[Ocfs2-devel] [RFC] Online File(system) check

[Goldwyn Rodrigues]

Hi Gang,

On 04/27/2015 10:00 PM, Gang He wrote:
> Hi Glodwyn,
>
> Very nice proposal.
> So far, there are some comments from me.
> 1) which task will we do in check/fix a file, we need to define the detailed requirements further, since we just do a light-level file check/fix according to inode number, we need to know which items can be done by online check, which items can be done by offline fsck.

For the first phase (regular files), these are all the reasons the disk 
validate function would fail. Some examples are 
ocfs2_validate_inode_block, ocfs2_validate_extent_block etc.
As we take up system inodes (phase 2), we will add more functionality.

> 2) can we keep check and fix two option, check option is to check if a file is good or bad, but not modify anything, fix option is to check and fix a file if the file is corrupted.

Yes, there are two options, CHECKS only checks wheras FIX fixes the 
errors. As a precautionary measure, a CHECK command should be provided 
before a FIX is issued. IOW, a file should be checked for errors before 
actually fixing it.

> 3) when users execute the command "echo CHECK <inode> > /sys/fs/ocfs2/filecheck" to check a file, how to give the feedback information besides printing the messages to syslog?

The output should be when you cat /sys/fs/ocfs2/filecheck. It would 
provide the results of the last (N) files checked. I don't want to flood 
the kernel log with this. Thanks for bringing this up, I will put it on 
the doc. Something like:

Inode Status Description
1234   ERROR Metadata incorrect
2352   FIXED Valid flag not set
9382   CHECKING -
8926   GOOD -
7230   CANT-FIX Please execute fsck.ocfs2 after taking filesystem offline.

So, for the current scenario, only 1234 can be fixed. An echo should err 
with EINVAL if any other inode number is provided with FIX.


> 4) we should support a list to accept the "check/fix" requests from user-space and queue them, then handle them one by one, right? what is the behavior for the request user which execute "echo check ..." from the user space? the user post a request to the kernel space, then the command will end or wait for the file check end?
>

I would not suggest that, atleast for now. This is to improve 
availability. However, if the filesystem is very bad, we should suggest 
an offline check. However, the user can provide multiple CHECK requests.

-- 
Goldwyn