From: Gao Xiang <hsiangkao@linux.alibaba.com> To: Yue Hu <zbestahu@gmail.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 13:02:14 +0800 [thread overview] Message-ID: <YPpNVoTg8xqRZOan@B-P7TQMD6M-0146.local> (raw) In-Reply-To: <20210723034945.1337-1-zbestahu@gmail.com> 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. 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 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
next prev parent reply other threads:[~2021-07-23 5:02 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-23 3:49 Yue Hu 2021-07-23 5:02 ` Gao Xiang [this message] 2021-07-23 6:10 ` Yue Hu
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