From: NeilBrown <neilb@suse.de>
Date: Fri, 9 Jul 2010 10:49:54 +0000 (+1000)
Subject: Make sure we don't wait forever on writeback
X-Git-Url: http://git.neil.brown.name/?a=commitdiff_plain;h=c921b7192b592faf80fa50cfce3237c9930c2897;p=LaFS.git

Make sure we don't wait forever on writeback

If we ever wait on writeback on a block, we need to cluster_flush
quite promptly or we could wait forever.

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

diff --git a/clean.c b/clean.c
index 54405d4..709dc92 100644
--- a/clean.c
+++ b/clean.c
@@ -92,6 +92,9 @@ static int cleaner(void *data)
 			 timeout);
 		clear_bit(CleanerNeeded, &fs->fsstate);
 
+		if (test_and_clear_bit(FlushNeeded, &fs->fsstate))
+			lafs_cluster_flush(fs, 0);
+
 		timeout = MAX_SCHEDULE_TIMEOUT;
 		to = lafs_do_checkpoint(fs);
 		if (to < timeout)
@@ -139,6 +142,15 @@ void lafs_wake_cleaner(struct fs *fs)
 	wake_up(&fs->async_complete);
 }
 
+void lafs_trigger_flush(struct block *b)
+{
+	struct fs *fs = fs_from_inode(b->inode);
+
+	if (test_bit(B_Writeback, &b->flags) &&
+	    !test_and_set_bit(FlushNeeded, &fs->fsstate))
+		lafs_wake_cleaner(fs);
+}
+
 static int mark_cleaning(struct block *b)
 {
 	int err;
diff --git a/io.c b/io.c
index 7d35a45..82d92a6 100644
--- a/io.c
+++ b/io.c
@@ -373,6 +373,7 @@ static void wait_writeback(struct block *b)
 {
 	if (test_bit(B_Writeback, &b->flags)) {
 		DEFINE_WAIT(wq);
+		lafs_trigger_flush(b);
 		for (;;) {
 			prepare_to_wait(&block_wait, &wq, TASK_UNINTERRUPTIBLE);
 			if (test_bit(B_Writeback, &b->flags))
@@ -404,6 +405,7 @@ int _lafs_iolock_written_async(struct block *b)
 			/* Writeback was set by a racing thread.. */
 			lafs_iounlock_block(b);
 		}
+		lafs_trigger_flush(b);
 		if (test_and_set_bit(B_Async, &b->flags))
 			return 0;
 
diff --git a/lafs.h b/lafs.h
index 1024a87..4043e9b 100644
--- a/lafs.h
+++ b/lafs.h
@@ -641,6 +641,7 @@ int lafs_start_cleaner(struct fs *fs);
 void lafs_stop_cleaner(struct fs *fs);
 void lafs_wake_cleaner(struct fs *fs);
 void lafs_unclean(struct datablock *db);
+void lafs_trigger_flush(struct block *b);
 
 /* cluster.c */
 int lafs_cluster_allocate(struct block *b, int cnum);
diff --git a/state.h b/state.h
index b9d462f..95b96c5 100644
--- a/state.h
+++ b/state.h
@@ -99,6 +99,9 @@ struct fs {
 			 * be full and new allocation requests get
 			 * -ENOSPC
 			 */
+#define FlushNeeded 8  /* Need to flush the current cluster because
+			* someone is waiting on writeback
+			*/
 
 	struct work_struct done_work;	/* used for handling
 					 * refile after write completes */