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Subject[PATCH v3 1/8] staging: erofs: add compacted ondisk compression indexes
Date
From: Gao Xiang <gaoxiang25@huawei.com>

This patch introduces new compacted compression indexes.

In contract to legacy compression indexes that
each 4k logical cluster has an 8-byte index,
compacted ondisk compression indexes will have
amortized 2 bytes for each 4k logical cluster (compacted 2B)
amortized 4 bytes for each 4k logical cluster (compacted 4B)

In detail, several continuous clusters will be encoded in
a compacted pack with cluster types, offsets, and one blkaddr
at the end of the pack to leave 4-byte margin for better
decoding performance, as illustrated below:
_____________________________________________
|___@_____ encoded bits __________|_ blkaddr _|
0 . amortized * vcnt
. .
. . amortized * vcnt - 4
. .
.___________________.
|_type_|_clusterofs_|

Note that compacted 2 / 4B should be aligned with 32 / 8 bytes
in order to avoid each pack crossing page boundary.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
change log v3:
- wrap up offset for better readability pointed out by Chao.

drivers/staging/erofs/data.c | 4 +-
drivers/staging/erofs/erofs_fs.h | 65 ++++++++++++++++++++++++-------
drivers/staging/erofs/inode.c | 5 +--
drivers/staging/erofs/internal.h | 11 ++----
drivers/staging/erofs/unzip_vle.c | 8 ++--
5 files changed, 62 insertions(+), 31 deletions(-)

diff --git a/drivers/staging/erofs/data.c b/drivers/staging/erofs/data.c
index 746685f90564..cc31c3e5984c 100644
--- a/drivers/staging/erofs/data.c
+++ b/drivers/staging/erofs/data.c
@@ -124,7 +124,7 @@ static int erofs_map_blocks_flatmode(struct inode *inode,
trace_erofs_map_blocks_flatmode_enter(inode, map, flags);

nblocks = DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
- lastblk = nblocks - is_inode_layout_inline(inode);
+ lastblk = nblocks - is_inode_flat_inline(inode);

if (unlikely(offset >= inode->i_size)) {
/* leave out-of-bound access unmapped */
@@ -139,7 +139,7 @@ static int erofs_map_blocks_flatmode(struct inode *inode,
if (offset < blknr_to_addr(lastblk)) {
map->m_pa = blknr_to_addr(vi->raw_blkaddr) + map->m_la;
map->m_plen = blknr_to_addr(lastblk) - offset;
- } else if (is_inode_layout_inline(inode)) {
+ } else if (is_inode_flat_inline(inode)) {
/* 2 - inode inline B: inode, [xattrs], inline last blk... */
struct erofs_sb_info *sbi = EROFS_SB(inode->i_sb);

diff --git a/drivers/staging/erofs/erofs_fs.h b/drivers/staging/erofs/erofs_fs.h
index 8ddb2b3e7d39..9a9aaf2d9fbb 100644
--- a/drivers/staging/erofs/erofs_fs.h
+++ b/drivers/staging/erofs/erofs_fs.h
@@ -49,19 +49,29 @@ struct erofs_super_block {
* erofs inode data mapping:
* 0 - inode plain without inline data A:
* inode, [xattrs], ... | ... | no-holed data
- * 1 - inode VLE compression B:
+ * 1 - inode VLE compression B (legacy):
* inode, [xattrs], extents ... | ...
* 2 - inode plain with inline data C:
* inode, [xattrs], last_inline_data, ... | ... | no-holed data
- * 3~7 - reserved
+ * 3 - inode compression D:
+ * inode, [xattrs], map_header, extents ... | ...
+ * 4~7 - reserved
*/
enum {
- EROFS_INODE_LAYOUT_PLAIN,
- EROFS_INODE_LAYOUT_COMPRESSION,
- EROFS_INODE_LAYOUT_INLINE,
+ EROFS_INODE_FLAT_PLAIN,
+ EROFS_INODE_FLAT_COMPRESSION_LEGACY,
+ EROFS_INODE_FLAT_INLINE,
+ EROFS_INODE_FLAT_COMPRESSION,
EROFS_INODE_LAYOUT_MAX
};

+static bool erofs_inode_is_data_compressed(unsigned int datamode)
+{
+ if (datamode == EROFS_INODE_FLAT_COMPRESSION)
+ return true;
+ return datamode == EROFS_INODE_FLAT_COMPRESSION_LEGACY;
+}
+
/* bit definitions of inode i_advise */
#define EROFS_I_VERSION_BITS 1
#define EROFS_I_DATA_MAPPING_BITS 3
@@ -176,11 +186,39 @@ struct erofs_xattr_entry {
sizeof(struct erofs_xattr_entry) + \
(entry)->e_name_len + le16_to_cpu((entry)->e_value_size))

-/* have to be aligned with 8 bytes on disk */
-struct erofs_extent_header {
- __le32 eh_checksum;
- __le32 eh_reserved[3];
-} __packed;
+/* available compression algorithm types */
+enum {
+ Z_EROFS_COMPRESSION_LZ4,
+ Z_EROFS_COMPRESSION_MAX
+};
+
+/*
+ * bit 0 : COMPACTED_2B indexes (0 - off; 1 - on)
+ * e.g. for 4k logical cluster size, 4B if compacted 2B is off;
+ * (4B) + 2B + (4B) if compacted 2B is on.
+ */
+#define Z_EROFS_ADVISE_COMPACTED_2B_BIT 0
+
+#define Z_EROFS_ADVISE_COMPACTED_2B (1 << Z_EROFS_ADVISE_COMPACTED_2B_BIT)
+
+struct z_erofs_map_header {
+ __le32 h_reserved1;
+ __le16 h_advise;
+ /*
+ * bit 0-3 : algorithm type of head 1 (logical cluster type 01);
+ * bit 4-7 : algorithm type of head 2 (logical cluster type 11).
+ */
+ __u8 h_algorithmtype;
+ /*
+ * bit 0-2 : logical cluster bits - 12, e.g. 0 for 4096;
+ * bit 3-4 : (physical - logical) cluster bits of head 1:
+ * For example, if logical clustersize = 4096, 1 for 8192.
+ * bit 5-7 : (physical - logical) cluster bits of head 2.
+ */
+ __u8 h_clusterbits;
+};
+
+#define Z_EROFS_VLE_LEGACY_HEADER_PADDING 8

/*
* Z_EROFS Variable-sized Logical Extent cluster type:
@@ -236,8 +274,9 @@ struct z_erofs_vle_decompressed_index {
} di_u __packed; /* 8 bytes */
} __packed;

-#define Z_EROFS_VLE_EXTENT_ALIGN(size) round_up(size, \
- sizeof(struct z_erofs_vle_decompressed_index))
+#define Z_EROFS_VLE_LEGACY_INDEX_ALIGN(size) \
+ (round_up(size, sizeof(struct z_erofs_vle_decompressed_index)) + \
+ sizeof(struct z_erofs_map_header) + Z_EROFS_VLE_LEGACY_HEADER_PADDING)

/* dirent sorts in alphabet order, thus we can do binary search */
struct erofs_dirent {
@@ -270,7 +309,7 @@ static inline void erofs_check_ondisk_layout_definitions(void)
BUILD_BUG_ON(sizeof(struct erofs_inode_v2) != 64);
BUILD_BUG_ON(sizeof(struct erofs_xattr_ibody_header) != 12);
BUILD_BUG_ON(sizeof(struct erofs_xattr_entry) != 4);
- BUILD_BUG_ON(sizeof(struct erofs_extent_header) != 16);
+ BUILD_BUG_ON(sizeof(struct z_erofs_map_header) != 8);
BUILD_BUG_ON(sizeof(struct z_erofs_vle_decompressed_index) != 8);
BUILD_BUG_ON(sizeof(struct erofs_dirent) != 12);

diff --git a/drivers/staging/erofs/inode.c b/drivers/staging/erofs/inode.c
index e51348f7e838..3539290b8e45 100644
--- a/drivers/staging/erofs/inode.c
+++ b/drivers/staging/erofs/inode.c
@@ -127,12 +127,9 @@ static int fill_inline_data(struct inode *inode, void *data,
{
struct erofs_vnode *vi = EROFS_V(inode);
struct erofs_sb_info *sbi = EROFS_I_SB(inode);
- const int mode = vi->datamode;
-
- DBG_BUGON(mode >= EROFS_INODE_LAYOUT_MAX);

/* should be inode inline C */
- if (mode != EROFS_INODE_LAYOUT_INLINE)
+ if (!is_inode_flat_inline(inode))
return 0;

/* fast symlink (following ext4) */
diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h
index 1666cceecb3c..c851d0be6cf6 100644
--- a/drivers/staging/erofs/internal.h
+++ b/drivers/staging/erofs/internal.h
@@ -382,19 +382,14 @@ static inline unsigned long inode_datablocks(struct inode *inode)
return DIV_ROUND_UP(inode->i_size, EROFS_BLKSIZ);
}

-static inline bool is_inode_layout_plain(struct inode *inode)
-{
- return EROFS_V(inode)->datamode == EROFS_INODE_LAYOUT_PLAIN;
-}
-
static inline bool is_inode_layout_compression(struct inode *inode)
{
- return EROFS_V(inode)->datamode == EROFS_INODE_LAYOUT_COMPRESSION;
+ return erofs_inode_is_data_compressed(EROFS_V(inode)->datamode);
}

-static inline bool is_inode_layout_inline(struct inode *inode)
+static inline bool is_inode_flat_inline(struct inode *inode)
{
- return EROFS_V(inode)->datamode == EROFS_INODE_LAYOUT_INLINE;
+ return EROFS_V(inode)->datamode == EROFS_INODE_FLAT_INLINE;
}

extern const struct super_operations erofs_sops;
diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
index f3d0d2c03939..ae62293d5a82 100644
--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -1642,8 +1642,8 @@ vle_extent_blkaddr(struct inode *inode, pgoff_t index)
struct erofs_sb_info *sbi = EROFS_I_SB(inode);
struct erofs_vnode *vi = EROFS_V(inode);

- unsigned int ofs = Z_EROFS_VLE_EXTENT_ALIGN(vi->inode_isize +
- vi->xattr_isize) + sizeof(struct erofs_extent_header) +
+ unsigned int ofs = Z_EROFS_VLE_LEGACY_INDEX_ALIGN(vi->inode_isize +
+ vi->xattr_isize) +
index * sizeof(struct z_erofs_vle_decompressed_index);

return erofs_blknr(iloc(sbi, vi->nid) + ofs);
@@ -1655,8 +1655,8 @@ vle_extent_blkoff(struct inode *inode, pgoff_t index)
struct erofs_sb_info *sbi = EROFS_I_SB(inode);
struct erofs_vnode *vi = EROFS_V(inode);

- unsigned int ofs = Z_EROFS_VLE_EXTENT_ALIGN(vi->inode_isize +
- vi->xattr_isize) + sizeof(struct erofs_extent_header) +
+ unsigned int ofs = Z_EROFS_VLE_LEGACY_INDEX_ALIGN(vi->inode_isize +
+ vi->xattr_isize) +
index * sizeof(struct z_erofs_vle_decompressed_index);

return erofs_blkoff(iloc(sbi, vi->nid) + ofs);
--
2.17.1
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