Although this patch has an amount of changes, it is hard to
separate into smaller patches.

Most changes are due to structure renaming for better understand
and straightforward,
 z_erofs_vle_workgroup to z_erofs_pcluster
             since it represents a physical cluster;
 z_erofs_vle_work to z_erofs_collection
             since it represents a collection of logical pages;
 z_erofs_vle_work_builder to z_erofs_collector
             since it's used to fill z_erofs_{pcluster,collection}.

struct z_erofs_vle_work_finder has no extra use compared with
struct z_erofs_collector, delete it.

FULL_LENGTH bit is integrated into .length of pcluster so that it
can be updated with the corresponding length change in atomic.

Minor, add comments for better description.

Reviewed-by: Chao Yu <yuch...@huawei.com>
Signed-off-by: Gao Xiang <gaoxian...@huawei.com>
---
 drivers/staging/erofs/zdata.c | 983 +++++++++++++++-------------------
 drivers/staging/erofs/zdata.h |  96 ++--
 2 files changed, 465 insertions(+), 614 deletions(-)

diff --git a/drivers/staging/erofs/zdata.c b/drivers/staging/erofs/zdata.c
index 88c8c4082498..6ebee2ca8dc5 100644
--- a/drivers/staging/erofs/zdata.c
+++ b/drivers/staging/erofs/zdata.c
@@ -18,7 +18,7 @@
  */
 #define PAGE_UNALLOCATED     ((void *)0x5F0E4B1D)
 
-/* how to allocate cached pages for a workgroup */
+/* how to allocate cached pages for a pcluster */
 enum z_erofs_cache_alloctype {
        DONTALLOC,      /* don't allocate any cached pages */
        DELAYEDALLOC,   /* delayed allocation (at the time of submitting io) */
@@ -34,156 +34,158 @@ typedef tagptr1_t compressed_page_t;
        tagptr_fold(compressed_page_t, page, 1)
 
 static struct workqueue_struct *z_erofs_workqueue __read_mostly;
-static struct kmem_cache *z_erofs_workgroup_cachep __read_mostly;
+static struct kmem_cache *pcluster_cachep __read_mostly;
 
 void z_erofs_exit_zip_subsystem(void)
 {
        destroy_workqueue(z_erofs_workqueue);
-       kmem_cache_destroy(z_erofs_workgroup_cachep);
+       kmem_cache_destroy(pcluster_cachep);
 }
 
 static inline int init_unzip_workqueue(void)
 {
        const unsigned int onlinecpus = num_possible_cpus();
+       const unsigned int flags = WQ_UNBOUND | WQ_HIGHPRI | WQ_CPU_INTENSIVE;
 
        /*
-        * we don't need too many threads, limiting threads
-        * could improve scheduling performance.
+        * no need to spawn too many threads, limiting threads could minimum
+        * scheduling overhead, perhaps per-CPU threads should be better?
         */
-       z_erofs_workqueue =
-               alloc_workqueue("erofs_unzipd",
-                               WQ_UNBOUND | WQ_HIGHPRI | WQ_CPU_INTENSIVE,
-                               onlinecpus + onlinecpus / 4);
-
+       z_erofs_workqueue = alloc_workqueue("erofs_unzipd", flags,
+                                           onlinecpus + onlinecpus / 4);
        return z_erofs_workqueue ? 0 : -ENOMEM;
 }
 
 static void init_once(void *ptr)
 {
-       struct z_erofs_vle_workgroup *grp = ptr;
-       struct z_erofs_vle_work *const work =
-               z_erofs_vle_grab_primary_work(grp);
+       struct z_erofs_pcluster *pcl = ptr;
+       struct z_erofs_collection *cl = z_erofs_primarycollection(pcl);
        unsigned int i;
 
-       mutex_init(&work->lock);
-       work->nr_pages = 0;
-       work->vcnt = 0;
+       mutex_init(&cl->lock);
+       cl->nr_pages = 0;
+       cl->vcnt = 0;
        for (i = 0; i < Z_EROFS_CLUSTER_MAX_PAGES; ++i)
-               grp->compressed_pages[i] = NULL;
+               pcl->compressed_pages[i] = NULL;
 }
 
-static void init_always(struct z_erofs_vle_workgroup *grp)
+static void init_always(struct z_erofs_pcluster *pcl)
 {
-       struct z_erofs_vle_work *const work =
-               z_erofs_vle_grab_primary_work(grp);
+       struct z_erofs_collection *cl = z_erofs_primarycollection(pcl);
 
-       atomic_set(&grp->obj.refcount, 1);
-       grp->flags = 0;
+       atomic_set(&pcl->obj.refcount, 1);
 
-       DBG_BUGON(work->nr_pages);
-       DBG_BUGON(work->vcnt);
+       DBG_BUGON(cl->nr_pages);
+       DBG_BUGON(cl->vcnt);
 }
 
 int __init z_erofs_init_zip_subsystem(void)
 {
-       z_erofs_workgroup_cachep =
-               kmem_cache_create("erofs_compress",
-                                 Z_EROFS_WORKGROUP_SIZE, 0,
-                                 SLAB_RECLAIM_ACCOUNT, init_once);
-
-       if (z_erofs_workgroup_cachep) {
+       pcluster_cachep = kmem_cache_create("erofs_compress",
+                                           Z_EROFS_WORKGROUP_SIZE, 0,
+                                           SLAB_RECLAIM_ACCOUNT, init_once);
+       if (pcluster_cachep) {
                if (!init_unzip_workqueue())
                        return 0;
 
-               kmem_cache_destroy(z_erofs_workgroup_cachep);
+               kmem_cache_destroy(pcluster_cachep);
        }
        return -ENOMEM;
 }
 
-enum z_erofs_vle_work_role {
-       Z_EROFS_VLE_WORK_SECONDARY,
-       Z_EROFS_VLE_WORK_PRIMARY,
+enum z_erofs_collectmode {
+       COLLECT_SECONDARY,
+       COLLECT_PRIMARY,
        /*
-        * The current work was the tail of an exist chain, and the previous
-        * processed chained works are all decided to be hooked up to it.
-        * A new chain should be created for the remaining unprocessed works,
-        * therefore different from Z_EROFS_VLE_WORK_PRIMARY_FOLLOWED,
-        * the next work cannot reuse the whole page in the following scenario:
+        * The current collection was the tail of an exist chain, in addition
+        * that the previous processed chained collections are all decided to
+        * be hooked up to it.
+        * A new chain will be created for the remaining collections which are
+        * not processed yet, therefore different from COLLECT_PRIMARY_FOLLOWED,
+        * the next collection cannot reuse the whole page safely in
+        * the following scenario:
         *  ________________________________________________________________
         * |      tail (partial) page     |       head (partial) page       |
-        * |  (belongs to the next work)  |  (belongs to the current work)  |
+        * |   (belongs to the next cl)   |   (belongs to the current cl)   |
         * |_______PRIMARY_FOLLOWED_______|________PRIMARY_HOOKED___________|
         */
-       Z_EROFS_VLE_WORK_PRIMARY_HOOKED,
+       COLLECT_PRIMARY_HOOKED,
+       COLLECT_PRIMARY_FOLLOWED_NOINPLACE,
        /*
-        * The current work has been linked with the processed chained works,
-        * and could be also linked with the potential remaining works, which
-        * means if the processing page is the tail partial page of the work,
-        * the current work can safely use the whole page (since the next work
-        * is under control) for in-place decompression, as illustrated below:
+        * The current collection has been linked with the owned chain, and
+        * could also be linked with the remaining collections, which means
+        * if the processing page is the tail page of the collection, thus
+        * the current collection can safely use the whole page (since
+        * the previous collection is under control) for in-place I/O, as
+        * illustrated below:
         *  ________________________________________________________________
-        * |  tail (partial) page  |          head (partial) page           |
-        * | (of the current work) |         (of the previous work)         |
-        * |  PRIMARY_FOLLOWED or  |                                        |
-        * |_____PRIMARY_HOOKED____|____________PRIMARY_FOLLOWED____________|
+        * |  tail (partial) page |          head (partial) page           |
+        * |  (of the current cl) |      (of the previous collection)      |
+        * |  PRIMARY_FOLLOWED or |                                        |
+        * |_____PRIMARY_HOOKED___|____________PRIMARY_FOLLOWED____________|
         *
-        * [  (*) the above page can be used for the current work itself.  ]
+        * [  (*) the above page can be used as inplace I/O.               ]
         */
-       Z_EROFS_VLE_WORK_PRIMARY_FOLLOWED,
-       Z_EROFS_VLE_WORK_MAX
+       COLLECT_PRIMARY_FOLLOWED,
 };
 
-struct z_erofs_vle_work_builder {
-       enum z_erofs_vle_work_role role;
-       /*
-        * 'hosted = false' means that the current workgroup doesn't belong to
-        * the owned chained workgroups. In the other words, it is none of our
-        * business to submit this workgroup.
-        */
-       bool hosted;
-
-       struct z_erofs_vle_workgroup *grp;
-       struct z_erofs_vle_work *work;
+struct z_erofs_collector {
        struct z_erofs_pagevec_ctor vector;
 
-       /* pages used for reading the compressed data */
-       struct page **compressed_pages;
-       unsigned int compressed_deficit;
+       struct z_erofs_pcluster *pcl;
+       struct z_erofs_collection *cl;
+       struct page **compressedpages;
+       z_erofs_next_pcluster_t owned_head;
+
+       enum z_erofs_collectmode mode;
 };
 
-#define VLE_WORK_BUILDER_INIT()        \
-       { .work = NULL, .role = Z_EROFS_VLE_WORK_PRIMARY_FOLLOWED }
+struct z_erofs_decompress_frontend {
+       struct inode *const inode;
+
+       struct z_erofs_collector clt;
+       struct erofs_map_blocks map;
+
+       /* used for applying cache strategy on the fly */
+       bool backmost;
+       erofs_off_t headoffset;
+};
+
+#define COLLECTOR_INIT() { \
+       .owned_head = Z_EROFS_PCLUSTER_TAIL, \
+       .mode = COLLECT_PRIMARY_FOLLOWED }
+
+#define DECOMPRESS_FRONTEND_INIT(__i) { \
+       .inode = __i, .clt = COLLECTOR_INIT(), \
+       .backmost = true, }
+
+static struct page *z_pagemap_global[Z_EROFS_VMAP_GLOBAL_PAGES];
+static DEFINE_MUTEX(z_pagemap_global_lock);
 
 #ifdef EROFS_FS_HAS_MANAGED_CACHE
-static void preload_compressed_pages(struct z_erofs_vle_work_builder *bl,
+static void preload_compressed_pages(struct z_erofs_collector *clt,
                                     struct address_space *mc,
-                                    pgoff_t index,
-                                    unsigned int clusterpages,
                                     enum z_erofs_cache_alloctype type,
-                                    struct list_head *pagepool,
-                                    gfp_t gfp)
+                                    struct list_head *pagepool)
 {
-       struct page **const pages = bl->compressed_pages;
-       const unsigned int remaining = bl->compressed_deficit;
+       const struct z_erofs_pcluster *pcl = clt->pcl;
+       const unsigned int clusterpages = BIT(pcl->clusterbits);
+       struct page **pages = clt->compressedpages;
+       pgoff_t index = pcl->obj.index + (pages - pcl->compressed_pages);
        bool standalone = true;
-       unsigned int i, j = 0;
 
-       if (bl->role < Z_EROFS_VLE_WORK_PRIMARY_FOLLOWED)
+       if (clt->mode < COLLECT_PRIMARY_FOLLOWED)
                return;
 
-       gfp = mapping_gfp_constraint(mc, gfp) & ~__GFP_RECLAIM;
-
-       index += clusterpages - remaining;
-
-       for (i = 0; i < remaining; ++i) {
+       for (; pages < pcl->compressed_pages + clusterpages; ++pages) {
                struct page *page;
                compressed_page_t t;
 
                /* the compressed page was loaded before */
-               if (READ_ONCE(pages[i]))
+               if (READ_ONCE(*pages))
                        continue;
 
-               page = find_get_page(mc, index + i);
+               page = find_get_page(mc, index);
 
                if (page) {
                        t = tag_compressed_page_justfound(page);
@@ -191,32 +193,30 @@ static void preload_compressed_pages(struct 
z_erofs_vle_work_builder *bl,
                        t = tagptr_init(compressed_page_t, PAGE_UNALLOCATED);
                } else {        /* DONTALLOC */
                        if (standalone)
-                               j = i;
+                               clt->compressedpages = pages;
                        standalone = false;
                        continue;
                }
 
-               if (!cmpxchg_relaxed(&pages[i], NULL, tagptr_cast_ptr(t)))
+               if (!cmpxchg_relaxed(pages, NULL, tagptr_cast_ptr(t)))
                        continue;
 
                if (page)
                        put_page(page);
        }
-       bl->compressed_pages += j;
-       bl->compressed_deficit = remaining - j;
 
-       if (standalone)
-               bl->role = Z_EROFS_VLE_WORK_PRIMARY;
+       if (standalone)         /* downgrade to PRIMARY_FOLLOWED_NOINPLACE */
+               clt->mode = COLLECT_PRIMARY_FOLLOWED_NOINPLACE;
 }
 
 /* called by erofs_shrinker to get rid of all compressed_pages */
 int erofs_try_to_free_all_cached_pages(struct erofs_sb_info *sbi,
-                                      struct erofs_workgroup *egrp)
+                                      struct erofs_workgroup *grp)
 {
-       struct z_erofs_vle_workgroup *const grp =
-               container_of(egrp, struct z_erofs_vle_workgroup, obj);
+       struct z_erofs_pcluster *const pcl =
+               container_of(grp, struct z_erofs_pcluster, obj);
        struct address_space *const mapping = MNGD_MAPPING(sbi);
-       const int clusterpages = erofs_clusterpages(sbi);
+       const unsigned int clusterpages = BIT(pcl->clusterbits);
        int i;
 
        /*
@@ -224,18 +224,20 @@ int erofs_try_to_free_all_cached_pages(struct 
erofs_sb_info *sbi,
         * therefore no need to worry about available decompression users.
         */
        for (i = 0; i < clusterpages; ++i) {
-               struct page *page = grp->compressed_pages[i];
+               struct page *page = pcl->compressed_pages[i];
 
-               if (!page || page->mapping != mapping)
+               if (!page)
                        continue;
 
                /* block other users from reclaiming or migrating the page */
                if (!trylock_page(page))
                        return -EBUSY;
 
-               /* barrier is implied in the following 'unlock_page' */
-               WRITE_ONCE(grp->compressed_pages[i], NULL);
+               if (unlikely(page->mapping != mapping))
+                       continue;
 
+               /* barrier is implied in the following 'unlock_page' */
+               WRITE_ONCE(pcl->compressed_pages[i], NULL);
                set_page_private(page, 0);
                ClearPagePrivate(page);
 
@@ -248,22 +250,21 @@ int erofs_try_to_free_all_cached_pages(struct 
erofs_sb_info *sbi,
 int erofs_try_to_free_cached_page(struct address_space *mapping,
                                  struct page *page)
 {
-       struct erofs_sb_info *const sbi = EROFS_SB(mapping->host->i_sb);
-       const unsigned int clusterpages = erofs_clusterpages(sbi);
-       struct z_erofs_vle_workgroup *const grp = (void *)page_private(page);
+       struct z_erofs_pcluster *const pcl = (void *)page_private(page);
+       const unsigned int clusterpages = BIT(pcl->clusterbits);
        int ret = 0;    /* 0 - busy */
 
-       if (erofs_workgroup_try_to_freeze(&grp->obj, 1)) {
+       if (erofs_workgroup_try_to_freeze(&pcl->obj, 1)) {
                unsigned int i;
 
                for (i = 0; i < clusterpages; ++i) {
-                       if (grp->compressed_pages[i] == page) {
-                               WRITE_ONCE(grp->compressed_pages[i], NULL);
+                       if (pcl->compressed_pages[i] == page) {
+                               WRITE_ONCE(pcl->compressed_pages[i], NULL);
                                ret = 1;
                                break;
                        }
                }
-               erofs_workgroup_unfreeze(&grp->obj, 1);
+               erofs_workgroup_unfreeze(&pcl->obj, 1);
 
                if (ret) {
                        ClearPagePrivate(page);
@@ -273,361 +274,267 @@ int erofs_try_to_free_cached_page(struct address_space 
*mapping,
        return ret;
 }
 #else
-static void preload_compressed_pages(struct z_erofs_vle_work_builder *bl,
+static void preload_compressed_pages(struct z_erofs_collector *clt,
                                     struct address_space *mc,
-                                    pgoff_t index,
-                                    unsigned int clusterpages,
                                     enum z_erofs_cache_alloctype type,
-                                    struct list_head *pagepool,
-                                    gfp_t gfp)
+                                    struct list_head *pagepool)
 {
        /* nowhere to load compressed pages from */
 }
 #endif
 
 /* page_type must be Z_EROFS_PAGE_TYPE_EXCLUSIVE */
-static inline bool try_to_reuse_as_compressed_page(
-       struct z_erofs_vle_work_builder *b,
-       struct page *page)
+static inline bool try_inplace_io(struct z_erofs_collector *clt,
+                                 struct page *page)
 {
-       while (b->compressed_deficit) {
-               --b->compressed_deficit;
-               if (!cmpxchg(b->compressed_pages++, NULL, page))
+       struct z_erofs_pcluster *const pcl = clt->pcl;
+       const unsigned int clusterpages = BIT(pcl->clusterbits);
+
+       while (clt->compressedpages < pcl->compressed_pages + clusterpages) {
+               if (!cmpxchg(clt->compressedpages++, NULL, page))
                        return true;
        }
-
        return false;
 }
 
-/* callers must be with work->lock held */
-static int z_erofs_vle_work_add_page(
-       struct z_erofs_vle_work_builder *builder,
-       struct page *page,
-       enum z_erofs_page_type type)
+/* callers must be with collection lock held */
+static int z_erofs_attach_page(struct z_erofs_collector *clt,
+                              struct page *page,
+                              enum z_erofs_page_type type)
 {
        int ret;
        bool occupied;
 
-       /* give priority for the compressed data storage */
-       if (builder->role >= Z_EROFS_VLE_WORK_PRIMARY &&
+       /* give priority for inplaceio */
+       if (clt->mode >= COLLECT_PRIMARY &&
            type == Z_EROFS_PAGE_TYPE_EXCLUSIVE &&
-           try_to_reuse_as_compressed_page(builder, page))
+           try_inplace_io(clt, page))
                return 0;
 
-       ret = z_erofs_pagevec_enqueue(&builder->vector,
+       ret = z_erofs_pagevec_enqueue(&clt->vector,
                                      page, type, &occupied);
-       builder->work->vcnt += (unsigned int)ret;
+       clt->cl->vcnt += (unsigned int)ret;
 
        return ret ? 0 : -EAGAIN;
 }
 
-static enum z_erofs_vle_work_role
-try_to_claim_workgroup(struct z_erofs_vle_workgroup *grp,
-                      z_erofs_vle_owned_workgrp_t *owned_head,
-                      bool *hosted)
+static enum z_erofs_collectmode
+try_to_claim_pcluster(struct z_erofs_pcluster *pcl,
+                     z_erofs_next_pcluster_t *owned_head)
 {
-       DBG_BUGON(*hosted);
-
-       /* let's claim these following types of workgroup */
+       /* let's claim these following types of pclusters */
 retry:
-       if (grp->next == Z_EROFS_VLE_WORKGRP_NIL) {
-               /* type 1, nil workgroup */
-               if (cmpxchg(&grp->next, Z_EROFS_VLE_WORKGRP_NIL,
-                           *owned_head) != Z_EROFS_VLE_WORKGRP_NIL)
+       if (pcl->next == Z_EROFS_PCLUSTER_NIL) {
+               /* type 1, nil pcluster */
+               if (cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_NIL,
+                           *owned_head) != Z_EROFS_PCLUSTER_NIL)
                        goto retry;
 
-               *owned_head = &grp->next;
-               *hosted = true;
+               *owned_head = &pcl->next;
                /* lucky, I am the followee :) */
-               return Z_EROFS_VLE_WORK_PRIMARY_FOLLOWED;
-
-       } else if (grp->next == Z_EROFS_VLE_WORKGRP_TAIL) {
+               return COLLECT_PRIMARY_FOLLOWED;
+       } else if (pcl->next == Z_EROFS_PCLUSTER_TAIL) {
                /*
                 * type 2, link to the end of a existing open chain,
                 * be careful that its submission itself is governed
                 * by the original owned chain.
                 */
-               if (cmpxchg(&grp->next, Z_EROFS_VLE_WORKGRP_TAIL,
-                           *owned_head) != Z_EROFS_VLE_WORKGRP_TAIL)
+               if (cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_TAIL,
+                           *owned_head) != Z_EROFS_PCLUSTER_TAIL)
                        goto retry;
-               *owned_head = Z_EROFS_VLE_WORKGRP_TAIL;
-               return Z_EROFS_VLE_WORK_PRIMARY_HOOKED;
+               *owned_head = Z_EROFS_PCLUSTER_TAIL;
+               return COLLECT_PRIMARY_HOOKED;
        }
-
-       return Z_EROFS_VLE_WORK_PRIMARY; /* :( better luck next time */
+       return COLLECT_PRIMARY; /* :( better luck next time */
 }
 
-struct z_erofs_vle_work_finder {
-       struct super_block *sb;
-       pgoff_t idx;
-       unsigned int pageofs;
-
-       struct z_erofs_vle_workgroup **grp_ret;
-       enum z_erofs_vle_work_role *role;
-       z_erofs_vle_owned_workgrp_t *owned_head;
-       bool *hosted;
-};
-
-static struct z_erofs_vle_work *
-z_erofs_vle_work_lookup(const struct z_erofs_vle_work_finder *f)
+static struct z_erofs_collection *cllookup(struct z_erofs_collector *clt,
+                                          struct inode *inode,
+                                          struct erofs_map_blocks *map)
 {
-       bool tag, primary;
-       struct erofs_workgroup *egrp;
-       struct z_erofs_vle_workgroup *grp;
-       struct z_erofs_vle_work *work;
-
-       egrp = erofs_find_workgroup(f->sb, f->idx, &tag);
-       if (!egrp) {
-               *f->grp_ret = NULL;
+       struct erofs_workgroup *grp;
+       struct z_erofs_pcluster *pcl;
+       struct z_erofs_collection *cl;
+       unsigned int length;
+       bool tag;
+
+       grp = erofs_find_workgroup(inode->i_sb, map->m_pa >> PAGE_SHIFT, &tag);
+       if (!grp)
                return NULL;
-       }
 
-       grp = container_of(egrp, struct z_erofs_vle_workgroup, obj);
-       *f->grp_ret = grp;
+       pcl = container_of(grp, struct z_erofs_pcluster, obj);
+
+       cl = z_erofs_primarycollection(pcl);
+       if (unlikely(cl->pageofs != (map->m_la & ~PAGE_MASK))) {
+               DBG_BUGON(1);
+               return ERR_PTR(-EIO);
+       }
 
-       work = z_erofs_vle_grab_work(grp, f->pageofs);
-       /* if multiref is disabled, `primary' is always true */
-       primary = true;
+       length = READ_ONCE(pcl->length);
+       if (length & Z_EROFS_PCLUSTER_FULL_LENGTH) {
+               if ((map->m_llen << Z_EROFS_PCLUSTER_LENGTH_BIT) > length) {
+                       DBG_BUGON(1);
+                       return ERR_PTR(-EIO);
+               }
+       } else {
+               unsigned int llen = map->m_llen << Z_EROFS_PCLUSTER_LENGTH_BIT;
 
-       DBG_BUGON(work->pageofs != f->pageofs);
+               if (map->m_flags & EROFS_MAP_FULL_MAPPED)
+                       llen |= Z_EROFS_PCLUSTER_FULL_LENGTH;
 
-       /*
-        * lock must be taken first to avoid grp->next == NIL between
-        * claiming workgroup and adding pages:
-        *                        grp->next != NIL
-        *   grp->next = NIL
-        *   mutex_unlock_all
-        *                        mutex_lock(&work->lock)
-        *                        add all pages to pagevec
-        *
-        * [correct locking case 1]:
-        *   mutex_lock(grp->work[a])
-        *   ...
-        *   mutex_lock(grp->work[b])     mutex_lock(grp->work[c])
-        *   ...                          *role = SECONDARY
-        *                                add all pages to pagevec
-        *                                ...
-        *                                mutex_unlock(grp->work[c])
-        *   mutex_lock(grp->work[c])
-        *   ...
-        *   grp->next = NIL
-        *   mutex_unlock_all
-        *
-        * [correct locking case 2]:
-        *   mutex_lock(grp->work[b])
-        *   ...
-        *   mutex_lock(grp->work[a])
-        *   ...
-        *   mutex_lock(grp->work[c])
-        *   ...
-        *   grp->next = NIL
-        *   mutex_unlock_all
-        *                                mutex_lock(grp->work[a])
-        *                                *role = PRIMARY_OWNER
-        *                                add all pages to pagevec
-        *                                ...
-        */
-       mutex_lock(&work->lock);
-
-       *f->hosted = false;
-       if (!primary)
-               *f->role = Z_EROFS_VLE_WORK_SECONDARY;
-       else    /* claim the workgroup if possible */
-               *f->role = try_to_claim_workgroup(grp, f->owned_head,
-                                                 f->hosted);
-       return work;
+               while (llen > length &&
+                      length != cmpxchg_relaxed(&pcl->length, length, llen)) {
+                       cpu_relax();
+                       length = READ_ONCE(pcl->length);
+               }
+       }
+       mutex_lock(&cl->lock);
+       clt->mode = try_to_claim_pcluster(pcl, &clt->owned_head);
+       clt->pcl = pcl;
+       clt->cl = cl;
+       return cl;
 }
 
-static struct z_erofs_vle_work *
-z_erofs_vle_work_register(const struct z_erofs_vle_work_finder *f,
-                         struct erofs_map_blocks *map)
+static struct z_erofs_collection *clregister(struct z_erofs_collector *clt,
+                                            struct inode *inode,
+                                            struct erofs_map_blocks *map)
 {
-       bool gnew = false;
-       struct z_erofs_vle_workgroup *grp = *f->grp_ret;
-       struct z_erofs_vle_work *work;
-
-       /* if multiref is disabled, grp should never be nullptr */
-       if (unlikely(grp)) {
-               DBG_BUGON(1);
-               return ERR_PTR(-EINVAL);
-       }
+       struct z_erofs_pcluster *pcl;
+       struct z_erofs_collection *cl;
+       int err;
 
        /* no available workgroup, let's allocate one */
-       grp = kmem_cache_alloc(z_erofs_workgroup_cachep, GFP_NOFS);
-       if (unlikely(!grp))
+       pcl = kmem_cache_alloc(pcluster_cachep, GFP_NOFS);
+       if (unlikely(!pcl))
                return ERR_PTR(-ENOMEM);
 
-       init_always(grp);
-       grp->obj.index = f->idx;
-       grp->llen = map->m_llen;
+       init_always(pcl);
+       pcl->obj.index = map->m_pa >> PAGE_SHIFT;
 
-       z_erofs_vle_set_workgrp_fmt(grp, (map->m_flags & EROFS_MAP_ZIPPED) ?
-                                   Z_EROFS_VLE_WORKGRP_FMT_LZ4 :
-                                   Z_EROFS_VLE_WORKGRP_FMT_PLAIN);
+       pcl->length = (map->m_llen << Z_EROFS_PCLUSTER_LENGTH_BIT) |
+               (map->m_flags & EROFS_MAP_FULL_MAPPED ?
+                       Z_EROFS_PCLUSTER_FULL_LENGTH : 0);
 
-       if (map->m_flags & EROFS_MAP_FULL_MAPPED)
-               grp->flags |= Z_EROFS_VLE_WORKGRP_FULL_LENGTH;
+       if (map->m_flags & EROFS_MAP_ZIPPED)
+               pcl->algorithmformat = Z_EROFS_COMPRESSION_LZ4;
+       else
+               pcl->algorithmformat = Z_EROFS_COMPRESSION_SHIFTED;
+
+       pcl->clusterbits = EROFS_V(inode)->z_physical_clusterbits[0];
+       pcl->clusterbits -= PAGE_SHIFT;
 
-       /* new workgrps have been claimed as type 1 */
-       WRITE_ONCE(grp->next, *f->owned_head);
-       /* primary and followed work for all new workgrps */
-       *f->role = Z_EROFS_VLE_WORK_PRIMARY_FOLLOWED;
-       /* it should be submitted by ourselves */
-       *f->hosted = true;
+       /* new pclusters should be claimed as type 1, primary and followed */
+       pcl->next = clt->owned_head;
+       clt->mode = COLLECT_PRIMARY_FOLLOWED;
 
-       gnew = true;
-       work = z_erofs_vle_grab_primary_work(grp);
-       work->pageofs = f->pageofs;
+       cl = z_erofs_primarycollection(pcl);
+       cl->pageofs = map->m_la & ~PAGE_MASK;
 
        /*
         * lock all primary followed works before visible to others
-        * and mutex_trylock *never* fails for a new workgroup.
+        * and mutex_trylock *never* fails for a new pcluster.
         */
-       mutex_trylock(&work->lock);
+       mutex_trylock(&cl->lock);
 
-       if (gnew) {
-               int err = erofs_register_workgroup(f->sb, &grp->obj, 0);
-
-               if (err) {
-                       mutex_unlock(&work->lock);
-                       kmem_cache_free(z_erofs_workgroup_cachep, grp);
-                       return ERR_PTR(-EAGAIN);
-               }
+       err = erofs_register_workgroup(inode->i_sb, &pcl->obj, 0);
+       if (err) {
+               mutex_unlock(&cl->lock);
+               kmem_cache_free(pcluster_cachep, pcl);
+               return ERR_PTR(-EAGAIN);
        }
-
-       *f->owned_head = &grp->next;
-       *f->grp_ret = grp;
-       return work;
+       clt->owned_head = &pcl->next;
+       clt->pcl = pcl;
+       clt->cl = cl;
+       return cl;
 }
 
-#define builder_is_hooked(builder) \
-       ((builder)->role >= Z_EROFS_VLE_WORK_PRIMARY_HOOKED)
+static int z_erofs_collector_begin(struct z_erofs_collector *clt,
+                                  struct inode *inode,
+                                  struct erofs_map_blocks *map)
+{
+       struct z_erofs_collection *cl;
 
-#define builder_is_followed(builder) \
-       ((builder)->role >= Z_EROFS_VLE_WORK_PRIMARY_FOLLOWED)
+       DBG_BUGON(clt->cl);
 
-static int z_erofs_vle_work_iter_begin(struct z_erofs_vle_work_builder 
*builder,
-                                      struct super_block *sb,
-                                      struct erofs_map_blocks *map,
-                                      z_erofs_vle_owned_workgrp_t *owned_head)
-{
-       const unsigned int clusterpages = erofs_clusterpages(EROFS_SB(sb));
-       struct z_erofs_vle_workgroup *grp;
-       const struct z_erofs_vle_work_finder finder = {
-               .sb = sb,
-               .idx = erofs_blknr(map->m_pa),
-               .pageofs = map->m_la & ~PAGE_MASK,
-               .grp_ret = &grp,
-               .role = &builder->role,
-               .owned_head = owned_head,
-               .hosted = &builder->hosted
-       };
-       struct z_erofs_vle_work *work;
-
-       DBG_BUGON(builder->work);
-
-       /* must be Z_EROFS_WORK_TAIL or the next chained work */
-       DBG_BUGON(*owned_head == Z_EROFS_VLE_WORKGRP_NIL);
-       DBG_BUGON(*owned_head == Z_EROFS_VLE_WORKGRP_TAIL_CLOSED);
-
-       DBG_BUGON(erofs_blkoff(map->m_pa));
+       /* must be Z_EROFS_PCLUSTER_TAIL or pointed to previous collection */
+       DBG_BUGON(clt->owned_head == Z_EROFS_PCLUSTER_NIL);
+       DBG_BUGON(clt->owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
 
-repeat:
-       work = z_erofs_vle_work_lookup(&finder);
-       if (work) {
-               unsigned int orig_llen;
-
-               /* increase workgroup `llen' if needed */
-               while ((orig_llen = READ_ONCE(grp->llen)) < map->m_llen &&
-                      orig_llen != cmpxchg_relaxed(&grp->llen,
-                                                   orig_llen, map->m_llen))
-                       cpu_relax();
-               goto got_it;
+       if (!PAGE_ALIGNED(map->m_pa)) {
+               DBG_BUGON(1);
+               return -EINVAL;
        }
 
-       work = z_erofs_vle_work_register(&finder, map);
-       if (unlikely(work == ERR_PTR(-EAGAIN)))
-               goto repeat;
-
-       if (IS_ERR(work))
-               return PTR_ERR(work);
-got_it:
-       z_erofs_pagevec_ctor_init(&builder->vector, Z_EROFS_NR_INLINE_PAGEVECS,
-                                 work->pagevec, work->vcnt);
+repeat:
+       cl = cllookup(clt, inode, map);
+       if (!cl) {
+               cl = clregister(clt, inode, map);
 
-       if (builder->role >= Z_EROFS_VLE_WORK_PRIMARY) {
-               /* enable possibly in-place decompression */
-               builder->compressed_pages = grp->compressed_pages;
-               builder->compressed_deficit = clusterpages;
-       } else {
-               builder->compressed_pages = NULL;
-               builder->compressed_deficit = 0;
+               if (unlikely(cl == ERR_PTR(-EAGAIN)))
+                       goto repeat;
        }
 
-       builder->grp = grp;
-       builder->work = work;
+       if (IS_ERR(cl))
+               return PTR_ERR(cl);
+
+       z_erofs_pagevec_ctor_init(&clt->vector, Z_EROFS_NR_INLINE_PAGEVECS,
+                                 cl->pagevec, cl->vcnt);
+
+       clt->compressedpages = clt->pcl->compressed_pages;
+       if (clt->mode <= COLLECT_PRIMARY) /* cannot do in-place I/O */
+               clt->compressedpages += Z_EROFS_CLUSTER_MAX_PAGES;
        return 0;
 }
 
 /*
- * keep in mind that no referenced workgroups will be freed
- * only after a RCU grace period, so rcu_read_lock() could
- * prevent a workgroup from being freed.
+ * keep in mind that no referenced pclusters will be freed
+ * only after a RCU grace period.
  */
 static void z_erofs_rcu_callback(struct rcu_head *head)
 {
-       struct z_erofs_vle_work *work = container_of(head,
-               struct z_erofs_vle_work, rcu);
-       struct z_erofs_vle_workgroup *grp =
-               z_erofs_vle_work_workgroup(work, true);
+       struct z_erofs_collection *const cl =
+               container_of(head, struct z_erofs_collection, rcu);
 
-       kmem_cache_free(z_erofs_workgroup_cachep, grp);
+       kmem_cache_free(pcluster_cachep,
+                       container_of(cl, struct z_erofs_pcluster,
+                                    primary_collection));
 }
 
 void erofs_workgroup_free_rcu(struct erofs_workgroup *grp)
 {
-       struct z_erofs_vle_workgroup *const vgrp = container_of(grp,
-               struct z_erofs_vle_workgroup, obj);
-       struct z_erofs_vle_work *const work = &vgrp->work;
+       struct z_erofs_pcluster *const pcl =
+               container_of(grp, struct z_erofs_pcluster, obj);
+       struct z_erofs_collection *const cl = z_erofs_primarycollection(pcl);
 
-       call_rcu(&work->rcu, z_erofs_rcu_callback);
+       call_rcu(&cl->rcu, z_erofs_rcu_callback);
 }
 
-static void
-__z_erofs_vle_work_release(struct z_erofs_vle_workgroup *grp,
-                          struct z_erofs_vle_work *work __maybe_unused)
+static void z_erofs_collection_put(struct z_erofs_collection *cl)
 {
-       erofs_workgroup_put(&grp->obj);
-}
+       struct z_erofs_pcluster *const pcl =
+               container_of(cl, struct z_erofs_pcluster, primary_collection);
 
-static void z_erofs_vle_work_release(struct z_erofs_vle_work *work)
-{
-       struct z_erofs_vle_workgroup *grp =
-               z_erofs_vle_work_workgroup(work, true);
-
-       __z_erofs_vle_work_release(grp, work);
+       erofs_workgroup_put(&pcl->obj);
 }
 
-static inline bool
-z_erofs_vle_work_iter_end(struct z_erofs_vle_work_builder *builder)
+static bool z_erofs_collector_end(struct z_erofs_collector *clt)
 {
-       struct z_erofs_vle_work *work = builder->work;
+       struct z_erofs_collection *cl = clt->cl;
 
-       if (!work)
+       if (!cl)
                return false;
 
-       z_erofs_pagevec_ctor_exit(&builder->vector, false);
-       mutex_unlock(&work->lock);
+       z_erofs_pagevec_ctor_exit(&clt->vector, false);
+       mutex_unlock(&cl->lock);
 
        /*
-        * if all pending pages are added, don't hold work reference
-        * any longer if the current work isn't hosted by ourselves.
+        * if all pending pages are added, don't hold its reference
+        * any longer if the pcluster isn't hosted by ourselves.
         */
-       if (!builder->hosted)
-               __z_erofs_vle_work_release(builder->grp, work);
+       if (clt->mode < COLLECT_PRIMARY_FOLLOWED_NOINPLACE)
+               z_erofs_collection_put(cl);
 
-       builder->work = NULL;
-       builder->grp = NULL;
+       clt->cl = NULL;
        return true;
 }
 
@@ -640,33 +547,9 @@ static inline struct page *__stagingpage_alloc(struct 
list_head *pagepool,
        return page;
 }
 
-struct z_erofs_vle_frontend {
-       struct inode *const inode;
-
-       struct z_erofs_vle_work_builder builder;
-       struct erofs_map_blocks map;
-
-       z_erofs_vle_owned_workgrp_t owned_head;
-
-       /* used for applying cache strategy on the fly */
-       bool backmost;
-       erofs_off_t headoffset;
-};
-
-#define VLE_FRONTEND_INIT(__i) { \
-       .inode = __i, \
-       .map = { \
-               .m_llen = 0, \
-               .m_plen = 0, \
-               .mpage = NULL \
-       }, \
-       .builder = VLE_WORK_BUILDER_INIT(), \
-       .owned_head = Z_EROFS_VLE_WORKGRP_TAIL, \
-       .backmost = true, }
-
 #ifdef EROFS_FS_HAS_MANAGED_CACHE
-static inline bool
-should_alloc_managed_pages(struct z_erofs_vle_frontend *fe, erofs_off_t la)
+static bool should_alloc_managed_pages(struct z_erofs_decompress_frontend *fe,
+                                      erofs_off_t la)
 {
        if (fe->backmost)
                return true;
@@ -677,25 +560,23 @@ should_alloc_managed_pages(struct z_erofs_vle_frontend 
*fe, erofs_off_t la)
        return false;
 }
 #else
-static inline bool
-should_alloc_managed_pages(struct z_erofs_vle_frontend *fe, erofs_off_t la)
+static bool should_alloc_managed_pages(struct z_erofs_decompress_frontend *fe,
+                                      erofs_off_t la)
 {
        return false;
 }
 #endif
 
-static int z_erofs_do_read_page(struct z_erofs_vle_frontend *fe,
+static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
                                struct page *page,
-                               struct list_head *page_pool)
+                               struct list_head *pagepool)
 {
-       struct super_block *const sb = fe->inode->i_sb;
-       struct erofs_sb_info *const sbi __maybe_unused = EROFS_SB(sb);
+       struct inode *const inode = fe->inode;
+       struct erofs_sb_info *const sbi __maybe_unused = EROFS_I_SB(inode);
        struct erofs_map_blocks *const map = &fe->map;
-       struct z_erofs_vle_work_builder *const builder = &fe->builder;
+       struct z_erofs_collector *const clt = &fe->clt;
        const loff_t offset = page_offset(page);
-
-       bool tight = builder_is_hooked(builder);
-       struct z_erofs_vle_work *work = builder->work;
+       bool tight = (clt->mode >= COLLECT_PRIMARY_HOOKED);
 
        enum z_erofs_cache_alloctype cache_strategy;
        enum z_erofs_page_type page_type;
@@ -713,8 +594,8 @@ static int z_erofs_do_read_page(struct z_erofs_vle_frontend 
*fe,
        /* lucky, within the range of the current map_blocks */
        if (offset + cur >= map->m_la &&
            offset + cur < map->m_la + map->m_llen) {
-               /* didn't get a valid unzip work previously (very rare) */
-               if (!builder->work)
+               /* didn't get a valid collection previously (very rare) */
+               if (!clt->cl)
                        goto restart_now;
                goto hitted;
        }
@@ -722,12 +603,12 @@ static int z_erofs_do_read_page(struct 
z_erofs_vle_frontend *fe,
        /* go ahead the next map_blocks */
        debugln("%s: [out-of-range] pos %llu", __func__, offset + cur);
 
-       if (z_erofs_vle_work_iter_end(builder))
+       if (z_erofs_collector_end(clt))
                fe->backmost = false;
 
        map->m_la = offset + cur;
        map->m_llen = 0;
-       err = z_erofs_map_blocks_iter(fe->inode, map, 0);
+       err = z_erofs_map_blocks_iter(inode, map, 0);
        if (unlikely(err))
                goto err_out;
 
@@ -735,10 +616,7 @@ static int z_erofs_do_read_page(struct 
z_erofs_vle_frontend *fe,
        if (unlikely(!(map->m_flags & EROFS_MAP_MAPPED)))
                goto hitted;
 
-       DBG_BUGON(map->m_plen != 1 << sbi->clusterbits);
-       DBG_BUGON(erofs_blkoff(map->m_pa));
-
-       err = z_erofs_vle_work_iter_begin(builder, sb, map, &fe->owned_head);
+       err = z_erofs_collector_begin(clt, inode, map);
        if (unlikely(err))
                goto err_out;
 
@@ -748,13 +626,10 @@ static int z_erofs_do_read_page(struct 
z_erofs_vle_frontend *fe,
        else
                cache_strategy = DONTALLOC;
 
-       preload_compressed_pages(builder, MNGD_MAPPING(sbi),
-                                map->m_pa / PAGE_SIZE,
-                                map->m_plen / PAGE_SIZE,
-                                cache_strategy, page_pool, GFP_KERNEL);
+       preload_compressed_pages(clt, MNGD_MAPPING(sbi),
+                                cache_strategy, pagepool);
 
-       tight &= builder_is_hooked(builder);
-       work = builder->work;
+       tight &= (clt->mode >= COLLECT_PRIMARY_HOOKED);
 hitted:
        cur = end - min_t(unsigned int, offset + end - map->m_la, end);
        if (unlikely(!(map->m_flags & EROFS_MAP_MAPPED))) {
@@ -769,17 +644,17 @@ static int z_erofs_do_read_page(struct 
z_erofs_vle_frontend *fe,
                                Z_EROFS_VLE_PAGE_TYPE_TAIL_SHARED));
 
        if (cur)
-               tight &= builder_is_followed(builder);
+               tight &= (clt->mode >= COLLECT_PRIMARY_FOLLOWED);
 
 retry:
-       err = z_erofs_vle_work_add_page(builder, page, page_type);
+       err = z_erofs_attach_page(clt, page, page_type);
        /* should allocate an additional staging page for pagevec */
        if (err == -EAGAIN) {
                struct page *const newpage =
-                       __stagingpage_alloc(page_pool, GFP_NOFS);
+                       __stagingpage_alloc(pagepool, GFP_NOFS);
 
-               err = z_erofs_vle_work_add_page(builder, newpage,
-                                               Z_EROFS_PAGE_TYPE_EXCLUSIVE);
+               err = z_erofs_attach_page(clt, newpage,
+                                         Z_EROFS_PAGE_TYPE_EXCLUSIVE);
                if (likely(!err))
                        goto retry;
        }
@@ -787,15 +662,14 @@ static int z_erofs_do_read_page(struct 
z_erofs_vle_frontend *fe,
        if (unlikely(err))
                goto err_out;
 
-       index = page->index - map->m_la / PAGE_SIZE;
+       index = page->index - (map->m_la >> PAGE_SHIFT);
 
-       /* FIXME! avoid the last relundant fixup & endio */
        z_erofs_onlinepage_fixup(page, index, true);
 
        /* bump up the number of spiltted parts of a page */
        ++spiltted;
        /* also update nr_pages */
-       work->nr_pages = max_t(pgoff_t, work->nr_pages, index + 1);
+       clt->cl->nr_pages = max_t(pgoff_t, clt->cl->nr_pages, index + 1);
 next_part:
        /* can be used for verification */
        map->m_llen = offset + cur - map->m_la;
@@ -805,7 +679,6 @@ static int z_erofs_do_read_page(struct z_erofs_vle_frontend 
*fe,
                goto repeat;
 
 out:
-       /* FIXME! avoid the last relundant fixup & endio */
        z_erofs_onlinepage_endio(page);
 
        debugln("%s, finish page: %pK spiltted: %u map->m_llen %llu",
@@ -821,7 +694,7 @@ static int z_erofs_do_read_page(struct z_erofs_vle_frontend 
*fe,
 static void z_erofs_vle_unzip_kickoff(void *ptr, int bios)
 {
        tagptr1_t t = tagptr_init(tagptr1_t, ptr);
-       struct z_erofs_vle_unzip_io *io = tagptr_unfold_ptr(t);
+       struct z_erofs_unzip_io *io = tagptr_unfold_ptr(t);
        bool background = tagptr_unfold_tags(t);
 
        if (!background) {
@@ -878,45 +751,38 @@ static inline void z_erofs_vle_read_endio(struct bio *bio)
        bio_put(bio);
 }
 
-static struct page *z_pagemap_global[Z_EROFS_VLE_VMAP_GLOBAL_PAGES];
-static DEFINE_MUTEX(z_pagemap_global_lock);
-
-static int z_erofs_vle_unzip(struct super_block *sb,
-                            struct z_erofs_vle_workgroup *grp,
-                            struct list_head *page_pool)
+static int z_erofs_decompress_pcluster(struct super_block *sb,
+                                      struct z_erofs_pcluster *pcl,
+                                      struct list_head *pagepool)
 {
        struct erofs_sb_info *const sbi = EROFS_SB(sb);
-       const unsigned int clusterpages = erofs_clusterpages(sbi);
-
+       const unsigned int clusterpages = BIT(pcl->clusterbits);
        struct z_erofs_pagevec_ctor ctor;
-       unsigned int nr_pages;
-       unsigned int sparsemem_pages = 0;
-       struct page *pages_onstack[Z_EROFS_VLE_VMAP_ONSTACK_PAGES];
+       unsigned int i, outputsize, llen, nr_pages;
+       struct page *pages_onstack[Z_EROFS_VMAP_ONSTACK_PAGES];
        struct page **pages, **compressed_pages, *page;
-       unsigned int algorithm;
-       unsigned int i, outputsize;
 
        enum z_erofs_page_type page_type;
        bool overlapped, partial;
-       struct z_erofs_vle_work *work;
+       struct z_erofs_collection *cl;
        int err;
 
        might_sleep();
-       work = z_erofs_vle_grab_primary_work(grp);
-       DBG_BUGON(!READ_ONCE(work->nr_pages));
+       cl = z_erofs_primarycollection(pcl);
+       DBG_BUGON(!READ_ONCE(cl->nr_pages));
 
-       mutex_lock(&work->lock);
-       nr_pages = work->nr_pages;
+       mutex_lock(&cl->lock);
+       nr_pages = cl->nr_pages;
 
-       if (likely(nr_pages <= Z_EROFS_VLE_VMAP_ONSTACK_PAGES))
+       if (likely(nr_pages <= Z_EROFS_VMAP_ONSTACK_PAGES)) {
                pages = pages_onstack;
-       else if (nr_pages <= Z_EROFS_VLE_VMAP_GLOBAL_PAGES &&
-                mutex_trylock(&z_pagemap_global_lock))
+       } else if (nr_pages <= Z_EROFS_VMAP_GLOBAL_PAGES &&
+                  mutex_trylock(&z_pagemap_global_lock)) {
                pages = z_pagemap_global;
-       else {
+       } else {
                gfp_t gfp_flags = GFP_KERNEL;
 
-               if (nr_pages > Z_EROFS_VLE_VMAP_GLOBAL_PAGES)
+               if (nr_pages > Z_EROFS_VMAP_GLOBAL_PAGES)
                        gfp_flags |= __GFP_NOFAIL;
 
                pages = kvmalloc_array(nr_pages, sizeof(struct page *),
@@ -933,9 +799,9 @@ static int z_erofs_vle_unzip(struct super_block *sb,
                pages[i] = NULL;
 
        z_erofs_pagevec_ctor_init(&ctor, Z_EROFS_NR_INLINE_PAGEVECS,
-                                 work->pagevec, 0);
+                                 cl->pagevec, 0);
 
-       for (i = 0; i < work->vcnt; ++i) {
+       for (i = 0; i < cl->vcnt; ++i) {
                unsigned int pagenr;
 
                page = z_erofs_pagevec_dequeue(&ctor, &page_type);
@@ -944,7 +810,7 @@ static int z_erofs_vle_unzip(struct super_block *sb,
                DBG_BUGON(!page);
                DBG_BUGON(!page->mapping);
 
-               if (z_erofs_put_stagingpage(page_pool, page))
+               if (z_erofs_put_stagingpage(pagepool, page))
                        continue;
 
                if (page_type == Z_EROFS_VLE_PAGE_TYPE_HEAD)
@@ -957,12 +823,10 @@ static int z_erofs_vle_unzip(struct super_block *sb,
 
                pages[pagenr] = page;
        }
-       sparsemem_pages = i;
-
        z_erofs_pagevec_ctor_exit(&ctor, true);
 
        overlapped = false;
-       compressed_pages = grp->compressed_pages;
+       compressed_pages = pcl->compressed_pages;
 
        err = 0;
        for (i = 0; i < clusterpages; ++i) {
@@ -989,7 +853,6 @@ static int z_erofs_vle_unzip(struct super_block *sb,
 
                        DBG_BUGON(pagenr >= nr_pages);
                        DBG_BUGON(pages[pagenr]);
-                       ++sparsemem_pages;
                        pages[pagenr] = page;
 
                        overlapped = true;
@@ -1005,30 +868,26 @@ static int z_erofs_vle_unzip(struct super_block *sb,
        if (unlikely(err))
                goto out;
 
-       if (nr_pages << PAGE_SHIFT >= work->pageofs + grp->llen) {
-               outputsize = grp->llen;
-               partial = !(grp->flags & Z_EROFS_VLE_WORKGRP_FULL_LENGTH);
+       llen = pcl->length >> Z_EROFS_PCLUSTER_LENGTH_BIT;
+       if (nr_pages << PAGE_SHIFT >= cl->pageofs + llen) {
+               outputsize = llen;
+               partial = !(pcl->length & Z_EROFS_PCLUSTER_FULL_LENGTH);
        } else {
-               outputsize = (nr_pages << PAGE_SHIFT) - work->pageofs;
+               outputsize = (nr_pages << PAGE_SHIFT) - cl->pageofs;
                partial = true;
        }
 
-       if (z_erofs_vle_workgrp_fmt(grp) == Z_EROFS_VLE_WORKGRP_FMT_PLAIN)
-               algorithm = Z_EROFS_COMPRESSION_SHIFTED;
-       else
-               algorithm = Z_EROFS_COMPRESSION_LZ4;
-
        err = z_erofs_decompress(&(struct z_erofs_decompress_req) {
                                        .sb = sb,
                                        .in = compressed_pages,
                                        .out = pages,
-                                       .pageofs_out = work->pageofs,
+                                       .pageofs_out = cl->pageofs,
                                        .inputsize = PAGE_SIZE,
                                        .outputsize = outputsize,
-                                       .alg = algorithm,
+                                       .alg = pcl->algorithmformat,
                                        .inplace_io = overlapped,
                                        .partial_decoding = partial
-                                }, page_pool);
+                                }, pagepool);
 
 out:
        /* must handle all compressed pages before endding pages */
@@ -1039,7 +898,7 @@ static int z_erofs_vle_unzip(struct super_block *sb,
                        continue;
 
                /* recycle all individual staging pages */
-               (void)z_erofs_put_stagingpage(page_pool, page);
+               (void)z_erofs_put_stagingpage(pagepool, page);
 
                WRITE_ONCE(compressed_pages[i], NULL);
        }
@@ -1052,7 +911,7 @@ static int z_erofs_vle_unzip(struct super_block *sb,
                DBG_BUGON(!page->mapping);
 
                /* recycle all individual staging pages */
-               if (z_erofs_put_stagingpage(page_pool, page))
+               if (z_erofs_put_stagingpage(pagepool, page))
                        continue;
 
                if (unlikely(err < 0))
@@ -1066,65 +925,63 @@ static int z_erofs_vle_unzip(struct super_block *sb,
        else if (unlikely(pages != pages_onstack))
                kvfree(pages);
 
-       work->nr_pages = 0;
-       work->vcnt = 0;
+       cl->nr_pages = 0;
+       cl->vcnt = 0;
 
-       /* all work locks MUST be taken before the following line */
+       /* all cl locks MUST be taken before the following line */
+       WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_NIL);
 
-       WRITE_ONCE(grp->next, Z_EROFS_VLE_WORKGRP_NIL);
+       /* all cl locks SHOULD be released right now */
+       mutex_unlock(&cl->lock);
 
-       /* all work locks SHOULD be released right now */
-       mutex_unlock(&work->lock);
-
-       z_erofs_vle_work_release(work);
+       z_erofs_collection_put(cl);
        return err;
 }
 
 static void z_erofs_vle_unzip_all(struct super_block *sb,
-                                 struct z_erofs_vle_unzip_io *io,
-                                 struct list_head *page_pool)
+                                 struct z_erofs_unzip_io *io,
+                                 struct list_head *pagepool)
 {
-       z_erofs_vle_owned_workgrp_t owned = io->head;
+       z_erofs_next_pcluster_t owned = io->head;
 
-       while (owned != Z_EROFS_VLE_WORKGRP_TAIL_CLOSED) {
-               struct z_erofs_vle_workgroup *grp;
+       while (owned != Z_EROFS_PCLUSTER_TAIL_CLOSED) {
+               struct z_erofs_pcluster *pcl;
 
                /* no possible that 'owned' equals Z_EROFS_WORK_TPTR_TAIL */
-               DBG_BUGON(owned == Z_EROFS_VLE_WORKGRP_TAIL);
+               DBG_BUGON(owned == Z_EROFS_PCLUSTER_TAIL);
 
                /* no possible that 'owned' equals NULL */
-               DBG_BUGON(owned == Z_EROFS_VLE_WORKGRP_NIL);
+               DBG_BUGON(owned == Z_EROFS_PCLUSTER_NIL);
 
-               grp = container_of(owned, struct z_erofs_vle_workgroup, next);
-               owned = READ_ONCE(grp->next);
+               pcl = container_of(owned, struct z_erofs_pcluster, next);
+               owned = READ_ONCE(pcl->next);
 
-               z_erofs_vle_unzip(sb, grp, page_pool);
+               z_erofs_decompress_pcluster(sb, pcl, pagepool);
        }
 }
 
 static void z_erofs_vle_unzip_wq(struct work_struct *work)
 {
-       struct z_erofs_vle_unzip_io_sb *iosb = container_of(work,
-               struct z_erofs_vle_unzip_io_sb, io.u.work);
-       LIST_HEAD(page_pool);
+       struct z_erofs_unzip_io_sb *iosb =
+               container_of(work, struct z_erofs_unzip_io_sb, io.u.work);
+       LIST_HEAD(pagepool);
 
-       DBG_BUGON(iosb->io.head == Z_EROFS_VLE_WORKGRP_TAIL_CLOSED);
-       z_erofs_vle_unzip_all(iosb->sb, &iosb->io, &page_pool);
+       DBG_BUGON(iosb->io.head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
+       z_erofs_vle_unzip_all(iosb->sb, &iosb->io, &pagepool);
 
-       put_pages_list(&page_pool);
+       put_pages_list(&pagepool);
        kvfree(iosb);
 }
 
-static struct page *
-pickup_page_for_submission(struct z_erofs_vle_workgroup *grp,
-                          unsigned int nr,
-                          struct list_head *pagepool,
-                          struct address_space *mc,
-                          gfp_t gfp)
+static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
+                                              unsigned int nr,
+                                              struct list_head *pagepool,
+                                              struct address_space *mc,
+                                              gfp_t gfp)
 {
        /* determined at compile time to avoid too many #ifdefs */
        const bool nocache = __builtin_constant_p(mc) ? !mc : false;
-       const pgoff_t index = grp->obj.index;
+       const pgoff_t index = pcl->obj.index;
        bool tocache = false;
 
        struct address_space *mapping;
@@ -1134,7 +991,7 @@ pickup_page_for_submission(struct z_erofs_vle_workgroup 
*grp,
        int justfound;
 
 repeat:
-       page = READ_ONCE(grp->compressed_pages[nr]);
+       page = READ_ONCE(pcl->compressed_pages[nr]);
        oldpage = page;
 
        if (!page)
@@ -1186,7 +1043,7 @@ pickup_page_for_submission(struct z_erofs_vle_workgroup 
*grp,
 
        /* the page is still in manage cache */
        if (page->mapping == mc) {
-               WRITE_ONCE(grp->compressed_pages[nr], page);
+               WRITE_ONCE(pcl->compressed_pages[nr], page);
 
                ClearPageError(page);
                if (!PagePrivate(page)) {
@@ -1198,7 +1055,7 @@ pickup_page_for_submission(struct z_erofs_vle_workgroup 
*grp,
                        DBG_BUGON(!justfound);
 
                        justfound = 0;
-                       set_page_private(page, (unsigned long)grp);
+                       set_page_private(page, (unsigned long)pcl);
                        SetPagePrivate(page);
                }
 
@@ -1222,7 +1079,7 @@ pickup_page_for_submission(struct z_erofs_vle_workgroup 
*grp,
        put_page(page);
 out_allocpage:
        page = __stagingpage_alloc(pagepool, gfp);
-       if (oldpage != cmpxchg(&grp->compressed_pages[nr], oldpage, page)) {
+       if (oldpage != cmpxchg(&pcl->compressed_pages[nr], oldpage, page)) {
                list_add(&page->lru, pagepool);
                cpu_relax();
                goto repeat;
@@ -1234,18 +1091,17 @@ pickup_page_for_submission(struct z_erofs_vle_workgroup 
*grp,
                goto out;
        }
 
-       set_page_private(page, (unsigned long)grp);
+       set_page_private(page, (unsigned long)pcl);
        SetPagePrivate(page);
 out:   /* the only exit (for tracing and debugging) */
        return page;
 }
 
-static struct z_erofs_vle_unzip_io *
-jobqueue_init(struct super_block *sb,
-             struct z_erofs_vle_unzip_io *io,
-             bool foreground)
+static struct z_erofs_unzip_io *jobqueue_init(struct super_block *sb,
+                                             struct z_erofs_unzip_io *io,
+                                             bool foreground)
 {
-       struct z_erofs_vle_unzip_io_sb *iosb;
+       struct z_erofs_unzip_io_sb *iosb;
 
        if (foreground) {
                /* waitqueue available for foreground io */
@@ -1264,11 +1120,11 @@ jobqueue_init(struct super_block *sb,
        iosb->sb = sb;
        INIT_WORK(&io->u.work, z_erofs_vle_unzip_wq);
 out:
-       io->head = Z_EROFS_VLE_WORKGRP_TAIL_CLOSED;
+       io->head = Z_EROFS_PCLUSTER_TAIL_CLOSED;
        return io;
 }
 
-/* define workgroup jobqueue types */
+/* define decompression jobqueue types */
 enum {
 #ifdef EROFS_FS_HAS_MANAGED_CACHE
        JQ_BYPASS,
@@ -1278,15 +1134,15 @@ enum {
 };
 
 static void *jobqueueset_init(struct super_block *sb,
-                             z_erofs_vle_owned_workgrp_t qtail[],
-                             struct z_erofs_vle_unzip_io *q[],
-                             struct z_erofs_vle_unzip_io *fgq,
+                             z_erofs_next_pcluster_t qtail[],
+                             struct z_erofs_unzip_io *q[],
+                             struct z_erofs_unzip_io *fgq,
                              bool forcefg)
 {
 #ifdef EROFS_FS_HAS_MANAGED_CACHE
        /*
         * if managed cache is enabled, bypass jobqueue is needed,
-        * no need to read from device for all workgroups in this queue.
+        * no need to read from device for all pclusters in this queue.
         */
        q[JQ_BYPASS] = jobqueue_init(sb, fgq + JQ_BYPASS, true);
        qtail[JQ_BYPASS] = &q[JQ_BYPASS]->head;
@@ -1299,26 +1155,26 @@ static void *jobqueueset_init(struct super_block *sb,
 }
 
 #ifdef EROFS_FS_HAS_MANAGED_CACHE
-static void move_to_bypass_jobqueue(struct z_erofs_vle_workgroup *grp,
-                                   z_erofs_vle_owned_workgrp_t qtail[],
-                                   z_erofs_vle_owned_workgrp_t owned_head)
+static void move_to_bypass_jobqueue(struct z_erofs_pcluster *pcl,
+                                   z_erofs_next_pcluster_t qtail[],
+                                   z_erofs_next_pcluster_t owned_head)
 {
-       z_erofs_vle_owned_workgrp_t *const submit_qtail = qtail[JQ_SUBMIT];
-       z_erofs_vle_owned_workgrp_t *const bypass_qtail = qtail[JQ_BYPASS];
+       z_erofs_next_pcluster_t *const submit_qtail = qtail[JQ_SUBMIT];
+       z_erofs_next_pcluster_t *const bypass_qtail = qtail[JQ_BYPASS];
 
-       DBG_BUGON(owned_head == Z_EROFS_VLE_WORKGRP_TAIL_CLOSED);
-       if (owned_head == Z_EROFS_VLE_WORKGRP_TAIL)
-               owned_head = Z_EROFS_VLE_WORKGRP_TAIL_CLOSED;
+       DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
+       if (owned_head == Z_EROFS_PCLUSTER_TAIL)
+               owned_head = Z_EROFS_PCLUSTER_TAIL_CLOSED;
 
-       WRITE_ONCE(grp->next, Z_EROFS_VLE_WORKGRP_TAIL_CLOSED);
+       WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_TAIL_CLOSED);
 
        WRITE_ONCE(*submit_qtail, owned_head);
-       WRITE_ONCE(*bypass_qtail, &grp->next);
+       WRITE_ONCE(*bypass_qtail, &pcl->next);
 
-       qtail[JQ_BYPASS] = &grp->next;
+       qtail[JQ_BYPASS] = &pcl->next;
 }
 
-static bool postsubmit_is_all_bypassed(struct z_erofs_vle_unzip_io *q[],
+static bool postsubmit_is_all_bypassed(struct z_erofs_unzip_io *q[],
                                       unsigned int nr_bios,
                                       bool force_fg)
 {
@@ -1329,21 +1185,19 @@ static bool postsubmit_is_all_bypassed(struct 
z_erofs_vle_unzip_io *q[],
        if (force_fg || nr_bios)
                return false;
 
-       kvfree(container_of(q[JQ_SUBMIT],
-                           struct z_erofs_vle_unzip_io_sb,
-                           io));
+       kvfree(container_of(q[JQ_SUBMIT], struct z_erofs_unzip_io_sb, io));
        return true;
 }
 #else
-static void move_to_bypass_jobqueue(struct z_erofs_vle_workgroup *grp,
-                                   z_erofs_vle_owned_workgrp_t qtail[],
-                                   z_erofs_vle_owned_workgrp_t owned_head)
+static void move_to_bypass_jobqueue(struct z_erofs_pcluster *pcl,
+                                   z_erofs_next_pcluster_t qtail[],
+                                   z_erofs_next_pcluster_t owned_head)
 {
        /* impossible to bypass submission for managed cache disabled */
        DBG_BUGON(1);
 }
 
-static bool postsubmit_is_all_bypassed(struct z_erofs_vle_unzip_io *q[],
+static bool postsubmit_is_all_bypassed(struct z_erofs_unzip_io *q[],
                                       unsigned int nr_bios,
                                       bool force_fg)
 {
@@ -1354,17 +1208,14 @@ static bool postsubmit_is_all_bypassed(struct 
z_erofs_vle_unzip_io *q[],
 #endif
 
 static bool z_erofs_vle_submit_all(struct super_block *sb,
-                                  z_erofs_vle_owned_workgrp_t owned_head,
+                                  z_erofs_next_pcluster_t owned_head,
                                   struct list_head *pagepool,
-                                  struct z_erofs_vle_unzip_io *fgq,
+                                  struct z_erofs_unzip_io *fgq,
                                   bool force_fg)
 {
-       struct erofs_sb_info *const sbi = EROFS_SB(sb);
-       const unsigned int clusterpages = erofs_clusterpages(sbi);
-       const gfp_t gfp = GFP_NOFS;
-
-       z_erofs_vle_owned_workgrp_t qtail[NR_JOBQUEUES];
-       struct z_erofs_vle_unzip_io *q[NR_JOBQUEUES];
+       struct erofs_sb_info *const sbi __maybe_unused = EROFS_SB(sb);
+       z_erofs_next_pcluster_t qtail[NR_JOBQUEUES];
+       struct z_erofs_unzip_io *q[NR_JOBQUEUES];
        struct bio *bio;
        void *bi_private;
        /* since bio will be NULL, no need to initialize last_index */
@@ -1372,7 +1223,7 @@ static bool z_erofs_vle_submit_all(struct super_block *sb,
        bool force_submit = false;
        unsigned int nr_bios;
 
-       if (unlikely(owned_head == Z_EROFS_VLE_WORKGRP_TAIL))
+       if (unlikely(owned_head == Z_EROFS_PCLUSTER_TAIL))
                return false;
 
        force_submit = false;
@@ -1384,29 +1235,32 @@ static bool z_erofs_vle_submit_all(struct super_block 
*sb,
        q[JQ_SUBMIT]->head = owned_head;
 
        do {
-               struct z_erofs_vle_workgroup *grp;
+               struct z_erofs_pcluster *pcl;
+               unsigned int clusterpages;
                pgoff_t first_index;
                struct page *page;
                unsigned int i = 0, bypass = 0;
                int err;
 
                /* no possible 'owned_head' equals the following */
-               DBG_BUGON(owned_head == Z_EROFS_VLE_WORKGRP_TAIL_CLOSED);
-               DBG_BUGON(owned_head == Z_EROFS_VLE_WORKGRP_NIL);
+               DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
+               DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_NIL);
+
+               pcl = container_of(owned_head, struct z_erofs_pcluster, next);
 
-               grp = container_of(owned_head,
-                                  struct z_erofs_vle_workgroup, next);
+               clusterpages = BIT(pcl->clusterbits);
 
                /* close the main owned chain at first */
-               owned_head = cmpxchg(&grp->next, Z_EROFS_VLE_WORKGRP_TAIL,
-                                    Z_EROFS_VLE_WORKGRP_TAIL_CLOSED);
+               owned_head = cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_TAIL,
+                                    Z_EROFS_PCLUSTER_TAIL_CLOSED);
 
-               first_index = grp->obj.index;
+               first_index = pcl->obj.index;
                force_submit |= (first_index != last_index + 1);
 
 repeat:
-               page = pickup_page_for_submission(grp, i, pagepool,
-                                                 MNGD_MAPPING(sbi), gfp);
+               page = pickup_page_for_submission(pcl, i, pagepool,
+                                                 MNGD_MAPPING(sbi),
+                                                 GFP_NOFS);
                if (!page) {
                        force_submit = true;
                        ++bypass;
@@ -1437,10 +1291,10 @@ static bool z_erofs_vle_submit_all(struct super_block 
*sb,
                        goto repeat;
 
                if (bypass < clusterpages)
-                       qtail[JQ_SUBMIT] = &grp->next;
+                       qtail[JQ_SUBMIT] = &pcl->next;
                else
-                       move_to_bypass_jobqueue(grp, qtail, owned_head);
-       } while (owned_head != Z_EROFS_VLE_WORKGRP_TAIL);
+                       move_to_bypass_jobqueue(pcl, qtail, owned_head);
+       } while (owned_head != Z_EROFS_PCLUSTER_TAIL);
 
        if (bio)
                __submit_bio(bio, REQ_OP_READ, 0);
@@ -1452,17 +1306,19 @@ static bool z_erofs_vle_submit_all(struct super_block 
*sb,
        return true;
 }
 
-static void z_erofs_submit_and_unzip(struct z_erofs_vle_frontend *f,
+static void z_erofs_submit_and_unzip(struct super_block *sb,
+                                    struct z_erofs_collector *clt,
                                     struct list_head *pagepool,
                                     bool force_fg)
 {
-       struct super_block *sb = f->inode->i_sb;
-       struct z_erofs_vle_unzip_io io[NR_JOBQUEUES];
+       struct z_erofs_unzip_io io[NR_JOBQUEUES];
 
-       if (!z_erofs_vle_submit_all(sb, f->owned_head, pagepool, io, force_fg))
+       if (!z_erofs_vle_submit_all(sb, clt->owned_head,
+                                   pagepool, io, force_fg))
                return;
 
 #ifdef EROFS_FS_HAS_MANAGED_CACHE
+       /* decompress no I/O pclusters immediately */
        z_erofs_vle_unzip_all(sb, &io[JQ_BYPASS], pagepool);
 #endif
        if (!force_fg)
@@ -1480,7 +1336,7 @@ static int z_erofs_vle_normalaccess_readpage(struct file 
*file,
                                             struct page *page)
 {
        struct inode *const inode = page->mapping->host;
-       struct z_erofs_vle_frontend f = VLE_FRONTEND_INIT(inode);
+       struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
        int err;
        LIST_HEAD(pagepool);
 
@@ -1489,14 +1345,14 @@ static int z_erofs_vle_normalaccess_readpage(struct 
file *file,
        f.headoffset = (erofs_off_t)page->index << PAGE_SHIFT;
 
        err = z_erofs_do_read_page(&f, page, &pagepool);
-       (void)z_erofs_vle_work_iter_end(&f.builder);
+       (void)z_erofs_collector_end(&f.clt);
 
        if (err) {
                errln("%s, failed to read, err [%d]", __func__, err);
                goto out;
        }
 
-       z_erofs_submit_and_unzip(&f, &pagepool, true);
+       z_erofs_submit_and_unzip(inode->i_sb, &f.clt, &pagepool, true);
 out:
        if (f.map.mpage)
                put_page(f.map.mpage);
@@ -1521,7 +1377,7 @@ static int z_erofs_vle_normalaccess_readpages(struct file 
*filp,
        struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
 
        bool sync = should_decompress_synchronously(sbi, nr_pages);
-       struct z_erofs_vle_frontend f = VLE_FRONTEND_INIT(inode);
+       struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
        gfp_t gfp = mapping_gfp_constraint(mapping, GFP_KERNEL);
        struct page *head = NULL;
        LIST_HEAD(pagepool);
@@ -1567,13 +1423,12 @@ static int z_erofs_vle_normalaccess_readpages(struct 
file *filp,
                        errln("%s, readahead error at page %lu of nid %llu",
                              __func__, page->index, vi->nid);
                }
-
                put_page(page);
        }
 
-       (void)z_erofs_vle_work_iter_end(&f.builder);
+       (void)z_erofs_collector_end(&f.clt);
 
-       z_erofs_submit_and_unzip(&f, &pagepool, sync);
+       z_erofs_submit_and_unzip(inode->i_sb, &f.clt, &pagepool, sync);
 
        if (f.map.mpage)
                put_page(f.map.mpage);
diff --git a/drivers/staging/erofs/zdata.h b/drivers/staging/erofs/zdata.h
index 6574d43ba877..1f51d80fa89f 100644
--- a/drivers/staging/erofs/zdata.h
+++ b/drivers/staging/erofs/zdata.h
@@ -18,80 +18,77 @@
  * Structure fields follow one of the following exclusion rules.
  *
  * I: Modifiable by initialization/destruction paths and read-only
- *    for everyone else.
+ *    for everyone else;
  *
+ * L: Field should be protected by pageset lock;
+ *
+ * A: Field should be accessed / updated in atomic for parallelized code.
  */
-
-struct z_erofs_vle_work {
+struct z_erofs_collection {
        struct mutex lock;
 
-       /* I: decompression offset in page */
+       /* I: page offset of start position of decompression */
        unsigned short pageofs;
+
+       /* L: maximum relative page index in pagevec[] */
        unsigned short nr_pages;
 
-       /* L: queued pages in pagevec[] */
+       /* L: total number of pages in pagevec[] */
        unsigned int vcnt;
 
        union {
-               /* L: pagevec */
+               /* L: inline a certain number of pagevecs for bootstrap */
                erofs_vtptr_t pagevec[Z_EROFS_NR_INLINE_PAGEVECS];
+
+               /* I: can be used to free the pcluster by RCU. */
                struct rcu_head rcu;
        };
 };
 
-#define Z_EROFS_VLE_WORKGRP_FMT_PLAIN        0
-#define Z_EROFS_VLE_WORKGRP_FMT_LZ4          1
-#define Z_EROFS_VLE_WORKGRP_FMT_MASK         1
-#define Z_EROFS_VLE_WORKGRP_FULL_LENGTH      2
+#define Z_EROFS_PCLUSTER_FULL_LENGTH    0x00000001
+#define Z_EROFS_PCLUSTER_LENGTH_BIT     1
 
-typedef void *z_erofs_vle_owned_workgrp_t;
+/*
+ * let's leave a type here in case of introducing
+ * another tagged pointer later.
+ */
+typedef void *z_erofs_next_pcluster_t;
 
-struct z_erofs_vle_workgroup {
+struct z_erofs_pcluster {
        struct erofs_workgroup obj;
-       struct z_erofs_vle_work work;
+       struct z_erofs_collection primary_collection;
 
-       /* point to next owned_workgrp_t */
-       z_erofs_vle_owned_workgrp_t next;
+       /* A: point to next chained pcluster or TAILs */
+       z_erofs_next_pcluster_t next;
 
-       /* compressed pages (including multi-usage pages) */
+       /* A: compressed pages (including multi-usage pages) */
        struct page *compressed_pages[Z_EROFS_CLUSTER_MAX_PAGES];
-       unsigned int llen, flags;
+
+       /* A: lower limit of decompressed length and if full length or not */
+       unsigned int length;
+
+       /* I: compression algorithm format */
+       unsigned char algorithmformat;
+       /* I: bit shift of physical cluster size */
+       unsigned char clusterbits;
 };
 
+#define z_erofs_primarycollection(pcluster) (&(pcluster)->primary_collection)
+
 /* let's avoid the valid 32-bit kernel addresses */
 
 /* the chained workgroup has't submitted io (still open) */
-#define Z_EROFS_VLE_WORKGRP_TAIL        ((void *)0x5F0ECAFE)
+#define Z_EROFS_PCLUSTER_TAIL           ((void *)0x5F0ECAFE)
 /* the chained workgroup has already submitted io */
-#define Z_EROFS_VLE_WORKGRP_TAIL_CLOSED ((void *)0x5F0EDEAD)
+#define Z_EROFS_PCLUSTER_TAIL_CLOSED    ((void *)0x5F0EDEAD)
 
-#define Z_EROFS_VLE_WORKGRP_NIL         (NULL)
+#define Z_EROFS_PCLUSTER_NIL            (NULL)
 
-#define z_erofs_vle_workgrp_fmt(grp)   \
-       ((grp)->flags & Z_EROFS_VLE_WORKGRP_FMT_MASK)
+#define Z_EROFS_WORKGROUP_SIZE  sizeof(struct z_erofs_pcluster)
 
-static inline void z_erofs_vle_set_workgrp_fmt(
-       struct z_erofs_vle_workgroup *grp,
-       unsigned int fmt)
-{
-       grp->flags = fmt | (grp->flags & ~Z_EROFS_VLE_WORKGRP_FMT_MASK);
-}
-
-
-/* definitions if multiref is disabled */
-#define z_erofs_vle_grab_primary_work(grp)     (&(grp)->work)
-#define z_erofs_vle_grab_work(grp, pageofs)    (&(grp)->work)
-#define z_erofs_vle_work_workgroup(wrk, primary)       \
-       ((primary) ? container_of(wrk,  \
-               struct z_erofs_vle_workgroup, work) : \
-               ({ BUG(); (void *)NULL; }))
-
-
-#define Z_EROFS_WORKGROUP_SIZE       sizeof(struct z_erofs_vle_workgroup)
-
-struct z_erofs_vle_unzip_io {
+struct z_erofs_unzip_io {
        atomic_t pending_bios;
-       z_erofs_vle_owned_workgrp_t head;
+       z_erofs_next_pcluster_t head;
 
        union {
                wait_queue_head_t wait;
@@ -99,8 +96,8 @@ struct z_erofs_vle_unzip_io {
        } u;
 };
 
-struct z_erofs_vle_unzip_io_sb {
-       struct z_erofs_vle_unzip_io io;
+struct z_erofs_unzip_io_sb {
+       struct z_erofs_unzip_io io;
        struct super_block *sb;
 };
 
@@ -117,8 +114,8 @@ static inline bool erofs_page_is_managed(const struct 
erofs_sb_info *sbi,
                                         struct page *page) { return false; }
 #endif /* !EROFS_FS_HAS_MANAGED_CACHE */
 
-#define Z_EROFS_ONLINEPAGE_COUNT_BITS 2
-#define Z_EROFS_ONLINEPAGE_COUNT_MASK ((1 << Z_EROFS_ONLINEPAGE_COUNT_BITS) - 
1)
+#define Z_EROFS_ONLINEPAGE_COUNT_BITS   2
+#define Z_EROFS_ONLINEPAGE_COUNT_MASK   ((1 << Z_EROFS_ONLINEPAGE_COUNT_BITS) 
- 1)
 #define Z_EROFS_ONLINEPAGE_INDEX_SHIFT  (Z_EROFS_ONLINEPAGE_COUNT_BITS)
 
 /*
@@ -193,13 +190,12 @@ static inline void z_erofs_onlinepage_endio(struct page 
*page)
                        SetPageUptodate(page);
                unlock_page(page);
        }
-
        debugln("%s, page %p value %x", __func__, page, atomic_read(u.o));
 }
 
-#define Z_EROFS_VLE_VMAP_ONSTACK_PAGES \
+#define Z_EROFS_VMAP_ONSTACK_PAGES     \
        min_t(unsigned int, THREAD_SIZE / 8 / sizeof(struct page *), 96U)
-#define Z_EROFS_VLE_VMAP_GLOBAL_PAGES  2048
+#define Z_EROFS_VMAP_GLOBAL_PAGES      2048
 
 #endif
 
-- 
2.17.1

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