-------- Original Message --------
Subject: Re: [PATCH RFC] btrfs: Add ctime/mtime update for btrfs device
add/remove.
From: Anand Jain <anand.j...@oracle.com>
To: Qu Wenruo <quwen...@cn.fujitsu.com>, linux-btrfs@vger.kernel.org
Date: 2014年05月30日 15:51
Hi Qu,
In line below...
On 16/04/14 17:02, Qu Wenruo wrote:
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-i...@jp.fujitsu.com>
Cc: Karel Zak <k...@redhat.com>
Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
fs/btrfs/volumes.c | 26 ++++++++++++++++++++++++--
1 file changed, 24 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 49d7fab..ce232d7 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;
+}
+
IMO /(I might be wrong) I think its not a good idea to explicitly
achieve this. Since this thread would have already scratched the
device's SB, shouldn't that take care of updating the mtime ?
Thanks, Anand
Yes, scratching SB will update the time of the device's inode.
But the problem is that, the *block file*'s ctime/mtime is not changed
according to the device's inode mtime/ctime.
So in the patch, I use the device's *full path* not the *device's inode*
to update ctime/mtime since kernel operations
will not update ctime/mtine of *device files under /dev*.
About your fix patch ([PATCH] btrfs: kobject_uevent should use bd_part
instead of bd_disk )
I am unable to reproduce the problem on 3.15-rc4 kernel with 3.14.1
btrfs-progs. :(
But the ctime/mtime things will not change as the following example:
------
# btrfs dev scan;stat /dev/sdd ; btrfs dev del /dev/sdd
/mnt/scratch/;stat /dev/sdd ; btrfs dev scan
Scanning for Btrfs filesystems
File: '/dev/sdd'
Size: 0 Blocks: 0 IO Block: 4096 block special
file
Device: 5h/5d Inode: 8569 Links: 1 Device type: 8,30
Access: (0660/brw-rw----) Uid: ( 0/ root) Gid: ( 6/ disk)
Access: 2014-05-30 16:39:06.104006687 +0800
Modify: 2014-05-30 16:38:57.638006272 +0800 <<<ctime/mtime does not change
Change: 2014-05-30 16:38:57.638006272 +0800
Birth: -
File: '/dev/sdd'
Size: 0 Blocks: 0 IO Block: 4096 block special
file
Device: 5h/5d Inode: 8569 Links: 1 Device type: 8,30
Access: (0660/brw-rw----) Uid: ( 0/ root) Gid: ( 6/ disk)
Access: 2014-05-30 16:39:06.104006687 +0800
Modify: 2014-05-30 16:38:57.638006272 +0800 <<<ctime/mtime does not change
Change: 2014-05-30 16:38:57.638006272 +0800
Birth: -
Scanning for Btrfs filesystems
^^^ But no error message now.... :(
------
Thanks,
Qu
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:
--
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