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Date:      Sun, 13 Aug 2017 18:09:22 +0000 (UTC)
From:      Kirk McKusick <mckusick@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r322464 - head/sys/geom/journal
Message-ID:  <201708131809.v7DI9MP3094462@repo.freebsd.org>
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Author: mckusick
Date: Sun Aug 13 18:09:22 2017
New Revision: 322464
URL: https://svnweb.freebsd.org/changeset/base/322464

Log:
  When read requests are sent from a filesystem running above g_journal,
  the g_journal level needs to check whether it is holding a newer
  copy of the block than that which exists on the disk. If so, it
  needs to return its copy. If not, it should pass the request down
  to the disk to fulfill. It currently considers six queues:
  
  0) delayed queue,
  1) unsent (current queue),
  2) in-flight to the journal (flush queue),
  3) active journal (active queue),
  4) inactive journal (inactive queue), and
  5) inflight to the disk (copy queue).
  
  Checking on two of these queues is unnecessary:
  
  0) The delayed requests should not be used for reads because they
     have not yet been entered into the journal, so their value should
     reflect the disk contents, not the future contents that are not
     yet committed.
  
  2) Because all the bio's in the flush queue are also found on the
     active queue, there is no need to inspect the flush queue for
     reads since they will be found when searching the active queue.
  
  Submitted by: Dr. Andreas Longwitz <longwitz@incore.de>
  Discussed with: kib
  MFC after: 1 week

Modified:
  head/sys/geom/journal/g_journal.c

Modified: head/sys/geom/journal/g_journal.c
==============================================================================
--- head/sys/geom/journal/g_journal.c	Sun Aug 13 18:06:38 2017	(r322463)
+++ head/sys/geom/journal/g_journal.c	Sun Aug 13 18:09:22 2017	(r322464)
@@ -1514,49 +1514,10 @@ g_journal_read_find(struct bio *head, int sorted, stru
 }
 
 /*
- * Try to find requested data in cache.
- */
-static struct bio *
-g_journal_read_queue_find(struct bio_queue *head, struct bio *pbp, off_t ostart,
-    off_t oend)
-{
-	off_t cstart, cend;
-	struct bio *bp;
-
-	TAILQ_FOREACH(bp, head, bio_queue) {
-		cstart = MAX(ostart, bp->bio_offset);
-		cend = MIN(oend, bp->bio_offset + bp->bio_length);
-		if (cend <= ostart)
-			continue;
-		else if (cstart >= oend)
-			continue;
-		KASSERT(bp->bio_data != NULL,
-		    ("%s: bio_data == NULL", __func__));
-		GJ_DEBUG(3, "READ(%p): (%jd, %jd) (bp=%p)", head, cstart, cend,
-		    bp);
-		bcopy(bp->bio_data + cstart - bp->bio_offset,
-		    pbp->bio_data + cstart - pbp->bio_offset, cend - cstart);
-		pbp->bio_completed += cend - cstart;
-		if (pbp->bio_completed == pbp->bio_length) {
-			/*
-			 * Cool, the whole request was in cache, deliver happy
-			 * message.
-			 */
-			g_io_deliver(pbp, 0);
-			return (pbp);
-		}
-		break;
-	}
-	return (bp);
-}
-
-/*
- * This function is used for colecting data on read.
+ * This function is used for collecting data on read.
  * The complexity is because parts of the data can be stored in four different
  * places:
- * - in delayed requests
  * - in memory - the data not yet send to the active journal provider
- * - in requests which are going to be sent to the active journal
  * - in the active journal
  * - in the inactive journal
  * - in the data provider
@@ -1574,20 +1535,14 @@ g_journal_read(struct g_journal_softc *sc, struct bio 
 	cstart = cend = -1;
 	bp = NULL;
 	head = NULL;
-	for (i = 0; i <= 5; i++) {
+	for (i = 1; i <= 5; i++) {
 		switch (i) {
-		case 0:	/* Delayed requests. */
-			head = NULL;
-			sorted = 0;
-			break;
 		case 1:	/* Not-yet-send data. */
 			head = sc->sc_current_queue;
 			sorted = 1;
 			break;
-		case 2:	/* In-flight to the active journal. */
-			head = sc->sc_flush_queue;
-			sorted = 0;
-			break;
+		case 2: /* Skip flush queue as they are also in active queue */
+			continue;
 		case 3:	/* Active journal. */
 			head = sc->sc_active.jj_queue;
 			sorted = 1;
@@ -1606,10 +1561,7 @@ g_journal_read(struct g_journal_softc *sc, struct bio 
 		default:
 			panic("gjournal %s: i=%d", __func__, i);
 		}
-		if (i == 0)
-			bp = g_journal_read_queue_find(&sc->sc_delayed_queue.queue, pbp, ostart, oend);
-		else
-			bp = g_journal_read_find(head, sorted, pbp, ostart, oend);
+		bp = g_journal_read_find(head, sorted, pbp, ostart, oend);
 		if (bp == pbp) { /* Got the whole request. */
 			GJ_DEBUG(2, "Got the whole request from %u.", i);
 			return;

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