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erofs: clean up z_erofs_extent_lookback 

Avoid the unnecessary tail recursion since it can be converted into
a loop directly in order to prevent potential stack overflow.

It's a pretty straightforward conversion.

Link: https://lore.kernel.org/r/20220310182743.102365-1-hsiangkao@linux.alibaba.com
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
This commit is contained in:
Gao Xiang 2022-03-11 02:27:42 +08:00
parent d467e980d0
commit ab474fccd0
1 changed files with 33 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

67
fs/erofs/zmap.c
View File

@ -431,48 +431,47 @@ static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m,
unsigned int lookback_distance)
{
struct erofs_inode *const vi = EROFS_I(m->inode);
struct erofs_map_blocks *const map = m->map;
const unsigned int lclusterbits = vi->z_logical_clusterbits;
unsigned long lcn = m->lcn;
int err;
if (lcn < lookback_distance) {
erofs_err(m->inode->i_sb,
"bogus lookback distance @ nid %llu", vi->nid);
DBG_BUGON(1);
return -EFSCORRUPTED;
}
while (m->lcn >= lookback_distance) {
unsigned long lcn = m->lcn - lookback_distance;
int err;
/* load extent head logical cluster if needed */
lcn -= lookback_distance;
err = z_erofs_load_cluster_from_disk(m, lcn, false);
if (err)
return err;
/* load extent head logical cluster if needed */
err = z_erofs_load_cluster_from_disk(m, lcn, false);
if (err)
return err;
switch (m->type) {
case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
if (!m->delta[0]) {
switch (m->type) {
case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
if (!m->delta[0]) {
erofs_err(m->inode->i_sb,
"invalid lookback distance 0 @ nid %llu",
vi->nid);
DBG_BUGON(1);
return -EFSCORRUPTED;
}
lookback_distance = m->delta[0];
continue;
case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1:
case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2:
m->headtype = m->type;
m->map->m_la = (lcn << lclusterbits) | m->clusterofs;
return 0;
default:
erofs_err(m->inode->i_sb,
"invalid lookback distance 0 @ nid %llu",
vi->nid);
"unknown type %u @ lcn %lu of nid %llu",
m->type, lcn, vi->nid);
DBG_BUGON(1);
return -EFSCORRUPTED;
return -EOPNOTSUPP;
}
return z_erofs_extent_lookback(m, m->delta[0]);
case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1:
case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2:
m->headtype = m->type;
map->m_la = (lcn << lclusterbits) | m->clusterofs;
break;
default:
erofs_err(m->inode->i_sb,
"unknown type %u @ lcn %lu of nid %llu",
m->type, lcn, vi->nid);
DBG_BUGON(1);
return -EOPNOTSUPP;
}
return 0;
erofs_err(m->inode->i_sb, "bogus lookback distance @ nid %llu",
vi->nid);
DBG_BUGON(1);
return -EFSCORRUPTED;
}
static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,