Re: [RFC PATCH 2/2] erofs: add on-disk compressed fragments support

From: Gao Xiang
Date: Wed Aug 24 2022 - 23:25:11 EST

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Hi Yue,

On Mon, Aug 22, 2022 at 01:53:01PM +0800, Yue Hu wrote:
> From: Yue Hu <huyue2@xxxxxxxxxxx>
>
> Introduce on-disk compressed fragments 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.
>
> Like 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.
>
> Moreover, enable the offset for shifted decompression since we are
> writing from 'pageofs_ofs' when compressing if this feature is used.
>
> Signed-off-by: Yue Hu <huyue2@xxxxxxxxxxx>
> ---
> fs/erofs/decompressor.c | 4 +--
> fs/erofs/erofs_fs.h | 26 ++++++++++++++-----
> fs/erofs/internal.h | 16 +++++++++---
> fs/erofs/super.c | 6 +++++
> fs/erofs/sysfs.c | 2 ++
> fs/erofs/zdata.c | 55 ++++++++++++++++++++++++++++++++++++++++-
> fs/erofs/zmap.c | 40 +++++++++++++++++++++++++++---
> 7 files changed, 133 insertions(+), 16 deletions(-)
>
> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> index dc02d95b52d7..fe4a34ac2de7 100644
> --- a/fs/erofs/decompressor.c
> +++ b/fs/erofs/decompressor.c
> @@ -338,8 +338,8 @@ static int z_erofs_shifted_transform(struct z_erofs_decompress_req *rq,
> return 0;
> }
>
> - /* set it to pageofs_out if fragments feature is used */
> - headofs_in = 0;
> + headofs_in = !erofs_sb_has_fragments(EROFS_SB(rq->sb)) ? 0 :

Same as I pointed out in the erofs-utils series.

> + rq->pageofs_out;
>
> src = kmap_atomic(*rq->in) + rq->pageofs_in;
> if (rq->out[0]) {
> diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
> index 2b48373f690b..3306cca5f03b 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];
> };
>
> /*
> @@ -295,16 +299,25 @@ struct z_erofs_lzma_cfgs {
> * bit 1 : HEAD1 big pcluster (0 - off; 1 - on)
> * bit 2 : HEAD2 big pcluster (0 - off; 1 - on)
> * bit 3 : tailpacking inline pcluster (0 - off; 1 - on)
> + * bit 4 : 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_FRAGMENT_PCLUSTER 0x0010
>
> +#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 {
> + /* direct addressing for fragment offset */
> + __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);
> @@ -313,7 +326,8 @@ 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;
> };
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index cfee49d33b95..7b9d31bab928 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..fde5ece36b2c 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -381,6 +381,8 @@ 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);
> + sbi->packed_inode = erofs_sb_has_fragments(sbi) ?
> + erofs_iget(sb, le64_to_cpu(dsb->packed_nid), false) : NULL;

iget could fail, what will we do next in such case?

> sbi->inos = le64_to_cpu(dsb->inos);
>
> sbi->build_time = le64_to_cpu(dsb->build_time);
> @@ -411,6 +413,8 @@ 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 +912,8 @@ 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..3dd3b829766f 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_data(struct page *page, unsigned int pageofs,
> + loff_t start, unsigned int len)
> +{
> + struct inode *const inode = page->mapping->host;
> + erofs_off_t offset = EROFS_I(inode)->z_fragmentoff + start;
> + struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
> + u8 *src, *dst;
> + unsigned int i, cnt;
> +
> + for (i = 0; i < len; i += cnt) {
> + cnt = min(EROFS_BLKSIZ - (unsigned int)erofs_blkoff(offset),
> + len - i);
> + src = erofs_bread(&buf, EROFS_I_SB(inode)->packed_inode,
> + erofs_blknr(offset), EROFS_KMAP);
> + if (IS_ERR(src))
> + return PTR_ERR(src);
> +
> + dst = kmap_atomic(page);
> + memcpy(dst + pageofs + i, src + erofs_blkoff(offset), cnt);
> + kunmap_atomic(dst);

Use kmap_local_page instead.

> +
> + offset += cnt;
> + }
> + erofs_put_metabuf(&buf);
> + return 0;
> +}
> +
> static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
> struct page *page, struct page **pagepool)
> {
> @@ -688,7 +715,8 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
> /* didn't get a valid pcluster previously (very rare) */
> }
>
> - if (!(map->m_flags & EROFS_MAP_MAPPED))
> + if (!(map->m_flags & EROFS_MAP_MAPPED) ||
> + map->m_flags & EROFS_MAP_FRAGMENT)
> goto hitted;
>
> err = z_erofs_collector_begin(fe);
> @@ -735,6 +763,31 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
> zero_user_segment(page, cur, end);
> goto next_part;
> }
> + if (map->m_flags & EROFS_MAP_FRAGMENT) {
> + unsigned int pageofs, skip, len;
> +
> + if (!map->m_la) {
> + len = (offset + cur + 1 == inode->i_size) ? (cur + 1) :
> + end;
> + err = z_erofs_read_fragment_data(page, 0, offset, len);
> + goto out;
> + }
> + if (map->m_la < offset) {
> + pageofs = 0;
> + skip = offset - map->m_la;
> + } else {
> + pageofs = map->m_la & ~PAGE_MASK;
> + skip = 0;
> + }
> + DBG_BUGON(map->m_llen - skip > PAGE_SIZE);

len = min(map->m_llen - skip, end - cur)?

> + err = z_erofs_read_fragment_data(page, pageofs, skip,
> + map->m_llen - skip);

len); ?

Thanks,
Gao Xiang

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