Re: [PATCH] jffs2: Move erasing from write_super to GC.

[David Woodhouse <dwmw2@infradead.org>]

On Tue, 2010-05-18 at 19:37 +0100, David Woodhouse wrote:
> 
> Hrm, and now everything which calls jffs2_erase_pending_trigger()
> needs
> _not_ to be holding c->erase_completion_lock, or it'll deadlock...

Playing with this incremental patch now...

I also moved the erasing into jffs2_garbage_collect_pass() itself rather
than having both callers of jffs2_garbage_collect_pass() do it for
themselves, under different circumstances. I think the one in
jffs2_reserve_space() was buggy anyway.

diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c
index 6cc014c..8c9ffdc 100644
--- a/fs/jffs2/background.c
+++ b/fs/jffs2/background.c
@@ -21,12 +21,11 @@
 
 static int jffs2_garbage_collect_thread(void *);
 
-void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
+void jffs2_erase_pending_trigger(struct jffs2_sb_info *c)
 {
-	spin_lock(&c->erase_completion_lock);
+	BUG_ON(spin_trylock(&c->erase_completion_lock));
 	if (c->gc_task && jffs2_thread_should_wake(c))
 		send_sig(SIGHUP, c->gc_task, 1);
-	spin_unlock(&c->erase_completion_lock);
 }
 
 /* This must only ever be called when no GC thread is currently running */
@@ -146,9 +145,8 @@ static int jffs2_garbage_collect_thread(void *_c)
 		disallow_signal(SIGHUP);
 
 		D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n"));
-		if (jffs2_erase_pending_blocks(c, 1))
-			/* Nothing more to do ATM */;
-		else if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
+
+		if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
 			printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n");
 			goto die;
 		}
diff --git a/fs/jffs2/erase.c b/fs/jffs2/erase.c
index 2a6cc6c..e8638f8 100644
--- a/fs/jffs2/erase.c
+++ b/fs/jffs2/erase.c
@@ -168,8 +168,11 @@ static void jffs2_erase_succeeded(struct jffs2_sb_info *c, struct jffs2_eraseblo
 	mutex_lock(&c->erase_free_sem);
 	spin_lock(&c->erase_completion_lock);
 	list_move_tail(&jeb->list, &c->erase_complete_list);
+	/* Wake the GC thread to mark them clean */
+	jffs2_erase_pending_trigger(c);
 	spin_unlock(&c->erase_completion_lock);
 	mutex_unlock(&c->erase_free_sem);
+	wake_up(&c->erase_wait);
 }
 
 static void jffs2_erase_failed(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb, uint32_t bad_offset)
@@ -488,9 +491,9 @@ filebad:
 
 refile:
 	/* Stick it back on the list from whence it came and come back later */
-	jffs2_erase_pending_trigger(c);
 	mutex_lock(&c->erase_free_sem);
 	spin_lock(&c->erase_completion_lock);
+	jffs2_erase_pending_trigger(c);
 	list_move(&jeb->list, &c->erase_complete_list);
 	spin_unlock(&c->erase_completion_lock);
 	mutex_unlock(&c->erase_free_sem);
diff --git a/fs/jffs2/gc.c b/fs/jffs2/gc.c
index 3b6f2fa..1ea4a84 100644
--- a/fs/jffs2/gc.c
+++ b/fs/jffs2/gc.c
@@ -214,6 +214,19 @@ int jffs2_garbage_collect_pass(struct jffs2_sb_info *c)
 		return ret;
 	}
 
+	/* If there are any blocks which need erasing, erase them now */
+	if (!list_empty(&c->erase_complete_list) ||
+	    !list_empty(&c->erase_pending_list)) {
+		spin_unlock(&c->erase_completion_lock);
+		D1(printk(KERN_DEBUG "jffs2_garbage_collect_pass() erasing pending blocks\n"));
+		if (jffs2_erase_pending_blocks(c, 1)) {
+			mutex_unlock(&c->alloc_sem);
+			return 0;
+		}
+		D1(printk(KERN_DEBUG "No progress from erasing blocks; doing GC anyway\n"));
+		spin_lock(&c->erase_completion_lock);
+	}
+
 	/* First, work out which block we're garbage-collecting */
 	jeb = c->gcblock;
 
@@ -222,7 +235,7 @@ int jffs2_garbage_collect_pass(struct jffs2_sb_info *c)
 
 	if (!jeb) {
 		/* Couldn't find a free block. But maybe we can just erase one and make 'progress'? */
-		if (!list_empty(&c->erase_pending_list)) {
+		if (c->nr_erasing_blocks) {
 			spin_unlock(&c->erase_completion_lock);
 			mutex_unlock(&c->alloc_sem);
 			return -EAGAIN;
diff --git a/fs/jffs2/nodemgmt.c b/fs/jffs2/nodemgmt.c
index 4779301..8ec436a 100644
--- a/fs/jffs2/nodemgmt.c
+++ b/fs/jffs2/nodemgmt.c
@@ -115,9 +115,21 @@ int jffs2_reserve_space(struct jffs2_sb_info *c, uint32_t minsize,
 			spin_unlock(&c->erase_completion_lock);
 
 			ret = jffs2_garbage_collect_pass(c);
-
-			if (ret == -EAGAIN)
-				jffs2_erase_pending_blocks(c, 1);
+			if (ret == -EAGAIN) {
+				spin_lock(&c->erase_completion_lock);
+				if (c->nr_erasing_blocks &&
+				    list_empty(&c->erase_pending_list) &&
+				    list_empty(&c->erase_complete_list)) {
+					DECLARE_WAITQUEUE(wait, current);
+					set_current_state(TASK_UNINTERRUPTIBLE);
+					add_wait_queue(&c->erase_wait, &wait);
+					D1(printk(KERN_DEBUG "%s waiting for erase to complete\n", __func__));
+					spin_unlock(&c->erase_completion_lock);
+					
+					schedule();
+				} else
+					spin_unlock(&c->erase_completion_lock);
+			}
 			else if (ret)
 				return ret;
 
@@ -469,7 +481,9 @@ struct jffs2_raw_node_ref *jffs2_add_physical_node_ref(struct jffs2_sb_info *c,
 void jffs2_complete_reservation(struct jffs2_sb_info *c)
 {
 	D1(printk(KERN_DEBUG "jffs2_complete_reservation()\n"));
-	jffs2_garbage_collect_trigger(c);
+	spin_lock(&c->erase_completion_lock);
+	jffs2_erase_pending_trigger(c);
+	spin_unlock(&c->erase_completion_lock);
 	mutex_unlock(&c->alloc_sem);
 }
 
diff --git a/fs/jffs2/os-linux.h b/fs/jffs2/os-linux.h
index 5d26362..64ac455 100644
--- a/fs/jffs2/os-linux.h
+++ b/fs/jffs2/os-linux.h
@@ -148,13 +148,7 @@ static inline void jffs2_dirty_trigger(struct jffs2_sb_info *c)
 /* background.c */
 int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c);
 void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c);
-void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c);
-
-/* erase.c */
-static inline void jffs2_erase_pending_trigger(struct jffs2_sb_info *c)
-{
-	jffs2_garbage_collect_trigger(c);
-}
+void jffs2_erase_pending_trigger(struct jffs2_sb_info *c);
 
 /* dir.c */
 extern const struct file_operations jffs2_dir_operations;
diff --git a/fs/jffs2/scan.c b/fs/jffs2/scan.c
index 696686c..1312552 100644
--- a/fs/jffs2/scan.c
+++ b/fs/jffs2/scan.c
@@ -260,7 +260,9 @@ int jffs2_scan_medium(struct jffs2_sb_info *c)
 			ret = -EIO;
 			goto out;
 		}
+		spin_lock(&c->erase_completion_lock);
 		jffs2_erase_pending_trigger(c);
+		spin_unlock(&c->erase_completion_lock);
 	}
 	ret = 0;
  out:


-- 
dwmw2