Hello Void,
"Void":
> Hi, I'm one of the lead developers of the Puppy
> Linux project. I've just gone over to using Aufs
> from Unionfs, and using CVS 20061125, with the
> compatibility turned on, so the directory opaque
> files are named '.wh.__dir_opaque' -- which I have
> done as have scripts that directly delete these
> files at bootup before the aufs is mounted, and I
> have not yet modified them for the new whiteout
> filename.
I'd like to suggest you to use the latest aufs.
Do you have any special reason to use such old aufs?
And it is not recommended to handle whiteout directly in general.
I don't know why you need to remove whiteout for diropq, but this aufs
mount option may help you,
(quote from <aufs CVS tree>/Histroy)
----------------------------------------------------------------------
20070129
- introduce diropq option.
the behaviour of mkdir(2) and rename(2) dir case is changed. now they don't
make '.wh..wh..opq' when it is not necessary. this is the default. if
you dislike this behaviour and still want to make it always, use
'diropq=always' mount option. see the manual in detail.
----------------------------------------------------------------------
> When boot from usb Flash, the top layer is a tmpfs,
> next down is a file with ext2 f.s. in it mounted by
> loop device. We flush the top layer (branch) down
> to the save layer periodically, which is a mechanism
> to minimise writes to Flash drive.
If you set '=ro' to the branch on Flash drive, aufs will not write
anything to Flash drive.
Additionally, unless you specify '=ro+wh', aufs will not lookup
any whiteouts including diropq.
> I'm using 'udba=reval' but I can't do a true
> flushing, in some cases can onl copy files down to
> the "save" layer. The two exceptions that prevent
> flushing are:
Do you mean that you mounted aufs as,
- /aufs = /rw(tmpfs) + /ro(loopback ext2, backend is on flash)
and execute such like this periodically?
- mv /rw/* /ro/*
Then, you should try 'udba=inotify' mount option.
Actually, I had an idea to develop similar feature as a mount option,
which will copy/move files between branches. But it is still just an
idea...
I guess your script which will be executed periodically will be such
like this (I didn't test it),
mount -o remount,udba=inotify /aufs
mv /rw/* /ro/*
mount -o remount,udba=reval /aufs
> 1. hidden directory.
> If I copy a file down to "save" layer then delete
> it on tmpfs layer, Aufs does not recognise this
> if there is a hidden directory in the path.
Unfortunately, I could not get what you meant. What do you mean "a
hidden directory"? Will you show me the actual example?
> 2. New directory.
> This has been our curse for so long, the creation
> of .wh.__dir_opaque files when a new directory is
> created. I know it is a POSIX standard, but in
> Puppy it is just a headache and in the case of
> booting from Flash we just don't save them.
Please try newer aufs or 'diropq' mount option.
> In the Flash case, the problem is in the current
> session, if say install a package that creates
> directories, we cannot flush from the tmpfs layer
> down to the save layer as Aufs refuses to look
> at new directories created directly in the save
> layer. After a reboot it is okay as we don't
> save the .wh.__dir_opaque files.
You need to use 'udba=inotify' or discard dentry cache (cached
filenames). Try newer version of aufs and read the manual.
> So, my question, and this is something I want
> very much to do, is where in the source can I
> comment-out the part that creates the
> .wh.__dir_opaque files?
> I had a quick look at the source and couldn't see
> where, so could someone familiar with the code
> kindly advise me how to do this?
>
> Of course, if this could become a configure option
> that would bereally great!
I don't understand what option you want, but I can tell you about source
code.
In the latest version,
- do_diropq():fs/aufs/whout.c handles .wh.__dir_opaque file.
- aufs_mkdir():fs/aufs/i_op_add.c and do_rename():fs/aufs/i_op_ren.c
calls
create_diropq() --> sio_diropq() --> do_diropq()
Junjiro Okajima
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