/*
* Copyright (c) 2000 Silicon Graphics, Inc. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of version 2 of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it would be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*
* Further, this software is distributed without any warranty that it is
* free of the rightful claim of any third person regarding infringement
* or the like. Any license provided herein, whether implied or
* otherwise, applies only to this software file. Patent licenses, if
* any, provided herein do not apply to combinations of this program with
* other software, or any other product whatsoever.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
* Mountain View, CA 94043, or:
*
* http://www.sgi.com
*
* For further information regarding this notice, see:
*
* http://oss.sgi.com/projects/GenInfo/NoticeExplan/
*/
/*
* This module contains code for logging writes to files, and for
* perusing the resultant logfile. The main intent of all this is
* to provide a 'write history' of a file which can be examined to
* judge the state of a file (ie. whether it is corrupted or not) based
* on the write activity.
*
* The main abstractions available to the user are the wlog_file, and
* the wlog_rec. A wlog_file is a handle encapsulating a write logfile.
* It is initialized with the wlog_open() function. This handle is
* then passed to the various wlog_xxx() functions to provide transparent
* access to the write logfile.
*
* The wlog_rec datatype is a structure which contains all the information
* about a file write. Examples include the file name, offset, length,
* pattern, etc. In addition there is a bit which is cleared/set based
* on whether or not the write has been confirmed as complete. This
* allows the write logfile to contain information on writes which have
* been initiated, but not yet completed (as in async io).
*
* There is also a function to scan a write logfile in reverse order.
*
* NOTE: For target file analysis based on a write logfile, the
* assumption is made that the file being written to is
* locked from simultaneous access, so that the order of
* write completion is predictable. This is an issue when
* more than 1 process is trying to write data to the same
* target file simultaneously.
*
* The history file created is a collection of variable length records
* described by scruct wlog_rec_disk in write_log.h. See that module for
* the layout of the data on disk.
*/
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>
#include "write_log.h"
#ifndef BSIZE
#ifdef DEV_BSIZE
#define BSIZE DEV_BSIZE
#else
#warning DEV_BSIZE is not defined, defaulting to 512
#define BSIZE 512
#endif
#endif
#ifndef PATH_MAX
#define PATH_MAX 255
/*#define PATH_MAX pathconf("/", _PC_PATH_MAX)*/
#endif
char Wlog_Error_String[256];
#if __STDC__
static int wlog_rec_pack(struct wlog_rec *wrec, char *buf, int flag);
static int wlog_rec_unpack(struct wlog_rec *wrec, char *buf);
#else
static int wlog_rec_pack();
static int wlog_rec_unpack();
#endif
/*
* Initialize a write logfile. wfile is a wlog_file structure that has
* the w_file field filled in. The rest of the information in the
* structure is initialized by the routine.
*
* The trunc flag is used to indicate whether or not the logfile should
* be truncated if it currently exists. If it is non-zero, the file will
* be truncated, otherwise it will be appended to.
*
* The mode argument is the [absolute] mode which the file will be
* given if it does not exist. This mode is not affected by your process
* umask.
*/
int wlog_open(struct wlog_file *wfile, int trunc, int mode)
{
int omask, oflags;
if (trunc)
trunc = O_TRUNC;
omask = umask(0);
/*
* Open 1 file descriptor as O_APPEND
*/
oflags = O_WRONLY | O_APPEND | O_CREAT | trunc;
wfile->w_afd = open(wfile->w_file, oflags, mode);
umask(omask);
if (wfile->w_afd == -1) {
sprintf(Wlog_Error_String,
"Could not open write_log - open(%s, %#o, %#o) failed: %s\n",
wfile->w_file, oflags, mode, strerror(errno));
return -1;
}
/*
* Open the next fd as a random access descriptor
*/
oflags = O_RDWR;
if ((wfile->w_rfd = open(wfile->w_file, oflags)) == -1) {
sprintf(Wlog_Error_String,
"Could not open write log - open(%s, %#o) failed: %s\n",
wfile->w_file, oflags, strerror(errno));
close(wfile->w_afd);
wfile->w_afd = -1;
return -1;
}
return 0;
}
/*
* Release all resources associated with a wlog_file structure allocated
* with the wlog_open() call.
*/
int wlog_close(struct wlog_file *wfile)
{
close(wfile->w_afd);
close(wfile->w_rfd);
return 0;
}
/*
* Write a wlog_rec structure to a write logfile. Offset is used to
* control where the record will be written. If offset is < 0, the
* record will be appended to the end of the logfile. Otherwise, the
* record which exists at the indicated offset will be overlayed. This
* is so that we can record writes which are outstanding (with the w_done
* bit in wrec cleared), but not completed, and then later update the
* logfile when the write request completes (as with async io). When
* offset is >= 0, only the fixed length portion of the record is
* rewritten. See text in write_log.h for details on the format of an
* on-disk record.
*
* The return value of the function is the byte offset in the logfile
* where the record begins.
*
* Note: It is the callers responsibility to make sure that the offset
* parameter 'points' to a valid record location when a record is to be
* overlayed. This is guarenteed by saving the return value of a previous
* call to wlog_record_write() which wrote the record to be overlayed.
*
* Note2: The on-disk version of the wlog_rec is MUCH different than
* the user version. Don't expect to od the logfile and see data formatted
* as it is in the wlog_rec structure. Considerable data packing takes
* place before the record is written.
*/
int wlog_record_write(struct wlog_file *wfile, struct wlog_rec *wrec,
long offset)
{
int reclen;
char wbuf[WLOG_REC_MAX_SIZE + 2];
/*
* If offset is -1, we append the record at the end of file
*
* Otherwise, we overlay wrec at the file offset indicated and assume
* that the caller passed us the correct offset. We do not record the
* fname in this case.
*/
reclen = wlog_rec_pack(wrec, wbuf, (offset < 0));
if (offset < 0) {
/*
* Since we're writing a complete new record, we must also tack
* its length onto the end so that wlog_scan_backward() will work.
* Length is asumed to fit into 2 bytes.
*/
wbuf[reclen] = reclen / 256;
wbuf[reclen + 1] = reclen % 256;
reclen += 2;
if (write(wfile->w_afd, wbuf, reclen) == -1) {
sprintf(Wlog_Error_String,
"Could not write log - write(%s, %s, %d) failed: %s\n",
wfile->w_file, wbuf, reclen, strerror(errno));
return -1;
} else {
offset = lseek(wfile->w_afd, 0, SEEK_CUR) - reclen;
if (offset == -1) {
sprintf(Wlog_Error_String,
"Could not reposition file pointer - lseek(%s, 0, SEEK_CUR) failed: %s\n",
wfile->w_file, strerror(errno));
return -1;
}
}
} else {
if ((lseek(wfile->w_rfd, offset, SEEK_SET)) == -1) {
sprintf(Wlog_Error_String,
"Could not reposition file pointer - lseek(%s, %ld, SEEK_SET) failed: %s\n",
wfile->w_file, offset, strerror(errno));
return -1;
} else {
if ((write(wfile->w_rfd, wbuf, reclen)) == -1) {
sprintf(Wlog_Error_String,
"Could not write log - write(%s, %s, %d) failed: %s\n",
wfile->w_file, wbuf, reclen,
strerror(errno));
return -1;
}
}
}
return offset;
}
/*
* Function to scan a logfile in reverse order. Wfile is a valid
* wlog_file structure initialized by wlog_open(). nrecs is the number
* of records to scan (all records are scanned if nrecs is 0). func is
* a user-supplied function to call for each record found. The function
* will be passed a single parameter - a wlog_rec structure .
*/
int wlog_scan_backward(struct wlog_file *wfile, int nrecs,
int (*func)(), long data)
{
int fd, leftover, nbytes, offset, recnum, reclen, rval;
char buf[BSIZE * 32], *bufend, *cp, *bufstart;
char albuf[WLOG_REC_MAX_SIZE];
struct wlog_rec wrec;
fd = wfile->w_rfd;
/*
* Move to EOF. offset will always hold the current file offset
*/
if ((lseek(fd, 0, SEEK_END)) == -1) {
sprintf(Wlog_Error_String,
"Could not reposition file pointer - lseek(%s, 0, SEEK_END) failed: %s\n",
wfile->w_file, strerror(errno));
return -1;
}
offset = lseek(fd, 0, SEEK_CUR);
if ((offset == -1)) {
sprintf(Wlog_Error_String,
"Could not reposition file pointer - lseek(%s, 0, SEEK_CUR) failed: %s\n",
wfile->w_file, strerror(errno));
return -1;
}
bufend = buf + sizeof(buf);
bufstart = buf;
recnum = 0;
leftover = 0;
while ((!nrecs || recnum < nrecs) && offset > 0) {
/*
* Check for beginning of file - if there aren't enough bytes
* remaining to fill buf, adjust bufstart.
*/
if ((unsigned int)offset + leftover < sizeof(buf)) {
bufstart = bufend - (offset + leftover);
offset = 0;
} else {
offset -= sizeof(buf) - leftover;
}
/*
* Move to the proper file offset, and read into buf
*/
if ((lseek(fd, offset, SEEK_SET)) == -1) {
sprintf(Wlog_Error_String,
"Could not reposition file pointer - lseek(%s, %d, SEEK_SET) failed: %s\n",
wfile->w_file, offset, strerror(errno));
return -1;
}
nbytes = read(fd, bufstart, bufend - bufstart - leftover);
if (nbytes == -1) {
sprintf(Wlog_Error_String,
"Could not read history file at offset %d - read(%d, %p, %d) failed: %s\n",
offset, fd, bufstart,
(int)(bufend - bufstart - leftover),
strerror(errno));
return -1;
}
cp = bufend;
leftover = 0;
while (cp >= bufstart) {
/*
* If cp-bufstart is not large enough to hold a piece
* of record length information, copy remainder to end
* of buf and continue reading the file.
*/
if (cp - bufstart < 2) {
leftover = cp - bufstart;
memcpy(bufend - leftover, bufstart, leftover);
break;
}
/*
* Extract the record length. We must do it this way
* instead of casting cp to an int because cp might
* not be word aligned.
*/
reclen = (*(cp - 2) * 256) + *(cp - 1);
/*
* If cp-bufstart isn't large enough to hold a
* complete record, plus the length information, copy
* the leftover bytes to the end of buf and continue
* reading.
*/
if (cp - bufstart < reclen + 2) {
leftover = cp - bufstart;
memcpy(bufend - leftover, bufstart, leftover);
break;
}
/*
* Adjust cp to point at the start of the record.
* Copy the record into wbuf so that it is word
* aligned and pass the record to the user supplied
* function.
*/
cp -= reclen + 2;
memcpy(albuf, cp, reclen);
wlog_rec_unpack(&wrec, albuf);
/*
* Call the user supplied function -
* stop if instructed to.
*/
if ((rval = (*func) (&wrec, data)) == WLOG_STOP_SCAN) {
break;
}
recnum++;
if (nrecs && recnum >= nrecs)
break;
}
}
return 0;
}
/*
* The following 2 routines are used to pack and unpack the user
* visible wlog_rec structure to/from a character buffer which is
* stored or read from the write logfile. Any changes to either of
* these routines must be reflected in the other.
*/
static int wlog_rec_pack(struct wlog_rec *wrec, char *buf, int flag)
{
char *file, *host, *pattern;
struct wlog_rec_disk *wrecd;
wrecd = (struct wlog_rec_disk *)buf;
wrecd->w_pid = (uint) wrec->w_pid;
wrecd->w_offset = (uint) wrec->w_offset;
wrecd->w_nbytes = (uint) wrec->w_nbytes;
wrecd->w_oflags = (uint) wrec->w_oflags;
wrecd->w_done = (uint) wrec->w_done;
wrecd->w_async = (uint) wrec->w_async;
wrecd->w_pathlen = (wrec->w_pathlen > 0) ? (uint) wrec->w_pathlen : 0;
wrecd->w_hostlen = (wrec->w_hostlen > 0) ? (uint) wrec->w_hostlen : 0;
wrecd->w_patternlen =
(wrec->w_patternlen > 0) ? (uint) wrec->w_patternlen : 0;
/*
* If flag is true, we should also pack the variable length parts
* of the wlog_rec. By default, we only pack the fixed length
* parts.
*/
if (flag) {
file = buf + sizeof(struct wlog_rec_disk);
host = file + wrecd->w_pathlen;
pattern = host + wrecd->w_hostlen;
if (wrecd->w_pathlen > 0)
memcpy(file, wrec->w_path, wrecd->w_pathlen);
if (wrecd->w_hostlen > 0)
memcpy(host, wrec->w_host, wrecd->w_hostlen);
if (wrecd->w_patternlen > 0)
memcpy(pattern, wrec->w_pattern, wrecd->w_patternlen);
return (sizeof(struct wlog_rec_disk) +
wrecd->w_pathlen + wrecd->w_hostlen +
wrecd->w_patternlen);
} else {
return sizeof(struct wlog_rec_disk);
}
}
static int wlog_rec_unpack(struct wlog_rec *wrec, char *buf)
{
char *file, *host, *pattern;
struct wlog_rec_disk *wrecd;
memset((char *)wrec, 0x00, sizeof(struct wlog_rec));
wrecd = (struct wlog_rec_disk *)buf;
wrec->w_pid = wrecd->w_pid;
wrec->w_offset = wrecd->w_offset;
wrec->w_nbytes = wrecd->w_nbytes;
wrec->w_oflags = wrecd->w_oflags;
wrec->w_hostlen = wrecd->w_hostlen;
wrec->w_pathlen = wrecd->w_pathlen;
wrec->w_patternlen = wrecd->w_patternlen;
wrec->w_done = wrecd->w_done;
wrec->w_async = wrecd->w_async;
if (wrec->w_pathlen > 0) {
file = buf + sizeof(struct wlog_rec_disk);
memcpy(wrec->w_path, file, wrec->w_pathlen);
}
if (wrec->w_hostlen > 0) {
host = buf + sizeof(struct wlog_rec_disk) + wrec->w_pathlen;
memcpy(wrec->w_host, host, wrec->w_hostlen);
}
if (wrec->w_patternlen > 0) {
pattern = buf + sizeof(struct wlog_rec_disk) +
wrec->w_pathlen + wrec->w_hostlen;
memcpy(wrec->w_pattern, pattern, wrec->w_patternlen);
}
return 0;
}