shithub: gefs

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blk: take consistent snapshot under mutlk before syncing

--- a/blk.c

+++ b/blk.c

@@ -1070,14 +1070,13 @@

 	}

 }

-vlong

+void

 wrbarrier(void)

 {

 	Qent qe;

-	vlong gen;

 	int i;

-	gen = aincv(&fs->qgen, 1);

+	aincv(&fs->qgen, 1);

 	fs->syncing = fs->nsyncers;

 	for(i = 0; i < fs->nsyncers; i++){

 		qe.op = Qfence;

@@ -1089,13 +1088,11 @@

 	}

 	while(fs->syncing != 0)

 		rsleep(&fs->syncrz);

-	return gen;

 }

 void

 sync(void)

 {

-	uvlong gen;

 	Arena *a;

 	int i;

@@ -1112,31 +1109,49 @@

 		qunlock(&fs->synclk);

 		nexterror();

 	}

+

+	/*

+	 * pass 0: Pack the blocks we want to sync

+	 *  while holding the write lock, and then

+	 *  wait until all the blocks they point at

+	 *  have hit disk; once they're on disk, we

+	 *  can take a consistent snapshot.

+         */

+	qlock(&fs->mutlk);

 	flushdlcache(1);

-	gen = wrbarrier();

-	/* pass 0: sync arena contents */

 	for(i = 0; i < fs->narena; i++){

 		a = &fs->arenas[i];

 		qlock(a);

-		logbarrier(a, gen);

 		setflag(a->logtl, Bdirty);

 		enqueue(a->logtl);

+		logbarrier(a, fs->qgen);

+

+		packarena(a->h0->data, Blksz, a);

+		packarena(a->h1->data, Blksz, a);

+		finalize(a->h0);

+		finalize(a->h1);

+		setflag(a->h0, Bdirty);

+		setflag(a->h1, Bdirty);

+		fs->arenabp[i] = a->h0->bp;

 		qunlock(a);

 	}

+

+	packsb(fs->sb0->buf, Blksz, fs);

+	packsb(fs->sb1->buf, Blksz, fs);

+	finalize(fs->sb0);

+	finalize(fs->sb1);

+	fs->snap.dirty = 0;

+	qunlock(&fs->mutlk);

+	wrbarrier();

 	/*

 	 * pass 1: sync block headers; if we crash here,

 	 *  the block footers are consistent, and we can

 	 *  use them.

-         */

-	for(i = 0; i < fs->narena; i++){

-		a = &fs->arenas[i];

-		qlock(a);

-		packarena(a->h0->data, Blksz, a);

-		setflag(a->h0, Bdirty);

-		enqueue(a->h0);

-		qunlock(a);

-	}

+	 */	wrbarrier();

+	for(i = 0; i < fs->narena; i++)

+		enqueue(fs->arenas[i].h0);

 	wrbarrier();

+

 	/*

 	 * pass 2: sync superblock; we have a consistent

 	 * set of block headers, so if we crash, we can

@@ -1144,28 +1159,17 @@

 	 * get synced after so that we can use them next

 	 * time around.

          */

-	for(i = 0; i < fs->narena; i++)

-		fs->arenabp[i] = fs->arenas[i].h0->bp;

-	packsb(fs->sb0->buf, Blksz, fs);

-	packsb(fs->sb1->buf, Blksz, fs);

-	finalize(fs->sb0);

-	finalize(fs->sb1);

 	syncblk(fs->sb0);

 	syncblk(fs->sb1);

-	fs->snap.dirty = 0;

+

 	/*

 	 * pass 3: sync block footers; if we crash here,

 	 *  the block headers are consistent, and we can

 	 *  use them.

          */

-	for(i = 0; i < fs->narena; i++){

-		a = &fs->arenas[i];

-		qlock(a);

-		packarena(a->h1->data, Blksz, a);

-		setflag(a->h1, Bdirty);

-		enqueue(a->h1);

-		qunlock(a);

-	}

+	for(i = 0; i < fs->narena; i++)

+		enqueue(fs->arenas[i].h1);

+

 	/*

 	 * Pass 4: clean up the old snap tree's deadlist

 	 */

--- a/fs.c

+++ b/fs.c

@@ -2277,10 +2277,11 @@

 			}

 			epochstart(id);

 			snapfs(am, &t);

-			sync();

 			epochend(id);

 			poperror();

 			qunlock(&fs->mutlk);

+

+			sync();

 			if(t != nil){

 				epochwait();

--- a/load.c

+++ b/load.c

@@ -30,13 +30,13 @@

 		h0 = getblk(bp, 0);

 		poperror();

 	}else

-		print("error %s\n", errmsg());

+		print("loading arena primary header: %s\n", errmsg());

 	bp.addr += Blksz;

 	if(!waserror()){

 		h1 = getblk(bp, 0);

 		poperror();

 	}else

-		print("error %s\n", errmsg());

+		print("loading arena backup header: %s\n", errmsg());

 	/* if neither head nor tail is consistent, we're hosed */

 	b = (h0 != nil) ? h0 : h1;