staging: lustre: llog: fix wrong offset in llog_process_thread()

- llh_cat_idx may become bigger than llog bitmap size in
  llog_cat_set_first_idx() function
- it is wrong to use previous cur_offset as new buffer offset,
  new offset should be calculated from value returned by
  llog_next_block().
- optimize llog_skip_over() to find llog entry offset by index
  for llog with fixed-size records.
Signed-off-by: Mikhail Pershin <mike.pershin@intel.com>
Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6714
Reviewed-on: http://review.whamcloud.com/15316
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6163
Reviewed-on: http://review.whamcloud.com/18819Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/obdclass/llog.c

@@ -217,8 +217,7 @@ static int llog_process_thread(void *arg)
 	struct llog_log_hdr		*llh = loghandle->lgh_hdr;
 	struct llog_process_cat_data	*cd  = lpi->lpi_catdata;
 	char				*buf;
-	__u64				 cur_offset;
-	__u64				 last_offset;
+	u64 cur_offset, tmp_offset;
 	int chunk_size;
 	int				 rc = 0, index = 1, last_index;
 	int				 saved_index = 0;
@@ -229,6 +228,8 @@ static int llog_process_thread(void *arg)
 
 	cur_offset = llh->llh_hdr.lrh_len;
 	chunk_size = llh->llh_hdr.lrh_len;
+	/* expect chunk_size to be power of two */
+	LASSERT(is_power_of_2(chunk_size));
 
 	buf = libcfs_kvzalloc(chunk_size, GFP_NOFS);
 	if (!buf) {
@@ -245,38 +246,50 @@ static int llog_process_thread(void *arg)
 	else
 		last_index = LLOG_HDR_BITMAP_SIZE(llh) - 1;
 
-	/* Record is not in this buffer. */
-	if (index > last_index)
-		goto out;
-
 	while (rc == 0) {
+		unsigned int buf_offset = 0;
 		struct llog_rec_hdr *rec;
+		bool partial_chunk;
+		off_t chunk_offset;
 
 		/* skip records not set in bitmap */
 		while (index <= last_index &&
 		       !ext2_test_bit(index, LLOG_HDR_BITMAP(llh)))
 			++index;
 
-		LASSERT(index <= last_index + 1);
-		if (index == last_index + 1)
+		if (index > last_index)
 			break;
-repeat:
+
 		CDEBUG(D_OTHER, "index: %d last_index %d\n",
 		       index, last_index);
-
+repeat:
 		/* get the buf with our target record; avoid old garbage */
 		memset(buf, 0, chunk_size);
-		last_offset = cur_offset;
 		rc = llog_next_block(lpi->lpi_env, loghandle, &saved_index,
 				     index, &cur_offset, buf, chunk_size);
 		if (rc)
 			goto out;
 
+		/*
+		 * NB: after llog_next_block() call the cur_offset is the
+		 * offset of the next block after read one.
+		 * The absolute offset of the current chunk is calculated
+		 * from cur_offset value and stored in chunk_offset variable.
+		 */
+		tmp_offset = cur_offset;
+		if (do_div(tmp_offset, chunk_size)) {
+			partial_chunk = true;
+			chunk_offset = cur_offset & ~(chunk_size - 1);
+		} else {
+			partial_chunk = false;
+			chunk_offset = cur_offset - chunk_size;
+		}
+
 		/* NB: when rec->lrh_len is accessed it is already swabbed
 		 * since it is used at the "end" of the loop and the rec
 		 * swabbing is done at the beginning of the loop.
 		 */
-		for (rec = (struct llog_rec_hdr *)buf;
+		for (rec = (struct llog_rec_hdr *)(buf + buf_offset);
 		     (char *)rec < buf + chunk_size;
 		     rec = llog_rec_hdr_next(rec)) {
 			CDEBUG(D_OTHER, "processing rec 0x%p type %#x\n",
@@ -288,13 +301,28 @@ static int llog_process_thread(void *arg)
 			CDEBUG(D_OTHER, "after swabbing, type=%#x idx=%d\n",
 			       rec->lrh_type, rec->lrh_index);
 
-			if (rec->lrh_index == 0) {
-				/* probably another rec just got added? */
-				rc = 0;
-				if (index <= loghandle->lgh_last_idx)
-					goto repeat;
-				goto out; /* no more records */
+			/*
+			 * for partial chunk the end of it is zeroed, check
+			 * for index 0 to distinguish it.
+			 */
+			if (partial_chunk && !rec->lrh_index) {
+				/* concurrent llog_add() might add new records
+				 * while llog_processing, check this is not
+				 * the case and re-read the current chunk
+				 * otherwise.
+				 */
+				if (index > loghandle->lgh_last_idx) {
+					rc = 0;
+					goto out;
+				}
+				CDEBUG(D_OTHER, "Re-read last llog buffer for new records, index %u, last %u\n",
+				       index, loghandle->lgh_last_idx);
+				/* save offset inside buffer for the re-read */
+				buf_offset = (char *)rec - (char *)buf;
+				cur_offset = chunk_offset;
+				goto repeat;
 			}
+
 			if (!rec->lrh_len || rec->lrh_len > chunk_size) {
 				CWARN("invalid length %d in llog record for index %d/%d\n",
 				      rec->lrh_len,
@@ -309,6 +337,14 @@ static int llog_process_thread(void *arg)
 				continue;
 			}
 
+			if (rec->lrh_index != index) {
+				CERROR("%s: Invalid record: index %u but expected %u\n",
+				       loghandle->lgh_ctxt->loc_obd->obd_name,
+				       rec->lrh_index, index);
+				rc = -ERANGE;
+				goto out;
+			}
+
 			CDEBUG(D_OTHER,
 			       "lrh_index: %d lrh_len: %d (%d remains)\n",
 			       rec->lrh_index, rec->lrh_len,
@@ -316,7 +352,7 @@ static int llog_process_thread(void *arg)
 
 			loghandle->lgh_cur_idx = rec->lrh_index;
 			loghandle->lgh_cur_offset = (char *)rec - (char *)buf +
-						    last_offset;
+						    chunk_offset;
 
 			/* if set, process the callback on this record */
 			if (ext2_test_bit(index, LLOG_HDR_BITMAP(llh))) {
@@ -325,16 +361,14 @@ static int llog_process_thread(void *arg)
 				last_called_index = index;
 				if (rc)
 					goto out;
-			} else {
-				CDEBUG(D_OTHER, "Skipped index %d\n", index);
 			}
 
-			/* next record, still in buffer? */
-			++index;
-			if (index > last_index) {
+			/* exit if the last index is reached */
+			if (index >= last_index) {
 				rc = 0;
 				goto out;
 			}
+			index++;
 		}
 	}