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