Re: [f2fs-dev] [PATCH v5] f2fs: introduce device aliasing file

[Christoph Hellwig]

On Mon, Oct 14, 2024 at 04:42:07PM +0000, Jaegeuk Kim wrote:
> > 
> > Plz, refer to this patch and the description there.
> > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git/commit/?h=dev-test&id=8cc4e257ec20bee207bb034d5ac406e1ab31eaea
> 
> Also, I added this in the description.
> 
> ---
>     For example,
>     "mkfs.f2fs -c /dev/block/test@test_alias /dev/block/main" gives
>     a file $root/test_alias which carves out /dev/block/test partition.

What partition?

So mkfs.f2fs adds additional devices based on the man page.

So the above creates a file system with two devices, but the second
device is not added to the general space pool, but mapped to a specific
file?  How does this file work.  I guess it can't be unlinked and
renamed.  It probably also can't be truncated and hole punched,
or use insert/collapse range.  How does the user find out about this
magic file?  What is the use case?  Are the exact semantics documented
somewhere?