Re: [PATCH] Btrfs: Add code to support file creation time.

[Li Zefan <lizefan@huawei.com>]

On 2012/7/5 9:52, Alexander Block wrote:

> On Thu, Jul 5, 2012 at 3:07 AM, Li Zefan <lizefan@huawei.com> wrote:
>> On 2012/7/4 19:04, Alexander Block wrote:
>>
>>> On Wed, Jul 4, 2012 at 9:56 AM, Li Zefan <lizefan@huawei.com> wrote:
>>>> On 2012/7/4 15:18, chandan r wrote:
>>>>
>>>>> This patch adds a new member to the 'struct btrfs_inode' structure to hold
>>>>> the file creation time.
>>>>>
>>>>
>>>>
>>>> Well, how do users use this file creation time? There's no syscall and there's
>>>> no ioctl that exports this information. That xstat syscall hasn't been accepted,
>>>> so you can revise and repost the patch when you see it happens.
>>> In my opinion we should still include this patch. Currently, otime is never even
>>> initialized, having undefined values. If it ever gets possible to
>>> access otime, we
>>> would at least have some inodes with valid otime fields.
>>
>>
>> otime (on disk) is initialized to 0, not some undefined value. But yeah, your point makes
>> some sense, that with this patch we can access valid otime in an old filesystem once we
>> update to a new kernel which has otime support.
> This is true for the inode items found in the root tree. But the inode
> items found in the filesystem trees are not initialized at all. I did
> a fast check by adding printing of the otime field in
> btrfs-debug-tree...and every inode's otime looks random.
> btrfs_new_inode uses btrfs_insert_empty_items which does not zero the
> new item, then fill_inode_item is used to initialize the fields and
> there otime is missing.
> 


That's bad..