jnlpool_size - jnldata_len))))
						read_size -= wrap_size;
					memcpy(buff, (sm_uc_ptr_t)jnl_header + SIZEOF(jnldata_hdr_struct), read_size);
					if (0 < wrap_size)
						memcpy(buff + read_size, jnldata_base, wrap_size);
					/* Now that we have read the content, we have to ensure that we haven't read content
					 * that may been overwritten. We rely on the memory barrier done in
					 * jnlpool_hasnt_overflowed for this
					 */
					if (jnlpool_hasnt_overflowed(jctl, jnlpool_size, read_addr))
					{	/* No overflow. Only now are we guaranteed a good value of "first_tr_len". */
						assert(first_tr_len % JNL_WRT_END_MODULUS == 0);
						REPL_DEBUG_ONLY(
							assert(repl_tr_good(buff, first_tr_len - SIZEOF(jnldata_hdr_struct),
									read_jnl_seqno));
							num_tr_read = 1;
						)
						next_read_seqno++;
						assert(next_read_seqno <= next_histinfo_seqno);
						if ((read_multiple) && (next_read_seqno < next_histinfo_seqno))
						{	/* Although stop_read_at - read_addr contains no partial transaction, it
							 * is possible that stop_read_at - read_addr is more than maxbufflen, and
							 * hence we read fewer bytes than stop_read_at - read_addr; scan what we
							 * read to figure out if the tail is an incomplete transaction.
							 */
							assert(first_tr_len < jnldata_len); /* must hold if multiple transactions
												were read */
							tr_p = buff + first_tr_len - SIZEOF(jnldata_hdr_struct);
							buf_top = buff + jnldata_len - SIZEOF(jnldata_hdr_struct);
							while (SIZEOF(jnldata_hdr_struct) < (buf_top - tr_p))
							{	/* more than hdr available */
								tr_len = ((jnldata_hdr_ptr_t)tr_p)->jnldata_len;
								assert(tr_len % JNL_WRT_END_MODULUS == 0);
								assert(0 < tr_len);
								assert(tr_len <= jnlpool_size);
								if (tr_len <= (buf_top - tr_p)) /* transaction completely read */
								{	/* The message type and len assignments are a violation of
									 * layering; ideally, this should be done in
									 * gtmsource_process(), but we choose to do it here for
									 * performance reasons. If we have to do it in
									 * gtmsource_process(), we have to scan the buffer again.
									 */
									((repl_msg_ptr_t)tr_p)->type = REPL_TR_JNL_RECS;
									((repl_msg_ptr_t)tr_p)->len = tr_len;
									REPL_DEBUG_ONLY(
										assert(repl_tr_good(tr_p + REPL_MSG_HDRLEN,
											tr_len - REPL_MSG_HDRLEN,
											read_jnl_seqno + num_tr_read));
										num_tr_read++;
									)
									next_read_seqno++;
									tr_p += tr_len;
									if (next_read_seqno >= next_histinfo_seqno)
									{	/* Dont read more than boundary of next histinfo */
										assert(next_read_seqno == next_histinfo_seqno);
										break;
									}
								} else
								{
									REPL_DPRINT5("Partial transaction read since jnldata_len"
										" %llu larger than maxbufflen %d, tr_len %d, "
										"remaining buffer %d\n", avail_data_qw, maxbufflen,
										tr_len, buf_top - tr_p);
									break;
								}
							}
							REPL_DEBUG_ONLY(
								if (0 != (buf_top - tr_p))
								{
									REPL_DPRINT4("Partial tr header read since jnldata_len "
										"%llu larger than maxbufflen %d, incomplete header"
										" length %d\n", avail_data_qw, maxbufflen,
										buf_top - tr_p);
								}
							)
							jnldata_len = (uint4)((tr_p - buff) + SIZEOF(jnldata_hdr_struct));
							wrap_size = (int4)(read - (jnlpool_size - jnldata_len));
						}
						REPL_DPRINT4("Pool read seqno : "INT8_FMT" Num Tr read : %d Total Tr len : %d\n",
						       INT8_PRINT(read_jnl_seqno), num_tr_read, jnldata_len);
						REPL_DPRINT4("Read %u : Next read : %u : %s\n", read,
							(0 > wrap_size) ? read + jnldata_len : wrap_size,
							(0 > wrap_size) ? "" : " READ WRAPPED");
						assert(next_read_seqno <= next_histinfo_seqno);
						/* Before sending the seqnos, check if a new histinfo got concurrently written */
						assert(gtmsource_local->next_histinfo_num <= gtmsource_local->num_histinfo);
						if ((gtmsource_local->next_histinfo_num == gtmsource_local->num_histinfo)
							&& (gtmsource_local->num_histinfo
									!= jnlpool.repl_inst_filehdr->num_histinfo))
						{	/* We are sending seqnos of the last histinfo (that is open-ended) and
							 * there has been at least one histinfo concurrently added to this instance
							 * file compared to what is in our private memory. Set the next histinfo's
							 * start_seqno and redo the read with the new "next_histinfo_seqno".
							 */
							assert(MAX_SEQNO == gtmsource_local->next_histinfo_seqno);
							gtmsource_set_next_histinfo_seqno(TRUE);
								/* Set the next histinfo's start_seqno and redo the read */
							if (GTMSOURCE_WAITING_FOR_CONNECTION == gtmsource_state)
							{	/* Connection reset in "gtmsource_set_next_histinfo_seqno" */
								return 0;
							}
							continue;
						}
						read = ((0 > wrap_size) ? read + jnldata_len : wrap_size);
						read_addr += jnldata_len;
						read_jnl_seqno = next_read_seqno;
						assert(read_jnl_seqno <= gtmsource_local->next_histinfo_seqno);
						assert(stop_read_at >= read_addr);
						assert(jnl_seqno >= read_jnl_seqno - 1);
						/* In the rare case when we read the transaction read_jnl_seqno just as
						 * it becomes available and before the GTM process that wrote it updates
						 * jctl->jnl_seqno in t_end/tp_tend, we may return from this function
						 * with read_jnl_seqno one more than jctl->jnl_seqno. This is such a rare
						 * case that we don't want to add a wait loop for jctl->jnl_seqno to become
						 * equal to read_jnl_seqno. We expect that by the time we send the just read
						 * transaction(s) using socket I/O, jctl->jnl_seqno would have been updated.
						 * In any case, we prevent ourselves from misinterpreting this condition when
						 * read_jnl_seqno is compared against jctl->jnl_seqno in gtmsource_process(),
						 * gtmsource_get_jnlrecs() and gtmsource_showbacklog().
						 */
						assert(read == read_addr % jnlpool_size);
						gtmsource_local->read = read;
						gtmsource_local->read_addr = read_addr;
						gtmsource_local->read_jnl_seqno = read_jnl_seqno;
						*data_len = first_tr_len - SIZEOF(jnldata_hdr_struct);
						return (jnldata_len);
					} /* else overflow happened, or about to happen */
				} else if (0 < read_size && jnlpool_hasnt_overflowed(jctl, jnlpool_size, read_addr))
				{ /* Buffer cannot accommodate data */
					*data_len = read_size;
					return (-1);
				} /* else
				   * We read a corrupt (overwritten) large value, or read_size == 0, both of which imply overflow.
				   * read_size == 0 => overflow because every transaction generates non-zero bytes of jnl data */
			} /* else
			   * We read a corrupt (overwritten) large value, or read 0, both of which imply overflow.
			   * jnldata_len == 0 => overflow because every transaction generates non-zero bytes of jnl data */
		} /* else overflow happened, or about to happen */
		break;
	} while (TRUE);
	*data_len = -1;
	return (-1); /* Error indication */
}