Sync up with in-kernel z_erofs_get_extent_compressedlen(), mainly
fix 1 lcluster-sized pcluster for big pcluster.

Signed-off-by: Gao Xiang <[email protected]>
---
 lib/zmap.c | 40 +++++++++++++++++++++++++++++++---------
 1 file changed, 31 insertions(+), 9 deletions(-)

diff --git a/lib/zmap.c b/lib/zmap.c
index 0c5c4f52bbd0..1084faa6e489 100644
--- a/lib/zmap.c
+++ b/lib/zmap.c
@@ -386,16 +386,13 @@ static int z_erofs_get_extent_compressedlen(struct 
z_erofs_maprecorder *m,
 
        DBG_BUGON(m->type != Z_EROFS_VLE_CLUSTER_TYPE_PLAIN &&
                  m->type != Z_EROFS_VLE_CLUSTER_TYPE_HEAD);
-       if (!((map->m_flags & EROFS_MAP_ZIPPED) &&
-             (vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1))) {
+       if (!(map->m_flags & EROFS_MAP_ZIPPED) ||
+           !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1)) {
                map->m_plen = 1 << lclusterbits;
                return 0;
        }
 
        lcn = m->lcn + 1;
-       if (lcn == initial_lcn && !m->compressedlcs)
-               m->compressedlcs = 2;
-
        if (m->compressedlcs)
                goto out;
 
@@ -403,21 +400,46 @@ static int z_erofs_get_extent_compressedlen(struct 
z_erofs_maprecorder *m,
        if (err)
                return err;
 
+       /*
+        * If the 1st NONHEAD lcluster has already been handled initially w/o
+        * valid compressedlcs, which means at least it mustn't be CBLKCNT, or
+        * an internal implemenatation error is detected.
+        *
+        * The following code can also handle it properly anyway, but let's
+        * BUG_ON in the debugging mode only for developers to notice that.
+        */
+       DBG_BUGON(lcn == initial_lcn &&
+                 m->type == Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD);
+
        switch (m->type) {
+       case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
+       case Z_EROFS_VLE_CLUSTER_TYPE_HEAD:
+               /*
+                * if the 1st NONHEAD lcluster is actually PLAIN or HEAD type
+                * rather than CBLKCNT, it's a 1 lcluster-sized pcluster.
+                */
+               m->compressedlcs = 1;
+               break;
        case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
-               DBG_BUGON(m->delta[0] != 1);
-               if (m->compressedlcs) {
+               if (m->delta[0] != 1)
+                       goto err_bonus_cblkcnt;
+               if (m->compressedlcs)
                        break;
-               }
+               /* fallthrough */
        default:
                erofs_err("cannot found CBLKCNT @ lcn %lu of nid %llu",
-                         lcn, (unsigned long long)vi->nid);
+                         lcn, vi->nid | 0ULL);
                DBG_BUGON(1);
                return -EFSCORRUPTED;
        }
 out:
        map->m_plen = m->compressedlcs << lclusterbits;
        return 0;
+err_bonus_cblkcnt:
+       erofs_err("bogus CBLKCNT @ lcn %lu of nid %llu",
+                 lcn, vi->nid | 0ULL);
+       DBG_BUGON(1);
+       return -EFSCORRUPTED;
 }
 
 int z_erofs_map_blocks_iter(struct erofs_inode *vi,
-- 
2.20.1

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