From: NeilBrown <neilb@suse.de>
Date: Fri, 9 Jul 2010 04:36:50 +0000 (+1000)
Subject: Clean up handling of B_Async
X-Git-Url: http://git.neil.brown.name/?a=commitdiff_plain;h=d353e95b645ace701e30a5b8a84321f95a787842;p=LaFS.git

Clean up handling of B_Async

Follow a uniform structure for the functions that set/clear this bit.

Make sure cleaner is always woken if a block becomes available while
this bit is set.

Signed-off-by: NeilBrown <neilb@suse.de>
---

diff --git a/clean.c b/clean.c
index 3744ec3..d59dc42 100644
--- a/clean.c
+++ b/clean.c
@@ -528,8 +528,10 @@ void lafs_unclean(struct datablock *db)
 			list_del_init(&db->cleaning);
 			putdref(db, MKREF(cleaning));
 			iput(db->b.inode);
-			if (test_and_clear_bit(B_Async, &db->b.flags))
+			if (test_and_clear_bit(B_Async, &db->b.flags)) {
 				putdref(db, MKREF(async));
+				lafs_wake_cleaner(fs);
+			}
 		}
 		mutex_unlock(&fs->cleaner.lock);
 	}
diff --git a/io.c b/io.c
index aa78a37..7d35a45 100644
--- a/io.c
+++ b/io.c
@@ -212,16 +212,20 @@ void _lafs_iolock_block(struct block *b)
 	}
 }
 
-int _lafs_iolock_block_async(struct block *b) {
-	if (test_bit(B_IOLock, &b->flags))
-		if (!test_and_set_bit(B_Async, &b->flags))
-			getref(b, MKREF(async));
-	if (test_and_set_bit(B_IOLock, &b->flags))
-		return 0;
-
-	if (test_and_clear_bit(B_Async, &b->flags))
-		putref(b, MKREF(async));
-	return 1;
+int _lafs_iolock_block_async(struct block *b)
+{
+	for(;;) {
+		if (!test_and_set_bit(B_IOLock, &b->flags)) {
+			/* just got the lock! */
+			if (test_and_clear_bit(B_Async, &b->flags))
+				putref(b, MKREF(async));
+			return 1;
+		}
+		if (test_and_set_bit(B_Async, &b->flags))
+			/* already have async set */
+			return 0;
+		getref(b, MKREF(async));
+	}
 }
 
 void
@@ -349,20 +353,20 @@ lafs_wait_block(struct block *b)
 int __must_check
 lafs_wait_block_async(struct block *b)
 {
-	if (test_bit(B_IOLock, &b->flags)) {
-		if (!test_and_set_bit(B_Async, &b->flags))
-			getref(b, MKREF(async));
+	for (;;) {
+		if (!test_bit(B_IOLock, &b->flags) ||
+		    test_bit(B_Valid, &b->flags)) {
+			if (test_and_clear_bit(B_Async, &b->flags))
+				putref(b, MKREF(async));
+			if (test_bit(B_Valid, &b->flags))
+				return 0;
+			else
+				return -EIO;
+		}
+		if (test_and_set_bit(B_Async, &b->flags))
+			return -EAGAIN;
+		getref(b, MKREF(async));
 	}
-	if (!test_bit(B_IOLock, &b->flags) ||
-	    test_bit(B_Valid, &b->flags)) {
-		if (test_and_clear_bit(B_Async, &b->flags))
-			putref(b, MKREF(async));
-		if (test_bit(B_Valid, &b->flags))
-			return 0;
-		else
-			return -EIO;
-	} else
-		return -EAGAIN;
 }
 
 static void wait_writeback(struct block *b)
@@ -388,17 +392,23 @@ void _lafs_iolock_written(struct block *b)
 
 int _lafs_iolock_written_async(struct block *b)
 {
-	if (!_lafs_iolock_block_async(b))
-		return 0;
-	if (test_bit(B_Writeback, &b->flags))
-		if (!test_and_set_bit(B_Async, &b->flags))
-			getref(b, MKREF(async));
-	if (test_bit(B_Writeback, &b->flags))
-		return 0;
+	for (;;) {
+		if (!test_bit(B_Writeback, &b->flags) &&
+		    !test_and_set_bit(B_IOLock, &b->flags)) {
+			if (!test_bit(B_Writeback, &b->flags)) {
+				/* Have lock without writeback */
+				if (test_and_clear_bit(B_Async, &b->flags))
+					putref(b, MKREF(async));
+				return 1;
+			}
+			/* Writeback was set by a racing thread.. */
+			lafs_iounlock_block(b);
+		}
+		if (test_and_set_bit(B_Async, &b->flags))
+			return 0;
 
-	if (test_and_clear_bit(B_Async, &b->flags))
-		putref(b, MKREF(async));
-	return 1;
+		getref(b, MKREF(async));
+	}
 }
 
 static void