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From:   Daeho Jeong <daeho43@gmail.com>
Date:   Thu, 10 Sep 2020 08:23:17 +0900
Message-ID: <CACOAw_zoA5PKY7sbzZtria+jjuFSQ3RormTYn83rz7NAOkxtxw@mail.gmail.com>
Subject: Re: [f2fs-dev] Question about STEP_DECOMPRESS_NOWQ
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com
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Got it. I misunderstood that is some residue of trying to implement
softirq context decompression. :)

2020=EB=85=84 9=EC=9B=94 9=EC=9D=BC (=EC=88=98) =EC=98=A4=ED=9B=84 4:15, Ch=
ao Yu <yuchao0@huawei.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> Hi Daeho,
>
> On 2020/9/9 12:43, Daeho Jeong wrote:
> > Hi Chao,
> >
> > I have a question about the below flag for decompression.
> >
> > STEP_DECOMPRESS_NOWQ,           /* handle normal cluster data inplace *=
/
> >
> > According to the comment, you added this for using inplace
>
> I added this for the condition that: in compressed inode, partial cluster=
s are
> written as normal (non-compressed) one due to bad compress ratio, during =
reading
> data in normal cluster, we don't need to queue them in workqueue, instead=
, we
> can just handle them in IRQ context (end_io()).
>
> That says, if all pages in bio are non-compressed, we tag step w/ STEP_DE=
COMPRESS_NOWQ,
> once there is at least one page is compressed, we change step to
> STEP_DECOMPRESS.
>
> > decompression but inplace decompression mode is not being activated
>
> 'inplace decompression' means decompress in
> a. reader thread or
> b. IRQ context ?
>
> Thanks
>
> > now, since we are setting STEP_DECOMPRESS right after bio_add_page().
> >
> >                  if (bio_add_page(bio, page, blocksize, 0) < blocksize)
> >                          goto submit_and_realloc;
> >
> >                  /* tag STEP_DECOMPRESS to handle IO in wq */
> >                  ctx =3D bio->bi_private;
> >                  if (!(ctx->enabled_steps & (1 << STEP_DECOMPRESS)))
> >                          ctx->enabled_steps |=3D 1 << STEP_DECOMPRESS;
> >
> > Did you mean to deactivate inplace decompression mode on purpose,
> > since it had an issue? I am a little bit confused about this.
> >
> >
> > _______________________________________________
> > Linux-f2fs-devel mailing list
> > Linux-f2fs-devel@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
> > .
> >