From: Yue Hu <zbestahu@gmail.com>
To: Gao Xiang <hsiangkao@linux.alibaba.com>
Cc: yuchao0@huawei.com, zbestahu@163.com, huyue2@yulong.com,
xiang@kernel.org, linux-erofs@lists.ozlabs.org
Subject: Re: [PATCH] erofs-utils: no compression case for tail-end block in vle_write_indexes()
Date: Fri, 23 Jul 2021 14:10:49 +0800 [thread overview]
Message-ID: <20210723141049.00004bff.zbestahu@gmail.com> (raw)
In-Reply-To: <YPpNVoTg8xqRZOan@B-P7TQMD6M-0146.local>
On Fri, 23 Jul 2021 13:02:14 +0800
Gao Xiang <hsiangkao@linux.alibaba.com> wrote:
> Hi Yue,
>
> On Fri, Jul 23, 2021 at 11:49:45AM +0800, Yue Hu wrote:
> > From: Yue Hu <huyue2@yulong.com>
> >
> > Note that count value will be always greater than EROFS_BLKSIZ when
> > calling erofs_compress_destsize() in vle_compress_one(). So, the d1
> > always >= 1 for compressed block in vle_write_indexes(). That is to
> > say tail-end block can't be compressed.
> >
> > Signed-off-by: Yue Hu <huyue2@yulong.com>
>
> I once thought tail end block can be compressed with < EROFS_BLKSIZ as
> well (as long as it has some benefit) and also tail-packing inline
> like uncompressed cases together after compress extents, so that when we
> reading the last compress extent meta block, the tail-packing compressed
> data can be loaded together.
Understood.
>
> Currently, I think we could do that, but could you add some DBG_BUGON
> like DBG_BUGON(!raw) right above
> "type = Z_EROFS_VLE_CLUSTER_TYPE_PLAIN;" and a TODO comment to mention
> tail-packing inline compressed cases is under TODO list? That would be
Will do it in v2.
Thanks.
> much better.
>
> Thanks,
> Gao Xiang
>
> > ---
> > lib/compress.c | 5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/lib/compress.c b/lib/compress.c
> > index af0c720..93fc543 100644
> > --- a/lib/compress.c
> > +++ b/lib/compress.c
> > @@ -73,10 +73,9 @@ static void vle_write_indexes(struct z_erofs_vle_compress_ctx *ctx,
> >
> > di.di_clusterofs = cpu_to_le16(ctx->clusterofs);
> >
> > - /* whether the tail-end (un)compressed block or not */
> > + /* whether the tail-end uncompressed block or not */
> > if (!d1) {
> > - type = raw ? Z_EROFS_VLE_CLUSTER_TYPE_PLAIN :
> > - Z_EROFS_VLE_CLUSTER_TYPE_HEAD;
> > + type = Z_EROFS_VLE_CLUSTER_TYPE_PLAIN;
> > advise = cpu_to_le16(type << Z_EROFS_VLE_DI_CLUSTER_TYPE_BIT);
> >
> > di.di_advise = advise;
> > --
> > 1.9.1
prev parent reply other threads:[~2021-07-23 6:10 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 3:49 [PATCH] erofs-utils: no compression case for tail-end block in vle_write_indexes() Yue Hu
2021-07-23 5:02 ` Gao Xiang
2021-07-23 6:10 ` Yue Hu [this message]
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