Commit 8d2517aa authored by Gao Xiang's avatar Gao Xiang
Browse files

erofs: fix up compacted indexes for block size < 4096 



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: default avatarYue Hu <huyue2@coolpad.com>
Reviewed-by: default avatarChao Yu <chao@kernel.org>
Signed-off-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20231206091057.87027-4-hsiangkao@linux.alibaba.com
parent 54ed3fdd

fs/erofs/zmap.c

+14 −18
Original line number Diff line number Diff line
@@ -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;