Hi, I am analyzing jfs and taking some modification on it, and I met a
failure when jfs redid log records in fsck.
So, I tried to find the reason why that fsck failure
occurred.(Unrecognize log type error)
and I found some strange code in lmWriteRecord. but I am not confident.
In function lmWriteRecord(), I expect jfs copy data in system buffer to
log buffer, But in moveData lable, jfs does not intialize *len*
variable. So, if linelock->index is larger than 2, the variable *len* is
added to previous *len* value.
415 moveData:
416 ASSERT(linelock->index <= linelock->maxcnt);
417
418 lv = linelock->lv;
419 for (i = 0; i < linelock->index; i++, lv++) {
420 if (lv->length == 0)
421 continue;
422
423 /* is page full ? */
424 if (dstoffset >= LOGPSIZE - LOGPTLRSIZE) {
425 /* page become full: move on to next page */
426 lmNextPage(log);
427
428 bp = log->bp;
429 lp = (struct logpage *) bp->l_ldata;
430 dstoffset = LOGPHDRSIZE;
431 }
432
433 /*
434 * move log vector data
435 */
436 src = (u8 *) p + (lv->offset << l2linesize);
437 srclen = lv->length << l2linesize;
* 438 len += srclen; <== here "len = srclen" isn't it?*
439 while (srclen > 0) {
440 freespace = (LOGPSIZE - LOGPTLRSIZE) - dstoffset;
441 nbytes = min(freespace, srclen);
442 dst = (caddr_t) lp + dstoffset;
443 memcpy(dst, src, nbytes);
444 dstoffset += nbytes;
For example, if jfs writes log of xtlckTREE type, it splits into 2 log
record. One is xtpage header, the other is xtpage entry. So first record
length is 32byte, and second is 4064 byte (in case all entry is
modified.), then the log record has to write to log buffer with length
36 byte (32 + 4(for log vector descriptor)), 4068 byte (4064 + 4), I
think. But jfs writes record with length 36 and 4104(4064 + 4 + 36). Why
the second log record adds previous record length 32 ?
Is it right?? I don't know why.. Somebody explain this to me..
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