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From:   Daeho Jeong <daeho43@gmail.com>
Date:   Fri, 4 Dec 2020 13:48:24 +0900
Message-ID: <CACOAw_xzKjZcpVTo3aj5sJUQ_BjLr=5ZhnfuyFwYerpyzZu+aw@mail.gmail.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix race of pending_pages in decompression
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com,
        Daeho Jeong <daehojeong@google.com>
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Eric,

I have another question.
I understand enabling the verity can be possible in the middle of I/O.
Is the opposite way also possible? Actually, I couldn't find any
disabling function of it, though.

2020=EB=85=84 12=EC=9B=94 4=EC=9D=BC (=EA=B8=88) =EC=98=A4=ED=9B=84 1:31, D=
aeho Jeong <daeho43@gmail.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> > Are you sure?  I thought that compression (and encryption) apply to the=
 whole
> > file, including any Merkle tree blocks past i_size.
>
> This "dic" structure is only for "de"compression, so we don't need to
> worry about going beyond i_size case.
>
> > Also, even if you include the i_size check, it's still wrong to check
> > fsverity_active() in the middle of the I/O because FS_IOC_ENABLE_VERITY=
 can
> > execute concurrently, causing fsverity_active() to return false at the =
beginning
> > of the I/O and true later in the I/O.  It needs to be checked only once=
, at the
> > beginning...
>
> Got it. Our previous implementation didn't consider this case. Need to fi=
x this.
>
> Thanks,