2 * Copyright (c) 2000 Silicon Graphics, Inc.
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License as
7 * published by the Free Software Foundation.
9 * This program is distributed in the hope that it would be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
19 * This module contains code for logging writes to files, and for
20 * perusing the resultant logfile. The main intent of all this is
21 * to provide a 'write history' of a file which can be examined to
22 * judge the state of a file (ie. whether it is corrupted or not) based
23 * on the write activity.
25 * The main abstractions available to the user are the wlog_file, and
26 * the wlog_rec. A wlog_file is a handle encapsulating a write logfile.
27 * It is initialized with the wlog_open() function. This handle is
28 * then passed to the various wlog_xxx() functions to provide transparent
29 * access to the write logfile.
31 * The wlog_rec datatype is a structure which contains all the information
32 * about a file write. Examples include the file name, offset, length,
33 * pattern, etc. In addition there is a bit which is cleared/set based
34 * on whether or not the write has been confirmed as complete. This
35 * allows the write logfile to contain information on writes which have
36 * been initiated, but not yet completed (as in async io).
38 * There is also a function to scan a write logfile in reverse order.
40 * NOTE: For target file analysis based on a write logfile, the
41 * assumption is made that the file being written to is
42 * locked from simultaneous access, so that the order of
43 * write completion is predictable. This is an issue when
44 * more than 1 process is trying to write data to the same
45 * target file simultaneously.
47 * The history file created is a collection of variable length records
48 * described by scruct wlog_rec_disk in write_log.h. See that module for
49 * the layout of the data on disk.
58 #include <sys/param.h>
60 #include <sys/types.h>
61 #include "write_log.h"
65 #define BSIZE DEV_BSIZE
73 /*#define PATH_MAX pathconf("/", _PC_PATH_MAX)*/
76 char Wlog_Error_String[256];
79 static int wlog_rec_pack(struct wlog_rec *wrec, char *buf, int flag);
80 static int wlog_rec_unpack(struct wlog_rec *wrec, char *buf);
82 static int wlog_rec_pack();
83 static int wlog_rec_unpack();
87 * Initialize a write logfile. wfile is a wlog_file structure that has
88 * the w_file field filled in. The rest of the information in the
89 * structure is initialized by the routine.
91 * The trunc flag is used to indicate whether or not the logfile should
92 * be truncated if it currently exists. If it is non-zero, the file will
93 * be truncated, otherwise it will be appended to.
95 * The mode argument is the [absolute] mode which the file will be
96 * given if it does not exist. This mode is not affected by your process
101 wlog_open(wfile, trunc, mode)
102 struct wlog_file *wfile;
114 * Open 1 file descriptor as O_APPEND
117 oflags = O_WRONLY | O_APPEND | O_CREAT | trunc;
119 open(wfile->w_file, oflags, mode);
122 if (wfile->w_afd == -1) {
123 sprintf(Wlog_Error_String,
124 "Could not open write_log - open(%s, %#o, %#o) failed: %s\n",
125 wfile->w_file, oflags, mode, strerror(errno));
130 * Open the next fd as a random access descriptor
134 if ((wfile->w_rfd = open(wfile->w_file, oflags)) == -1) {
135 sprintf(Wlog_Error_String,
136 "Could not open write log - open(%s, %#o) failed: %s\n",
137 wfile->w_file, oflags, strerror(errno));
147 * Release all resources associated with a wlog_file structure allocated
148 * with the wlog_open() call.
153 struct wlog_file *wfile;
161 * Write a wlog_rec structure to a write logfile. Offset is used to
162 * control where the record will be written. If offset is < 0, the
163 * record will be appended to the end of the logfile. Otherwise, the
164 * record which exists at the indicated offset will be overlayed. This
165 * is so that we can record writes which are outstanding (with the w_done
166 * bit in wrec cleared), but not completed, and then later update the
167 * logfile when the write request completes (as with async io). When
168 * offset is >= 0, only the fixed length portion of the record is
169 * rewritten. See text in write_log.h for details on the format of an
172 * The return value of the function is the byte offset in the logfile
173 * where the record begins.
175 * Note: It is the callers responsibility to make sure that the offset
176 * parameter 'points' to a valid record location when a record is to be
177 * overlayed. This is guarenteed by saving the return value of a previous
178 * call to wlog_record_write() which wrote the record to be overlayed.
180 * Note2: The on-disk version of the wlog_rec is MUCH different than
181 * the user version. Don't expect to od the logfile and see data formatted
182 * as it is in the wlog_rec structure. Considerable data packing takes
183 * place before the record is written.
187 wlog_record_write(wfile, wrec, offset)
188 struct wlog_file *wfile;
189 struct wlog_rec *wrec;
193 char wbuf[WLOG_REC_MAX_SIZE + 2];
196 * If offset is -1, we append the record at the end of file
198 * Otherwise, we overlay wrec at the file offset indicated and assume
199 * that the caller passed us the correct offset. We do not record the
200 * fname in this case.
203 reclen = wlog_rec_pack(wrec, wbuf, (offset < 0));
207 * Since we're writing a complete new record, we must also tack
208 * its length onto the end so that wlog_scan_backward() will work.
209 * Length is asumed to fit into 2 bytes.
212 wbuf[reclen] = reclen / 256;
213 wbuf[reclen+1] = reclen % 256;
216 write(wfile->w_afd, wbuf, reclen);
217 offset = lseek(wfile->w_afd, 0, SEEK_CUR) - reclen;
219 lseek(wfile->w_rfd, offset, SEEK_SET);
220 write(wfile->w_rfd, wbuf, reclen);
227 * Function to scan a logfile in reverse order. Wfile is a valid
228 * wlog_file structure initialized by wlog_open(). nrecs is the number
229 * of records to scan (all records are scanned if nrecs is 0). func is
230 * a user-supplied function to call for each record found. The function
231 * will be passed a single parameter - a wlog_rec structure .
235 wlog_scan_backward(wfile, nrecs, func, data)
236 struct wlog_file *wfile;
241 int fd, leftover, nbytes, offset, recnum, reclen;
242 char buf[BSIZE*32], *bufend, *cp, *bufstart;
243 char albuf[WLOG_REC_MAX_SIZE];
244 struct wlog_rec wrec;
249 * Move to EOF. offset will always hold the current file offset
252 lseek(fd, 0, SEEK_END);
253 offset = lseek(fd, 0, SEEK_CUR);
255 bufend = buf + sizeof(buf);
260 while ((!nrecs || recnum < nrecs) && offset > 0) {
262 * Check for beginning of file - if there aren't enough bytes
263 * remaining to fill buf, adjust bufstart.
266 if (offset + leftover < sizeof(buf)) {
267 bufstart = bufend - (offset + leftover);
270 offset -= sizeof(buf) - leftover;
274 * Move to the proper file offset, and read into buf
277 lseek(fd, offset, SEEK_SET);
278 nbytes = read(fd, bufstart, bufend - bufstart - leftover);
281 sprintf(Wlog_Error_String,
282 "Could not read history file at offset %d - read(%d, %p, %d) failed: %s\n",
283 offset, fd, bufstart,
284 (int)(bufend - bufstart - leftover), strerror(errno));
291 while (cp >= bufstart) {
294 * If cp-bufstart is not large enough to hold a piece
295 * of record length information, copy remainder to end
296 * of buf and continue reading the file.
299 if (cp - bufstart < 2) {
300 leftover = cp - bufstart;
301 memcpy(bufend - leftover, bufstart, leftover);
306 * Extract the record length. We must do it this way
307 * instead of casting cp to an int because cp might
308 * not be word aligned.
311 reclen = (*(cp-2) * 256) + *(cp -1);
314 * If cp-bufstart isn't large enough to hold a
315 * complete record, plus the length information, copy
316 * the leftover bytes to the end of buf and continue
320 if (cp - bufstart < reclen + 2) {
321 leftover = cp - bufstart;
322 memcpy(bufend - leftover, bufstart, leftover);
327 * Adjust cp to point at the start of the record.
328 * Copy the record into wbuf so that it is word
329 * aligned and pass the record to the user supplied
334 memcpy(albuf, cp, reclen);
336 wlog_rec_unpack(&wrec, albuf);
339 * Call the user supplied function -
340 * stop if instructed to.
343 if ((*func)(&wrec, data) == WLOG_STOP_SCAN) {
349 if (nrecs && recnum >= nrecs)
358 * The following 2 routines are used to pack and unpack the user
359 * visible wlog_rec structure to/from a character buffer which is
360 * stored or read from the write logfile. Any changes to either of
361 * these routines must be reflected in the other.
365 wlog_rec_pack(wrec, buf, flag)
366 struct wlog_rec *wrec;
370 char *file, *host, *pattern;
371 struct wlog_rec_disk *wrecd;
373 wrecd = (struct wlog_rec_disk *)buf;
375 wrecd->w_pid = (uint)wrec->w_pid;
376 wrecd->w_offset = (uint)wrec->w_offset;
377 wrecd->w_nbytes = (uint)wrec->w_nbytes;
378 wrecd->w_oflags = (uint)wrec->w_oflags;
379 wrecd->w_done = (uint)wrec->w_done;
380 wrecd->w_async = (uint)wrec->w_async;
382 wrecd->w_pathlen = (wrec->w_pathlen > 0) ? (uint)wrec->w_pathlen : 0;
383 wrecd->w_hostlen = (wrec->w_hostlen > 0) ? (uint)wrec->w_hostlen : 0;
384 wrecd->w_patternlen = (wrec->w_patternlen > 0) ? (uint)wrec->w_patternlen : 0;
387 * If flag is true, we should also pack the variable length parts
388 * of the wlog_rec. By default, we only pack the fixed length
393 file = buf + sizeof(struct wlog_rec_disk);
394 host = file + wrecd->w_pathlen;
395 pattern = host + wrecd->w_hostlen;
397 if (wrecd->w_pathlen > 0)
398 memcpy(file, wrec->w_path, wrecd->w_pathlen);
400 if (wrecd->w_hostlen > 0)
401 memcpy(host, wrec->w_host, wrecd->w_hostlen);
403 if (wrecd->w_patternlen > 0)
404 memcpy(pattern, wrec->w_pattern, wrecd->w_patternlen);
406 return (sizeof(struct wlog_rec_disk) +
407 wrecd->w_pathlen + wrecd->w_hostlen + wrecd->w_patternlen);
409 return sizeof(struct wlog_rec_disk);
414 wlog_rec_unpack(wrec, buf)
415 struct wlog_rec *wrec;
418 char *file, *host, *pattern;
419 struct wlog_rec_disk *wrecd;
421 bzero((char *)wrec, sizeof(struct wlog_rec));
422 wrecd = (struct wlog_rec_disk *)buf;
424 wrec->w_pid = wrecd->w_pid;
425 wrec->w_offset = wrecd->w_offset;
426 wrec->w_nbytes = wrecd->w_nbytes;
427 wrec->w_oflags = wrecd->w_oflags;
428 wrec->w_hostlen = wrecd->w_hostlen;
429 wrec->w_pathlen = wrecd->w_pathlen;
430 wrec->w_patternlen = wrecd->w_patternlen;
431 wrec->w_done = wrecd->w_done;
432 wrec->w_async = wrecd->w_async;
434 if (wrec->w_pathlen > 0) {
435 file = buf + sizeof(struct wlog_rec_disk);
436 memcpy(wrec->w_path, file, wrec->w_pathlen);
439 if (wrec->w_hostlen > 0) {
440 host = buf + sizeof(struct wlog_rec_disk) + wrec->w_pathlen;
441 memcpy(wrec->w_host, host, wrec->w_hostlen);
444 if (wrec->w_patternlen > 0) {
445 pattern = buf + sizeof(struct wlog_rec_disk) +
446 wrec->w_pathlen + wrec->w_hostlen;
447 memcpy(wrec->w_pattern, pattern, wrec->w_patternlen);