Hi Ju Hyung,
On 2019/10/23 1:53, Ju Hyung Park wrote:
> Hi Jaegeuk and Chao,
>
> Nice to see this finally getting into shape :) Great work
> I'm excited to see possible use-cases for this in the future.
>
> Would f2fs compress files automatically like how btrfs' "compress" option
> works?
> Or is it per-extension basis for now?
We support three ways to active file compression:
Quoted:
- To enable compression on regular inode, there are three ways:
* chattr +c file
* chattr +c dir; touch dir/file
* mount w/ -o compress_extension=ext; touch file.ext
>
> On Wed, Oct 23, 2019 at 2:16 AM Jaegeuk Kim <jaeg...@kernel.org> wrote:
>> +compress_algorithm=%s Control compress algorithm, currently f2fs supports
>> "lzo"
>> + and "lz4" algorithm.
>
> I see absolutely no reason to support regular lzo variant at this time.
> Everyone should use lz4 instead of lzo. If one wants zlib-level
> compression, they should use zstd.
>
> However, there's recent conversation on new lzo-rle and how it could
> be a better candidate than lz4.
>
> Since the mainline now have lz4, zstd and lzo-rle, I don't think
> supporting lzo is a good idea.
This is just RFC version, we can change it anytime, let's decide whether
deleting it before final version.
>
>> diff --git a/fs/f2fs/Kconfig b/fs/f2fs/Kconfig
>> index 652fd2e2b23d..c12854c3b1a1 100644
>> --- a/fs/f2fs/Kconfig
>> +++ b/fs/f2fs/Kconfig
>> @@ -6,6 +6,10 @@ config F2FS_FS
>> select CRYPTO
>> select CRYPTO_CRC32
>> select F2FS_FS_XATTR if FS_ENCRYPTION
>> + select LZO_COMPRESS
>> + select LZO_DECOMPRESS
>> + select LZ4_COMPRESS
>> + select LZ4_DECOMPRESS
>
> This is a bad idea.
> This unnecessarily increases kernel binary image when no the user
> intends to change the defaults.
>
> For example, my Android kernel doesn't use lzo anywhere and this
> wouldn't be welcome.
Agreed, maybe we need a kconfig entry for compress.c as well.
>
>> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
>> new file mode 100644
>> index 000000000000..f276d82a67aa
>> --- /dev/null
>> +++ b/fs/f2fs/compress.c
>> @@ -0,0 +1,1066 @@
>> +static unsigned int offset_in_cluster(struct compress_ctx *cc, pgoff_t
>> index)
>> +static unsigned int cluster_idx(struct compress_ctx *cc, pgoff_t index)
>> +static unsigned int start_idx_of_cluster(struct compress_ctx *cc)
>
> Looks like these would be better if they were explicitly marked as inline.
>
>> +static void f2fs_init_compress_ops(struct f2fs_sb_info *sbi)
>> +{
>> + sbi->cops[COMPRESS_LZO] = &f2fs_lzo_ops;
>> + sbi->cops[COMPRESS_LZ4] = &f2fs_lz4_ops;
>> +}
>
> Would it be possible for f2fs to use generic crypto compression APIs?
> Hardcoding for lzo/lz4 would make it harder to venture future different
> options.
>
> Have a look at mm/zswap.c:__zswap_pool_create_fallback().
Not sure, I think I could look into it later, now Jaegeuk and I have to
stabilize codes first.
Thanks for your advice anyway.
>
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index c681f51e351b..775c96291490 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -155,6 +163,7 @@ struct f2fs_mount_info {
>> #define F2FS_FEATURE_VERITY 0x0400
>> #define F2FS_FEATURE_SB_CHKSUM 0x0800
>> #define F2FS_FEATURE_CASEFOLD 0x1000
>> +#define F2FS_FEATURE_COMPRESSION 0x2000
>
> How would older versions of f2fs behave if an image was used by the
> latest f2fs and have compressed pages?
> I hope fail-safes are in place.
That patch haven't merged yet, since there is detailed implementation which is
under discussion.
Thanks,
>
> Thanks.
>
>> --
>> 2.19.0.605.g01d371f741-goog
>>
>>
>>
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> .
>
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