Question about the condition of fsck.overlay

Question about the condition of fsck.overlay

[Chengguang Xu]

Hi Zhangyi,

Please let me ask a simple question about fsck.overlay,
is it possible to run any kernel version of overlayfs?

I know some advanced features are only implemented in high
kernel version, I just want to make sure if the common check
and repair functions are available for 4.4 kernel? Any conditions?


Thanks,
Chengguang.

Re: Question about the condition of fsck.overlay

[zhangyi (F)]

Hi Chengguang,

On 2018/3/14 15:20, Chengguang Xu Wrote:
> Hi Zhangyi,
> 
> Please let me ask a simple question about fsck.overlay,
> is it possible to run any kernel version of overlayfs?
> 

No, current fsck.overlay can recognize whiteout/redirect_dir/impure
xattr feature only, it don't know index and nfs_export features. So,
if run current version of fsck.overlay on overlayfs which was mounted
with index=on or nfs_export=on, if cannot guarantee the relationship
between dirs/files in indexdir and upper dir, so may lead to
inconsistency in indexdir.

This drawback will be addressed through introduce overlay feature
set as Amir suggested, I will post it soon and maybe write a NOTE
or BUG in README is better before everything is done.

> I know some advanced features are only implemented in high
> kernel version, I just want to make sure if the common check
> and repair functions are available for 4.4 kernel? Any conditions?
> 

Yes, I think current fsck.overlay can support <= 4.12 kernel well(not
check origin xattr, but not harmful), it can support overlayfs without
index dir.

Thanks,
Yi.

Re: Question about the condition of fsck.overlay

[Chengguang Xu]

Hi Zhangyi,

Thanks for your kind explanation!

> Sent: Wednesday, March 14, 2018 at 4:38 PM
> From: "zhangyi (F)" <yi.zhang@huawei.com>
> To: "Chengguang Xu" <cgxu519@gmx.com>
> Cc: overlayfs <linux-unionfs@vger.kernel.org>
> Subject: Re: Question about the condition of fsck.overlay
>
> Hi Chengguang,
> 
> On 2018/3/14 15:20, Chengguang Xu Wrote:
> > Hi Zhangyi,
> > 
> > Please let me ask a simple question about fsck.overlay,
> > is it possible to run any kernel version of overlayfs?
> > 
> 
> No, current fsck.overlay can recognize whiteout/redirect_dir/impure
> xattr feature only, it don't know index and nfs_export features. So,
> if run current version of fsck.overlay on overlayfs which was mounted
> with index=on or nfs_export=on, if cannot guarantee the relationship
> between dirs/files in indexdir and upper dir, so may lead to
> inconsistency in indexdir.
> 
> This drawback will be addressed through introduce overlay feature
> set as Amir suggested, I will post it soon and maybe write a NOTE
> or BUG in README is better before everything is done.
> 
> > I know some advanced features are only implemented in high
> > kernel version, I just want to make sure if the common check
> > and repair functions are available for 4.4 kernel? Any conditions?
> > 
> 
> Yes, I think current fsck.overlay can support <= 4.12 kernel well(not
> check origin xattr, but not harmful), it can support overlayfs without
> index dir.
> 
> Thanks,
> Yi.
> 
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