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Date:   Sat, 17 Sep 2022 11:56:01 +0800
From:   Yue Hu <zbestahu@gmail.com>
To:     Gao Xiang <hsiangkao@linux.alibaba.com>
Cc:     xiang@kernel.org, chao@kernel.org, linux-erofs@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, zhangwen@coolpad.com,
        shaojunjun@coolpad.com, Yue Hu <huyue2@coolpad.com>
Subject: Re: [RFC PATCH v4 2/2] erofs: support on-disk compressed fragments
 data
Message-ID: <20220917115601.00004eb5.zbestahu@gmail.com>
In-Reply-To: <YyQ9I5aJh/acVbjD@B-P7TQMD6M-0146.local>
References: <cover.1663066966.git.huyue2@coolpad.com>
        <6ded0c212d7da65b70c853fd04f21da229cdefb1.1663066966.git.huyue2@coolpad.com>
        <YyQ9I5aJh/acVbjD@B-P7TQMD6M-0146.local>
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On Fri, 16 Sep 2022 17:08:51 +0800
Gao Xiang <hsiangkao@linux.alibaba.com> wrote:

> On Tue, Sep 13, 2022 at 07:05:52PM +0800, Yue Hu wrote:
> > From: Yue Hu <huyue2@coolpad.com>
> > 
> > Introduce on-disk compressed fragments data feature.
> > 
> > This approach adds a new field called `h_fragmentoff' in the per-file
> > compression header to indicate the fragment offset of each tail pcluster
> > or the whole file in the special packed inode.
> > 
> > Similar to ztailpacking, it will also find and record the 'headlcn'
> > of the tail pcluster when initializing per-inode zmap for making
> > follow-on requests more easy.
> > 
> > Signed-off-by: Yue Hu <huyue2@coolpad.com>
> > ---
> >  fs/erofs/erofs_fs.h | 29 +++++++++++++++++++++------
> >  fs/erofs/internal.h | 16 ++++++++++++---
> >  fs/erofs/super.c    | 15 ++++++++++++++
> >  fs/erofs/sysfs.c    |  2 ++
> >  fs/erofs/zdata.c    | 48 ++++++++++++++++++++++++++++++++++++++++++++-
> >  fs/erofs/zmap.c     | 48 +++++++++++++++++++++++++++++++++++++++++++--
> >  6 files changed, 146 insertions(+), 12 deletions(-)
> > 
> > diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
> > index 5c1de6d7ad71..aa976757328b 100644
> > --- a/fs/erofs/erofs_fs.h
> > +++ b/fs/erofs/erofs_fs.h
> > @@ -25,6 +25,7 @@
> >  #define EROFS_FEATURE_INCOMPAT_DEVICE_TABLE	0x00000008
> >  #define EROFS_FEATURE_INCOMPAT_COMPR_HEAD2	0x00000008
> >  #define EROFS_FEATURE_INCOMPAT_ZTAILPACKING	0x00000010
> > +#define EROFS_FEATURE_INCOMPAT_FRAGMENTS	0x00000020
> >  #define EROFS_ALL_FEATURE_INCOMPAT		\
> >  	(EROFS_FEATURE_INCOMPAT_ZERO_PADDING | \
> >  	 EROFS_FEATURE_INCOMPAT_COMPR_CFGS | \
> > @@ -32,7 +33,8 @@
> >  	 EROFS_FEATURE_INCOMPAT_CHUNKED_FILE | \
> >  	 EROFS_FEATURE_INCOMPAT_DEVICE_TABLE | \
> >  	 EROFS_FEATURE_INCOMPAT_COMPR_HEAD2 | \
> > -	 EROFS_FEATURE_INCOMPAT_ZTAILPACKING)
> > +	 EROFS_FEATURE_INCOMPAT_ZTAILPACKING | \
> > +	 EROFS_FEATURE_INCOMPAT_FRAGMENTS)
> >  
> >  #define EROFS_SB_EXTSLOT_SIZE	16
> >  
> > @@ -71,7 +73,9 @@ struct erofs_super_block {
> >  	} __packed u1;
> >  	__le16 extra_devices;	/* # of devices besides the primary device */
> >  	__le16 devt_slotoff;	/* startoff = devt_slotoff * devt_slotsize */
> > -	__u8 reserved2[38];
> > +	__u8 reserved[6];
> > +	__le64 packed_nid;	/* nid of the special packed inode */
> > +	__u8 reserved2[24];
> >  };
> >  
> >  /*
> > @@ -296,17 +300,26 @@ struct z_erofs_lzma_cfgs {
> >   * bit 2 : HEAD2 big pcluster (0 - off; 1 - on)
> >   * bit 3 : tailpacking inline pcluster (0 - off; 1 - on)
> >   * bit 4 : interlaced plain pcluster (0 - off; 1 - on)
> > + * bit 5 : fragment pcluster (0 - off; 1 - on)
> >   */
> >  #define Z_EROFS_ADVISE_COMPACTED_2B		0x0001
> >  #define Z_EROFS_ADVISE_BIG_PCLUSTER_1		0x0002
> >  #define Z_EROFS_ADVISE_BIG_PCLUSTER_2		0x0004
> >  #define Z_EROFS_ADVISE_INLINE_PCLUSTER		0x0008
> >  #define Z_EROFS_ADVISE_INTERLACED_PCLUSTER	0x0010
> > +#define Z_EROFS_ADVISE_FRAGMENT_PCLUSTER	0x0020
> >  
> > +#define Z_EROFS_FRAGMENT_INODE_BIT              7
> >  struct z_erofs_map_header {
> > -	__le16	h_reserved1;
> > -	/* indicates the encoded size of tailpacking data */
> > -	__le16  h_idata_size;
> > +	union {
> > +		/* fragment data offset in the packed inode */
> > +		__le32  h_fragmentoff;
> > +		struct {
> > +			__le16  h_reserved1;
> > +			/* indicates the encoded size of tailpacking data */
> > +			__le16  h_idata_size;
> > +		};
> > +	};
> >  	__le16	h_advise;
> >  	/*
> >  	 * bit 0-3 : algorithm type of head 1 (logical cluster type 01);
> > @@ -315,7 +328,8 @@ struct z_erofs_map_header {
> >  	__u8	h_algorithmtype;
> >  	/*
> >  	 * bit 0-2 : logical cluster bits - 12, e.g. 0 for 4096;
> > -	 * bit 3-7 : reserved.
> > +	 * bit 3-6 : reserved;
> > +	 * bit 7   : move the whole file into packed inode or not.
> >  	 */
> >  	__u8	h_clusterbits;
> >  };
> > @@ -421,6 +435,9 @@ static inline void erofs_check_ondisk_layout_definitions(void)
> >  
> >  	BUILD_BUG_ON(BIT(Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS) <
> >  		     Z_EROFS_VLE_CLUSTER_TYPE_MAX - 1);
> > +	WARN_ON(*(__le64 *)&(struct z_erofs_map_header) {
> > +			.h_clusterbits = 1 << Z_EROFS_FRAGMENT_INODE_BIT
> > +		} != cpu_to_le64(1ULL << 63));  
> 
> why not BUILD_BUG_ON here?

There's compiling error, let me check further.

> 
> >  }
> >  
> >  #endif
> > diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> > index f3ed36445d73..b133664b4ad2 100644
> > --- a/fs/erofs/internal.h
> > +++ b/fs/erofs/internal.h
> > @@ -120,6 +120,7 @@ struct erofs_sb_info {
> >  	struct inode *managed_cache;
> >  
> >  	struct erofs_sb_lz4_info lz4;
> > +	struct inode *packed_inode;
> >  #endif	/* CONFIG_EROFS_FS_ZIP */
> >  	struct erofs_dev_context *devs;
> >  	struct dax_device *dax_dev;
> > @@ -306,6 +307,7 @@ EROFS_FEATURE_FUNCS(chunked_file, incompat, INCOMPAT_CHUNKED_FILE)
> >  EROFS_FEATURE_FUNCS(device_table, incompat, INCOMPAT_DEVICE_TABLE)
> >  EROFS_FEATURE_FUNCS(compr_head2, incompat, INCOMPAT_COMPR_HEAD2)
> >  EROFS_FEATURE_FUNCS(ztailpacking, incompat, INCOMPAT_ZTAILPACKING)
> > +EROFS_FEATURE_FUNCS(fragments, incompat, INCOMPAT_FRAGMENTS)
> >  EROFS_FEATURE_FUNCS(sb_chksum, compat, COMPAT_SB_CHKSUM)
> >  
> >  /* atomic flag definitions */
> > @@ -341,8 +343,13 @@ struct erofs_inode {
> >  			unsigned char  z_algorithmtype[2];
> >  			unsigned char  z_logical_clusterbits;
> >  			unsigned long  z_tailextent_headlcn;
> > -			erofs_off_t    z_idataoff;
> > -			unsigned short z_idata_size;
> > +			union {
> > +				struct {
> > +					erofs_off_t    z_idataoff;
> > +					unsigned short z_idata_size;
> > +				};
> > +				erofs_off_t z_fragmentoff;
> > +			};
> >  		};
> >  #endif	/* CONFIG_EROFS_FS_ZIP */
> >  	};
> > @@ -400,6 +407,7 @@ extern const struct address_space_operations z_erofs_aops;
> >  enum {
> >  	BH_Encoded = BH_PrivateStart,
> >  	BH_FullMapped,
> > +	BH_Fragment,
> >  };
> >  
> >  /* Has a disk mapping */
> > @@ -410,6 +418,8 @@ enum {
> >  #define EROFS_MAP_ENCODED	(1 << BH_Encoded)
> >  /* The length of extent is full */
> >  #define EROFS_MAP_FULL_MAPPED	(1 << BH_FullMapped)
> > +/* Located in the special packed inode */
> > +#define EROFS_MAP_FRAGMENT	(1 << BH_Fragment)
> >  
> >  struct erofs_map_blocks {
> >  	struct erofs_buf buf;
> > @@ -431,7 +441,7 @@ struct erofs_map_blocks {
> >  #define EROFS_GET_BLOCKS_FIEMAP	0x0002
> >  /* Used to map the whole extent if non-negligible data is requested for LZMA */
> >  #define EROFS_GET_BLOCKS_READMORE	0x0004
> > -/* Used to map tail extent for tailpacking inline pcluster */
> > +/* Used to map tail extent for tailpacking inline or fragment pcluster */
> >  #define EROFS_GET_BLOCKS_FINDTAIL	0x0008
> >  
> >  enum {
> > diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> > index 3173debeaa5a..8170c0d8ab92 100644
> > --- a/fs/erofs/super.c
> > +++ b/fs/erofs/super.c
> > @@ -381,6 +381,17 @@ static int erofs_read_superblock(struct super_block *sb)
> >  #endif
> >  	sbi->islotbits = ilog2(sizeof(struct erofs_inode_compact));
> >  	sbi->root_nid = le16_to_cpu(dsb->root_nid);
> > +#ifdef CONFIG_EROFS_FS_ZIP
> > +	sbi->packed_inode = NULL;
> > +	if (erofs_sb_has_fragments(sbi)) {
> > +		sbi->packed_inode =
> > +			erofs_iget(sb, le64_to_cpu(dsb->packed_nid), false);
> > +		if (IS_ERR(sbi->packed_inode)) {
> > +			ret = PTR_ERR(sbi->packed_inode);
> > +			goto out;
> > +		}
> > +	}
> > +#endif
> >  	sbi->inos = le64_to_cpu(dsb->inos);
> >  
> >  	sbi->build_time = le64_to_cpu(dsb->build_time);
> > @@ -411,6 +422,8 @@ static int erofs_read_superblock(struct super_block *sb)
> >  		erofs_info(sb, "EXPERIMENTAL compressed inline data feature in use. Use at your own risk!");
> >  	if (erofs_is_fscache_mode(sb))
> >  		erofs_info(sb, "EXPERIMENTAL fscache-based on-demand read feature in use. Use at your own risk!");
> > +	if (erofs_sb_has_fragments(sbi))
> > +		erofs_info(sb, "EXPERIMENTAL compressed fragments feature in use. Use at your own risk!");
> >  out:
> >  	erofs_put_metabuf(&buf);
> >  	return ret;
> > @@ -908,6 +921,8 @@ static void erofs_put_super(struct super_block *sb)
> >  #ifdef CONFIG_EROFS_FS_ZIP
> >  	iput(sbi->managed_cache);
> >  	sbi->managed_cache = NULL;
> > +	iput(sbi->packed_inode);
> > +	sbi->packed_inode = NULL;
> >  #endif
> >  	erofs_fscache_unregister_cookie(&sbi->s_fscache);
> >  }
> > diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> > index c1383e508bbe..1b52395be82a 100644
> > --- a/fs/erofs/sysfs.c
> > +++ b/fs/erofs/sysfs.c
> > @@ -76,6 +76,7 @@ EROFS_ATTR_FEATURE(device_table);
> >  EROFS_ATTR_FEATURE(compr_head2);
> >  EROFS_ATTR_FEATURE(sb_chksum);
> >  EROFS_ATTR_FEATURE(ztailpacking);
> > +EROFS_ATTR_FEATURE(fragments);
> >  
> >  static struct attribute *erofs_feat_attrs[] = {
> >  	ATTR_LIST(zero_padding),
> > @@ -86,6 +87,7 @@ static struct attribute *erofs_feat_attrs[] = {
> >  	ATTR_LIST(compr_head2),
> >  	ATTR_LIST(sb_chksum),
> >  	ATTR_LIST(ztailpacking),
> > +	ATTR_LIST(fragments),
> >  	NULL,
> >  };
> >  ATTRIBUTE_GROUPS(erofs_feat);
> > diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> > index 5792ca9e0d5e..aa2a3cdeea57 100644
> > --- a/fs/erofs/zdata.c
> > +++ b/fs/erofs/zdata.c
> > @@ -650,6 +650,33 @@ static bool should_alloc_managed_pages(struct z_erofs_decompress_frontend *fe,
> >  		la < fe->headoffset;
> >  }
> >  
> > +static int z_erofs_read_fragment(struct inode *inode, erofs_off_t pos,
> > +				 struct page *page, unsigned int pageofs,
> > +				 unsigned int len)
> > +{
> > +	struct inode *packed_inode = EROFS_I_SB(inode)->packed_inode;
> > +	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
> > +	u8 *src, *dst;
> > +	unsigned int i, cnt;
> > +
> > +	pos += EROFS_I(inode)->z_fragmentoff;
> > +	for (i = 0; i < len; i += cnt) {
> > +		cnt = min_t(unsigned int, len - i,
> > +			    EROFS_BLKSIZ - erofs_blkoff(pos));
> > +		src = erofs_bread(&buf, packed_inode,
> > +				  erofs_blknr(pos), EROFS_KMAP);
> > +		if (IS_ERR(src))  
> 
> 			^
> 			need to erofs_put_metabuf() here anyway?

rt, need it.

Thanks.

> 
> > +			return PTR_ERR(src);
> > +
> > +		dst = kmap_local_page(page);
> > +		memcpy(dst + pageofs + i, src + erofs_blkoff(pos), cnt);
> > +		kunmap_local(dst);
> > +		pos += cnt;
> > +	}
> > +	erofs_put_metabuf(&buf);
> > +	return 0;
> > +}  
> 
> Thanks,
> Gao Xiang