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  * Copyright (C) 2022 Alibaba Cloud
   6  */
   7 #include "compress.h"
   8 #include <linux/psi.h>
   9 #include <linux/cpuhotplug.h>
  10 #include <trace/events/erofs.h>
  11
  12 #define Z_EROFS_PCLUSTER_MAX_PAGES      (Z_EROFS_PCLUSTER_MAX_SIZE / PAGE_SIZE)
  13 #define Z_EROFS_INLINE_BVECS            2
  14
  15 /*
  16  * let's leave a type here in case of introducing
  17  * another tagged pointer later.
  18  */
  19 typedef void *z_erofs_next_pcluster_t;
  20
  21 struct z_erofs_bvec {
  22         struct page *page;
  23         int offset;
  24         unsigned int end;
  25 };
  26
  27 #define __Z_EROFS_BVSET(name, total) \
  28 struct name { \
  29         /* point to the next page which contains the following bvecs */ \
  30         struct page *nextpage; \
  31         struct z_erofs_bvec bvec[total]; \
  32 }
  33 __Z_EROFS_BVSET(z_erofs_bvset,);
  34 __Z_EROFS_BVSET(z_erofs_bvset_inline, Z_EROFS_INLINE_BVECS);
  35
  36 /*
  37  * Structure fields follow one of the following exclusion rules.
  38  *
  39  * I: Modifiable by initialization/destruction paths and read-only
  40  *    for everyone else;
  41  *
  42  * L: Field should be protected by the pcluster lock;
  43  *
  44  * A: Field should be accessed / updated in atomic for parallelized code.
  45  */
  46 struct z_erofs_pcluster {
  47         struct erofs_workgroup obj;
  48         struct mutex lock;
  49
  50         /* A: point to next chained pcluster or TAILs */
  51         z_erofs_next_pcluster_t next;
  52
  53         /* L: the maximum decompression size of this round */
  54         unsigned int length;
  55
  56         /* L: total number of bvecs */
  57         unsigned int vcnt;
  58
  59         /* I: page offset of start position of decompression */
  60         unsigned short pageofs_out;
  61
  62         /* I: page offset of inline compressed data */
  63         unsigned short pageofs_in;
  64
  65         union {
  66                 /* L: inline a certain number of bvec for bootstrap */
  67                 struct z_erofs_bvset_inline bvset;
  68
  69                 /* I: can be used to free the pcluster by RCU. */
  70                 struct rcu_head rcu;
  71         };
  72
  73         union {
  74                 /* I: physical cluster size in pages */
  75                 unsigned short pclusterpages;
  76
  77                 /* I: tailpacking inline compressed size */
  78                 unsigned short tailpacking_size;
  79         };
  80
  81         /* I: compression algorithm format */
  82         unsigned char algorithmformat;
  83
  84         /* L: whether partial decompression or not */
  85         bool partial;
  86
  87         /* L: indicate several pageofs_outs or not */
  88         bool multibases;
  89
  90         /* A: compressed bvecs (can be cached or inplaced pages) */
  91         struct z_erofs_bvec compressed_bvecs[];
  92 };
  93
  94 /* the end of a chain of pclusters */
  95 #define Z_EROFS_PCLUSTER_TAIL           ((void *) 0x700 + POISON_POINTER_DELTA)
  96 #define Z_EROFS_PCLUSTER_NIL            (NULL)
  97
  98 struct z_erofs_decompressqueue {
  99         struct super_block *sb;
 100         atomic_t pending_bios;
 101         z_erofs_next_pcluster_t head;
 102
 103         union {
 104                 struct completion done;
 105                 struct work_struct work;
 106                 struct kthread_work kthread_work;
 107         } u;
 108         bool eio, sync;
 109 };
 110
 111 static inline bool z_erofs_is_inline_pcluster(struct z_erofs_pcluster *pcl)
 112 {
 113         return !pcl->obj.index;
 114 }
 115
 116 static inline unsigned int z_erofs_pclusterpages(struct z_erofs_pcluster *pcl)
 117 {
 118         if (z_erofs_is_inline_pcluster(pcl))
 119                 return 1;
 120         return pcl->pclusterpages;
 121 }
 122
 123 /*
 124  * bit 30: I/O error occurred on this page
 125  * bit 0 - 29: remaining parts to complete this page
 126  */
 127 #define Z_EROFS_PAGE_EIO                        (1 << 30)
 128
 129 static inline void z_erofs_onlinepage_init(struct page *page)
 130 {
 131         union {
 132                 atomic_t o;
 133                 unsigned long v;
 134         } u = { .o = ATOMIC_INIT(1) };
 135
 136         set_page_private(page, u.v);
 137         smp_wmb();
 138         SetPagePrivate(page);
 139 }
 140
 141 static inline void z_erofs_onlinepage_split(struct page *page)
 142 {
 143         atomic_inc((atomic_t *)&page->private);
 144 }
 145
 146 static inline void z_erofs_page_mark_eio(struct page *page)
 147 {
 148         int orig;
 149
 150         do {
 151                 orig = atomic_read((atomic_t *)&page->private);
 152         } while (atomic_cmpxchg((atomic_t *)&page->private, orig,
 153                                 orig | Z_EROFS_PAGE_EIO) != orig);
 154 }
 155
 156 static inline void z_erofs_onlinepage_endio(struct page *page)
 157 {
 158         unsigned int v;
 159
 160         DBG_BUGON(!PagePrivate(page));
 161         v = atomic_dec_return((atomic_t *)&page->private);
 162         if (!(v & ~Z_EROFS_PAGE_EIO)) {
 163                 set_page_private(page, 0);
 164                 ClearPagePrivate(page);
 165                 if (!(v & Z_EROFS_PAGE_EIO))
 166                         SetPageUptodate(page);
 167                 unlock_page(page);
 168         }
 169 }
 170
 171 #define Z_EROFS_ONSTACK_PAGES           32
 172
 173 /*
 174  * since pclustersize is variable for big pcluster feature, introduce slab
 175  * pools implementation for different pcluster sizes.
 176  */
 177 struct z_erofs_pcluster_slab {
 178         struct kmem_cache *slab;
 179         unsigned int maxpages;
 180         char name[48];
 181 };
 182
 183 #define _PCLP(n) { .maxpages = n }
 184
 185 static struct z_erofs_pcluster_slab pcluster_pool[] __read_mostly = {
 186         _PCLP(1), _PCLP(4), _PCLP(16), _PCLP(64), _PCLP(128),
 187         _PCLP(Z_EROFS_PCLUSTER_MAX_PAGES)
 188 };
 189
 190 struct z_erofs_bvec_iter {
 191         struct page *bvpage;
 192         struct z_erofs_bvset *bvset;
 193         unsigned int nr, cur;
 194 };
 195
 196 static struct page *z_erofs_bvec_iter_end(struct z_erofs_bvec_iter *iter)
 197 {
 198         if (iter->bvpage)
 199                 kunmap_local(iter->bvset);
 200         return iter->bvpage;
 201 }
 202
 203 static struct page *z_erofs_bvset_flip(struct z_erofs_bvec_iter *iter)
 204 {
 205         unsigned long base = (unsigned long)((struct z_erofs_bvset *)0)->bvec;
 206         /* have to access nextpage in advance, otherwise it will be unmapped */
 207         struct page *nextpage = iter->bvset->nextpage;
 208         struct page *oldpage;
 209
 210         DBG_BUGON(!nextpage);
 211         oldpage = z_erofs_bvec_iter_end(iter);
 212         iter->bvpage = nextpage;
 213         iter->bvset = kmap_local_page(nextpage);
 214         iter->nr = (PAGE_SIZE - base) / sizeof(struct z_erofs_bvec);
 215         iter->cur = 0;
 216         return oldpage;
 217 }
 218
 219 static void z_erofs_bvec_iter_begin(struct z_erofs_bvec_iter *iter,
 220                                     struct z_erofs_bvset_inline *bvset,
 221                                     unsigned int bootstrap_nr,
 222                                     unsigned int cur)
 223 {
 224         *iter = (struct z_erofs_bvec_iter) {
 225                 .nr = bootstrap_nr,
 226                 .bvset = (struct z_erofs_bvset *)bvset,
 227         };
 228
 229         while (cur > iter->nr) {
 230                 cur -= iter->nr;
 231                 z_erofs_bvset_flip(iter);
 232         }
 233         iter->cur = cur;
 234 }
 235
 236 static int z_erofs_bvec_enqueue(struct z_erofs_bvec_iter *iter,
 237                                 struct z_erofs_bvec *bvec,
 238                                 struct page **candidate_bvpage,
 239                                 struct page **pagepool)
 240 {
 241         if (iter->cur >= iter->nr) {
 242                 struct page *nextpage = *candidate_bvpage;
 243
 244                 if (!nextpage) {
 245                         nextpage = erofs_allocpage(pagepool, GFP_NOFS);
 246                         if (!nextpage)
 247                                 return -ENOMEM;
 248                         set_page_private(nextpage, Z_EROFS_SHORTLIVED_PAGE);
 249                 }
 250                 DBG_BUGON(iter->bvset->nextpage);
 251                 iter->bvset->nextpage = nextpage;
 252                 z_erofs_bvset_flip(iter);
 253
 254                 iter->bvset->nextpage = NULL;
 255                 *candidate_bvpage = NULL;
 256         }
 257         iter->bvset->bvec[iter->cur++] = *bvec;
 258         return 0;
 259 }
 260
 261 static void z_erofs_bvec_dequeue(struct z_erofs_bvec_iter *iter,
 262                                  struct z_erofs_bvec *bvec,
 263                                  struct page **old_bvpage)
 264 {
 265         if (iter->cur == iter->nr)
 266                 *old_bvpage = z_erofs_bvset_flip(iter);
 267         else
 268                 *old_bvpage = NULL;
 269         *bvec = iter->bvset->bvec[iter->cur++];
 270 }
 271
 272 static void z_erofs_destroy_pcluster_pool(void)
 273 {
 274         int i;
 275
 276         for (i = 0; i < ARRAY_SIZE(pcluster_pool); ++i) {
 277                 if (!pcluster_pool[i].slab)
 278                         continue;
 279                 kmem_cache_destroy(pcluster_pool[i].slab);
 280                 pcluster_pool[i].slab = NULL;
 281         }
 282 }
 283
 284 static int z_erofs_create_pcluster_pool(void)
 285 {
 286         struct z_erofs_pcluster_slab *pcs;
 287         struct z_erofs_pcluster *a;
 288         unsigned int size;
 289
 290         for (pcs = pcluster_pool;
 291              pcs < pcluster_pool + ARRAY_SIZE(pcluster_pool); ++pcs) {
 292                 size = struct_size(a, compressed_bvecs, pcs->maxpages);
 293
 294                 sprintf(pcs->name, "erofs_pcluster-%u", pcs->maxpages);
 295                 pcs->slab = kmem_cache_create(pcs->name, size, 0,
 296                                               SLAB_RECLAIM_ACCOUNT, NULL);
 297                 if (pcs->slab)
 298                         continue;
 299
 300                 z_erofs_destroy_pcluster_pool();
 301                 return -ENOMEM;
 302         }
 303         return 0;
 304 }
 305
 306 static struct z_erofs_pcluster *z_erofs_alloc_pcluster(unsigned int nrpages)
 307 {
 308         int i;
 309
 310         for (i = 0; i < ARRAY_SIZE(pcluster_pool); ++i) {
 311                 struct z_erofs_pcluster_slab *pcs = pcluster_pool + i;
 312                 struct z_erofs_pcluster *pcl;
 313
 314                 if (nrpages > pcs->maxpages)
 315                         continue;
 316
 317                 pcl = kmem_cache_zalloc(pcs->slab, GFP_NOFS);
 318                 if (!pcl)
 319                         return ERR_PTR(-ENOMEM);
 320                 pcl->pclusterpages = nrpages;
 321                 return pcl;
 322         }
 323         return ERR_PTR(-EINVAL);
 324 }
 325
 326 static void z_erofs_free_pcluster(struct z_erofs_pcluster *pcl)
 327 {
 328         unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
 329         int i;
 330
 331         for (i = 0; i < ARRAY_SIZE(pcluster_pool); ++i) {
 332                 struct z_erofs_pcluster_slab *pcs = pcluster_pool + i;
 333
 334                 if (pclusterpages > pcs->maxpages)
 335                         continue;
 336
 337                 kmem_cache_free(pcs->slab, pcl);
 338                 return;
 339         }
 340         DBG_BUGON(1);
 341 }
 342
 343 static struct workqueue_struct *z_erofs_workqueue __read_mostly;
 344
 345 #ifdef CONFIG_EROFS_FS_PCPU_KTHREAD
 346 static struct kthread_worker __rcu **z_erofs_pcpu_workers;
 347
 348 static void erofs_destroy_percpu_workers(void)
 349 {
 350         struct kthread_worker *worker;
 351         unsigned int cpu;
 352
 353         for_each_possible_cpu(cpu) {
 354                 worker = rcu_dereference_protected(
 355                                         z_erofs_pcpu_workers[cpu], 1);
 356                 rcu_assign_pointer(z_erofs_pcpu_workers[cpu], NULL);
 357                 if (worker)
 358                         kthread_destroy_worker(worker);
 359         }
 360         kfree(z_erofs_pcpu_workers);
 361 }
 362
 363 static struct kthread_worker *erofs_init_percpu_worker(int cpu)
 364 {
 365         struct kthread_worker *worker =
 366                 kthread_create_worker_on_cpu(cpu, 0, "erofs_worker/%u", cpu);
 367
 368         if (IS_ERR(worker))
 369                 return worker;
 370         if (IS_ENABLED(CONFIG_EROFS_FS_PCPU_KTHREAD_HIPRI))
 371                 sched_set_fifo_low(worker->task);
 372         return worker;
 373 }
 374
 375 static int erofs_init_percpu_workers(void)
 376 {
 377         struct kthread_worker *worker;
 378         unsigned int cpu;
 379
 380         z_erofs_pcpu_workers = kcalloc(num_possible_cpus(),
 381                         sizeof(struct kthread_worker *), GFP_ATOMIC);
 382         if (!z_erofs_pcpu_workers)
 383                 return -ENOMEM;
 384
 385         for_each_online_cpu(cpu) {      /* could miss cpu{off,on}line? */
 386                 worker = erofs_init_percpu_worker(cpu);
 387                 if (!IS_ERR(worker))
 388                         rcu_assign_pointer(z_erofs_pcpu_workers[cpu], worker);
 389         }
 390         return 0;
 391 }
 392 #else
 393 static inline void erofs_destroy_percpu_workers(void) {}
 394 static inline int erofs_init_percpu_workers(void) { return 0; }
 395 #endif
 396
 397 #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_EROFS_FS_PCPU_KTHREAD)
 398 static DEFINE_SPINLOCK(z_erofs_pcpu_worker_lock);
 399 static enum cpuhp_state erofs_cpuhp_state;
 400
 401 static int erofs_cpu_online(unsigned int cpu)
 402 {
 403         struct kthread_worker *worker, *old;
 404
 405         worker = erofs_init_percpu_worker(cpu);
 406         if (IS_ERR(worker))
 407                 return PTR_ERR(worker);
 408
 409         spin_lock(&z_erofs_pcpu_worker_lock);
 410         old = rcu_dereference_protected(z_erofs_pcpu_workers[cpu],
 411                         lockdep_is_held(&z_erofs_pcpu_worker_lock));
 412         if (!old)
 413                 rcu_assign_pointer(z_erofs_pcpu_workers[cpu], worker);
 414         spin_unlock(&z_erofs_pcpu_worker_lock);
 415         if (old)
 416                 kthread_destroy_worker(worker);
 417         return 0;
 418 }
 419
 420 static int erofs_cpu_offline(unsigned int cpu)
 421 {
 422         struct kthread_worker *worker;
 423
 424         spin_lock(&z_erofs_pcpu_worker_lock);
 425         worker = rcu_dereference_protected(z_erofs_pcpu_workers[cpu],
 426                         lockdep_is_held(&z_erofs_pcpu_worker_lock));
 427         rcu_assign_pointer(z_erofs_pcpu_workers[cpu], NULL);
 428         spin_unlock(&z_erofs_pcpu_worker_lock);
 429
 430         synchronize_rcu();
 431         if (worker)
 432                 kthread_destroy_worker(worker);
 433         return 0;
 434 }
 435
 436 static int erofs_cpu_hotplug_init(void)
 437 {
 438         int state;
 439
 440         state = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
 441                         "fs/erofs:online", erofs_cpu_online, erofs_cpu_offline);
 442         if (state < 0)
 443                 return state;
 444
 445         erofs_cpuhp_state = state;
 446         return 0;
 447 }
 448
 449 static void erofs_cpu_hotplug_destroy(void)
 450 {
 451         if (erofs_cpuhp_state)
 452                 cpuhp_remove_state_nocalls(erofs_cpuhp_state);
 453 }
 454 #else /* !CONFIG_HOTPLUG_CPU || !CONFIG_EROFS_FS_PCPU_KTHREAD */
 455 static inline int erofs_cpu_hotplug_init(void) { return 0; }
 456 static inline void erofs_cpu_hotplug_destroy(void) {}
 457 #endif
 458
 459 void z_erofs_exit_zip_subsystem(void)
 460 {
 461         erofs_cpu_hotplug_destroy();
 462         erofs_destroy_percpu_workers();
 463         destroy_workqueue(z_erofs_workqueue);
 464         z_erofs_destroy_pcluster_pool();
 465 }
 466
 467 int __init z_erofs_init_zip_subsystem(void)
 468 {
 469         int err = z_erofs_create_pcluster_pool();
 470
 471         if (err)
 472                 goto out_error_pcluster_pool;
 473
 474         z_erofs_workqueue = alloc_workqueue("erofs_worker",
 475                         WQ_UNBOUND | WQ_HIGHPRI, num_possible_cpus());
 476         if (!z_erofs_workqueue) {
 477                 err = -ENOMEM;
 478                 goto out_error_workqueue_init;
 479         }
 480
 481         err = erofs_init_percpu_workers();
 482         if (err)
 483                 goto out_error_pcpu_worker;
 484
 485         err = erofs_cpu_hotplug_init();
 486         if (err < 0)
 487                 goto out_error_cpuhp_init;
 488         return err;
 489
 490 out_error_cpuhp_init:
 491         erofs_destroy_percpu_workers();
 492 out_error_pcpu_worker:
 493         destroy_workqueue(z_erofs_workqueue);
 494 out_error_workqueue_init:
 495         z_erofs_destroy_pcluster_pool();
 496 out_error_pcluster_pool:
 497         return err;
 498 }
 499
 500 enum z_erofs_pclustermode {
 501         Z_EROFS_PCLUSTER_INFLIGHT,
 502         /*
 503          * a weak form of Z_EROFS_PCLUSTER_FOLLOWED, the difference is that it
 504          * could be dispatched into bypass queue later due to uptodated managed
 505          * pages. All related online pages cannot be reused for inplace I/O (or
 506          * bvpage) since it can be directly decoded without I/O submission.
 507          */
 508         Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE,
 509         /*
 510          * The current collection has been linked with the owned chain, and
 511          * could also be linked with the remaining collections, which means
 512          * if the processing page is the tail page of the collection, thus
 513          * the current collection can safely use the whole page (since
 514          * the previous collection is under control) for in-place I/O, as
 515          * illustrated below:
 516          *  ________________________________________________________________
 517          * |  tail (partial) page |          head (partial) page           |
 518          * |  (of the current cl) |      (of the previous collection)      |
 519          * |                      |                                        |
 520          * |__PCLUSTER_FOLLOWED___|___________PCLUSTER_FOLLOWED____________|
 521          *
 522          * [  (*) the above page can be used as inplace I/O.               ]
 523          */
 524         Z_EROFS_PCLUSTER_FOLLOWED,
 525 };
 526
 527 struct z_erofs_decompress_frontend {
 528         struct inode *const inode;
 529         struct erofs_map_blocks map;
 530         struct z_erofs_bvec_iter biter;
 531
 532         struct page *pagepool;
 533         struct page *candidate_bvpage;
 534         struct z_erofs_pcluster *pcl;
 535         z_erofs_next_pcluster_t owned_head;
 536         enum z_erofs_pclustermode mode;
 537
 538         /* used for applying cache strategy on the fly */
 539         bool backmost;
 540         erofs_off_t headoffset;
 541
 542         /* a pointer used to pick up inplace I/O pages */
 543         unsigned int icur;
 544 };
 545
 546 #define DECOMPRESS_FRONTEND_INIT(__i) { \
 547         .inode = __i, .owned_head = Z_EROFS_PCLUSTER_TAIL, \
 548         .mode = Z_EROFS_PCLUSTER_FOLLOWED, .backmost = true }
 549
 550 static bool z_erofs_should_alloc_cache(struct z_erofs_decompress_frontend *fe)
 551 {
 552         unsigned int cachestrategy = EROFS_I_SB(fe->inode)->opt.cache_strategy;
 553
 554         if (cachestrategy <= EROFS_ZIP_CACHE_DISABLED)
 555                 return false;
 556
 557         if (fe->backmost)
 558                 return true;
 559
 560         if (cachestrategy >= EROFS_ZIP_CACHE_READAROUND &&
 561             fe->map.m_la < fe->headoffset)
 562                 return true;
 563
 564         return false;
 565 }
 566
 567 static void z_erofs_bind_cache(struct z_erofs_decompress_frontend *fe)
 568 {
 569         struct address_space *mc = MNGD_MAPPING(EROFS_I_SB(fe->inode));
 570         struct z_erofs_pcluster *pcl = fe->pcl;
 571         bool shouldalloc = z_erofs_should_alloc_cache(fe);
 572         bool standalone = true;
 573         /*
 574          * optimistic allocation without direct reclaim since inplace I/O
 575          * can be used if low memory otherwise.
 576          */
 577         gfp_t gfp = (mapping_gfp_mask(mc) & ~__GFP_DIRECT_RECLAIM) |
 578                         __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
 579         unsigned int i;
 580
 581         if (fe->mode < Z_EROFS_PCLUSTER_FOLLOWED)
 582                 return;
 583
 584         for (i = 0; i < pcl->pclusterpages; ++i) {
 585                 struct page *page;
 586                 void *t;        /* mark pages just found for debugging */
 587                 struct page *newpage = NULL;
 588
 589                 /* the compressed page was loaded before */
 590                 if (READ_ONCE(pcl->compressed_bvecs[i].page))
 591                         continue;
 592
 593                 page = find_get_page(mc, pcl->obj.index + i);
 594
 595                 if (page) {
 596                         t = (void *)((unsigned long)page | 1);
 597                 } else {
 598                         /* I/O is needed, no possible to decompress directly */
 599                         standalone = false;
 600                         if (!shouldalloc)
 601                                 continue;
 602
 603                         /*
 604                          * try to use cached I/O if page allocation
 605                          * succeeds or fallback to in-place I/O instead
 606                          * to avoid any direct reclaim.
 607                          */
 608                         newpage = erofs_allocpage(&fe->pagepool, gfp);
 609                         if (!newpage)
 610                                 continue;
 611                         set_page_private(newpage, Z_EROFS_PREALLOCATED_PAGE);
 612                         t = (void *)((unsigned long)newpage | 1);
 613                 }
 614
 615                 if (!cmpxchg_relaxed(&pcl->compressed_bvecs[i].page, NULL, t))
 616                         continue;
 617
 618                 if (page)
 619                         put_page(page);
 620                 else if (newpage)
 621                         erofs_pagepool_add(&fe->pagepool, newpage);
 622         }
 623
 624         /*
 625          * don't do inplace I/O if all compressed pages are available in
 626          * managed cache since it can be moved to the bypass queue instead.
 627          */
 628         if (standalone)
 629                 fe->mode = Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE;
 630 }
 631
 632 /* called by erofs_shrinker to get rid of all compressed_pages */
 633 int erofs_try_to_free_all_cached_pages(struct erofs_sb_info *sbi,
 634                                        struct erofs_workgroup *grp)
 635 {
 636         struct z_erofs_pcluster *const pcl =
 637                 container_of(grp, struct z_erofs_pcluster, obj);
 638         int i;
 639
 640         DBG_BUGON(z_erofs_is_inline_pcluster(pcl));
 641         /*
 642          * refcount of workgroup is now freezed as 0,
 643          * therefore no need to worry about available decompression users.
 644          */
 645         for (i = 0; i < pcl->pclusterpages; ++i) {
 646                 struct page *page = pcl->compressed_bvecs[i].page;
 647
 648                 if (!page)
 649                         continue;
 650
 651                 /* block other users from reclaiming or migrating the page */
 652                 if (!trylock_page(page))
 653                         return -EBUSY;
 654
 655                 if (!erofs_page_is_managed(sbi, page))
 656                         continue;
 657
 658                 /* barrier is implied in the following 'unlock_page' */
 659                 WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
 660                 detach_page_private(page);
 661                 unlock_page(page);
 662         }
 663         return 0;
 664 }
 665
 666 static bool z_erofs_cache_release_folio(struct folio *folio, gfp_t gfp)
 667 {
 668         struct z_erofs_pcluster *pcl = folio_get_private(folio);
 669         bool ret;
 670         int i;
 671
 672         if (!folio_test_private(folio))
 673                 return true;
 674
 675         ret = false;
 676         spin_lock(&pcl->obj.lockref.lock);
 677         if (pcl->obj.lockref.count > 0)
 678                 goto out;
 679
 680         DBG_BUGON(z_erofs_is_inline_pcluster(pcl));
 681         for (i = 0; i < pcl->pclusterpages; ++i) {
 682                 if (pcl->compressed_bvecs[i].page == &folio->page) {
 683                         WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
 684                         ret = true;
 685                         break;
 686                 }
 687         }
 688         if (ret)
 689                 folio_detach_private(folio);
 690 out:
 691         spin_unlock(&pcl->obj.lockref.lock);
 692         return ret;
 693 }
 694
 695 /*
 696  * It will be called only on inode eviction. In case that there are still some
 697  * decompression requests in progress, wait with rescheduling for a bit here.
 698  * An extra lock could be introduced instead but it seems unnecessary.
 699  */
 700 static void z_erofs_cache_invalidate_folio(struct folio *folio,
 701                                            size_t offset, size_t length)
 702 {
 703         const size_t stop = length + offset;
 704
 705         /* Check for potential overflow in debug mode */
 706         DBG_BUGON(stop > folio_size(folio) || stop < length);
 707
 708         if (offset == 0 && stop == folio_size(folio))
 709                 while (!z_erofs_cache_release_folio(folio, GFP_NOFS))
 710                         cond_resched();
 711 }
 712
 713 static const struct address_space_operations z_erofs_cache_aops = {
 714         .release_folio = z_erofs_cache_release_folio,
 715         .invalidate_folio = z_erofs_cache_invalidate_folio,
 716 };
 717
 718 int erofs_init_managed_cache(struct super_block *sb)
 719 {
 720         struct inode *const inode = new_inode(sb);
 721
 722         if (!inode)
 723                 return -ENOMEM;
 724
 725         set_nlink(inode, 1);
 726         inode->i_size = OFFSET_MAX;
 727         inode->i_mapping->a_ops = &z_erofs_cache_aops;
 728         mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
 729         EROFS_SB(sb)->managed_cache = inode;
 730         return 0;
 731 }
 732
 733 static bool z_erofs_try_inplace_io(struct z_erofs_decompress_frontend *fe,
 734                                    struct z_erofs_bvec *bvec)
 735 {
 736         struct z_erofs_pcluster *const pcl = fe->pcl;
 737
 738         while (fe->icur > 0) {
 739                 if (!cmpxchg(&pcl->compressed_bvecs[--fe->icur].page,
 740                              NULL, bvec->page)) {
 741                         pcl->compressed_bvecs[fe->icur] = *bvec;
 742                         return true;
 743                 }
 744         }
 745         return false;
 746 }
 747
 748 /* callers must be with pcluster lock held */
 749 static int z_erofs_attach_page(struct z_erofs_decompress_frontend *fe,
 750                                struct z_erofs_bvec *bvec, bool exclusive)
 751 {
 752         int ret;
 753
 754         if (exclusive) {
 755                 /* give priority for inplaceio to use file pages first */
 756                 if (z_erofs_try_inplace_io(fe, bvec))
 757                         return 0;
 758                 /* otherwise, check if it can be used as a bvpage */
 759                 if (fe->mode >= Z_EROFS_PCLUSTER_FOLLOWED &&
 760                     !fe->candidate_bvpage)
 761                         fe->candidate_bvpage = bvec->page;
 762         }
 763         ret = z_erofs_bvec_enqueue(&fe->biter, bvec, &fe->candidate_bvpage,
 764                                    &fe->pagepool);
 765         fe->pcl->vcnt += (ret >= 0);
 766         return ret;
 767 }
 768
 769 static void z_erofs_try_to_claim_pcluster(struct z_erofs_decompress_frontend *f)
 770 {
 771         struct z_erofs_pcluster *pcl = f->pcl;
 772         z_erofs_next_pcluster_t *owned_head = &f->owned_head;
 773
 774         /* type 1, nil pcluster (this pcluster doesn't belong to any chain.) */
 775         if (cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_NIL,
 776                     *owned_head) == Z_EROFS_PCLUSTER_NIL) {
 777                 *owned_head = &pcl->next;
 778                 /* so we can attach this pcluster to our submission chain. */
 779                 f->mode = Z_EROFS_PCLUSTER_FOLLOWED;
 780                 return;
 781         }
 782
 783         /* type 2, it belongs to an ongoing chain */
 784         f->mode = Z_EROFS_PCLUSTER_INFLIGHT;
 785 }
 786
 787 static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
 788 {
 789         struct erofs_map_blocks *map = &fe->map;
 790         bool ztailpacking = map->m_flags & EROFS_MAP_META;
 791         struct z_erofs_pcluster *pcl;
 792         struct erofs_workgroup *grp;
 793         int err;
 794
 795         if (!(map->m_flags & EROFS_MAP_ENCODED) ||
 796             (!ztailpacking && !(map->m_pa >> PAGE_SHIFT))) {
 797                 DBG_BUGON(1);
 798                 return -EFSCORRUPTED;
 799         }
 800
 801         /* no available pcluster, let's allocate one */
 802         pcl = z_erofs_alloc_pcluster(ztailpacking ? 1 :
 803                                      map->m_plen >> PAGE_SHIFT);
 804         if (IS_ERR(pcl))
 805                 return PTR_ERR(pcl);
 806
 807         spin_lock_init(&pcl->obj.lockref.lock);
 808         pcl->algorithmformat = map->m_algorithmformat;
 809         pcl->length = 0;
 810         pcl->partial = true;
 811
 812         /* new pclusters should be claimed as type 1, primary and followed */
 813         pcl->next = fe->owned_head;
 814         pcl->pageofs_out = map->m_la & ~PAGE_MASK;
 815         fe->mode = Z_EROFS_PCLUSTER_FOLLOWED;
 816
 817         /*
 818          * lock all primary followed works before visible to others
 819          * and mutex_trylock *never* fails for a new pcluster.
 820          */
 821         mutex_init(&pcl->lock);
 822         DBG_BUGON(!mutex_trylock(&pcl->lock));
 823
 824         if (ztailpacking) {
 825                 pcl->obj.index = 0;     /* which indicates ztailpacking */
 826                 pcl->pageofs_in = erofs_blkoff(fe->inode->i_sb, map->m_pa);
 827                 pcl->tailpacking_size = map->m_plen;
 828         } else {
 829                 pcl->obj.index = map->m_pa >> PAGE_SHIFT;
 830
 831                 grp = erofs_insert_workgroup(fe->inode->i_sb, &pcl->obj);
 832                 if (IS_ERR(grp)) {
 833                         err = PTR_ERR(grp);
 834                         goto err_out;
 835                 }
 836
 837                 if (grp != &pcl->obj) {
 838                         fe->pcl = container_of(grp,
 839                                         struct z_erofs_pcluster, obj);
 840                         err = -EEXIST;
 841                         goto err_out;
 842                 }
 843         }
 844         fe->owned_head = &pcl->next;
 845         fe->pcl = pcl;
 846         return 0;
 847
 848 err_out:
 849         mutex_unlock(&pcl->lock);
 850         z_erofs_free_pcluster(pcl);
 851         return err;
 852 }
 853
 854 static int z_erofs_collector_begin(struct z_erofs_decompress_frontend *fe)
 855 {
 856         struct erofs_map_blocks *map = &fe->map;
 857         struct erofs_workgroup *grp = NULL;
 858         int ret;
 859
 860         DBG_BUGON(fe->pcl);
 861
 862         /* must be Z_EROFS_PCLUSTER_TAIL or pointed to previous pcluster */
 863         DBG_BUGON(fe->owned_head == Z_EROFS_PCLUSTER_NIL);
 864
 865         if (!(map->m_flags & EROFS_MAP_META)) {
 866                 grp = erofs_find_workgroup(fe->inode->i_sb,
 867                                            map->m_pa >> PAGE_SHIFT);
 868         } else if ((map->m_pa & ~PAGE_MASK) + map->m_plen > PAGE_SIZE) {
 869                 DBG_BUGON(1);
 870                 return -EFSCORRUPTED;
 871         }
 872
 873         if (grp) {
 874                 fe->pcl = container_of(grp, struct z_erofs_pcluster, obj);
 875                 ret = -EEXIST;
 876         } else {
 877                 ret = z_erofs_register_pcluster(fe);
 878         }
 879
 880         if (ret == -EEXIST) {
 881                 mutex_lock(&fe->pcl->lock);
 882                 z_erofs_try_to_claim_pcluster(fe);
 883         } else if (ret) {
 884                 return ret;
 885         }
 886         z_erofs_bvec_iter_begin(&fe->biter, &fe->pcl->bvset,
 887                                 Z_EROFS_INLINE_BVECS, fe->pcl->vcnt);
 888         /* since file-backed online pages are traversed in reverse order */
 889         fe->icur = z_erofs_pclusterpages(fe->pcl);
 890         return 0;
 891 }
 892
 893 /*
 894  * keep in mind that no referenced pclusters will be freed
 895  * only after a RCU grace period.
 896  */
 897 static void z_erofs_rcu_callback(struct rcu_head *head)
 898 {
 899         z_erofs_free_pcluster(container_of(head,
 900                         struct z_erofs_pcluster, rcu));
 901 }
 902
 903 void erofs_workgroup_free_rcu(struct erofs_workgroup *grp)
 904 {
 905         struct z_erofs_pcluster *const pcl =
 906                 container_of(grp, struct z_erofs_pcluster, obj);
 907
 908         call_rcu(&pcl->rcu, z_erofs_rcu_callback);
 909 }
 910
 911 static bool z_erofs_collector_end(struct z_erofs_decompress_frontend *fe)
 912 {
 913         struct z_erofs_pcluster *pcl = fe->pcl;
 914
 915         if (!pcl)
 916                 return false;
 917
 918         z_erofs_bvec_iter_end(&fe->biter);
 919         mutex_unlock(&pcl->lock);
 920
 921         if (fe->candidate_bvpage)
 922                 fe->candidate_bvpage = NULL;
 923
 924         /*
 925          * if all pending pages are added, don't hold its reference
 926          * any longer if the pcluster isn't hosted by ourselves.
 927          */
 928         if (fe->mode < Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE)
 929                 erofs_workgroup_put(&pcl->obj);
 930
 931         fe->pcl = NULL;
 932         return true;
 933 }
 934
 935 static int z_erofs_read_fragment(struct inode *inode, erofs_off_t pos,
 936                                  struct page *page, unsigned int pageofs,
 937                                  unsigned int len)
 938 {
 939         struct super_block *sb = inode->i_sb;
 940         struct inode *packed_inode = EROFS_I_SB(inode)->packed_inode;
 941         struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
 942         u8 *src, *dst;
 943         unsigned int i, cnt;
 944
 945         if (!packed_inode)
 946                 return -EFSCORRUPTED;
 947
 948         buf.inode = packed_inode;
 949         pos += EROFS_I(inode)->z_fragmentoff;
 950         for (i = 0; i < len; i += cnt) {
 951                 cnt = min_t(unsigned int, len - i,
 952                             sb->s_blocksize - erofs_blkoff(sb, pos));
 953                 src = erofs_bread(&buf, erofs_blknr(sb, pos), EROFS_KMAP);
 954                 if (IS_ERR(src)) {
 955                         erofs_put_metabuf(&buf);
 956                         return PTR_ERR(src);
 957                 }
 958
 959                 dst = kmap_local_page(page);
 960                 memcpy(dst + pageofs + i, src + erofs_blkoff(sb, pos), cnt);
 961                 kunmap_local(dst);
 962                 pos += cnt;
 963         }
 964         erofs_put_metabuf(&buf);
 965         return 0;
 966 }
 967
 968 static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 969                                 struct page *page)
 970 {
 971         struct inode *const inode = fe->inode;
 972         struct erofs_map_blocks *const map = &fe->map;
 973         const loff_t offset = page_offset(page);
 974         bool tight = true, exclusive;
 975         unsigned int cur, end, spiltted;
 976         int err = 0;
 977
 978         /* register locked file pages as online pages in pack */
 979         z_erofs_onlinepage_init(page);
 980
 981         spiltted = 0;
 982         end = PAGE_SIZE;
 983 repeat:
 984         cur = end - 1;
 985
 986         if (offset + cur < map->m_la ||
 987             offset + cur >= map->m_la + map->m_llen) {
 988                 if (z_erofs_collector_end(fe))
 989                         fe->backmost = false;
 990                 map->m_la = offset + cur;
 991                 map->m_llen = 0;
 992                 err = z_erofs_map_blocks_iter(inode, map, 0);
 993                 if (err)
 994                         goto out;
 995         } else {
 996                 if (fe->pcl)
 997                         goto hitted;
 998                 /* didn't get a valid pcluster previously (very rare) */
 999         }
1000
1001         if (!(map->m_flags & EROFS_MAP_MAPPED) ||
1002             map->m_flags & EROFS_MAP_FRAGMENT)
1003                 goto hitted;
1004
1005         err = z_erofs_collector_begin(fe);
1006         if (err)
1007                 goto out;
1008
1009         if (z_erofs_is_inline_pcluster(fe->pcl)) {
1010                 void *mp;
1011
1012                 mp = erofs_read_metabuf(&fe->map.buf, inode->i_sb,
1013                                         erofs_blknr(inode->i_sb, map->m_pa),
1014                                         EROFS_NO_KMAP);
1015                 if (IS_ERR(mp)) {
1016                         err = PTR_ERR(mp);
1017                         erofs_err(inode->i_sb,
1018                                   "failed to get inline page, err %d", err);
1019                         goto out;
1020                 }
1021                 get_page(fe->map.buf.page);
1022                 WRITE_ONCE(fe->pcl->compressed_bvecs[0].page,
1023                            fe->map.buf.page);
1024                 fe->mode = Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE;
1025         } else {
1026                 /* bind cache first when cached decompression is preferred */
1027                 z_erofs_bind_cache(fe);
1028         }
1029 hitted:
1030         /*
1031          * Ensure the current partial page belongs to this submit chain rather
1032          * than other concurrent submit chains or the noio(bypass) chain since
1033          * those chains are handled asynchronously thus the page cannot be used
1034          * for inplace I/O or bvpage (should be processed in a strict order.)
1035          */
1036         tight &= (fe->mode > Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE);
1037
1038         cur = end - min_t(erofs_off_t, offset + end - map->m_la, end);
1039         if (!(map->m_flags & EROFS_MAP_MAPPED)) {
1040                 zero_user_segment(page, cur, end);
1041                 goto next_part;
1042         }
1043         if (map->m_flags & EROFS_MAP_FRAGMENT) {
1044                 unsigned int pageofs, skip, len;
1045
1046                 if (offset > map->m_la) {
1047                         pageofs = 0;
1048                         skip = offset - map->m_la;
1049                 } else {
1050                         pageofs = map->m_la & ~PAGE_MASK;
1051                         skip = 0;
1052                 }
1053                 len = min_t(unsigned int, map->m_llen - skip, end - cur);
1054                 err = z_erofs_read_fragment(inode, skip, page, pageofs, len);
1055                 if (err)
1056                         goto out;
1057                 ++spiltted;
1058                 tight = false;
1059                 goto next_part;
1060         }
1061
1062         exclusive = (!cur && (!spiltted || tight));
1063         if (cur)
1064                 tight &= (fe->mode >= Z_EROFS_PCLUSTER_FOLLOWED);
1065
1066         err = z_erofs_attach_page(fe, &((struct z_erofs_bvec) {
1067                                         .page = page,
1068                                         .offset = offset - map->m_la,
1069                                         .end = end,
1070                                   }), exclusive);
1071         if (err)
1072                 goto out;
1073
1074         z_erofs_onlinepage_split(page);
1075         /* bump up the number of spiltted parts of a page */
1076         ++spiltted;
1077         if (fe->pcl->pageofs_out != (map->m_la & ~PAGE_MASK))
1078                 fe->pcl->multibases = true;
1079         if (fe->pcl->length < offset + end - map->m_la) {
1080                 fe->pcl->length = offset + end - map->m_la;
1081                 fe->pcl->pageofs_out = map->m_la & ~PAGE_MASK;
1082         }
1083         if ((map->m_flags & EROFS_MAP_FULL_MAPPED) &&
1084             !(map->m_flags & EROFS_MAP_PARTIAL_REF) &&
1085             fe->pcl->length == map->m_llen)
1086                 fe->pcl->partial = false;
1087 next_part:
1088         /* shorten the remaining extent to update progress */
1089         map->m_llen = offset + cur - map->m_la;
1090         map->m_flags &= ~EROFS_MAP_FULL_MAPPED;
1091
1092         end = cur;
1093         if (end > 0)
1094                 goto repeat;
1095
1096 out:
1097         if (err)
1098                 z_erofs_page_mark_eio(page);
1099         z_erofs_onlinepage_endio(page);
1100         return err;
1101 }
1102
1103 static bool z_erofs_is_sync_decompress(struct erofs_sb_info *sbi,
1104                                        unsigned int readahead_pages)
1105 {
1106         /* auto: enable for read_folio, disable for readahead */
1107         if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO) &&
1108             !readahead_pages)
1109                 return true;
1110
1111         if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_FORCE_ON) &&
1112             (readahead_pages <= sbi->opt.max_sync_decompress_pages))
1113                 return true;
1114
1115         return false;
1116 }
1117
1118 static bool z_erofs_page_is_invalidated(struct page *page)
1119 {
1120         return !page->mapping && !z_erofs_is_shortlived_page(page);
1121 }
1122
1123 struct z_erofs_decompress_backend {
1124         struct page *onstack_pages[Z_EROFS_ONSTACK_PAGES];
1125         struct super_block *sb;
1126         struct z_erofs_pcluster *pcl;
1127
1128         /* pages with the longest decompressed length for deduplication */
1129         struct page **decompressed_pages;
1130         /* pages to keep the compressed data */
1131         struct page **compressed_pages;
1132
1133         struct list_head decompressed_secondary_bvecs;
1134         struct page **pagepool;
1135         unsigned int onstack_used, nr_pages;
1136 };
1137
1138 struct z_erofs_bvec_item {
1139         struct z_erofs_bvec bvec;
1140         struct list_head list;
1141 };
1142
1143 static void z_erofs_do_decompressed_bvec(struct z_erofs_decompress_backend *be,
1144                                          struct z_erofs_bvec *bvec)
1145 {
1146         struct z_erofs_bvec_item *item;
1147         unsigned int pgnr;
1148
1149         if (!((bvec->offset + be->pcl->pageofs_out) & ~PAGE_MASK) &&
1150             (bvec->end == PAGE_SIZE ||
1151              bvec->offset + bvec->end == be->pcl->length)) {
1152                 pgnr = (bvec->offset + be->pcl->pageofs_out) >> PAGE_SHIFT;
1153                 DBG_BUGON(pgnr >= be->nr_pages);
1154                 if (!be->decompressed_pages[pgnr]) {
1155                         be->decompressed_pages[pgnr] = bvec->page;
1156                         return;
1157                 }
1158         }
1159
1160         /* (cold path) one pcluster is requested multiple times */
1161         item = kmalloc(sizeof(*item), GFP_KERNEL | __GFP_NOFAIL);
1162         item->bvec = *bvec;
1163         list_add(&item->list, &be->decompressed_secondary_bvecs);
1164 }
1165
1166 static void z_erofs_fill_other_copies(struct z_erofs_decompress_backend *be,
1167                                       int err)
1168 {
1169         unsigned int off0 = be->pcl->pageofs_out;
1170         struct list_head *p, *n;
1171
1172         list_for_each_safe(p, n, &be->decompressed_secondary_bvecs) {
1173                 struct z_erofs_bvec_item *bvi;
1174                 unsigned int end, cur;
1175                 void *dst, *src;
1176
1177                 bvi = container_of(p, struct z_erofs_bvec_item, list);
1178                 cur = bvi->bvec.offset < 0 ? -bvi->bvec.offset : 0;
1179                 end = min_t(unsigned int, be->pcl->length - bvi->bvec.offset,
1180                             bvi->bvec.end);
1181                 dst = kmap_local_page(bvi->bvec.page);
1182                 while (cur < end) {
1183                         unsigned int pgnr, scur, len;
1184
1185                         pgnr = (bvi->bvec.offset + cur + off0) >> PAGE_SHIFT;
1186                         DBG_BUGON(pgnr >= be->nr_pages);
1187
1188                         scur = bvi->bvec.offset + cur -
1189                                         ((pgnr << PAGE_SHIFT) - off0);
1190                         len = min_t(unsigned int, end - cur, PAGE_SIZE - scur);
1191                         if (!be->decompressed_pages[pgnr]) {
1192                                 err = -EFSCORRUPTED;
1193                                 cur += len;
1194                                 continue;
1195                         }
1196                         src = kmap_local_page(be->decompressed_pages[pgnr]);
1197                         memcpy(dst + cur, src + scur, len);
1198                         kunmap_local(src);
1199                         cur += len;
1200                 }
1201                 kunmap_local(dst);
1202                 if (err)
1203                         z_erofs_page_mark_eio(bvi->bvec.page);
1204                 z_erofs_onlinepage_endio(bvi->bvec.page);
1205                 list_del(p);
1206                 kfree(bvi);
1207         }
1208 }
1209
1210 static void z_erofs_parse_out_bvecs(struct z_erofs_decompress_backend *be)
1211 {
1212         struct z_erofs_pcluster *pcl = be->pcl;
1213         struct z_erofs_bvec_iter biter;
1214         struct page *old_bvpage;
1215         int i;
1216
1217         z_erofs_bvec_iter_begin(&biter, &pcl->bvset, Z_EROFS_INLINE_BVECS, 0);
1218         for (i = 0; i < pcl->vcnt; ++i) {
1219                 struct z_erofs_bvec bvec;
1220
1221                 z_erofs_bvec_dequeue(&biter, &bvec, &old_bvpage);
1222
1223                 if (old_bvpage)
1224                         z_erofs_put_shortlivedpage(be->pagepool, old_bvpage);
1225
1226                 DBG_BUGON(z_erofs_page_is_invalidated(bvec.page));
1227                 z_erofs_do_decompressed_bvec(be, &bvec);
1228         }
1229
1230         old_bvpage = z_erofs_bvec_iter_end(&biter);
1231         if (old_bvpage)
1232                 z_erofs_put_shortlivedpage(be->pagepool, old_bvpage);
1233 }
1234
1235 static int z_erofs_parse_in_bvecs(struct z_erofs_decompress_backend *be,
1236                                   bool *overlapped)
1237 {
1238         struct z_erofs_pcluster *pcl = be->pcl;
1239         unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
1240         int i, err = 0;
1241
1242         *overlapped = false;
1243         for (i = 0; i < pclusterpages; ++i) {
1244                 struct z_erofs_bvec *bvec = &pcl->compressed_bvecs[i];
1245                 struct page *page = bvec->page;
1246
1247                 /* compressed pages ought to be present before decompressing */
1248                 if (!page) {
1249                         DBG_BUGON(1);
1250                         continue;
1251                 }
1252                 be->compressed_pages[i] = page;
1253
1254                 if (z_erofs_is_inline_pcluster(pcl)) {
1255                         if (!PageUptodate(page))
1256                                 err = -EIO;
1257                         continue;
1258                 }
1259
1260                 DBG_BUGON(z_erofs_page_is_invalidated(page));
1261                 if (!z_erofs_is_shortlived_page(page)) {
1262                         if (erofs_page_is_managed(EROFS_SB(be->sb), page)) {
1263                                 if (!PageUptodate(page))
1264                                         err = -EIO;
1265                                 continue;
1266                         }
1267                         z_erofs_do_decompressed_bvec(be, bvec);
1268                         *overlapped = true;
1269                 }
1270         }
1271
1272         if (err)
1273                 return err;
1274         return 0;
1275 }
1276
1277 static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
1278                                        int err)
1279 {
1280         struct erofs_sb_info *const sbi = EROFS_SB(be->sb);
1281         struct z_erofs_pcluster *pcl = be->pcl;
1282         unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
1283         const struct z_erofs_decompressor *decompressor =
1284                                 &erofs_decompressors[pcl->algorithmformat];
1285         unsigned int i, inputsize;
1286         int err2;
1287         struct page *page;
1288         bool overlapped;
1289
1290         mutex_lock(&pcl->lock);
1291         be->nr_pages = PAGE_ALIGN(pcl->length + pcl->pageofs_out) >> PAGE_SHIFT;
1292
1293         /* allocate (de)compressed page arrays if cannot be kept on stack */
1294         be->decompressed_pages = NULL;
1295         be->compressed_pages = NULL;
1296         be->onstack_used = 0;
1297         if (be->nr_pages <= Z_EROFS_ONSTACK_PAGES) {
1298                 be->decompressed_pages = be->onstack_pages;
1299                 be->onstack_used = be->nr_pages;
1300                 memset(be->decompressed_pages, 0,
1301                        sizeof(struct page *) * be->nr_pages);
1302         }
1303
1304         if (pclusterpages + be->onstack_used <= Z_EROFS_ONSTACK_PAGES)
1305                 be->compressed_pages = be->onstack_pages + be->onstack_used;
1306
1307         if (!be->decompressed_pages)
1308                 be->decompressed_pages =
1309                         kvcalloc(be->nr_pages, sizeof(struct page *),
1310                                  GFP_KERNEL | __GFP_NOFAIL);
1311         if (!be->compressed_pages)
1312                 be->compressed_pages =
1313                         kvcalloc(pclusterpages, sizeof(struct page *),
1314                                  GFP_KERNEL | __GFP_NOFAIL);
1315
1316         z_erofs_parse_out_bvecs(be);
1317         err2 = z_erofs_parse_in_bvecs(be, &overlapped);
1318         if (err2)
1319                 err = err2;
1320         if (err)
1321                 goto out;
1322
1323         if (z_erofs_is_inline_pcluster(pcl))
1324                 inputsize = pcl->tailpacking_size;
1325         else
1326                 inputsize = pclusterpages * PAGE_SIZE;
1327
1328         err = decompressor->decompress(&(struct z_erofs_decompress_req) {
1329                                         .sb = be->sb,
1330                                         .in = be->compressed_pages,
1331                                         .out = be->decompressed_pages,
1332                                         .pageofs_in = pcl->pageofs_in,
1333                                         .pageofs_out = pcl->pageofs_out,
1334                                         .inputsize = inputsize,
1335                                         .outputsize = pcl->length,
1336                                         .alg = pcl->algorithmformat,
1337                                         .inplace_io = overlapped,
1338                                         .partial_decoding = pcl->partial,
1339                                         .fillgaps = pcl->multibases,
1340                                  }, be->pagepool);
1341
1342 out:
1343         /* must handle all compressed pages before actual file pages */
1344         if (z_erofs_is_inline_pcluster(pcl)) {
1345                 page = pcl->compressed_bvecs[0].page;
1346                 WRITE_ONCE(pcl->compressed_bvecs[0].page, NULL);
1347                 put_page(page);
1348         } else {
1349                 for (i = 0; i < pclusterpages; ++i) {
1350                         page = pcl->compressed_bvecs[i].page;
1351
1352                         if (erofs_page_is_managed(sbi, page))
1353                                 continue;
1354
1355                         /* recycle all individual short-lived pages */
1356                         (void)z_erofs_put_shortlivedpage(be->pagepool, page);
1357                         WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
1358                 }
1359         }
1360         if (be->compressed_pages < be->onstack_pages ||
1361             be->compressed_pages >= be->onstack_pages + Z_EROFS_ONSTACK_PAGES)
1362                 kvfree(be->compressed_pages);
1363         z_erofs_fill_other_copies(be, err);
1364
1365         for (i = 0; i < be->nr_pages; ++i) {
1366                 page = be->decompressed_pages[i];
1367                 if (!page)
1368                         continue;
1369
1370                 DBG_BUGON(z_erofs_page_is_invalidated(page));
1371
1372                 /* recycle all individual short-lived pages */
1373                 if (z_erofs_put_shortlivedpage(be->pagepool, page))
1374                         continue;
1375                 if (err)
1376                         z_erofs_page_mark_eio(page);
1377                 z_erofs_onlinepage_endio(page);
1378         }
1379
1380         if (be->decompressed_pages != be->onstack_pages)
1381                 kvfree(be->decompressed_pages);
1382
1383         pcl->length = 0;
1384         pcl->partial = true;
1385         pcl->multibases = false;
1386         pcl->bvset.nextpage = NULL;
1387         pcl->vcnt = 0;
1388
1389         /* pcluster lock MUST be taken before the following line */
1390         WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_NIL);
1391         mutex_unlock(&pcl->lock);
1392         return err;
1393 }
1394
1395 static void z_erofs_decompress_queue(const struct z_erofs_decompressqueue *io,
1396                                      struct page **pagepool)
1397 {
1398         struct z_erofs_decompress_backend be = {
1399                 .sb = io->sb,
1400                 .pagepool = pagepool,
1401                 .decompressed_secondary_bvecs =
1402                         LIST_HEAD_INIT(be.decompressed_secondary_bvecs),
1403         };
1404         z_erofs_next_pcluster_t owned = io->head;
1405
1406         while (owned != Z_EROFS_PCLUSTER_TAIL) {
1407                 DBG_BUGON(owned == Z_EROFS_PCLUSTER_NIL);
1408
1409                 be.pcl = container_of(owned, struct z_erofs_pcluster, next);
1410                 owned = READ_ONCE(be.pcl->next);
1411
1412                 z_erofs_decompress_pcluster(&be, io->eio ? -EIO : 0);
1413                 erofs_workgroup_put(&be.pcl->obj);
1414         }
1415 }
1416
1417 static void z_erofs_decompressqueue_work(struct work_struct *work)
1418 {
1419         struct z_erofs_decompressqueue *bgq =
1420                 container_of(work, struct z_erofs_decompressqueue, u.work);
1421         struct page *pagepool = NULL;
1422
1423         DBG_BUGON(bgq->head == Z_EROFS_PCLUSTER_TAIL);
1424         z_erofs_decompress_queue(bgq, &pagepool);
1425         erofs_release_pages(&pagepool);
1426         kvfree(bgq);
1427 }
1428
1429 #ifdef CONFIG_EROFS_FS_PCPU_KTHREAD
1430 static void z_erofs_decompressqueue_kthread_work(struct kthread_work *work)
1431 {
1432         z_erofs_decompressqueue_work((struct work_struct *)work);
1433 }
1434 #endif
1435
1436 static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
1437                                        int bios)
1438 {
1439         struct erofs_sb_info *const sbi = EROFS_SB(io->sb);
1440
1441         /* wake up the caller thread for sync decompression */
1442         if (io->sync) {
1443                 if (!atomic_add_return(bios, &io->pending_bios))
1444                         complete(&io->u.done);
1445                 return;
1446         }
1447
1448         if (atomic_add_return(bios, &io->pending_bios))
1449                 return;
1450         /* Use (kthread_)work and sync decompression for atomic contexts only */
1451         if (!in_task() || irqs_disabled() || rcu_read_lock_any_held()) {
1452 #ifdef CONFIG_EROFS_FS_PCPU_KTHREAD
1453                 struct kthread_worker *worker;
1454
1455                 rcu_read_lock();
1456                 worker = rcu_dereference(
1457                                 z_erofs_pcpu_workers[raw_smp_processor_id()]);
1458                 if (!worker) {
1459                         INIT_WORK(&io->u.work, z_erofs_decompressqueue_work);
1460                         queue_work(z_erofs_workqueue, &io->u.work);
1461                 } else {
1462                         kthread_queue_work(worker, &io->u.kthread_work);
1463                 }
1464                 rcu_read_unlock();
1465 #else
1466                 queue_work(z_erofs_workqueue, &io->u.work);
1467 #endif
1468                 /* enable sync decompression for readahead */
1469                 if (sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO)
1470                         sbi->opt.sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON;
1471                 return;
1472         }
1473         z_erofs_decompressqueue_work(&io->u.work);
1474 }
1475
1476 static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
1477                                                unsigned int nr,
1478                                                struct page **pagepool,
1479                                                struct address_space *mc)
1480 {
1481         const pgoff_t index = pcl->obj.index;
1482         gfp_t gfp = mapping_gfp_mask(mc);
1483         bool tocache = false;
1484
1485         struct address_space *mapping;
1486         struct page *oldpage, *page;
1487         int justfound;
1488
1489 repeat:
1490         page = READ_ONCE(pcl->compressed_bvecs[nr].page);
1491         oldpage = page;
1492
1493         if (!page)
1494                 goto out_allocpage;
1495
1496         justfound = (unsigned long)page & 1UL;
1497         page = (struct page *)((unsigned long)page & ~1UL);
1498
1499         /*
1500          * preallocated cached pages, which is used to avoid direct reclaim
1501          * otherwise, it will go inplace I/O path instead.
1502          */
1503         if (page->private == Z_EROFS_PREALLOCATED_PAGE) {
1504                 WRITE_ONCE(pcl->compressed_bvecs[nr].page, page);
1505                 set_page_private(page, 0);
1506                 tocache = true;
1507                 goto out_tocache;
1508         }
1509         mapping = READ_ONCE(page->mapping);
1510
1511         /*
1512          * file-backed online pages in plcuster are all locked steady,
1513          * therefore it is impossible for `mapping' to be NULL.
1514          */
1515         if (mapping && mapping != mc)
1516                 /* ought to be unmanaged pages */
1517                 goto out;
1518
1519         /* directly return for shortlived page as well */
1520         if (z_erofs_is_shortlived_page(page))
1521                 goto out;
1522
1523         lock_page(page);
1524
1525         /* only true if page reclaim goes wrong, should never happen */
1526         DBG_BUGON(justfound && PagePrivate(page));
1527
1528         /* the page is still in manage cache */
1529         if (page->mapping == mc) {
1530                 WRITE_ONCE(pcl->compressed_bvecs[nr].page, page);
1531
1532                 if (!PagePrivate(page)) {
1533                         /*
1534                          * impossible to be !PagePrivate(page) for
1535                          * the current restriction as well if
1536                          * the page is already in compressed_bvecs[].
1537                          */
1538                         DBG_BUGON(!justfound);
1539
1540                         justfound = 0;
1541                         set_page_private(page, (unsigned long)pcl);
1542                         SetPagePrivate(page);
1543                 }
1544
1545                 /* no need to submit io if it is already up-to-date */
1546                 if (PageUptodate(page)) {
1547                         unlock_page(page);
1548                         page = NULL;
1549                 }
1550                 goto out;
1551         }
1552
1553         /*
1554          * the managed page has been truncated, it's unsafe to
1555          * reuse this one, let's allocate a new cache-managed page.
1556          */
1557         DBG_BUGON(page->mapping);
1558         DBG_BUGON(!justfound);
1559
1560         tocache = true;
1561         unlock_page(page);
1562         put_page(page);
1563 out_allocpage:
1564         page = erofs_allocpage(pagepool, gfp | __GFP_NOFAIL);
1565         if (oldpage != cmpxchg(&pcl->compressed_bvecs[nr].page,
1566                                oldpage, page)) {
1567                 erofs_pagepool_add(pagepool, page);
1568                 cond_resched();
1569                 goto repeat;
1570         }
1571 out_tocache:
1572         if (!tocache || add_to_page_cache_lru(page, mc, index + nr, gfp)) {
1573                 /* turn into temporary page if fails (1 ref) */
1574                 set_page_private(page, Z_EROFS_SHORTLIVED_PAGE);
1575                 goto out;
1576         }
1577         attach_page_private(page, pcl);
1578         /* drop a refcount added by allocpage (then we have 2 refs here) */
1579         put_page(page);
1580
1581 out:    /* the only exit (for tracing and debugging) */
1582         return page;
1583 }
1584
1585 static struct z_erofs_decompressqueue *jobqueue_init(struct super_block *sb,
1586                               struct z_erofs_decompressqueue *fgq, bool *fg)
1587 {
1588         struct z_erofs_decompressqueue *q;
1589
1590         if (fg && !*fg) {
1591                 q = kvzalloc(sizeof(*q), GFP_KERNEL | __GFP_NOWARN);
1592                 if (!q) {
1593                         *fg = true;
1594                         goto fg_out;
1595                 }
1596 #ifdef CONFIG_EROFS_FS_PCPU_KTHREAD
1597                 kthread_init_work(&q->u.kthread_work,
1598                                   z_erofs_decompressqueue_kthread_work);
1599 #else
1600                 INIT_WORK(&q->u.work, z_erofs_decompressqueue_work);
1601 #endif
1602         } else {
1603 fg_out:
1604                 q = fgq;
1605                 init_completion(&fgq->u.done);
1606                 atomic_set(&fgq->pending_bios, 0);
1607                 q->eio = false;
1608                 q->sync = true;
1609         }
1610         q->sb = sb;
1611         q->head = Z_EROFS_PCLUSTER_TAIL;
1612         return q;
1613 }
1614
1615 /* define decompression jobqueue types */
1616 enum {
1617         JQ_BYPASS,
1618         JQ_SUBMIT,
1619         NR_JOBQUEUES,
1620 };
1621
1622 static void move_to_bypass_jobqueue(struct z_erofs_pcluster *pcl,
1623                                     z_erofs_next_pcluster_t qtail[],
1624                                     z_erofs_next_pcluster_t owned_head)
1625 {
1626         z_erofs_next_pcluster_t *const submit_qtail = qtail[JQ_SUBMIT];
1627         z_erofs_next_pcluster_t *const bypass_qtail = qtail[JQ_BYPASS];
1628
1629         WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_TAIL);
1630
1631         WRITE_ONCE(*submit_qtail, owned_head);
1632         WRITE_ONCE(*bypass_qtail, &pcl->next);
1633
1634         qtail[JQ_BYPASS] = &pcl->next;
1635 }
1636
1637 static void z_erofs_decompressqueue_endio(struct bio *bio)
1638 {
1639         struct z_erofs_decompressqueue *q = bio->bi_private;
1640         blk_status_t err = bio->bi_status;
1641         struct bio_vec *bvec;
1642         struct bvec_iter_all iter_all;
1643
1644         bio_for_each_segment_all(bvec, bio, iter_all) {
1645                 struct page *page = bvec->bv_page;
1646
1647                 DBG_BUGON(PageUptodate(page));
1648                 DBG_BUGON(z_erofs_page_is_invalidated(page));
1649
1650                 if (erofs_page_is_managed(EROFS_SB(q->sb), page)) {
1651                         if (!err)
1652                                 SetPageUptodate(page);
1653                         unlock_page(page);
1654                 }
1655         }
1656         if (err)
1657                 q->eio = true;
1658         z_erofs_decompress_kickoff(q, -1);
1659         bio_put(bio);
1660 }
1661
1662 static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f,
1663                                  struct z_erofs_decompressqueue *fgq,
1664                                  bool *force_fg, bool readahead)
1665 {
1666         struct super_block *sb = f->inode->i_sb;
1667         struct address_space *mc = MNGD_MAPPING(EROFS_SB(sb));
1668         z_erofs_next_pcluster_t qtail[NR_JOBQUEUES];
1669         struct z_erofs_decompressqueue *q[NR_JOBQUEUES];
1670         z_erofs_next_pcluster_t owned_head = f->owned_head;
1671         /* bio is NULL initially, so no need to initialize last_{index,bdev} */
1672         pgoff_t last_index;
1673         struct block_device *last_bdev;
1674         unsigned int nr_bios = 0;
1675         struct bio *bio = NULL;
1676         unsigned long pflags;
1677         int memstall = 0;
1678
1679         /*
1680          * if managed cache is enabled, bypass jobqueue is needed,
1681          * no need to read from device for all pclusters in this queue.
1682          */
1683         q[JQ_BYPASS] = jobqueue_init(sb, fgq + JQ_BYPASS, NULL);
1684         q[JQ_SUBMIT] = jobqueue_init(sb, fgq + JQ_SUBMIT, force_fg);
1685
1686         qtail[JQ_BYPASS] = &q[JQ_BYPASS]->head;
1687         qtail[JQ_SUBMIT] = &q[JQ_SUBMIT]->head;
1688
1689         /* by default, all need io submission */
1690         q[JQ_SUBMIT]->head = owned_head;
1691
1692         do {
1693                 struct erofs_map_dev mdev;
1694                 struct z_erofs_pcluster *pcl;
1695                 pgoff_t cur, end;
1696                 unsigned int i = 0;
1697                 bool bypass = true;
1698
1699                 DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_NIL);
1700                 pcl = container_of(owned_head, struct z_erofs_pcluster, next);
1701                 owned_head = READ_ONCE(pcl->next);
1702
1703                 if (z_erofs_is_inline_pcluster(pcl)) {
1704                         move_to_bypass_jobqueue(pcl, qtail, owned_head);
1705                         continue;
1706                 }
1707
1708                 /* no device id here, thus it will always succeed */
1709                 mdev = (struct erofs_map_dev) {
1710                         .m_pa = erofs_pos(sb, pcl->obj.index),
1711                 };
1712                 (void)erofs_map_dev(sb, &mdev);
1713
1714                 cur = erofs_blknr(sb, mdev.m_pa);
1715                 end = cur + pcl->pclusterpages;
1716
1717                 do {
1718                         struct page *page;
1719
1720                         page = pickup_page_for_submission(pcl, i++,
1721                                         &f->pagepool, mc);
1722                         if (!page)
1723                                 continue;
1724
1725                         if (bio && (cur != last_index + 1 ||
1726                                     last_bdev != mdev.m_bdev)) {
1727 submit_bio_retry:
1728                                 submit_bio(bio);
1729                                 if (memstall) {
1730                                         psi_memstall_leave(&pflags);
1731                                         memstall = 0;
1732                                 }
1733                                 bio = NULL;
1734                         }
1735
1736                         if (unlikely(PageWorkingset(page)) && !memstall) {
1737                                 psi_memstall_enter(&pflags);
1738                                 memstall = 1;
1739                         }
1740
1741                         if (!bio) {
1742                                 bio = bio_alloc(mdev.m_bdev, BIO_MAX_VECS,
1743                                                 REQ_OP_READ, GFP_NOIO);
1744                                 bio->bi_end_io = z_erofs_decompressqueue_endio;
1745
1746                                 last_bdev = mdev.m_bdev;
1747                                 bio->bi_iter.bi_sector = (sector_t)cur <<
1748                                         (sb->s_blocksize_bits - 9);
1749                                 bio->bi_private = q[JQ_SUBMIT];
1750                                 if (readahead)
1751                                         bio->bi_opf |= REQ_RAHEAD;
1752                                 ++nr_bios;
1753                         }
1754
1755                         if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE)
1756                                 goto submit_bio_retry;
1757
1758                         last_index = cur;
1759                         bypass = false;
1760                 } while (++cur < end);
1761
1762                 if (!bypass)
1763                         qtail[JQ_SUBMIT] = &pcl->next;
1764                 else
1765                         move_to_bypass_jobqueue(pcl, qtail, owned_head);
1766         } while (owned_head != Z_EROFS_PCLUSTER_TAIL);
1767
1768         if (bio) {
1769                 submit_bio(bio);
1770                 if (memstall)
1771                         psi_memstall_leave(&pflags);
1772         }
1773
1774         /*
1775          * although background is preferred, no one is pending for submission.
1776          * don't issue decompression but drop it directly instead.
1777          */
1778         if (!*force_fg && !nr_bios) {
1779                 kvfree(q[JQ_SUBMIT]);
1780                 return;
1781         }
1782         z_erofs_decompress_kickoff(q[JQ_SUBMIT], nr_bios);
1783 }
1784
1785 static void z_erofs_runqueue(struct z_erofs_decompress_frontend *f,
1786                              bool force_fg, bool ra)
1787 {
1788         struct z_erofs_decompressqueue io[NR_JOBQUEUES];
1789
1790         if (f->owned_head == Z_EROFS_PCLUSTER_TAIL)
1791                 return;
1792         z_erofs_submit_queue(f, io, &force_fg, ra);
1793
1794         /* handle bypass queue (no i/o pclusters) immediately */
1795         z_erofs_decompress_queue(&io[JQ_BYPASS], &f->pagepool);
1796
1797         if (!force_fg)
1798                 return;
1799
1800         /* wait until all bios are completed */
1801         wait_for_completion_io(&io[JQ_SUBMIT].u.done);
1802
1803         /* handle synchronous decompress queue in the caller context */
1804         z_erofs_decompress_queue(&io[JQ_SUBMIT], &f->pagepool);
1805 }
1806
1807 /*
1808  * Since partial uptodate is still unimplemented for now, we have to use
1809  * approximate readmore strategies as a start.
1810  */
1811 static void z_erofs_pcluster_readmore(struct z_erofs_decompress_frontend *f,
1812                 struct readahead_control *rac, bool backmost)
1813 {
1814         struct inode *inode = f->inode;
1815         struct erofs_map_blocks *map = &f->map;
1816         erofs_off_t cur, end, headoffset = f->headoffset;
1817         int err;
1818
1819         if (backmost) {
1820                 if (rac)
1821                         end = headoffset + readahead_length(rac) - 1;
1822                 else
1823                         end = headoffset + PAGE_SIZE - 1;
1824                 map->m_la = end;
1825                 err = z_erofs_map_blocks_iter(inode, map,
1826                                               EROFS_GET_BLOCKS_READMORE);
1827                 if (err)
1828                         return;
1829
1830                 /* expand ra for the trailing edge if readahead */
1831                 if (rac) {
1832                         cur = round_up(map->m_la + map->m_llen, PAGE_SIZE);
1833                         readahead_expand(rac, headoffset, cur - headoffset);
1834                         return;
1835                 }
1836                 end = round_up(end, PAGE_SIZE);
1837         } else {
1838                 end = round_up(map->m_la, PAGE_SIZE);
1839
1840                 if (!map->m_llen)
1841                         return;
1842         }
1843
1844         cur = map->m_la + map->m_llen - 1;
1845         while ((cur >= end) && (cur < i_size_read(inode))) {
1846                 pgoff_t index = cur >> PAGE_SHIFT;
1847                 struct page *page;
1848
1849                 page = erofs_grab_cache_page_nowait(inode->i_mapping, index);
1850                 if (page) {
1851                         if (PageUptodate(page)) {
1852                                 unlock_page(page);
1853                         } else {
1854                                 err = z_erofs_do_read_page(f, page);
1855                                 if (err)
1856                                         erofs_err(inode->i_sb,
1857                                                   "readmore error at page %lu @ nid %llu",
1858                                                   index, EROFS_I(inode)->nid);
1859                         }
1860                         put_page(page);
1861                 }
1862
1863                 if (cur < PAGE_SIZE)
1864                         break;
1865                 cur = (index << PAGE_SHIFT) - 1;
1866         }
1867 }
1868
1869 static int z_erofs_read_folio(struct file *file, struct folio *folio)
1870 {
1871         struct page *page = &folio->page;
1872         struct inode *const inode = page->mapping->host;
1873         struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
1874         struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
1875         int err;
1876
1877         trace_erofs_readpage(page, false);
1878         f.headoffset = (erofs_off_t)page->index << PAGE_SHIFT;
1879
1880         z_erofs_pcluster_readmore(&f, NULL, true);
1881         err = z_erofs_do_read_page(&f, page);
1882         z_erofs_pcluster_readmore(&f, NULL, false);
1883         (void)z_erofs_collector_end(&f);
1884
1885         /* if some compressed cluster ready, need submit them anyway */
1886         z_erofs_runqueue(&f, z_erofs_is_sync_decompress(sbi, 0), false);
1887
1888         if (err)
1889                 erofs_err(inode->i_sb, "failed to read, err [%d]", err);
1890
1891         erofs_put_metabuf(&f.map.buf);
1892         erofs_release_pages(&f.pagepool);
1893         return err;
1894 }
1895
1896 static void z_erofs_readahead(struct readahead_control *rac)
1897 {
1898         struct inode *const inode = rac->mapping->host;
1899         struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
1900         struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
1901         struct page *head = NULL, *page;
1902         unsigned int nr_pages;
1903
1904         f.headoffset = readahead_pos(rac);
1905
1906         z_erofs_pcluster_readmore(&f, rac, true);
1907         nr_pages = readahead_count(rac);
1908         trace_erofs_readpages(inode, readahead_index(rac), nr_pages, false);
1909
1910         while ((page = readahead_page(rac))) {
1911                 set_page_private(page, (unsigned long)head);
1912                 head = page;
1913         }
1914
1915         while (head) {
1916                 struct page *page = head;
1917                 int err;
1918
1919                 /* traversal in reverse order */
1920                 head = (void *)page_private(page);
1921
1922                 err = z_erofs_do_read_page(&f, page);
1923                 if (err)
1924                         erofs_err(inode->i_sb,
1925                                   "readahead error at page %lu @ nid %llu",
1926                                   page->index, EROFS_I(inode)->nid);
1927                 put_page(page);
1928         }
1929         z_erofs_pcluster_readmore(&f, rac, false);
1930         (void)z_erofs_collector_end(&f);
1931
1932         z_erofs_runqueue(&f, z_erofs_is_sync_decompress(sbi, nr_pages), true);
1933         erofs_put_metabuf(&f.map.buf);
1934         erofs_release_pages(&f.pagepool);
1935 }
1936
1937 const struct address_space_operations z_erofs_aops = {
1938         .read_folio = z_erofs_read_folio,
1939         .readahead = z_erofs_readahead,
1940 };