fs/erofs/zdata.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2018 HUAWEI, Inc.
   4  *             https://www.huawei.com/
   5  */
   6 #include "zdata.h"
   7 #include "compress.h"
   8 #include <linux/prefetch.h>
   9
  10 #include <trace/events/erofs.h>
  11
  12 /*
  13  * since pclustersize is variable for big pcluster feature, introduce slab
  14  * pools implementation for different pcluster sizes.
  15  */
  16 struct z_erofs_pcluster_slab {
  17         struct kmem_cache *slab;
  18         unsigned int maxpages;
  19         char name[48];
  20 };
  21
  22 #define _PCLP(n) { .maxpages = n }
  23
  24 static struct z_erofs_pcluster_slab pcluster_pool[] __read_mostly = {
  25         _PCLP(1), _PCLP(4), _PCLP(16), _PCLP(64), _PCLP(128),
  26         _PCLP(Z_EROFS_PCLUSTER_MAX_PAGES)
  27 };
  28
  29 static void z_erofs_destroy_pcluster_pool(void)
  30 {
  31         int i;
  32
  33         for (i = 0; i < ARRAY_SIZE(pcluster_pool); ++i) {
  34                 if (!pcluster_pool[i].slab)
  35                         continue;
  36                 kmem_cache_destroy(pcluster_pool[i].slab);
  37                 pcluster_pool[i].slab = NULL;
  38         }
  39 }
  40
  41 static int z_erofs_create_pcluster_pool(void)
  42 {
  43         struct z_erofs_pcluster_slab *pcs;
  44         struct z_erofs_pcluster *a;
  45         unsigned int size;
  46
  47         for (pcs = pcluster_pool;
  48              pcs < pcluster_pool + ARRAY_SIZE(pcluster_pool); ++pcs) {
  49                 size = struct_size(a, compressed_pages, pcs->maxpages);
  50
  51                 sprintf(pcs->name, "erofs_pcluster-%u", pcs->maxpages);
  52                 pcs->slab = kmem_cache_create(pcs->name, size, 0,
  53                                               SLAB_RECLAIM_ACCOUNT, NULL);
  54                 if (pcs->slab)
  55                         continue;
  56
  57                 z_erofs_destroy_pcluster_pool();
  58                 return -ENOMEM;
  59         }
  60         return 0;
  61 }
  62
  63 static struct z_erofs_pcluster *z_erofs_alloc_pcluster(unsigned int nrpages)
  64 {
  65         int i;
  66
  67         for (i = 0; i < ARRAY_SIZE(pcluster_pool); ++i) {
  68                 struct z_erofs_pcluster_slab *pcs = pcluster_pool + i;
  69                 struct z_erofs_pcluster *pcl;
  70
  71                 if (nrpages > pcs->maxpages)
  72                         continue;
  73
  74                 pcl = kmem_cache_zalloc(pcs->slab, GFP_NOFS);
  75                 if (!pcl)
  76                         return ERR_PTR(-ENOMEM);
  77                 pcl->pclusterpages = nrpages;
  78                 return pcl;
  79         }
  80         return ERR_PTR(-EINVAL);
  81 }
  82
  83 static void z_erofs_free_pcluster(struct z_erofs_pcluster *pcl)
  84 {
  85         int i;
  86
  87         for (i = 0; i < ARRAY_SIZE(pcluster_pool); ++i) {
  88                 struct z_erofs_pcluster_slab *pcs = pcluster_pool + i;
  89
  90                 if (pcl->pclusterpages > pcs->maxpages)
  91                         continue;
  92
  93                 kmem_cache_free(pcs->slab, pcl);
  94                 return;
  95         }
  96         DBG_BUGON(1);
  97 }
  98
  99 /* how to allocate cached pages for a pcluster */
 100 enum z_erofs_cache_alloctype {
 101         DONTALLOC,      /* don't allocate any cached pages */
 102         /*
 103          * try to use cached I/O if page allocation succeeds or fallback
 104          * to in-place I/O instead to avoid any direct reclaim.
 105          */
 106         TRYALLOC,
 107 };
 108
 109 /*
 110  * tagged pointer with 1-bit tag for all compressed pages
 111  * tag 0 - the page is just found with an extra page reference
 112  */
 113 typedef tagptr1_t compressed_page_t;
 114
 115 #define tag_compressed_page_justfound(page) \
 116         tagptr_fold(compressed_page_t, page, 1)
 117
 118 static struct workqueue_struct *z_erofs_workqueue __read_mostly;
 119
 120 void z_erofs_exit_zip_subsystem(void)
 121 {
 122         destroy_workqueue(z_erofs_workqueue);
 123         z_erofs_destroy_pcluster_pool();
 124 }
 125
 126 static inline int z_erofs_init_workqueue(void)
 127 {
 128         const unsigned int onlinecpus = num_possible_cpus();
 129
 130         /*
 131          * no need to spawn too many threads, limiting threads could minimum
 132          * scheduling overhead, perhaps per-CPU threads should be better?
 133          */
 134         z_erofs_workqueue = alloc_workqueue("erofs_unzipd",
 135                                             WQ_UNBOUND | WQ_HIGHPRI,
 136                                             onlinecpus + onlinecpus / 4);
 137         return z_erofs_workqueue ? 0 : -ENOMEM;
 138 }
 139
 140 int __init z_erofs_init_zip_subsystem(void)
 141 {
 142         int err = z_erofs_create_pcluster_pool();
 143
 144         if (err)
 145                 return err;
 146         err = z_erofs_init_workqueue();
 147         if (err)
 148                 z_erofs_destroy_pcluster_pool();
 149         return err;
 150 }
 151
 152 enum z_erofs_collectmode {
 153         COLLECT_SECONDARY,
 154         COLLECT_PRIMARY,
 155         /*
 156          * The current collection was the tail of an exist chain, in addition
 157          * that the previous processed chained collections are all decided to
 158          * be hooked up to it.
 159          * A new chain will be created for the remaining collections which are
 160          * not processed yet, therefore different from COLLECT_PRIMARY_FOLLOWED,
 161          * the next collection cannot reuse the whole page safely in
 162          * the following scenario:
 163          *  ________________________________________________________________
 164          * |      tail (partial) page     |       head (partial) page       |
 165          * |   (belongs to the next cl)   |   (belongs to the current cl)   |
 166          * |_______PRIMARY_FOLLOWED_______|________PRIMARY_HOOKED___________|
 167          */
 168         COLLECT_PRIMARY_HOOKED,
 169         /*
 170          * a weak form of COLLECT_PRIMARY_FOLLOWED, the difference is that it
 171          * could be dispatched into bypass queue later due to uptodated managed
 172          * pages. All related online pages cannot be reused for inplace I/O (or
 173          * pagevec) since it can be directly decoded without I/O submission.
 174          */
 175         COLLECT_PRIMARY_FOLLOWED_NOINPLACE,
 176         /*
 177          * The current collection has been linked with the owned chain, and
 178          * could also be linked with the remaining collections, which means
 179          * if the processing page is the tail page of the collection, thus
 180          * the current collection can safely use the whole page (since
 181          * the previous collection is under control) for in-place I/O, as
 182          * illustrated below:
 183          *  ________________________________________________________________
 184          * |  tail (partial) page |          head (partial) page           |
 185          * |  (of the current cl) |      (of the previous collection)      |
 186          * |  PRIMARY_FOLLOWED or |                                        |
 187          * |_____PRIMARY_HOOKED___|____________PRIMARY_FOLLOWED____________|
 188          *
 189          * [  (*) the above page can be used as inplace I/O.               ]
 190          */
 191         COLLECT_PRIMARY_FOLLOWED,
 192 };
 193
 194 struct z_erofs_collector {
 195         struct z_erofs_pagevec_ctor vector;
 196
 197         struct z_erofs_pcluster *pcl, *tailpcl;
 198         struct z_erofs_collection *cl;
 199         /* a pointer used to pick up inplace I/O pages */
 200         struct page **icpage_ptr;
 201         z_erofs_next_pcluster_t owned_head;
 202
 203         enum z_erofs_collectmode mode;
 204 };
 205
 206 struct z_erofs_decompress_frontend {
 207         struct inode *const inode;
 208
 209         struct z_erofs_collector clt;
 210         struct erofs_map_blocks map;
 211
 212         bool readahead;
 213         /* used for applying cache strategy on the fly */
 214         bool backmost;
 215         erofs_off_t headoffset;
 216 };
 217
 218 #define COLLECTOR_INIT() { \
 219         .owned_head = Z_EROFS_PCLUSTER_TAIL, \
 220         .mode = COLLECT_PRIMARY_FOLLOWED }
 221
 222 #define DECOMPRESS_FRONTEND_INIT(__i) { \
 223         .inode = __i, .clt = COLLECTOR_INIT(), \
 224         .backmost = true, }
 225
 226 static struct page *z_pagemap_global[Z_EROFS_VMAP_GLOBAL_PAGES];
 227 static DEFINE_MUTEX(z_pagemap_global_lock);
 228
 229 static void preload_compressed_pages(struct z_erofs_collector *clt,
 230                                      struct address_space *mc,
 231                                      enum z_erofs_cache_alloctype type,
 232                                      struct page **pagepool)
 233 {
 234         struct z_erofs_pcluster *pcl = clt->pcl;
 235         bool standalone = true;
 236         gfp_t gfp = (mapping_gfp_mask(mc) & ~__GFP_DIRECT_RECLAIM) |
 237                         __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
 238         struct page **pages;
 239         pgoff_t index;
 240
 241         if (clt->mode < COLLECT_PRIMARY_FOLLOWED)
 242                 return;
 243
 244         pages = pcl->compressed_pages;
 245         index = pcl->obj.index;
 246         for (; index < pcl->obj.index + pcl->pclusterpages; ++index, ++pages) {
 247                 struct page *page;
 248                 compressed_page_t t;
 249                 struct page *newpage = NULL;
 250
 251                 /* the compressed page was loaded before */
 252                 if (READ_ONCE(*pages))
 253                         continue;
 254
 255                 page = find_get_page(mc, index);
 256
 257                 if (page) {
 258                         t = tag_compressed_page_justfound(page);
 259                 } else {
 260                         /* I/O is needed, no possible to decompress directly */
 261                         standalone = false;
 262                         switch (type) {
 263                         case TRYALLOC:
 264                                 newpage = erofs_allocpage(pagepool, gfp);
 265                                 if (!newpage)
 266                                         continue;
 267                                 set_page_private(newpage,
 268                                                  Z_EROFS_PREALLOCATED_PAGE);
 269                                 t = tag_compressed_page_justfound(newpage);
 270                                 break;
 271                         default:        /* DONTALLOC */
 272                                 continue;
 273                         }
 274                 }
 275
 276                 if (!cmpxchg_relaxed(pages, NULL, tagptr_cast_ptr(t)))
 277                         continue;
 278
 279                 if (page)
 280                         put_page(page);
 281                 else if (newpage)
 282                         erofs_pagepool_add(pagepool, newpage);
 283         }
 284
 285         /*
 286          * don't do inplace I/O if all compressed pages are available in
 287          * managed cache since it can be moved to the bypass queue instead.
 288          */
 289         if (standalone)
 290                 clt->mode = COLLECT_PRIMARY_FOLLOWED_NOINPLACE;
 291 }
 292
 293 /* called by erofs_shrinker to get rid of all compressed_pages */
 294 int erofs_try_to_free_all_cached_pages(struct erofs_sb_info *sbi,
 295                                        struct erofs_workgroup *grp)
 296 {
 297         struct z_erofs_pcluster *const pcl =
 298                 container_of(grp, struct z_erofs_pcluster, obj);
 299         int i;
 300
 301         /*
 302          * refcount of workgroup is now freezed as 1,
 303          * therefore no need to worry about available decompression users.
 304          */
 305         for (i = 0; i < pcl->pclusterpages; ++i) {
 306                 struct page *page = pcl->compressed_pages[i];
 307
 308                 if (!page)
 309                         continue;
 310
 311                 /* block other users from reclaiming or migrating the page */
 312                 if (!trylock_page(page))
 313                         return -EBUSY;
 314
 315                 if (!erofs_page_is_managed(sbi, page))
 316                         continue;
 317
 318                 /* barrier is implied in the following 'unlock_page' */
 319                 WRITE_ONCE(pcl->compressed_pages[i], NULL);
 320                 detach_page_private(page);
 321                 unlock_page(page);
 322         }
 323         return 0;
 324 }
 325
 326 int erofs_try_to_free_cached_page(struct page *page)
 327 {
 328         struct z_erofs_pcluster *const pcl = (void *)page_private(page);
 329         int ret = 0;    /* 0 - busy */
 330
 331         if (erofs_workgroup_try_to_freeze(&pcl->obj, 1)) {
 332                 unsigned int i;
 333
 334                 for (i = 0; i < pcl->pclusterpages; ++i) {
 335                         if (pcl->compressed_pages[i] == page) {
 336                                 WRITE_ONCE(pcl->compressed_pages[i], NULL);
 337                                 ret = 1;
 338                                 break;
 339                         }
 340                 }
 341                 erofs_workgroup_unfreeze(&pcl->obj, 1);
 342
 343                 if (ret)
 344                         detach_page_private(page);
 345         }
 346         return ret;
 347 }
 348
 349 /* page_type must be Z_EROFS_PAGE_TYPE_EXCLUSIVE */
 350 static bool z_erofs_try_inplace_io(struct z_erofs_collector *clt,
 351                                    struct page *page)
 352 {
 353         struct z_erofs_pcluster *const pcl = clt->pcl;
 354
 355         while (clt->icpage_ptr > pcl->compressed_pages)
 356                 if (!cmpxchg(--clt->icpage_ptr, NULL, page))
 357                         return true;
 358         return false;
 359 }
 360
 361 /* callers must be with collection lock held */
 362 static int z_erofs_attach_page(struct z_erofs_collector *clt,
 363                                struct page *page, enum z_erofs_page_type type,
 364                                bool pvec_safereuse)
 365 {
 366         int ret;
 367
 368         /* give priority for inplaceio */
 369         if (clt->mode >= COLLECT_PRIMARY &&
 370             type == Z_EROFS_PAGE_TYPE_EXCLUSIVE &&
 371             z_erofs_try_inplace_io(clt, page))
 372                 return 0;
 373
 374         ret = z_erofs_pagevec_enqueue(&clt->vector, page, type,
 375                                       pvec_safereuse);
 376         clt->cl->vcnt += (unsigned int)ret;
 377         return ret ? 0 : -EAGAIN;
 378 }
 379
 380 static void z_erofs_try_to_claim_pcluster(struct z_erofs_collector *clt)
 381 {
 382         struct z_erofs_pcluster *pcl = clt->pcl;
 383         z_erofs_next_pcluster_t *owned_head = &clt->owned_head;
 384
 385         /* type 1, nil pcluster (this pcluster doesn't belong to any chain.) */
 386         if (cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_NIL,
 387                     *owned_head) == Z_EROFS_PCLUSTER_NIL) {
 388                 *owned_head = &pcl->next;
 389                 /* so we can attach this pcluster to our submission chain. */
 390                 clt->mode = COLLECT_PRIMARY_FOLLOWED;
 391                 return;
 392         }
 393
 394         /*
 395          * type 2, link to the end of an existing open chain, be careful
 396          * that its submission is controlled by the original attached chain.
 397          */
 398         if (cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_TAIL,
 399                     *owned_head) == Z_EROFS_PCLUSTER_TAIL) {
 400                 *owned_head = Z_EROFS_PCLUSTER_TAIL;
 401                 clt->mode = COLLECT_PRIMARY_HOOKED;
 402                 clt->tailpcl = NULL;
 403                 return;
 404         }
 405         /* type 3, it belongs to a chain, but it isn't the end of the chain */
 406         clt->mode = COLLECT_PRIMARY;
 407 }
 408
 409 static int z_erofs_lookup_collection(struct z_erofs_collector *clt,
 410                                      struct inode *inode,
 411                                      struct erofs_map_blocks *map)
 412 {
 413         struct z_erofs_pcluster *pcl = clt->pcl;
 414         struct z_erofs_collection *cl;
 415         unsigned int length;
 416
 417         /* to avoid unexpected loop formed by corrupted images */
 418         if (clt->owned_head == &pcl->next || pcl == clt->tailpcl) {
 419                 DBG_BUGON(1);
 420                 return -EFSCORRUPTED;
 421         }
 422
 423         cl = z_erofs_primarycollection(pcl);
 424         if (cl->pageofs != (map->m_la & ~PAGE_MASK)) {
 425                 DBG_BUGON(1);
 426                 return -EFSCORRUPTED;
 427         }
 428
 429         length = READ_ONCE(pcl->length);
 430         if (length & Z_EROFS_PCLUSTER_FULL_LENGTH) {
 431                 if ((map->m_llen << Z_EROFS_PCLUSTER_LENGTH_BIT) > length) {
 432                         DBG_BUGON(1);
 433                         return -EFSCORRUPTED;
 434                 }
 435         } else {
 436                 unsigned int llen = map->m_llen << Z_EROFS_PCLUSTER_LENGTH_BIT;
 437
 438                 if (map->m_flags & EROFS_MAP_FULL_MAPPED)
 439                         llen |= Z_EROFS_PCLUSTER_FULL_LENGTH;
 440
 441                 while (llen > length &&
 442                        length != cmpxchg_relaxed(&pcl->length, length, llen)) {
 443                         cpu_relax();
 444                         length = READ_ONCE(pcl->length);
 445                 }
 446         }
 447         mutex_lock(&cl->lock);
 448         /* used to check tail merging loop due to corrupted images */
 449         if (clt->owned_head == Z_EROFS_PCLUSTER_TAIL)
 450                 clt->tailpcl = pcl;
 451
 452         z_erofs_try_to_claim_pcluster(clt);
 453         clt->cl = cl;
 454         return 0;
 455 }
 456
 457 static int z_erofs_register_collection(struct z_erofs_collector *clt,
 458                                        struct inode *inode,
 459                                        struct erofs_map_blocks *map)
 460 {
 461         struct z_erofs_pcluster *pcl;
 462         struct z_erofs_collection *cl;
 463         struct erofs_workgroup *grp;
 464         int err;
 465
 466         if (!(map->m_flags & EROFS_MAP_ENCODED)) {
 467                 DBG_BUGON(1);
 468                 return -EFSCORRUPTED;
 469         }
 470
 471         /* no available pcluster, let's allocate one */
 472         pcl = z_erofs_alloc_pcluster(map->m_plen >> PAGE_SHIFT);
 473         if (IS_ERR(pcl))
 474                 return PTR_ERR(pcl);
 475
 476         atomic_set(&pcl->obj.refcount, 1);
 477         pcl->obj.index = map->m_pa >> PAGE_SHIFT;
 478         pcl->algorithmformat = map->m_algorithmformat;
 479         pcl->length = (map->m_llen << Z_EROFS_PCLUSTER_LENGTH_BIT) |
 480                 (map->m_flags & EROFS_MAP_FULL_MAPPED ?
 481                         Z_EROFS_PCLUSTER_FULL_LENGTH : 0);
 482
 483         /* new pclusters should be claimed as type 1, primary and followed */
 484         pcl->next = clt->owned_head;
 485         clt->mode = COLLECT_PRIMARY_FOLLOWED;
 486
 487         cl = z_erofs_primarycollection(pcl);
 488         cl->pageofs = map->m_la & ~PAGE_MASK;
 489
 490         /*
 491          * lock all primary followed works before visible to others
 492          * and mutex_trylock *never* fails for a new pcluster.
 493          */
 494         mutex_init(&cl->lock);
 495         DBG_BUGON(!mutex_trylock(&cl->lock));
 496
 497         grp = erofs_insert_workgroup(inode->i_sb, &pcl->obj);
 498         if (IS_ERR(grp)) {
 499                 err = PTR_ERR(grp);
 500                 goto err_out;
 501         }
 502
 503         if (grp != &pcl->obj) {
 504                 clt->pcl = container_of(grp, struct z_erofs_pcluster, obj);
 505                 err = -EEXIST;
 506                 goto err_out;
 507         }
 508         /* used to check tail merging loop due to corrupted images */
 509         if (clt->owned_head == Z_EROFS_PCLUSTER_TAIL)
 510                 clt->tailpcl = pcl;
 511         clt->owned_head = &pcl->next;
 512         clt->pcl = pcl;
 513         clt->cl = cl;
 514         return 0;
 515
 516 err_out:
 517         mutex_unlock(&cl->lock);
 518         z_erofs_free_pcluster(pcl);
 519         return err;
 520 }
 521
 522 static int z_erofs_collector_begin(struct z_erofs_collector *clt,
 523                                    struct inode *inode,
 524                                    struct erofs_map_blocks *map)
 525 {
 526         struct erofs_workgroup *grp;
 527         int ret;
 528
 529         DBG_BUGON(clt->cl);
 530
 531         /* must be Z_EROFS_PCLUSTER_TAIL or pointed to previous collection */
 532         DBG_BUGON(clt->owned_head == Z_EROFS_PCLUSTER_NIL);
 533         DBG_BUGON(clt->owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
 534
 535         if (!PAGE_ALIGNED(map->m_pa)) {
 536                 DBG_BUGON(1);
 537                 return -EINVAL;
 538         }
 539
 540         grp = erofs_find_workgroup(inode->i_sb, map->m_pa >> PAGE_SHIFT);
 541         if (grp) {
 542                 clt->pcl = container_of(grp, struct z_erofs_pcluster, obj);
 543         } else {
 544                 ret = z_erofs_register_collection(clt, inode, map);
 545
 546                 if (!ret)
 547                         goto out;
 548                 if (ret != -EEXIST)
 549                         return ret;
 550         }
 551
 552         ret = z_erofs_lookup_collection(clt, inode, map);
 553         if (ret) {
 554                 erofs_workgroup_put(&clt->pcl->obj);
 555                 return ret;
 556         }
 557
 558 out:
 559         z_erofs_pagevec_ctor_init(&clt->vector, Z_EROFS_NR_INLINE_PAGEVECS,
 560                                   clt->cl->pagevec, clt->cl->vcnt);
 561
 562         /* since file-backed online pages are traversed in reverse order */
 563         clt->icpage_ptr = clt->pcl->compressed_pages + clt->pcl->pclusterpages;
 564         return 0;
 565 }
 566
 567 /*
 568  * keep in mind that no referenced pclusters will be freed
 569  * only after a RCU grace period.
 570  */
 571 static void z_erofs_rcu_callback(struct rcu_head *head)
 572 {
 573         struct z_erofs_collection *const cl =
 574                 container_of(head, struct z_erofs_collection, rcu);
 575
 576         z_erofs_free_pcluster(container_of(cl, struct z_erofs_pcluster,
 577                                            primary_collection));
 578 }
 579
 580 void erofs_workgroup_free_rcu(struct erofs_workgroup *grp)
 581 {
 582         struct z_erofs_pcluster *const pcl =
 583                 container_of(grp, struct z_erofs_pcluster, obj);
 584         struct z_erofs_collection *const cl = z_erofs_primarycollection(pcl);
 585
 586         call_rcu(&cl->rcu, z_erofs_rcu_callback);
 587 }
 588
 589 static void z_erofs_collection_put(struct z_erofs_collection *cl)
 590 {
 591         struct z_erofs_pcluster *const pcl =
 592                 container_of(cl, struct z_erofs_pcluster, primary_collection);
 593
 594         erofs_workgroup_put(&pcl->obj);
 595 }
 596
 597 static bool z_erofs_collector_end(struct z_erofs_collector *clt)
 598 {
 599         struct z_erofs_collection *cl = clt->cl;
 600
 601         if (!cl)
 602                 return false;
 603
 604         z_erofs_pagevec_ctor_exit(&clt->vector, false);
 605         mutex_unlock(&cl->lock);
 606
 607         /*
 608          * if all pending pages are added, don't hold its reference
 609          * any longer if the pcluster isn't hosted by ourselves.
 610          */
 611         if (clt->mode < COLLECT_PRIMARY_FOLLOWED_NOINPLACE)
 612                 z_erofs_collection_put(cl);
 613
 614         clt->cl = NULL;
 615         return true;
 616 }
 617
 618 static bool should_alloc_managed_pages(struct z_erofs_decompress_frontend *fe,
 619                                        unsigned int cachestrategy,
 620                                        erofs_off_t la)
 621 {
 622         if (cachestrategy <= EROFS_ZIP_CACHE_DISABLED)
 623                 return false;
 624
 625         if (fe->backmost)
 626                 return true;
 627
 628         return cachestrategy >= EROFS_ZIP_CACHE_READAROUND &&
 629                 la < fe->headoffset;
 630 }
 631
 632 static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 633                                 struct page *page, struct page **pagepool)
 634 {
 635         struct inode *const inode = fe->inode;
 636         struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
 637         struct erofs_map_blocks *const map = &fe->map;
 638         struct z_erofs_collector *const clt = &fe->clt;
 639         const loff_t offset = page_offset(page);
 640         bool tight = true;
 641
 642         enum z_erofs_cache_alloctype cache_strategy;
 643         enum z_erofs_page_type page_type;
 644         unsigned int cur, end, spiltted, index;
 645         int err = 0;
 646
 647         /* register locked file pages as online pages in pack */
 648         z_erofs_onlinepage_init(page);
 649
 650         spiltted = 0;
 651         end = PAGE_SIZE;
 652 repeat:
 653         cur = end - 1;
 654
 655         /* lucky, within the range of the current map_blocks */
 656         if (offset + cur >= map->m_la &&
 657             offset + cur < map->m_la + map->m_llen) {
 658                 /* didn't get a valid collection previously (very rare) */
 659                 if (!clt->cl)
 660                         goto restart_now;
 661                 goto hitted;
 662         }
 663
 664         /* go ahead the next map_blocks */
 665         erofs_dbg("%s: [out-of-range] pos %llu", __func__, offset + cur);
 666
 667         if (z_erofs_collector_end(clt))
 668                 fe->backmost = false;
 669
 670         map->m_la = offset + cur;
 671         map->m_llen = 0;
 672         err = z_erofs_map_blocks_iter(inode, map, 0);
 673         if (err)
 674                 goto err_out;
 675
 676 restart_now:
 677         if (!(map->m_flags & EROFS_MAP_MAPPED))
 678                 goto hitted;
 679
 680         err = z_erofs_collector_begin(clt, inode, map);
 681         if (err)
 682                 goto err_out;
 683
 684         /* preload all compressed pages (maybe downgrade role if necessary) */
 685         if (should_alloc_managed_pages(fe, sbi->opt.cache_strategy, map->m_la))
 686                 cache_strategy = TRYALLOC;
 687         else
 688                 cache_strategy = DONTALLOC;
 689
 690         preload_compressed_pages(clt, MNGD_MAPPING(sbi),
 691                                  cache_strategy, pagepool);
 692
 693 hitted:
 694         /*
 695          * Ensure the current partial page belongs to this submit chain rather
 696          * than other concurrent submit chains or the noio(bypass) chain since
 697          * those chains are handled asynchronously thus the page cannot be used
 698          * for inplace I/O or pagevec (should be processed in strict order.)
 699          */
 700         tight &= (clt->mode >= COLLECT_PRIMARY_HOOKED &&
 701                   clt->mode != COLLECT_PRIMARY_FOLLOWED_NOINPLACE);
 702
 703         cur = end - min_t(unsigned int, offset + end - map->m_la, end);
 704         if (!(map->m_flags & EROFS_MAP_MAPPED)) {
 705                 zero_user_segment(page, cur, end);
 706                 goto next_part;
 707         }
 708
 709         /* let's derive page type */
 710         page_type = cur ? Z_EROFS_VLE_PAGE_TYPE_HEAD :
 711                 (!spiltted ? Z_EROFS_PAGE_TYPE_EXCLUSIVE :
 712                         (tight ? Z_EROFS_PAGE_TYPE_EXCLUSIVE :
 713                                 Z_EROFS_VLE_PAGE_TYPE_TAIL_SHARED));
 714
 715         if (cur)
 716                 tight &= (clt->mode >= COLLECT_PRIMARY_FOLLOWED);
 717
 718 retry:
 719         err = z_erofs_attach_page(clt, page, page_type,
 720                                   clt->mode >= COLLECT_PRIMARY_FOLLOWED);
 721         /* should allocate an additional short-lived page for pagevec */
 722         if (err == -EAGAIN) {
 723                 struct page *const newpage =
 724                                 alloc_page(GFP_NOFS | __GFP_NOFAIL);
 725
 726                 set_page_private(newpage, Z_EROFS_SHORTLIVED_PAGE);
 727                 err = z_erofs_attach_page(clt, newpage,
 728                                           Z_EROFS_PAGE_TYPE_EXCLUSIVE, true);
 729                 if (!err)
 730                         goto retry;
 731         }
 732
 733         if (err)
 734                 goto err_out;
 735
 736         index = page->index - (map->m_la >> PAGE_SHIFT);
 737
 738         z_erofs_onlinepage_fixup(page, index, true);
 739
 740         /* bump up the number of spiltted parts of a page */
 741         ++spiltted;
 742         /* also update nr_pages */
 743         clt->cl->nr_pages = max_t(pgoff_t, clt->cl->nr_pages, index + 1);
 744 next_part:
 745         /* can be used for verification */
 746         map->m_llen = offset + cur - map->m_la;
 747
 748         end = cur;
 749         if (end > 0)
 750                 goto repeat;
 751
 752 out:
 753         z_erofs_onlinepage_endio(page);
 754
 755         erofs_dbg("%s, finish page: %pK spiltted: %u map->m_llen %llu",
 756                   __func__, page, spiltted, map->m_llen);
 757         return err;
 758
 759         /* if some error occurred while processing this page */
 760 err_out:
 761         SetPageError(page);
 762         goto out;
 763 }
 764
 765 static void z_erofs_decompressqueue_work(struct work_struct *work);
 766 static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 767                                        bool sync, int bios)
 768 {
 769         struct erofs_sb_info *const sbi = EROFS_SB(io->sb);
 770
 771         /* wake up the caller thread for sync decompression */
 772         if (sync) {
 773                 unsigned long flags;
 774
 775                 spin_lock_irqsave(&io->u.wait.lock, flags);
 776                 if (!atomic_add_return(bios, &io->pending_bios))
 777                         wake_up_locked(&io->u.wait);
 778                 spin_unlock_irqrestore(&io->u.wait.lock, flags);
 779                 return;
 780         }
 781
 782         if (atomic_add_return(bios, &io->pending_bios))
 783                 return;
 784         /* Use workqueue and sync decompression for atomic contexts only */
 785         if (in_atomic() || irqs_disabled()) {
 786                 queue_work(z_erofs_workqueue, &io->u.work);
 787                 sbi->opt.readahead_sync_decompress = true;
 788                 return;
 789         }
 790         z_erofs_decompressqueue_work(&io->u.work);
 791 }
 792
 793 static bool z_erofs_page_is_invalidated(struct page *page)
 794 {
 795         return !page->mapping && !z_erofs_is_shortlived_page(page);
 796 }
 797
 798 static void z_erofs_decompressqueue_endio(struct bio *bio)
 799 {
 800         tagptr1_t t = tagptr_init(tagptr1_t, bio->bi_private);
 801         struct z_erofs_decompressqueue *q = tagptr_unfold_ptr(t);
 802         blk_status_t err = bio->bi_status;
 803         struct bio_vec *bvec;
 804         struct bvec_iter_all iter_all;
 805
 806         bio_for_each_segment_all(bvec, bio, iter_all) {
 807                 struct page *page = bvec->bv_page;
 808
 809                 DBG_BUGON(PageUptodate(page));
 810                 DBG_BUGON(z_erofs_page_is_invalidated(page));
 811
 812                 if (err)
 813                         SetPageError(page);
 814
 815                 if (erofs_page_is_managed(EROFS_SB(q->sb), page)) {
 816                         if (!err)
 817                                 SetPageUptodate(page);
 818                         unlock_page(page);
 819                 }
 820         }
 821         z_erofs_decompress_kickoff(q, tagptr_unfold_tags(t), -1);
 822         bio_put(bio);
 823 }
 824
 825 static int z_erofs_decompress_pcluster(struct super_block *sb,
 826                                        struct z_erofs_pcluster *pcl,
 827                                        struct page **pagepool)
 828 {
 829         struct erofs_sb_info *const sbi = EROFS_SB(sb);
 830         struct z_erofs_pagevec_ctor ctor;
 831         unsigned int i, inputsize, outputsize, llen, nr_pages;
 832         struct page *pages_onstack[Z_EROFS_VMAP_ONSTACK_PAGES];
 833         struct page **pages, **compressed_pages, *page;
 834
 835         enum z_erofs_page_type page_type;
 836         bool overlapped, partial;
 837         struct z_erofs_collection *cl;
 838         int err;
 839
 840         might_sleep();
 841         cl = z_erofs_primarycollection(pcl);
 842         DBG_BUGON(!READ_ONCE(cl->nr_pages));
 843
 844         mutex_lock(&cl->lock);
 845         nr_pages = cl->nr_pages;
 846
 847         if (nr_pages <= Z_EROFS_VMAP_ONSTACK_PAGES) {
 848                 pages = pages_onstack;
 849         } else if (nr_pages <= Z_EROFS_VMAP_GLOBAL_PAGES &&
 850                    mutex_trylock(&z_pagemap_global_lock)) {
 851                 pages = z_pagemap_global;
 852         } else {
 853                 gfp_t gfp_flags = GFP_KERNEL;
 854
 855                 if (nr_pages > Z_EROFS_VMAP_GLOBAL_PAGES)
 856                         gfp_flags |= __GFP_NOFAIL;
 857
 858                 pages = kvmalloc_array(nr_pages, sizeof(struct page *),
 859                                        gfp_flags);
 860
 861                 /* fallback to global pagemap for the lowmem scenario */
 862                 if (!pages) {
 863                         mutex_lock(&z_pagemap_global_lock);
 864                         pages = z_pagemap_global;
 865                 }
 866         }
 867
 868         for (i = 0; i < nr_pages; ++i)
 869                 pages[i] = NULL;
 870
 871         err = 0;
 872         z_erofs_pagevec_ctor_init(&ctor, Z_EROFS_NR_INLINE_PAGEVECS,
 873                                   cl->pagevec, 0);
 874
 875         for (i = 0; i < cl->vcnt; ++i) {
 876                 unsigned int pagenr;
 877
 878                 page = z_erofs_pagevec_dequeue(&ctor, &page_type);
 879
 880                 /* all pages in pagevec ought to be valid */
 881                 DBG_BUGON(!page);
 882                 DBG_BUGON(z_erofs_page_is_invalidated(page));
 883
 884                 if (z_erofs_put_shortlivedpage(pagepool, page))
 885                         continue;
 886
 887                 if (page_type == Z_EROFS_VLE_PAGE_TYPE_HEAD)
 888                         pagenr = 0;
 889                 else
 890                         pagenr = z_erofs_onlinepage_index(page);
 891
 892                 DBG_BUGON(pagenr >= nr_pages);
 893
 894                 /*
 895                  * currently EROFS doesn't support multiref(dedup),
 896                  * so here erroring out one multiref page.
 897                  */
 898                 if (pages[pagenr]) {
 899                         DBG_BUGON(1);
 900                         SetPageError(pages[pagenr]);
 901                         z_erofs_onlinepage_endio(pages[pagenr]);
 902                         err = -EFSCORRUPTED;
 903                 }
 904                 pages[pagenr] = page;
 905         }
 906         z_erofs_pagevec_ctor_exit(&ctor, true);
 907
 908         overlapped = false;
 909         compressed_pages = pcl->compressed_pages;
 910
 911         for (i = 0; i < pcl->pclusterpages; ++i) {
 912                 unsigned int pagenr;
 913
 914                 page = compressed_pages[i];
 915
 916                 /* all compressed pages ought to be valid */
 917                 DBG_BUGON(!page);
 918                 DBG_BUGON(z_erofs_page_is_invalidated(page));
 919
 920                 if (!z_erofs_is_shortlived_page(page)) {
 921                         if (erofs_page_is_managed(sbi, page)) {
 922                                 if (!PageUptodate(page))
 923                                         err = -EIO;
 924                                 continue;
 925                         }
 926
 927                         /*
 928                          * only if non-head page can be selected
 929                          * for inplace decompression
 930                          */
 931                         pagenr = z_erofs_onlinepage_index(page);
 932
 933                         DBG_BUGON(pagenr >= nr_pages);
 934                         if (pages[pagenr]) {
 935                                 DBG_BUGON(1);
 936                                 SetPageError(pages[pagenr]);
 937                                 z_erofs_onlinepage_endio(pages[pagenr]);
 938                                 err = -EFSCORRUPTED;
 939                         }
 940                         pages[pagenr] = page;
 941
 942                         overlapped = true;
 943                 }
 944
 945                 /* PG_error needs checking for all non-managed pages */
 946                 if (PageError(page)) {
 947                         DBG_BUGON(PageUptodate(page));
 948                         err = -EIO;
 949                 }
 950         }
 951
 952         if (err)
 953                 goto out;
 954
 955         llen = pcl->length >> Z_EROFS_PCLUSTER_LENGTH_BIT;
 956         if (nr_pages << PAGE_SHIFT >= cl->pageofs + llen) {
 957                 outputsize = llen;
 958                 partial = !(pcl->length & Z_EROFS_PCLUSTER_FULL_LENGTH);
 959         } else {
 960                 outputsize = (nr_pages << PAGE_SHIFT) - cl->pageofs;
 961                 partial = true;
 962         }
 963
 964         inputsize = pcl->pclusterpages * PAGE_SIZE;
 965         err = z_erofs_decompress(&(struct z_erofs_decompress_req) {
 966                                         .sb = sb,
 967                                         .in = compressed_pages,
 968                                         .out = pages,
 969                                         .pageofs_out = cl->pageofs,
 970                                         .inputsize = inputsize,
 971                                         .outputsize = outputsize,
 972                                         .alg = pcl->algorithmformat,
 973                                         .inplace_io = overlapped,
 974                                         .partial_decoding = partial
 975                                  }, pagepool);
 976
 977 out:
 978         /* must handle all compressed pages before ending pages */
 979         for (i = 0; i < pcl->pclusterpages; ++i) {
 980                 page = compressed_pages[i];
 981
 982                 if (erofs_page_is_managed(sbi, page))
 983                         continue;
 984
 985                 /* recycle all individual short-lived pages */
 986                 (void)z_erofs_put_shortlivedpage(pagepool, page);
 987
 988                 WRITE_ONCE(compressed_pages[i], NULL);
 989         }
 990
 991         for (i = 0; i < nr_pages; ++i) {
 992                 page = pages[i];
 993                 if (!page)
 994                         continue;
 995
 996                 DBG_BUGON(z_erofs_page_is_invalidated(page));
 997
 998                 /* recycle all individual short-lived pages */
 999                 if (z_erofs_put_shortlivedpage(pagepool, page))
1000                         continue;
1001
1002                 if (err < 0)
1003                         SetPageError(page);
1004
1005                 z_erofs_onlinepage_endio(page);
1006         }
1007
1008         if (pages == z_pagemap_global)
1009                 mutex_unlock(&z_pagemap_global_lock);
1010         else if (pages != pages_onstack)
1011                 kvfree(pages);
1012
1013         cl->nr_pages = 0;
1014         cl->vcnt = 0;
1015
1016         /* all cl locks MUST be taken before the following line */
1017         WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_NIL);
1018
1019         /* all cl locks SHOULD be released right now */
1020         mutex_unlock(&cl->lock);
1021
1022         z_erofs_collection_put(cl);
1023         return err;
1024 }
1025
1026 static void z_erofs_decompress_queue(const struct z_erofs_decompressqueue *io,
1027                                      struct page **pagepool)
1028 {
1029         z_erofs_next_pcluster_t owned = io->head;
1030
1031         while (owned != Z_EROFS_PCLUSTER_TAIL_CLOSED) {
1032                 struct z_erofs_pcluster *pcl;
1033
1034                 /* no possible that 'owned' equals Z_EROFS_WORK_TPTR_TAIL */
1035                 DBG_BUGON(owned == Z_EROFS_PCLUSTER_TAIL);
1036
1037                 /* no possible that 'owned' equals NULL */
1038                 DBG_BUGON(owned == Z_EROFS_PCLUSTER_NIL);
1039
1040                 pcl = container_of(owned, struct z_erofs_pcluster, next);
1041                 owned = READ_ONCE(pcl->next);
1042
1043                 z_erofs_decompress_pcluster(io->sb, pcl, pagepool);
1044         }
1045 }
1046
1047 static void z_erofs_decompressqueue_work(struct work_struct *work)
1048 {
1049         struct z_erofs_decompressqueue *bgq =
1050                 container_of(work, struct z_erofs_decompressqueue, u.work);
1051         struct page *pagepool = NULL;
1052
1053         DBG_BUGON(bgq->head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
1054         z_erofs_decompress_queue(bgq, &pagepool);
1055
1056         erofs_release_pages(&pagepool);
1057         kvfree(bgq);
1058 }
1059
1060 static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
1061                                                unsigned int nr,
1062                                                struct page **pagepool,
1063                                                struct address_space *mc,
1064                                                gfp_t gfp)
1065 {
1066         const pgoff_t index = pcl->obj.index;
1067         bool tocache = false;
1068
1069         struct address_space *mapping;
1070         struct page *oldpage, *page;
1071
1072         compressed_page_t t;
1073         int justfound;
1074
1075 repeat:
1076         page = READ_ONCE(pcl->compressed_pages[nr]);
1077         oldpage = page;
1078
1079         if (!page)
1080                 goto out_allocpage;
1081
1082         /* process the target tagged pointer */
1083         t = tagptr_init(compressed_page_t, page);
1084         justfound = tagptr_unfold_tags(t);
1085         page = tagptr_unfold_ptr(t);
1086
1087         /*
1088          * preallocated cached pages, which is used to avoid direct reclaim
1089          * otherwise, it will go inplace I/O path instead.
1090          */
1091         if (page->private == Z_EROFS_PREALLOCATED_PAGE) {
1092                 WRITE_ONCE(pcl->compressed_pages[nr], page);
1093                 set_page_private(page, 0);
1094                 tocache = true;
1095                 goto out_tocache;
1096         }
1097         mapping = READ_ONCE(page->mapping);
1098
1099         /*
1100          * file-backed online pages in plcuster are all locked steady,
1101          * therefore it is impossible for `mapping' to be NULL.
1102          */
1103         if (mapping && mapping != mc)
1104                 /* ought to be unmanaged pages */
1105                 goto out;
1106
1107         /* directly return for shortlived page as well */
1108         if (z_erofs_is_shortlived_page(page))
1109                 goto out;
1110
1111         lock_page(page);
1112
1113         /* only true if page reclaim goes wrong, should never happen */
1114         DBG_BUGON(justfound && PagePrivate(page));
1115
1116         /* the page is still in manage cache */
1117         if (page->mapping == mc) {
1118                 WRITE_ONCE(pcl->compressed_pages[nr], page);
1119
1120                 ClearPageError(page);
1121                 if (!PagePrivate(page)) {
1122                         /*
1123                          * impossible to be !PagePrivate(page) for
1124                          * the current restriction as well if
1125                          * the page is already in compressed_pages[].
1126                          */
1127                         DBG_BUGON(!justfound);
1128
1129                         justfound = 0;
1130                         set_page_private(page, (unsigned long)pcl);
1131                         SetPagePrivate(page);
1132                 }
1133
1134                 /* no need to submit io if it is already up-to-date */
1135                 if (PageUptodate(page)) {
1136                         unlock_page(page);
1137                         page = NULL;
1138                 }
1139                 goto out;
1140         }
1141
1142         /*
1143          * the managed page has been truncated, it's unsafe to
1144          * reuse this one, let's allocate a new cache-managed page.
1145          */
1146         DBG_BUGON(page->mapping);
1147         DBG_BUGON(!justfound);
1148
1149         tocache = true;
1150         unlock_page(page);
1151         put_page(page);
1152 out_allocpage:
1153         page = erofs_allocpage(pagepool, gfp | __GFP_NOFAIL);
1154         if (oldpage != cmpxchg(&pcl->compressed_pages[nr], oldpage, page)) {
1155                 erofs_pagepool_add(pagepool, page);
1156                 cond_resched();
1157                 goto repeat;
1158         }
1159 out_tocache:
1160         if (!tocache || add_to_page_cache_lru(page, mc, index + nr, gfp)) {
1161                 /* turn into temporary page if fails (1 ref) */
1162                 set_page_private(page, Z_EROFS_SHORTLIVED_PAGE);
1163                 goto out;
1164         }
1165         attach_page_private(page, pcl);
1166         /* drop a refcount added by allocpage (then we have 2 refs here) */
1167         put_page(page);
1168
1169 out:    /* the only exit (for tracing and debugging) */
1170         return page;
1171 }
1172
1173 static struct z_erofs_decompressqueue *
1174 jobqueue_init(struct super_block *sb,
1175               struct z_erofs_decompressqueue *fgq, bool *fg)
1176 {
1177         struct z_erofs_decompressqueue *q;
1178
1179         if (fg && !*fg) {
1180                 q = kvzalloc(sizeof(*q), GFP_KERNEL | __GFP_NOWARN);
1181                 if (!q) {
1182                         *fg = true;
1183                         goto fg_out;
1184                 }
1185                 INIT_WORK(&q->u.work, z_erofs_decompressqueue_work);
1186         } else {
1187 fg_out:
1188                 q = fgq;
1189                 init_waitqueue_head(&fgq->u.wait);
1190                 atomic_set(&fgq->pending_bios, 0);
1191         }
1192         q->sb = sb;
1193         q->head = Z_EROFS_PCLUSTER_TAIL_CLOSED;
1194         return q;
1195 }
1196
1197 /* define decompression jobqueue types */
1198 enum {
1199         JQ_BYPASS,
1200         JQ_SUBMIT,
1201         NR_JOBQUEUES,
1202 };
1203
1204 static void *jobqueueset_init(struct super_block *sb,
1205                               struct z_erofs_decompressqueue *q[],
1206                               struct z_erofs_decompressqueue *fgq, bool *fg)
1207 {
1208         /*
1209          * if managed cache is enabled, bypass jobqueue is needed,
1210          * no need to read from device for all pclusters in this queue.
1211          */
1212         q[JQ_BYPASS] = jobqueue_init(sb, fgq + JQ_BYPASS, NULL);
1213         q[JQ_SUBMIT] = jobqueue_init(sb, fgq + JQ_SUBMIT, fg);
1214
1215         return tagptr_cast_ptr(tagptr_fold(tagptr1_t, q[JQ_SUBMIT], *fg));
1216 }
1217
1218 static void move_to_bypass_jobqueue(struct z_erofs_pcluster *pcl,
1219                                     z_erofs_next_pcluster_t qtail[],
1220                                     z_erofs_next_pcluster_t owned_head)
1221 {
1222         z_erofs_next_pcluster_t *const submit_qtail = qtail[JQ_SUBMIT];
1223         z_erofs_next_pcluster_t *const bypass_qtail = qtail[JQ_BYPASS];
1224
1225         DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
1226         if (owned_head == Z_EROFS_PCLUSTER_TAIL)
1227                 owned_head = Z_EROFS_PCLUSTER_TAIL_CLOSED;
1228
1229         WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_TAIL_CLOSED);
1230
1231         WRITE_ONCE(*submit_qtail, owned_head);
1232         WRITE_ONCE(*bypass_qtail, &pcl->next);
1233
1234         qtail[JQ_BYPASS] = &pcl->next;
1235 }
1236
1237 static void z_erofs_submit_queue(struct super_block *sb,
1238                                  struct z_erofs_decompress_frontend *f,
1239                                  struct page **pagepool,
1240                                  struct z_erofs_decompressqueue *fgq,
1241                                  bool *force_fg)
1242 {
1243         struct erofs_sb_info *const sbi = EROFS_SB(sb);
1244         z_erofs_next_pcluster_t qtail[NR_JOBQUEUES];
1245         struct z_erofs_decompressqueue *q[NR_JOBQUEUES];
1246         void *bi_private;
1247         z_erofs_next_pcluster_t owned_head = f->clt.owned_head;
1248         /* bio is NULL initially, so no need to initialize last_{index,bdev} */
1249         pgoff_t last_index;
1250         struct block_device *last_bdev;
1251         unsigned int nr_bios = 0;
1252         struct bio *bio = NULL;
1253
1254         bi_private = jobqueueset_init(sb, q, fgq, force_fg);
1255         qtail[JQ_BYPASS] = &q[JQ_BYPASS]->head;
1256         qtail[JQ_SUBMIT] = &q[JQ_SUBMIT]->head;
1257
1258         /* by default, all need io submission */
1259         q[JQ_SUBMIT]->head = owned_head;
1260
1261         do {
1262                 struct erofs_map_dev mdev;
1263                 struct z_erofs_pcluster *pcl;
1264                 pgoff_t cur, end;
1265                 unsigned int i = 0;
1266                 bool bypass = true;
1267
1268                 /* no possible 'owned_head' equals the following */
1269                 DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
1270                 DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_NIL);
1271
1272                 pcl = container_of(owned_head, struct z_erofs_pcluster, next);
1273
1274                 /* no device id here, thus it will always succeed */
1275                 mdev = (struct erofs_map_dev) {
1276                         .m_pa = blknr_to_addr(pcl->obj.index),
1277                 };
1278                 (void)erofs_map_dev(sb, &mdev);
1279
1280                 cur = erofs_blknr(mdev.m_pa);
1281                 end = cur + pcl->pclusterpages;
1282
1283                 /* close the main owned chain at first */
1284                 owned_head = cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_TAIL,
1285                                      Z_EROFS_PCLUSTER_TAIL_CLOSED);
1286
1287                 do {
1288                         struct page *page;
1289
1290                         page = pickup_page_for_submission(pcl, i++, pagepool,
1291                                                           MNGD_MAPPING(sbi),
1292                                                           GFP_NOFS);
1293                         if (!page)
1294                                 continue;
1295
1296                         if (bio && (cur != last_index + 1 ||
1297                                     last_bdev != mdev.m_bdev)) {
1298 submit_bio_retry:
1299                                 submit_bio(bio);
1300                                 bio = NULL;
1301                         }
1302
1303                         if (!bio) {
1304                                 bio = bio_alloc(GFP_NOIO, BIO_MAX_VECS);
1305                                 bio->bi_end_io = z_erofs_decompressqueue_endio;
1306
1307                                 bio_set_dev(bio, mdev.m_bdev);
1308                                 last_bdev = mdev.m_bdev;
1309                                 bio->bi_iter.bi_sector = (sector_t)cur <<
1310                                         LOG_SECTORS_PER_BLOCK;
1311                                 bio->bi_private = bi_private;
1312                                 bio->bi_opf = REQ_OP_READ;
1313                                 if (f->readahead)
1314                                         bio->bi_opf |= REQ_RAHEAD;
1315                                 ++nr_bios;
1316                         }
1317
1318                         if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE)
1319                                 goto submit_bio_retry;
1320
1321                         last_index = cur;
1322                         bypass = false;
1323                 } while (++cur < end);
1324
1325                 if (!bypass)
1326                         qtail[JQ_SUBMIT] = &pcl->next;
1327                 else
1328                         move_to_bypass_jobqueue(pcl, qtail, owned_head);
1329         } while (owned_head != Z_EROFS_PCLUSTER_TAIL);
1330
1331         if (bio)
1332                 submit_bio(bio);
1333
1334         /*
1335          * although background is preferred, no one is pending for submission.
1336          * don't issue workqueue for decompression but drop it directly instead.
1337          */
1338         if (!*force_fg && !nr_bios) {
1339                 kvfree(q[JQ_SUBMIT]);
1340                 return;
1341         }
1342         z_erofs_decompress_kickoff(q[JQ_SUBMIT], *force_fg, nr_bios);
1343 }
1344
1345 static void z_erofs_runqueue(struct super_block *sb,
1346                              struct z_erofs_decompress_frontend *f,
1347                              struct page **pagepool, bool force_fg)
1348 {
1349         struct z_erofs_decompressqueue io[NR_JOBQUEUES];
1350
1351         if (f->clt.owned_head == Z_EROFS_PCLUSTER_TAIL)
1352                 return;
1353         z_erofs_submit_queue(sb, f, pagepool, io, &force_fg);
1354
1355         /* handle bypass queue (no i/o pclusters) immediately */
1356         z_erofs_decompress_queue(&io[JQ_BYPASS], pagepool);
1357
1358         if (!force_fg)
1359                 return;
1360
1361         /* wait until all bios are completed */
1362         io_wait_event(io[JQ_SUBMIT].u.wait,
1363                       !atomic_read(&io[JQ_SUBMIT].pending_bios));
1364
1365         /* handle synchronous decompress queue in the caller context */
1366         z_erofs_decompress_queue(&io[JQ_SUBMIT], pagepool);
1367 }
1368
1369 /*
1370  * Since partial uptodate is still unimplemented for now, we have to use
1371  * approximate readmore strategies as a start.
1372  */
1373 static void z_erofs_pcluster_readmore(struct z_erofs_decompress_frontend *f,
1374                                       struct readahead_control *rac,
1375                                       erofs_off_t end,
1376                                       struct page **pagepool,
1377                                       bool backmost)
1378 {
1379         struct inode *inode = f->inode;
1380         struct erofs_map_blocks *map = &f->map;
1381         erofs_off_t cur;
1382         int err;
1383
1384         if (backmost) {
1385                 map->m_la = end;
1386                 err = z_erofs_map_blocks_iter(inode, map,
1387                                               EROFS_GET_BLOCKS_READMORE);
1388                 if (err)
1389                         return;
1390
1391                 /* expend ra for the trailing edge if readahead */
1392                 if (rac) {
1393                         loff_t newstart = readahead_pos(rac);
1394
1395                         cur = round_up(map->m_la + map->m_llen, PAGE_SIZE);
1396                         readahead_expand(rac, newstart, cur - newstart);
1397                         return;
1398                 }
1399                 end = round_up(end, PAGE_SIZE);
1400         } else {
1401                 end = round_up(map->m_la, PAGE_SIZE);
1402
1403                 if (!map->m_llen)
1404                         return;
1405         }
1406
1407         cur = map->m_la + map->m_llen - 1;
1408         while (cur >= end) {
1409                 pgoff_t index = cur >> PAGE_SHIFT;
1410                 struct page *page;
1411
1412                 page = erofs_grab_cache_page_nowait(inode->i_mapping, index);
1413                 if (!page)
1414                         goto skip;
1415
1416                 if (PageUptodate(page)) {
1417                         unlock_page(page);
1418                         put_page(page);
1419                         goto skip;
1420                 }
1421
1422                 err = z_erofs_do_read_page(f, page, pagepool);
1423                 if (err)
1424                         erofs_err(inode->i_sb,
1425                                   "readmore error at page %lu @ nid %llu",
1426                                   index, EROFS_I(inode)->nid);
1427                 put_page(page);
1428 skip:
1429                 if (cur < PAGE_SIZE)
1430                         break;
1431                 cur = (index << PAGE_SHIFT) - 1;
1432         }
1433 }
1434
1435 static int z_erofs_readpage(struct file *file, struct page *page)
1436 {
1437         struct inode *const inode = page->mapping->host;
1438         struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
1439         struct page *pagepool = NULL;
1440         int err;
1441
1442         trace_erofs_readpage(page, false);
1443         f.headoffset = (erofs_off_t)page->index << PAGE_SHIFT;
1444
1445         z_erofs_pcluster_readmore(&f, NULL, f.headoffset + PAGE_SIZE - 1,
1446                                   &pagepool, true);
1447         err = z_erofs_do_read_page(&f, page, &pagepool);
1448         z_erofs_pcluster_readmore(&f, NULL, 0, &pagepool, false);
1449
1450         (void)z_erofs_collector_end(&f.clt);
1451
1452         /* if some compressed cluster ready, need submit them anyway */
1453         z_erofs_runqueue(inode->i_sb, &f, &pagepool, true);
1454
1455         if (err)
1456                 erofs_err(inode->i_sb, "failed to read, err [%d]", err);
1457
1458         if (f.map.mpage)
1459                 put_page(f.map.mpage);
1460
1461         erofs_release_pages(&pagepool);
1462         return err;
1463 }
1464
1465 static void z_erofs_readahead(struct readahead_control *rac)
1466 {
1467         struct inode *const inode = rac->mapping->host;
1468         struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
1469         struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
1470         struct page *pagepool = NULL, *head = NULL, *page;
1471         unsigned int nr_pages;
1472
1473         f.readahead = true;
1474         f.headoffset = readahead_pos(rac);
1475
1476         z_erofs_pcluster_readmore(&f, rac, f.headoffset +
1477                                   readahead_length(rac) - 1, &pagepool, true);
1478         nr_pages = readahead_count(rac);
1479         trace_erofs_readpages(inode, readahead_index(rac), nr_pages, false);
1480
1481         while ((page = readahead_page(rac))) {
1482                 set_page_private(page, (unsigned long)head);
1483                 head = page;
1484         }
1485
1486         while (head) {
1487                 struct page *page = head;
1488                 int err;
1489
1490                 /* traversal in reverse order */
1491                 head = (void *)page_private(page);
1492
1493                 err = z_erofs_do_read_page(&f, page, &pagepool);
1494                 if (err)
1495                         erofs_err(inode->i_sb,
1496                                   "readahead error at page %lu @ nid %llu",
1497                                   page->index, EROFS_I(inode)->nid);
1498                 put_page(page);
1499         }
1500         z_erofs_pcluster_readmore(&f, rac, 0, &pagepool, false);
1501         (void)z_erofs_collector_end(&f.clt);
1502
1503         z_erofs_runqueue(inode->i_sb, &f, &pagepool,
1504                          sbi->opt.readahead_sync_decompress &&
1505                          nr_pages <= sbi->opt.max_sync_decompress_pages);
1506         if (f.map.mpage)
1507                 put_page(f.map.mpage);
1508         erofs_release_pages(&pagepool);
1509 }
1510
1511 const struct address_space_operations z_erofs_aops = {
1512         .readpage = z_erofs_readpage,
1513         .readahead = z_erofs_readahead,
1514 };