[Btrfs-devel][PATCH] return value checking in module init

[Wyatt Banks]

Hi,

Thanks for the feedback on my last version of this.

Is anyone using kernel versions under 2.6.23 for development?

Also, I was going to ask about the use of labels in the classic sense of:

alloc1
if alloc1 fails
	exit
alloc2
if alloc2 fails
	goto free1
alloc3
if alloc3 fails
	goto free2
return 0

free2:
free1:
return foo

Since btrfs_destroy_cachep() just uses branching to free memory.  I'm guessing the
feedback on this label heavy patch will explain either:

A. branching is the quick and dirty, while we're in development method.
B. I'm missing the point of how Btrfs is intending to use labels
C. something else I missed?

Apparently I got so caught up in seeing how and why memory is freed in a
certain way I forgot to free any in my last send. :-)

This patch compiles cleanly except for files I did not touch.  I created a new
file system on my external usb drive I use for experimentation and created a few files
to test.

Anyone who can suggest other ways I can test, please let me know.

Thanks
Wyatt Banks

Patched against http://oss.oracle.com/mercurial/mason/btrfs-unstable

diff -r 454189bdd3ed extent_map.c
--- a/extent_map.c	Fri Nov 16 11:45:54 2007 -0500
+++ b/extent_map.c	Fri Nov 16 19:54:26 2007 -0500
@@ -43,17 +43,31 @@ struct extent_page_data {
	get_extent_t *get_extent;
 };

-void __init extent_map_init(void)
+int __init extent_map_init(void)
 {
	extent_map_cache = btrfs_cache_create("extent_map",
					    sizeof(struct extent_map), 0,
					    NULL);
+	if (!extent_map_cache)
+		return -ENOMEM;
	extent_state_cache = btrfs_cache_create("extent_state",
					    sizeof(struct extent_state), 0,
					    NULL);
+	if (!extent_state_cache)
+		goto free_map_cache;
	extent_buffer_cache = btrfs_cache_create("extent_buffers",
					    sizeof(struct extent_buffer), 0,
					    NULL);
+	if (!extent_buffer_cache)
+		goto free_state_cache;
+
+	return 0;
+
+free_state_cache:
+	kmem_cache_destroy(extent_state_cache);
+free_map_cache:
+	kmem_cache_destroy(extent_map_cache);
+	return -ENOMEM;
 }

 void __exit extent_map_exit(void)
diff -r 454189bdd3ed extent_map.h
--- a/extent_map.h	Fri Nov 16 11:45:54 2007 -0500
+++ b/extent_map.h	Fri Nov 16 19:54:26 2007 -0500
@@ -110,7 +110,7 @@ void free_extent_map(struct extent_map *
 void free_extent_map(struct extent_map *em);
 int extent_read_full_page(struct extent_map_tree *tree, struct page *page,
			  get_extent_t *get_extent);
-void __init extent_map_init(void);
+int __init extent_map_init(void);
 void __exit extent_map_exit(void);

 int test_range_bit(struct extent_map_tree *tree, u64 start, u64 end,
diff -r 454189bdd3ed super.c
--- a/super.c	Fri Nov 16 11:45:54 2007 -0500
+++ b/super.c	Fri Nov 16 19:54:26 2007 -0500
@@ -347,9 +347,24 @@ static int __init init_btrfs_fs(void)
	btrfs_init_transaction_sys();
	err = btrfs_init_cachep();
        if (err)
-		return err;
-	extent_map_init();
-	return register_filesystem(&btrfs_fs_type);
+		goto free_transaction_sys;
+	err = extent_map_init();
+	if (err)
+		goto free_cachep;
+
+	err = register_filesystem(&btrfs_fs_type);
+	if (err)
+		goto free_extent_map;
+	return 0;
+
+free_extent_map:
+	extent_map_exit();
+free_cachep:
+	btrfs_destroy_cachep();
+free_transaction_sys:
+	btrfs_exit_transaction_sys();
+	btrfs_exit_sysfs();
+	return err;
 }

 static void __exit exit_btrfs_fs(void)