[PATCH 6.6 034/322] erofs: fix up compacted indexes for block size < 4096

Greg Kroah-Hartman
2024-02-03T04:11:42Z

From: Gao Xiang <hsiangkao@linux.alibaba.com>

[ Upstream commit 8d2517aaeea3ab8651bb517bca8f3c8664d318ea ]

Previously, the block size always equaled to PAGE_SIZE, therefore
`lclusterbits` couldn't be less than 12.

Since sub-page compressed blocks are now considered, `lobits` for
a lcluster in each pack cannot always be `lclusterbits` as before.
Otherwise, there is no enough room for the special value
`Z_EROFS_LI_D0_CBLKCNT`.

To support smaller block sizes, `lobits` for each compacted lcluster is
now calculated as:
lobits = max(lclusterbits, ilog2(Z_EROFS_LI_D0_CBLKCNT) + 1)

Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20231206091057.87027-4-hsiangkao@linux.alibaba.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/erofs/zmap.c | 32 ++++++++++++++------------------
1 file changed, 14 insertions(+), 18 deletions(-)

diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index 7a1a24ae4a2d..e313c936351d 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -82,29 +82,26 @@ static int z_erofs_load_full_lcluster(struct z_erofs_maprecorder *m,
}

static unsigned int decode_compactedbits(unsigned int lobits,
- unsigned int lomask,
u8 *in, unsigned int pos, u8 *type)
{
const unsigned int v = get_unaligned_le32(in + pos / 8) >> (pos & 7);
- const unsigned int lo = v & lomask;
+ const unsigned int lo = v & ((1 << lobits) - 1);

*type = (v >> lobits) & 3;
return lo;
}

-static int get_compacted_la_distance(unsigned int lclusterbits,
+static int get_compacted_la_distance(unsigned int lobits,
unsigned int encodebits,
unsigned int vcnt, u8 *in, int i)
{
- const unsigned int lomask = (1 << lclusterbits) - 1;
unsigned int lo, d1 = 0;
u8 type;

DBG_BUGON(i >= vcnt);

do {
- lo = decode_compactedbits(lclusterbits, lomask,
- in, encodebits * i, &type);
+ lo = decode_compactedbits(lobits, in, encodebits * i, &type);

if (type != Z_EROFS_LCLUSTER_TYPE_NONHEAD)
return d1;
@@ -123,15 +120,14 @@ static int unpack_compacted_index(struct z_erofs_maprecorder *m,
{
struct erofs_inode *const vi = EROFS_I(m->inode);
const unsigned int lclusterbits = vi->z_logical_clusterbits;
- const unsigned int lomask = (1 << lclusterbits) - 1;
- unsigned int vcnt, base, lo, encodebits, nblk, eofs;
+ unsigned int vcnt, base, lo, lobits, encodebits, nblk, eofs;
int i;
u8 *in, type;
bool big_pcluster;

if (1 << amortizedshift == 4 && lclusterbits <= 14)
vcnt = 2;
- else if (1 << amortizedshift == 2 && lclusterbits == 12)
+ else if (1 << amortizedshift == 2 && lclusterbits <= 12)
vcnt = 16;
else
return -EOPNOTSUPP;
@@ -140,6 +136,7 @@ static int unpack_compacted_index(struct z_erofs_maprecorder *m,
m->nextpackoff = round_down(pos, vcnt << amortizedshift) +
(vcnt << amortizedshift);
big_pcluster = vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1;
+ lobits = max(lclusterbits, ilog2(Z_EROFS_LI_D0_CBLKCNT) + 1U);
encodebits = ((vcnt << amortizedshift) - sizeof(__le32)) * 8 / vcnt;
eofs = erofs_blkoff(m->inode->i_sb, pos);
base = round_down(eofs, vcnt << amortizedshift);
@@ -147,15 +144,14 @@ static int unpack_compacted_index(struct z_erofs_maprecorder *m,

i = (eofs - base) >> amortizedshift;

- lo = decode_compactedbits(lclusterbits, lomask,
- in, encodebits * i, &type);
+ lo = decode_compactedbits(lobits, in, encodebits * i, &type);
m->type = type;
if (type == Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
m->clusterofs = 1 << lclusterbits;

/* figure out lookahead_distance: delta[1] if needed */
if (lookahead)
- m->delta[1] = get_compacted_la_distance(lclusterbits,
+ m->delta[1] = get_compacted_la_distance(lobits,
encodebits, vcnt, in, i);
if (lo & Z_EROFS_LI_D0_CBLKCNT) {
if (!big_pcluster) {
@@ -174,8 +170,8 @@ static int unpack_compacted_index(struct z_erofs_maprecorder *m,
* of which lo saves delta[1] rather than delta[0].
* Hence, get delta[0] by the previous lcluster indirectly.
*/
- lo = decode_compactedbits(lclusterbits, lomask,
- in, encodebits * (i - 1), &type);
+ lo = decode_compactedbits(lobits, in,
+ encodebits * (i - 1), &type);
if (type != Z_EROFS_LCLUSTER_TYPE_NONHEAD)
lo = 0;
else if (lo & Z_EROFS_LI_D0_CBLKCNT)
@@ -190,8 +186,8 @@ static int unpack_compacted_index(struct z_erofs_maprecorder *m,
nblk = 1;
while (i > 0) {
--i;
- lo = decode_compactedbits(lclusterbits, lomask,
- in, encodebits * i, &type);
+ lo = decode_compactedbits(lobits, in,
+ encodebits * i, &type);
if (type == Z_EROFS_LCLUSTER_TYPE_NONHEAD)
i -= lo;

@@ -202,8 +198,8 @@ static int unpack_compacted_index(struct z_erofs_maprecorder *m,
nblk = 0;
while (i > 0) {
--i;
- lo = decode_compactedbits(lclusterbits, lomask,
- in, encodebits * i, &type);
+ lo = decode_compactedbits(lobits, in,
+ encodebits * i, &type);
if (type == Z_EROFS_LCLUSTER_TYPE_NONHEAD) {
if (lo & Z_EROFS_LI_D0_CBLKCNT) {
--i;
--
2.43.0