Messages in this thread | | | Date | Thu, 10 Dec 2020 08:22:56 -0800 | From | Jaegeuk Kim <> | Subject | Re: [f2fs-dev] [PATCH v3 2/3] f2fs-tools:sload.f2fs compression support |
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On 12/10, 徐瑞斌 wrote: > Hi, Jaegeuk, > > I comment here the patch your provided (3 parts, since the patch contains 3 > fixes): > 1. + dn->data_blkaddr = blkaddr; > ret = reserve_new_block(sbi, &dn->data_blkaddr, &sum, type, 0); > > We cannot assign dn->data_blkaddr here. The old one is to be used in > reserve_new_block() function. Also, reserve_new_block() function actually > will set dn->data_blkaddr to blkaddr in the end.
This tries to avoid deleting the block address used in the previous offset. Otherwise, we'll see wrong i_blocks.
> > 2. Added condition "n < (1 << c.sldc_cc.log_cluster_size) * BLOCK_SZ" > > The semantic meaning of the whole if statement is to say: > When the compression fail (ret != 0) or the original read size is > smaller than the compressed size plus (the minimum block saved (specified > by the user) x block size), we will not do compression but just write the > data as is.
This is missing the last block having < 4Kb.
> > The right hand side (RHS) of your added condition is exactly the read size, > i.e. the cluster size. That means the condition is always false except the > read of the last part of the file, when the file size is not exactly the > multiple of the cluster size. That means we will never try to compress the > last part of the file (when the last part is not a multiple of the cluster > size) > > IMHO, the original implementation should be correct. > > 3. node_blk->i.i_blocks += cpu_to_le64(cblocks); > > I am not quite sure of the i_blocks count. Did you mean that when the file > is mutable, meaning that the file reserves some blocks for future write, > we will add count to i_blocks to mark the block as a used block by the > file, right? I thought we only need to increment the allocated count...
Should add it.
> > Regards, > Robin Hsu 徐瑞斌 > > > On Thu, Dec 10, 2020 at 4:42 PM Chao Yu <yuchao0@huawei.com> wrote: > > > On 2020/12/8 16:15, Robin Hsu wrote: > > > From: Robin Hsu <robinhsu@google.com> > > > > > > Add F2FS compression support for sload > > > * Support file extension filter, either default-accept or default-deny > > > policy > > > * Support choice of compression algorithm, LZO (version 2) or LZ4 > > > (default) > > > * Support custom log of cluster size > > > * Support minimum number of compressed blocks per cluster (default 1). > > > A cluster will not be compressed if the number can not be met. > > > * suuport -r (read-only) option > > > > Could you please update manual as well? > > > > > + > > > + /* sldc: sload compression support */ > > > > Personally, I don't like the naming method of adding "sldc_" prefix... :( > > > > > + bool sldc_en; > > > + bool sldc_use_allow_list; /* default false to use the deny list */ > > > + struct compress_ctx sldc_cc; > > > + u8 sldc_ca; /* compress algorithm: 0 = LZO, 1 = LZ4 */ > > > + compress_ops *sldc_compr; > > > + enum filter_policy sldc_policy; > > > + /* max_cppc can used to specify minimum compression rate */ > > > + unsigned int sldc_min_cbpc; /* min compressed pages per cluster */ > > > + bool sldc_got_opt; > > > + bool sldc_immutable; > > > + struct ext_tbl_op *sldc_ef; /* extension filter */ > > > > The variables name like sldc_en, sldc_ca, min_cbpc, sldc_ef makes > > developers > > hard to understand w/o comments, and also there is no comments for several > > variable like sldc_en, sldc_cc... > > > > Could you please improve the naming like f2fs-tools style? > > > > Thanks, > >
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