[PATCH] Show a warning message if one of highest objectid reaches its max value

[Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>]

- It's better to show a warning message for the exceptional case
  that one of highest objectid (in most case, inode number)
  reaches its max value, BTRFS_LAST_FREE_OBJECTID. Show this
  message only once to avoid filling dmesg with it.
- EOVERFLOW is more proper return value for this case.
  ENOSPC is for "No space left on device" case and objectid isn't
  related to any device.

Signed-off-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
---
This patch can be applied to v4.5-rc6
---
 fs/btrfs/inode-map.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index e50316c..a4860fd 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -555,8 +555,10 @@ int btrfs_find_free_objectid(struct btrfs_root *root, u64 *objectid)
 	int ret;
 	mutex_lock(&root->objectid_mutex);

-	if (unlikely(root->highest_objectid >= BTRFS_LAST_FREE_OBJECTID)) {
-		ret = -ENOSPC;
+	if (WARN_ONCE(root->highest_objectid >= BTRFS_LAST_FREE_OBJECTID,
+		      "BTRFS: The highest objectid reaches its max value %llu.\n",
+		      BTRFS_LAST_FREE_OBJECTID)) {
+		ret = -EOVERFLOW;
 		goto out;
 	}

-- 
2.5.0
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