1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (c) 2000 Silicon Graphics, Inc.
7 * This module contains code for logging writes to files, and for
8 * perusing the resultant logfile. The main intent of all this is
9 * to provide a 'write history' of a file which can be examined to
10 * judge the state of a file (ie. whether it is corrupted or not) based
11 * on the write activity.
13 * The main abstractions available to the user are the wlog_file, and
14 * the wlog_rec. A wlog_file is a handle encapsulating a write logfile.
15 * It is initialized with the wlog_open() function. This handle is
16 * then passed to the various wlog_xxx() functions to provide transparent
17 * access to the write logfile.
19 * The wlog_rec datatype is a structure which contains all the information
20 * about a file write. Examples include the file name, offset, length,
21 * pattern, etc. In addition there is a bit which is cleared/set based
22 * on whether or not the write has been confirmed as complete. This
23 * allows the write logfile to contain information on writes which have
24 * been initiated, but not yet completed (as in async io).
26 * There is also a function to scan a write logfile in reverse order.
28 * NOTE: For target file analysis based on a write logfile, the
29 * assumption is made that the file being written to is
30 * locked from simultaneous access, so that the order of
31 * write completion is predictable. This is an issue when
32 * more than 1 process is trying to write data to the same
33 * target file simultaneously.
35 * The history file created is a collection of variable length records
36 * described by scruct wlog_rec_disk in write_log.h. See that module for
37 * the layout of the data on disk.
46 #include <sys/param.h>
48 #include <sys/types.h>
49 #include "write_log.h"
53 #define BSIZE DEV_BSIZE
61 /*#define PATH_MAX pathconf("/", _PC_PATH_MAX)*/
64 #define ERROR_STRING_LEN 1280
65 char Wlog_Error_String[ERROR_STRING_LEN];
68 static int wlog_rec_pack(struct wlog_rec *wrec, char *buf, int flag);
69 static int wlog_rec_unpack(struct wlog_rec *wrec, char *buf);
71 static int wlog_rec_pack();
72 static int wlog_rec_unpack();
76 * Initialize a write logfile. wfile is a wlog_file structure that has
77 * the w_file field filled in. The rest of the information in the
78 * structure is initialized by the routine.
80 * The trunc flag is used to indicate whether or not the logfile should
81 * be truncated if it currently exists. If it is non-zero, the file will
82 * be truncated, otherwise it will be appended to.
84 * The mode argument is the [absolute] mode which the file will be
85 * given if it does not exist. This mode is not affected by your process
90 wlog_open(wfile, trunc, mode)
91 struct wlog_file *wfile;
103 * Open 1 file descriptor as O_APPEND
106 oflags = O_WRONLY | O_APPEND | O_CREAT | trunc;
108 open(wfile->w_file, oflags, mode);
111 if (wfile->w_afd == -1) {
112 snprintf(Wlog_Error_String, ERROR_STRING_LEN,
113 "Could not open write_log - open(%s, %#o, %#o) failed: %s\n",
114 wfile->w_file, oflags, mode, strerror(errno));
119 * Open the next fd as a random access descriptor
123 if ((wfile->w_rfd = open(wfile->w_file, oflags)) == -1) {
124 snprintf(Wlog_Error_String, ERROR_STRING_LEN,
125 "Could not open write log - open(%s, %#o) failed: %s\n",
126 wfile->w_file, oflags, strerror(errno));
136 * Release all resources associated with a wlog_file structure allocated
137 * with the wlog_open() call.
142 struct wlog_file *wfile;
150 * Write a wlog_rec structure to a write logfile. Offset is used to
151 * control where the record will be written. If offset is < 0, the
152 * record will be appended to the end of the logfile. Otherwise, the
153 * record which exists at the indicated offset will be overlayed. This
154 * is so that we can record writes which are outstanding (with the w_done
155 * bit in wrec cleared), but not completed, and then later update the
156 * logfile when the write request completes (as with async io). When
157 * offset is >= 0, only the fixed length portion of the record is
158 * rewritten. See text in write_log.h for details on the format of an
161 * The return value of the function is the byte offset in the logfile
162 * where the record begins.
164 * Note: It is the callers responsibility to make sure that the offset
165 * parameter 'points' to a valid record location when a record is to be
166 * overlayed. This is guarenteed by saving the return value of a previous
167 * call to wlog_record_write() which wrote the record to be overlayed.
169 * Note2: The on-disk version of the wlog_rec is MUCH different than
170 * the user version. Don't expect to od the logfile and see data formatted
171 * as it is in the wlog_rec structure. Considerable data packing takes
172 * place before the record is written.
176 wlog_record_write(wfile, wrec, offset)
177 struct wlog_file *wfile;
178 struct wlog_rec *wrec;
182 char wbuf[WLOG_REC_MAX_SIZE + 2];
185 * If offset is -1, we append the record at the end of file
187 * Otherwise, we overlay wrec at the file offset indicated and assume
188 * that the caller passed us the correct offset. We do not record the
189 * fname in this case.
192 reclen = wlog_rec_pack(wrec, wbuf, (offset < 0));
196 * Since we're writing a complete new record, we must also tack
197 * its length onto the end so that wlog_scan_backward() will work.
198 * Length is asumed to fit into 2 bytes.
201 wbuf[reclen] = reclen / 256;
202 wbuf[reclen+1] = reclen % 256;
205 write(wfile->w_afd, wbuf, reclen);
206 offset = lseek(wfile->w_afd, 0, SEEK_CUR) - reclen;
208 lseek(wfile->w_rfd, offset, SEEK_SET);
209 write(wfile->w_rfd, wbuf, reclen);
216 * Function to scan a logfile in reverse order. Wfile is a valid
217 * wlog_file structure initialized by wlog_open(). nrecs is the number
218 * of records to scan (all records are scanned if nrecs is 0). func is
219 * a user-supplied function to call for each record found. The function
220 * will be passed a single parameter - a wlog_rec structure .
224 wlog_scan_backward(wfile, nrecs, func, data)
225 struct wlog_file *wfile;
230 int fd, leftover, nbytes, offset, recnum, reclen;
231 char buf[BSIZE*32], *bufend, *cp, *bufstart;
232 char albuf[WLOG_REC_MAX_SIZE];
233 struct wlog_rec wrec;
238 * Move to EOF. offset will always hold the current file offset
241 lseek(fd, 0, SEEK_END);
242 offset = lseek(fd, 0, SEEK_CUR);
244 bufend = buf + sizeof(buf);
249 while ((!nrecs || recnum < nrecs) && offset > 0) {
251 * Check for beginning of file - if there aren't enough bytes
252 * remaining to fill buf, adjust bufstart.
255 if (offset + leftover < sizeof(buf)) {
256 bufstart = bufend - (offset + leftover);
259 offset -= sizeof(buf) - leftover;
263 * Move to the proper file offset, and read into buf
266 lseek(fd, offset, SEEK_SET);
267 nbytes = read(fd, bufstart, bufend - bufstart - leftover);
270 sprintf(Wlog_Error_String,
271 "Could not read history file at offset %d - read(%d, %p, %d) failed: %s\n",
272 offset, fd, bufstart,
273 (int)(bufend - bufstart - leftover), strerror(errno));
280 while (cp >= bufstart) {
283 * If cp-bufstart is not large enough to hold a piece
284 * of record length information, copy remainder to end
285 * of buf and continue reading the file.
288 if (cp - bufstart < 2) {
289 leftover = cp - bufstart;
290 memcpy(bufend - leftover, bufstart, leftover);
295 * Extract the record length. We must do it this way
296 * instead of casting cp to an int because cp might
297 * not be word aligned.
300 reclen = (*(cp-2) * 256) + *(cp -1);
303 * If cp-bufstart isn't large enough to hold a
304 * complete record, plus the length information, copy
305 * the leftover bytes to the end of buf and continue
309 if (cp - bufstart < reclen + 2) {
310 leftover = cp - bufstart;
311 memcpy(bufend - leftover, bufstart, leftover);
316 * Adjust cp to point at the start of the record.
317 * Copy the record into wbuf so that it is word
318 * aligned and pass the record to the user supplied
323 memcpy(albuf, cp, reclen);
325 wlog_rec_unpack(&wrec, albuf);
328 * Call the user supplied function -
329 * stop if instructed to.
332 if ((*func)(&wrec, data) == WLOG_STOP_SCAN) {
338 if (nrecs && recnum >= nrecs)
347 * The following 2 routines are used to pack and unpack the user
348 * visible wlog_rec structure to/from a character buffer which is
349 * stored or read from the write logfile. Any changes to either of
350 * these routines must be reflected in the other.
354 wlog_rec_pack(wrec, buf, flag)
355 struct wlog_rec *wrec;
359 char *file, *host, *pattern;
360 struct wlog_rec_disk *wrecd;
362 wrecd = (struct wlog_rec_disk *)buf;
364 wrecd->w_pid = (uint)wrec->w_pid;
365 wrecd->w_offset = (uint)wrec->w_offset;
366 wrecd->w_nbytes = (uint)wrec->w_nbytes;
367 wrecd->w_oflags = (uint)wrec->w_oflags;
368 wrecd->w_done = (uint)wrec->w_done;
369 wrecd->w_async = (uint)wrec->w_async;
371 wrecd->w_pathlen = (wrec->w_pathlen > 0) ? (uint)wrec->w_pathlen : 0;
372 wrecd->w_hostlen = (wrec->w_hostlen > 0) ? (uint)wrec->w_hostlen : 0;
373 wrecd->w_patternlen = (wrec->w_patternlen > 0) ? (uint)wrec->w_patternlen : 0;
376 * If flag is true, we should also pack the variable length parts
377 * of the wlog_rec. By default, we only pack the fixed length
382 file = buf + sizeof(struct wlog_rec_disk);
383 host = file + wrecd->w_pathlen;
384 pattern = host + wrecd->w_hostlen;
386 if (wrecd->w_pathlen > 0)
387 memcpy(file, wrec->w_path, wrecd->w_pathlen);
389 if (wrecd->w_hostlen > 0)
390 memcpy(host, wrec->w_host, wrecd->w_hostlen);
392 if (wrecd->w_patternlen > 0)
393 memcpy(pattern, wrec->w_pattern, wrecd->w_patternlen);
395 return (sizeof(struct wlog_rec_disk) +
396 wrecd->w_pathlen + wrecd->w_hostlen + wrecd->w_patternlen);
398 return sizeof(struct wlog_rec_disk);
403 wlog_rec_unpack(wrec, buf)
404 struct wlog_rec *wrec;
407 char *file, *host, *pattern;
408 struct wlog_rec_disk *wrecd;
410 bzero((char *)wrec, sizeof(struct wlog_rec));
411 wrecd = (struct wlog_rec_disk *)buf;
413 wrec->w_pid = wrecd->w_pid;
414 wrec->w_offset = wrecd->w_offset;
415 wrec->w_nbytes = wrecd->w_nbytes;
416 wrec->w_oflags = wrecd->w_oflags;
417 wrec->w_hostlen = wrecd->w_hostlen;
418 wrec->w_pathlen = wrecd->w_pathlen;
419 wrec->w_patternlen = wrecd->w_patternlen;
420 wrec->w_done = wrecd->w_done;
421 wrec->w_async = wrecd->w_async;
423 if (wrec->w_pathlen > 0) {
424 file = buf + sizeof(struct wlog_rec_disk);
425 memcpy(wrec->w_path, file, wrec->w_pathlen);
428 if (wrec->w_hostlen > 0) {
429 host = buf + sizeof(struct wlog_rec_disk) + wrec->w_pathlen;
430 memcpy(wrec->w_host, host, wrec->w_hostlen);
433 if (wrec->w_patternlen > 0) {
434 pattern = buf + sizeof(struct wlog_rec_disk) +
435 wrec->w_pathlen + wrec->w_hostlen;
436 memcpy(wrec->w_pattern, pattern, wrec->w_patternlen);