[PATCH 1/4] btrfs: add NO_FS_INFO to btrfs_printk

[Anand Jain <anand.jain@oracle.com>]

The first argument to btrfs_printk() wrappers such as
btrfs_warn_in_rcu(), btrfs_info_in_rcu(), etc.. is fs_info, but in some
context like scan and assembling of the volumes there isn't fs_info yet,
so those code generally don't use the btrfs_printk() wrappers and it
could could still use NULL but then it would become hard to distinguish
whether fs_info is NULL for genuine reason or a bug.

So introduce a define NO_FS_INFO to be used instead of NULL so that we
know the code where fs_info isn't initialized and also we have a
consistent logging functions. Thanks.

Suggested-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/ctree.h |  5 +++++
 fs/btrfs/super.c | 14 +++++++++++---
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 569931dd0ce5..625c7eee3d0f 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -110,6 +110,11 @@ struct btrfs_ref;
 #define BTRFS_STAT_CURR		0
 #define BTRFS_STAT_PREV		1
 
+/*
+ * Used when we know that fs_info is not yet initialized.
+ */
+#define	NO_FS_INFO	((void *)0x1)
+
 /*
  * Count how many BTRFS_MAX_EXTENT_SIZE cover the @size
  */
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index a906315efd19..5bd8a889fed0 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -216,9 +216,17 @@ void __cold btrfs_printk(const struct btrfs_fs_info *fs_info, const char *fmt, .
 	vaf.fmt = fmt;
 	vaf.va = &args;
 
-	if (__ratelimit(ratelimit))
-		printk("%sBTRFS %s (device %s): %pV\n", lvl, type,
-			fs_info ? fs_info->sb->s_id : "<unknown>", &vaf);
+	if (__ratelimit(ratelimit)) {
+		if (fs_info == NULL)
+			printk("%sBTRFS %s (device %s): %pV\n", lvl, type,
+				"<unknown>", &vaf);
+		else if (fs_info == NO_FS_INFO)
+			printk("%sBTRFS %s (device %s): %pV\n", lvl, type,
+				"...", &vaf);
+		else
+			printk("%sBTRFS %s (device %s): %pV\n", lvl, type,
+				fs_info->sb->s_id, &vaf);
+	}
 
 	va_end(args);
 }
-- 
2.23.0