linux-kernel - Re: [f2fs-dev] [PATCH 2/2] f2fs: add F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS

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Date:   Mon, 23 Nov 2020 15:29:55 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Daeho Jeong <daeho43@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
        Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH 2/2] f2fs: add F2FS_IOC_DECOMPRESS_FILE and
 F2FS_IOC_COMPRESS_FILE

On Tue, Nov 24, 2020 at 08:02:21AM +0900, Daeho Jeong wrote:
> Jaegeuk,
> 
> My mistake~
> 
> Eric,
> 
> What I want is like do_page_cache_ra(), but I used
> page_cache_ra_unbounded() directly, because we already checked that
> read is within i_size.
>
> Or we could use do_page_cache_ra(), but it might do the same check in it again.
> What do you think?

page_cache_ra_unbounded() is basically a quirk for how fs-verity is implemented
in ext4 and f2fs.  I don't think people would be happy if it's used in other
cases, where it's not needed.  Checking against i_size multiple times is fine.

> 
> I could add some description about these in
> Documentation/filesystems/f2fs.rst and I implemented tests internally.

Documentation in f2fs.rst sounds good.  All the f2fs ioctls should be
documented there.

The tests should be runnable by any kernel developer; "internal" tests aren't
very useful.  Could you add tests to xfstests?

- Eric