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erofs: implement encoded extent metadata
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Implement the extent metadata parsing described in the previous commit.
For 16-byte and 32-byte extent records, currently it is just a trivial
binary search without considering the last access footprint, but it can
be optimized for better sequential performance later.

Tail fragments are supported, but ztailpacking feature is not
for simplicity.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Acked-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20250310095459.2620647-9-hsiangkao@linux.alibaba.com
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Gao Xiang committed Mar 17, 2025
1 parent efb2aef commit 1d191b4
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Showing 2 changed files with 135 additions and 12 deletions.
5 changes: 4 additions & 1 deletion fs/erofs/internal.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -263,7 +263,10 @@ struct erofs_inode {
unsigned short z_advise;
unsigned char z_algorithmtype[2];
unsigned char z_lclusterbits;
unsigned long z_tailextent_headlcn;
union {
u64 z_tailextent_headlcn;
u64 z_extents;
};
erofs_off_t z_fragmentoff;
unsigned short z_idata_size;
};
Expand Down
142 changes: 131 additions & 11 deletions fs/erofs/zmap.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -391,7 +391,7 @@ static int z_erofs_get_extent_decompressedlen(struct z_erofs_maprecorder *m)
return 0;
}

static int z_erofs_do_map_blocks(struct inode *inode,
static int z_erofs_map_blocks_fo(struct inode *inode,
struct erofs_map_blocks *map, int flags)
{
struct erofs_inode *vi = EROFS_I(inode);
Expand All @@ -409,6 +409,14 @@ static int z_erofs_do_map_blocks(struct inode *inode,
unsigned long long ofs, end;

ofs = flags & EROFS_GET_BLOCKS_FINDTAIL ? inode->i_size - 1 : map->m_la;
if (fragment && !(flags & EROFS_GET_BLOCKS_FINDTAIL) &&
!vi->z_tailextent_headlcn) {
map->m_la = 0;
map->m_llen = inode->i_size;
map->m_flags = EROFS_MAP_MAPPED |
EROFS_MAP_FULL_MAPPED | EROFS_MAP_FRAGMENT;
return 0;
}
initial_lcn = ofs >> lclusterbits;
endoff = ofs & ((1 << lclusterbits) - 1);

Expand Down Expand Up @@ -526,6 +534,115 @@ static int z_erofs_do_map_blocks(struct inode *inode,
return err;
}

static int z_erofs_map_blocks_ext(struct inode *inode,
struct erofs_map_blocks *map, int flags)
{
struct erofs_inode *vi = EROFS_I(inode);
struct super_block *sb = inode->i_sb;
bool interlaced = vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER;
unsigned int recsz = z_erofs_extent_recsize(vi->z_advise);
erofs_off_t pos = round_up(Z_EROFS_MAP_HEADER_END(erofs_iloc(inode) +
vi->inode_isize + vi->xattr_isize), recsz);
erofs_off_t lend = inode->i_size;
erofs_off_t l, r, mid, pa, la, lstart;
struct z_erofs_extent *ext;
unsigned int fmt;
bool last;

map->m_flags = 0;
if (recsz <= offsetof(struct z_erofs_extent, pstart_hi)) {
if (recsz <= offsetof(struct z_erofs_extent, pstart_lo)) {
ext = erofs_read_metabuf(&map->buf, sb, pos, true);
if (IS_ERR(ext))
return PTR_ERR(ext);
pa = le64_to_cpu(*(__le64 *)ext);
pos += sizeof(__le64);
lstart = 0;
} else {
lstart = map->m_la >> vi->z_lclusterbits;
pa = EROFS_NULL_ADDR;
}

for (; lstart <= map->m_la; lstart += 1 << vi->z_lclusterbits) {
ext = erofs_read_metabuf(&map->buf, sb, pos, true);
if (IS_ERR(ext))
return PTR_ERR(ext);
map->m_plen = le32_to_cpu(ext->plen);
if (pa != EROFS_NULL_ADDR) {
map->m_pa = pa;
pa += map->m_plen & Z_EROFS_EXTENT_PLEN_MASK;
} else {
map->m_pa = le32_to_cpu(ext->pstart_lo);
}
pos += recsz;
}
last = (lstart >= round_up(lend, 1 << vi->z_lclusterbits));
lend = min(lstart, lend);
lstart -= 1 << vi->z_lclusterbits;
} else {
lstart = lend;
for (l = 0, r = vi->z_extents; l < r; ) {
mid = l + (r - l) / 2;
ext = erofs_read_metabuf(&map->buf, sb,
pos + mid * recsz, true);
if (IS_ERR(ext))
return PTR_ERR(ext);

la = le32_to_cpu(ext->lstart_lo);
pa = le32_to_cpu(ext->pstart_lo) |
(u64)le32_to_cpu(ext->pstart_hi) << 32;
if (recsz > offsetof(struct z_erofs_extent, lstart_hi))
la |= (u64)le32_to_cpu(ext->lstart_hi) << 32;

if (la > map->m_la) {
r = mid;
lend = la;
} else {
l = mid + 1;
if (map->m_la == la)
r = min(l + 1, r);
lstart = la;
map->m_plen = le32_to_cpu(ext->plen);
map->m_pa = pa;
}
}
last = (l >= vi->z_extents);
}

if (lstart < lend) {
map->m_la = lstart;
if (last && (vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER)) {
map->m_flags |= EROFS_MAP_MAPPED | EROFS_MAP_FRAGMENT;
vi->z_fragmentoff = map->m_plen;
if (recsz >= offsetof(struct z_erofs_extent, pstart_lo))
vi->z_fragmentoff |= map->m_pa << 32;
} else if (map->m_plen) {
map->m_flags |= EROFS_MAP_MAPPED |
EROFS_MAP_FULL_MAPPED | EROFS_MAP_ENCODED;
fmt = map->m_plen >> Z_EROFS_EXTENT_PLEN_FMT_BIT;
if (fmt)
map->m_algorithmformat = fmt - 1;
else if (interlaced && !erofs_blkoff(sb, map->m_pa))
map->m_algorithmformat =
Z_EROFS_COMPRESSION_INTERLACED;
else
map->m_algorithmformat =
Z_EROFS_COMPRESSION_SHIFTED;
if (map->m_plen & Z_EROFS_EXTENT_PLEN_PARTIAL)
map->m_flags |= EROFS_MAP_PARTIAL_REF;
map->m_plen &= Z_EROFS_EXTENT_PLEN_MASK;
}
}
map->m_llen = lend - map->m_la;
if (!last && map->m_llen < sb->s_blocksize) {
erofs_err(sb, "extent too small %llu @ offset %llu of nid %llu",
map->m_llen, map->m_la, vi->nid);
DBG_BUGON(1);
return -EFSCORRUPTED;
}
return 0;
}

static int z_erofs_fill_inode_lazy(struct inode *inode)
{
struct erofs_inode *const vi = EROFS_I(inode);
Expand Down Expand Up @@ -570,6 +687,13 @@ static int z_erofs_fill_inode_lazy(struct inode *inode)
}
vi->z_advise = le16_to_cpu(h->h_advise);
vi->z_lclusterbits = sb->s_blocksize_bits + (h->h_clusterbits & 15);
if (vi->datalayout == EROFS_INODE_COMPRESSED_FULL &&
(vi->z_advise & Z_EROFS_ADVISE_EXTENTS)) {
vi->z_extents = le32_to_cpu(h->h_extents_lo) |
((u64)le16_to_cpu(h->h_extents_hi) << 32);
goto done;
}

vi->z_algorithmtype[0] = h->h_algorithmtype & 15;
vi->z_algorithmtype[1] = h->h_algorithmtype >> 4;
if (vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER)
Expand Down Expand Up @@ -609,7 +733,7 @@ static int z_erofs_fill_inode_lazy(struct inode *inode)
.buf = __EROFS_BUF_INITIALIZER
};

err = z_erofs_do_map_blocks(inode, &map,
err = z_erofs_map_blocks_fo(inode, &map,
EROFS_GET_BLOCKS_FINDTAIL);
erofs_put_metabuf(&map.buf);
if (err < 0)
Expand Down Expand Up @@ -640,15 +764,11 @@ int z_erofs_map_blocks_iter(struct inode *inode, struct erofs_map_blocks *map,
} else {
err = z_erofs_fill_inode_lazy(inode);
if (!err) {
if ((vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER) &&
!vi->z_tailextent_headlcn) {
map->m_la = 0;
map->m_llen = inode->i_size;
map->m_flags = EROFS_MAP_MAPPED |
EROFS_MAP_FULL_MAPPED | EROFS_MAP_FRAGMENT;
} else {
err = z_erofs_do_map_blocks(inode, map, flags);
}
if (vi->datalayout == EROFS_INODE_COMPRESSED_FULL &&
(vi->z_advise & Z_EROFS_ADVISE_EXTENTS))
err = z_erofs_map_blocks_ext(inode, map, flags);
else
err = z_erofs_map_blocks_fo(inode, map, flags);
}
if (!err && (map->m_flags & EROFS_MAP_ENCODED) &&
unlikely(map->m_plen > Z_EROFS_PCLUSTER_MAX_SIZE ||
Expand Down

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