btrfs: Add ctime/mtime update for btrfs device add/remove.

Btrfs will send uevent to udev inform the device change,
but ctime/mtime for the block device inode is not udpated, which cause
libblkid used by btrfs-progs unable to detect device change and use old
cache, causing 'btrfs dev scan; btrfs dev rmove; btrfs dev scan' give an
error message.

Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Cc: Karel Zak <kzak@redhat.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 24 insertions, 2 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 3b761a456acd..ad8e342c4b78 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1452,6 +1452,22 @@ out:
         return ret;
 }
 
+/*
+ * Function to update ctime/mtime for a given device path.
+ * Mainly used for ctime/mtime based probe like libblkid.
+ */
+static void update_dev_time(char *path_name)
+{
+        struct file *filp;
+
+        filp = filp_open(path_name, O_RDWR, 0);
+        if (!filp)
+                return;
+        file_update_time(filp);
+        filp_close(filp, NULL);
+        return;
+}
+
 static int btrfs_rm_dev_item(struct btrfs_root *root,
                              struct btrfs_device *device)
 {
@@ -1704,10 +1720,14 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 
         ret = 0;
 
-        /* Notify udev that device has changed */
-        if (bdev)
+        if (bdev) {
+                /* Notify udev that device has changed */
                 btrfs_kobject_uevent(bdev, KOBJ_CHANGE);
 
+                /* Update ctime/mtime for device path for libblkid */
+                update_dev_time(device_path);
+        }
+
 error_brelse:
         brelse(bh);
         if (bdev)
@@ -2146,6 +2166,8 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
                 ret = btrfs_commit_transaction(trans, root);
         }
 
+        /* Update ctime/mtime for libblkid */
+        update_dev_time(device_path);
         return ret;
 
 error_trans: