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/prefetch.h>
   9 #include <linux/psi.h>
  10 #include <linux/cpuhotplug.h>
  11 #include <trace/events/erofs.h>
  12
  13 #define Z_EROFS_PCLUSTER_MAX_PAGES      (Z_EROFS_PCLUSTER_MAX_SIZE / PAGE_SIZE)
  14 #define Z_EROFS_INLINE_BVECS            2
  15
  16 /*
  17  * let's leave a type here in case of introducing
  18  * another tagged pointer later.
  19  */
  20 typedef void *z_erofs_next_pcluster_t;
  21
  22 struct z_erofs_bvec {
  23         struct page *page;
  24         int offset;
  25         unsigned int end;
  26 };
  27
  28 #define __Z_EROFS_BVSET(name, total) \
  29 struct name { \
  30         /* point to the next page which contains the following bvecs */ \
  31         struct page *nextpage; \
  32         struct z_erofs_bvec bvec[total]; \
  33 }
  34 __Z_EROFS_BVSET(z_erofs_bvset,);
  35 __Z_EROFS_BVSET(z_erofs_bvset_inline, Z_EROFS_INLINE_BVECS);
  36
  37 /*
  38  * Structure fields follow one of the following exclusion rules.
  39  *
  40  * I: Modifiable by initialization/destruction paths and read-only
  41  *    for everyone else;
  42  *
  43  * L: Field should be protected by the pcluster lock;
  44  *
  45  * A: Field should be accessed / updated in atomic for parallelized code.
  46  */
  47 struct z_erofs_pcluster {
  48         struct erofs_workgroup obj;
  49         struct mutex lock;
  50
  51         /* A: point to next chained pcluster or TAILs */
  52         z_erofs_next_pcluster_t next;
  53
  54         /* L: the maximum decompression size of this round */
  55         unsigned int length;
  56
  57         /* L: total number of bvecs */
  58         unsigned int vcnt;
  59
  60         /* I: page offset of start position of decompression */
  61         unsigned short pageofs_out;
  62
  63         /* I: page offset of inline compressed data */
  64         unsigned short pageofs_in;
  65
  66         union {
  67                 /* L: inline a certain number of bvec for bootstrap */
  68                 struct z_erofs_bvset_inline bvset;
  69
  70                 /* I: can be used to free the pcluster by RCU. */
  71                 struct rcu_head rcu;
  72         };
  73
  74         union {
  75                 /* I: physical cluster size in pages */
  76                 unsigned short pclusterpages;
  77
  78                 /* I: tailpacking inline compressed size */
  79                 unsigned short tailpacking_size;
  80         };
  81
  82         /* I: compression algorithm format */
  83         unsigned char algorithmformat;
  84
  85         /* L: whether partial decompression or not */
  86         bool partial;
  87
  88         /* L: indicate several pageofs_outs or not */
  89         bool multibases;
  90
  91         /* A: compressed bvecs (can be cached or inplaced pages) */
  92         struct z_erofs_bvec compressed_bvecs[];
  93 };
  94
  95 /* let's avoid the valid 32-bit kernel addresses */
  96
  97 /* the chained workgroup has't submitted io (still open) */
  98 #define Z_EROFS_PCLUSTER_TAIL           ((void *)0x5F0ECAFE)
  99 /* the chained workgroup has already submitted io */
 100 #define Z_EROFS_PCLUSTER_TAIL_CLOSED    ((void *)0x5F0EDEAD)
 101
 102 #define Z_EROFS_PCLUSTER_NIL            (NULL)
 103
 104 struct z_erofs_decompressqueue {
 105         struct super_block *sb;
 106         atomic_t pending_bios;
 107         z_erofs_next_pcluster_t head;
 108
 109         union {
 110                 struct completion done;
 111                 struct work_struct work;
 112                 struct kthread_work kthread_work;
 113         } u;
 114         bool eio, sync;
 115 };
 116
 117 static inline bool z_erofs_is_inline_pcluster(struct z_erofs_pcluster *pcl)
 118 {
 119         return !pcl->obj.index;
 120 }
 121
 122 static inline unsigned int z_erofs_pclusterpages(struct z_erofs_pcluster *pcl)
 123 {
 124         if (z_erofs_is_inline_pcluster(pcl))
 125                 return 1;
 126         return pcl->pclusterpages;
 127 }
 128
 129 /*
 130  * bit 30: I/O error occurred on this page
 131  * bit 0 - 29: remaining parts to complete this page
 132  */
 133 #define Z_EROFS_PAGE_EIO                        (1 << 30)
 134
 135 static inline void z_erofs_onlinepage_init(struct page *page)
 136 {
 137         union {
 138                 atomic_t o;
 139                 unsigned long v;
 140         } u = { .o = ATOMIC_INIT(1) };
 141
 142         set_page_private(page, u.v);
 143         smp_wmb();
 144         SetPagePrivate(page);
 145 }
 146
 147 static inline void z_erofs_onlinepage_split(struct page *page)
 148 {
 149         atomic_inc((atomic_t *)&page->private);
 150 }
 151
 152 static inline void z_erofs_page_mark_eio(struct page *page)
 153 {
 154         int orig;
 155
 156         do {
 157                 orig = atomic_read((atomic_t *)&page->private);
 158         } while (atomic_cmpxchg((atomic_t *)&page->private, orig,
 159                                 orig | Z_EROFS_PAGE_EIO) != orig);
 160 }
 161
 162 static inline void z_erofs_onlinepage_endio(struct page *page)
 163 {
 164         unsigned int v;
 165
 166         DBG_BUGON(!PagePrivate(page));
 167         v = atomic_dec_return((atomic_t *)&page->private);
 168         if (!(v & ~Z_EROFS_PAGE_EIO)) {
 169                 set_page_private(page, 0);
 170                 ClearPagePrivate(page);
 171                 if (!(v & Z_EROFS_PAGE_EIO))
 172                         SetPageUptodate(page);
 173                 unlock_page(page);
 174         }
 175 }
 176
 177 #define Z_EROFS_ONSTACK_PAGES           32
 178
 179 /*
 180  * since pclustersize is variable for big pcluster feature, introduce slab
 181  * pools implementation for different pcluster sizes.
 182  */
 183 struct z_erofs_pcluster_slab {
 184         struct kmem_cache *slab;
 185         unsigned int maxpages;
 186         char name[48];
 187 };
 188
 189 #define _PCLP(n) { .maxpages = n }
 190
 191 static struct z_erofs_pcluster_slab pcluster_pool[] __read_mostly = {
 192         _PCLP(1), _PCLP(4), _PCLP(16), _PCLP(64), _PCLP(128),
 193         _PCLP(Z_EROFS_PCLUSTER_MAX_PAGES)
 194 };
 195
 196 struct z_erofs_bvec_iter {
 197         struct page *bvpage;
 198         struct z_erofs_bvset *bvset;
 199         unsigned int nr, cur;
 200 };
 201
 202 static struct page *z_erofs_bvec_iter_end(struct z_erofs_bvec_iter *iter)
 203 {
 204         if (iter->bvpage)
 205                 kunmap_local(iter->bvset);
 206         return iter->bvpage;
 207 }
 208
 209 static struct page *z_erofs_bvset_flip(struct z_erofs_bvec_iter *iter)
 210 {
 211         unsigned long base = (unsigned long)((struct z_erofs_bvset *)0)->bvec;
 212         /* have to access nextpage in advance, otherwise it will be unmapped */
 213         struct page *nextpage = iter->bvset->nextpage;
 214         struct page *oldpage;
 215
 216         DBG_BUGON(!nextpage);
 217         oldpage = z_erofs_bvec_iter_end(iter);
 218         iter->bvpage = nextpage;
 219         iter->bvset = kmap_local_page(nextpage);
 220         iter->nr = (PAGE_SIZE - base) / sizeof(struct z_erofs_bvec);
 221         iter->cur = 0;
 222         return oldpage;
 223 }
 224
 225 static void z_erofs_bvec_iter_begin(struct z_erofs_bvec_iter *iter,
 226                                     struct z_erofs_bvset_inline *bvset,
 227                                     unsigned int bootstrap_nr,
 228                                     unsigned int cur)
 229 {
 230         *iter = (struct z_erofs_bvec_iter) {
 231                 .nr = bootstrap_nr,
 232                 .bvset = (struct z_erofs_bvset *)bvset,
 233         };
 234
 235         while (cur > iter->nr) {
 236                 cur -= iter->nr;
 237                 z_erofs_bvset_flip(iter);
 238         }
 239         iter->cur = cur;
 240 }
 241
 242 static int z_erofs_bvec_enqueue(struct z_erofs_bvec_iter *iter,
 243                                 struct z_erofs_bvec *bvec,
 244                                 struct page **candidate_bvpage)
 245 {
 246         if (iter->cur == iter->nr) {
 247                 if (!*candidate_bvpage)
 248                         return -EAGAIN;
 249
 250                 DBG_BUGON(iter->bvset->nextpage);
 251                 iter->bvset->nextpage = *candidate_bvpage;
 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          * The current pclusters was the tail of an exist chain, in addition
 504          * that the previous processed chained pclusters are all decided to
 505          * be hooked up to it.
 506          * A new chain will be created for the remaining pclusters which are
 507          * not processed yet, so different from Z_EROFS_PCLUSTER_FOLLOWED,
 508          * the next pcluster cannot reuse the whole page safely for inplace I/O
 509          * in the following scenario:
 510          *  ________________________________________________________________
 511          * |      tail (partial) page     |       head (partial) page       |
 512          * |   (belongs to the next pcl)  |   (belongs to the current pcl)  |
 513          * |_______PCLUSTER_FOLLOWED______|________PCLUSTER_HOOKED__________|
 514          */
 515         Z_EROFS_PCLUSTER_HOOKED,
 516         /*
 517          * a weak form of Z_EROFS_PCLUSTER_FOLLOWED, the difference is that it
 518          * could be dispatched into bypass queue later due to uptodated managed
 519          * pages. All related online pages cannot be reused for inplace I/O (or
 520          * bvpage) since it can be directly decoded without I/O submission.
 521          */
 522         Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE,
 523         /*
 524          * The current collection has been linked with the owned chain, and
 525          * could also be linked with the remaining collections, which means
 526          * if the processing page is the tail page of the collection, thus
 527          * the current collection can safely use the whole page (since
 528          * the previous collection is under control) for in-place I/O, as
 529          * illustrated below:
 530          *  ________________________________________________________________
 531          * |  tail (partial) page |          head (partial) page           |
 532          * |  (of the current cl) |      (of the previous collection)      |
 533          * | PCLUSTER_FOLLOWED or |                                        |
 534          * |_____PCLUSTER_HOOKED__|___________PCLUSTER_FOLLOWED____________|
 535          *
 536          * [  (*) the above page can be used as inplace I/O.               ]
 537          */
 538         Z_EROFS_PCLUSTER_FOLLOWED,
 539 };
 540
 541 struct z_erofs_decompress_frontend {
 542         struct inode *const inode;
 543         struct erofs_map_blocks map;
 544         struct z_erofs_bvec_iter biter;
 545
 546         struct page *candidate_bvpage;
 547         struct z_erofs_pcluster *pcl, *tailpcl;
 548         z_erofs_next_pcluster_t owned_head;
 549         enum z_erofs_pclustermode mode;
 550
 551         bool readahead;
 552         /* used for applying cache strategy on the fly */
 553         bool backmost;
 554         erofs_off_t headoffset;
 555
 556         /* a pointer used to pick up inplace I/O pages */
 557         unsigned int icur;
 558 };
 559
 560 #define DECOMPRESS_FRONTEND_INIT(__i) { \
 561         .inode = __i, .owned_head = Z_EROFS_PCLUSTER_TAIL, \
 562         .mode = Z_EROFS_PCLUSTER_FOLLOWED, .backmost = true }
 563
 564 static bool z_erofs_should_alloc_cache(struct z_erofs_decompress_frontend *fe)
 565 {
 566         unsigned int cachestrategy = EROFS_I_SB(fe->inode)->opt.cache_strategy;
 567
 568         if (cachestrategy <= EROFS_ZIP_CACHE_DISABLED)
 569                 return false;
 570
 571         if (fe->backmost)
 572                 return true;
 573
 574         if (cachestrategy >= EROFS_ZIP_CACHE_READAROUND &&
 575             fe->map.m_la < fe->headoffset)
 576                 return true;
 577
 578         return false;
 579 }
 580
 581 static void z_erofs_bind_cache(struct z_erofs_decompress_frontend *fe,
 582                                struct page **pagepool)
 583 {
 584         struct address_space *mc = MNGD_MAPPING(EROFS_I_SB(fe->inode));
 585         struct z_erofs_pcluster *pcl = fe->pcl;
 586         bool shouldalloc = z_erofs_should_alloc_cache(fe);
 587         bool standalone = true;
 588         /*
 589          * optimistic allocation without direct reclaim since inplace I/O
 590          * can be used if low memory otherwise.
 591          */
 592         gfp_t gfp = (mapping_gfp_mask(mc) & ~__GFP_DIRECT_RECLAIM) |
 593                         __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
 594         unsigned int i;
 595
 596         if (fe->mode < Z_EROFS_PCLUSTER_FOLLOWED)
 597                 return;
 598
 599         for (i = 0; i < pcl->pclusterpages; ++i) {
 600                 struct page *page;
 601                 void *t;        /* mark pages just found for debugging */
 602                 struct page *newpage = NULL;
 603
 604                 /* the compressed page was loaded before */
 605                 if (READ_ONCE(pcl->compressed_bvecs[i].page))
 606                         continue;
 607
 608                 page = find_get_page(mc, pcl->obj.index + i);
 609
 610                 if (page) {
 611                         t = (void *)((unsigned long)page | 1);
 612                 } else {
 613                         /* I/O is needed, no possible to decompress directly */
 614                         standalone = false;
 615                         if (!shouldalloc)
 616                                 continue;
 617
 618                         /*
 619                          * try to use cached I/O if page allocation
 620                          * succeeds or fallback to in-place I/O instead
 621                          * to avoid any direct reclaim.
 622                          */
 623                         newpage = erofs_allocpage(pagepool, gfp);
 624                         if (!newpage)
 625                                 continue;
 626                         set_page_private(newpage, Z_EROFS_PREALLOCATED_PAGE);
 627                         t = (void *)((unsigned long)newpage | 1);
 628                 }
 629
 630                 if (!cmpxchg_relaxed(&pcl->compressed_bvecs[i].page, NULL, t))
 631                         continue;
 632
 633                 if (page)
 634                         put_page(page);
 635                 else if (newpage)
 636                         erofs_pagepool_add(pagepool, newpage);
 637         }
 638
 639         /*
 640          * don't do inplace I/O if all compressed pages are available in
 641          * managed cache since it can be moved to the bypass queue instead.
 642          */
 643         if (standalone)
 644                 fe->mode = Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE;
 645 }
 646
 647 /* called by erofs_shrinker to get rid of all compressed_pages */
 648 int erofs_try_to_free_all_cached_pages(struct erofs_sb_info *sbi,
 649                                        struct erofs_workgroup *grp)
 650 {
 651         struct z_erofs_pcluster *const pcl =
 652                 container_of(grp, struct z_erofs_pcluster, obj);
 653         int i;
 654
 655         DBG_BUGON(z_erofs_is_inline_pcluster(pcl));
 656         /*
 657          * refcount of workgroup is now freezed as 1,
 658          * therefore no need to worry about available decompression users.
 659          */
 660         for (i = 0; i < pcl->pclusterpages; ++i) {
 661                 struct page *page = pcl->compressed_bvecs[i].page;
 662
 663                 if (!page)
 664                         continue;
 665
 666                 /* block other users from reclaiming or migrating the page */
 667                 if (!trylock_page(page))
 668                         return -EBUSY;
 669
 670                 if (!erofs_page_is_managed(sbi, page))
 671                         continue;
 672
 673                 /* barrier is implied in the following 'unlock_page' */
 674                 WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
 675                 detach_page_private(page);
 676                 unlock_page(page);
 677         }
 678         return 0;
 679 }
 680
 681 int erofs_try_to_free_cached_page(struct page *page)
 682 {
 683         struct z_erofs_pcluster *const pcl = (void *)page_private(page);
 684         int ret, i;
 685
 686         if (!erofs_workgroup_try_to_freeze(&pcl->obj, 1))
 687                 return 0;
 688
 689         ret = 0;
 690         DBG_BUGON(z_erofs_is_inline_pcluster(pcl));
 691         for (i = 0; i < pcl->pclusterpages; ++i) {
 692                 if (pcl->compressed_bvecs[i].page == page) {
 693                         WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
 694                         ret = 1;
 695                         break;
 696                 }
 697         }
 698         erofs_workgroup_unfreeze(&pcl->obj, 1);
 699         if (ret)
 700                 detach_page_private(page);
 701         return ret;
 702 }
 703
 704 static bool z_erofs_try_inplace_io(struct z_erofs_decompress_frontend *fe,
 705                                    struct z_erofs_bvec *bvec)
 706 {
 707         struct z_erofs_pcluster *const pcl = fe->pcl;
 708
 709         while (fe->icur > 0) {
 710                 if (!cmpxchg(&pcl->compressed_bvecs[--fe->icur].page,
 711                              NULL, bvec->page)) {
 712                         pcl->compressed_bvecs[fe->icur] = *bvec;
 713                         return true;
 714                 }
 715         }
 716         return false;
 717 }
 718
 719 /* callers must be with pcluster lock held */
 720 static int z_erofs_attach_page(struct z_erofs_decompress_frontend *fe,
 721                                struct z_erofs_bvec *bvec, bool exclusive)
 722 {
 723         int ret;
 724
 725         if (exclusive) {
 726                 /* give priority for inplaceio to use file pages first */
 727                 if (z_erofs_try_inplace_io(fe, bvec))
 728                         return 0;
 729                 /* otherwise, check if it can be used as a bvpage */
 730                 if (fe->mode >= Z_EROFS_PCLUSTER_FOLLOWED &&
 731                     !fe->candidate_bvpage)
 732                         fe->candidate_bvpage = bvec->page;
 733         }
 734         ret = z_erofs_bvec_enqueue(&fe->biter, bvec, &fe->candidate_bvpage);
 735         fe->pcl->vcnt += (ret >= 0);
 736         return ret;
 737 }
 738
 739 static void z_erofs_try_to_claim_pcluster(struct z_erofs_decompress_frontend *f)
 740 {
 741         struct z_erofs_pcluster *pcl = f->pcl;
 742         z_erofs_next_pcluster_t *owned_head = &f->owned_head;
 743
 744         /* type 1, nil pcluster (this pcluster doesn't belong to any chain.) */
 745         if (cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_NIL,
 746                     *owned_head) == Z_EROFS_PCLUSTER_NIL) {
 747                 *owned_head = &pcl->next;
 748                 /* so we can attach this pcluster to our submission chain. */
 749                 f->mode = Z_EROFS_PCLUSTER_FOLLOWED;
 750                 return;
 751         }
 752
 753         /*
 754          * type 2, link to the end of an existing open chain, be careful
 755          * that its submission is controlled by the original attached chain.
 756          */
 757         if (*owned_head != &pcl->next && pcl != f->tailpcl &&
 758             cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_TAIL,
 759                     *owned_head) == Z_EROFS_PCLUSTER_TAIL) {
 760                 *owned_head = Z_EROFS_PCLUSTER_TAIL;
 761                 f->mode = Z_EROFS_PCLUSTER_HOOKED;
 762                 f->tailpcl = NULL;
 763                 return;
 764         }
 765         /* type 3, it belongs to a chain, but it isn't the end of the chain */
 766         f->mode = Z_EROFS_PCLUSTER_INFLIGHT;
 767 }
 768
 769 static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
 770 {
 771         struct erofs_map_blocks *map = &fe->map;
 772         bool ztailpacking = map->m_flags & EROFS_MAP_META;
 773         struct z_erofs_pcluster *pcl;
 774         struct erofs_workgroup *grp;
 775         int err;
 776
 777         if (!(map->m_flags & EROFS_MAP_ENCODED) ||
 778             (!ztailpacking && !(map->m_pa >> PAGE_SHIFT))) {
 779                 DBG_BUGON(1);
 780                 return -EFSCORRUPTED;
 781         }
 782
 783         /* no available pcluster, let's allocate one */
 784         pcl = z_erofs_alloc_pcluster(ztailpacking ? 1 :
 785                                      map->m_plen >> PAGE_SHIFT);
 786         if (IS_ERR(pcl))
 787                 return PTR_ERR(pcl);
 788
 789         atomic_set(&pcl->obj.refcount, 1);
 790         pcl->algorithmformat = map->m_algorithmformat;
 791         pcl->length = 0;
 792         pcl->partial = true;
 793
 794         /* new pclusters should be claimed as type 1, primary and followed */
 795         pcl->next = fe->owned_head;
 796         pcl->pageofs_out = map->m_la & ~PAGE_MASK;
 797         fe->mode = Z_EROFS_PCLUSTER_FOLLOWED;
 798
 799         /*
 800          * lock all primary followed works before visible to others
 801          * and mutex_trylock *never* fails for a new pcluster.
 802          */
 803         mutex_init(&pcl->lock);
 804         DBG_BUGON(!mutex_trylock(&pcl->lock));
 805
 806         if (ztailpacking) {
 807                 pcl->obj.index = 0;     /* which indicates ztailpacking */
 808                 pcl->pageofs_in = erofs_blkoff(fe->inode->i_sb, map->m_pa);
 809                 pcl->tailpacking_size = map->m_plen;
 810         } else {
 811                 pcl->obj.index = map->m_pa >> PAGE_SHIFT;
 812
 813                 grp = erofs_insert_workgroup(fe->inode->i_sb, &pcl->obj);
 814                 if (IS_ERR(grp)) {
 815                         err = PTR_ERR(grp);
 816                         goto err_out;
 817                 }
 818
 819                 if (grp != &pcl->obj) {
 820                         fe->pcl = container_of(grp,
 821                                         struct z_erofs_pcluster, obj);
 822                         err = -EEXIST;
 823                         goto err_out;
 824                 }
 825         }
 826         /* used to check tail merging loop due to corrupted images */
 827         if (fe->owned_head == Z_EROFS_PCLUSTER_TAIL)
 828                 fe->tailpcl = pcl;
 829         fe->owned_head = &pcl->next;
 830         fe->pcl = pcl;
 831         return 0;
 832
 833 err_out:
 834         mutex_unlock(&pcl->lock);
 835         z_erofs_free_pcluster(pcl);
 836         return err;
 837 }
 838
 839 static int z_erofs_collector_begin(struct z_erofs_decompress_frontend *fe)
 840 {
 841         struct erofs_map_blocks *map = &fe->map;
 842         struct erofs_workgroup *grp = NULL;
 843         int ret;
 844
 845         DBG_BUGON(fe->pcl);
 846
 847         /* must be Z_EROFS_PCLUSTER_TAIL or pointed to previous pcluster */
 848         DBG_BUGON(fe->owned_head == Z_EROFS_PCLUSTER_NIL);
 849         DBG_BUGON(fe->owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
 850
 851         if (!(map->m_flags & EROFS_MAP_META)) {
 852                 grp = erofs_find_workgroup(fe->inode->i_sb,
 853                                            map->m_pa >> PAGE_SHIFT);
 854         } else if ((map->m_pa & ~PAGE_MASK) + map->m_plen > PAGE_SIZE) {
 855                 DBG_BUGON(1);
 856                 return -EFSCORRUPTED;
 857         }
 858
 859         if (grp) {
 860                 fe->pcl = container_of(grp, struct z_erofs_pcluster, obj);
 861                 ret = -EEXIST;
 862         } else {
 863                 ret = z_erofs_register_pcluster(fe);
 864         }
 865
 866         if (ret == -EEXIST) {
 867                 mutex_lock(&fe->pcl->lock);
 868                 /* used to check tail merging loop due to corrupted images */
 869                 if (fe->owned_head == Z_EROFS_PCLUSTER_TAIL)
 870                         fe->tailpcl = fe->pcl;
 871
 872                 z_erofs_try_to_claim_pcluster(fe);
 873         } else if (ret) {
 874                 return ret;
 875         }
 876         z_erofs_bvec_iter_begin(&fe->biter, &fe->pcl->bvset,
 877                                 Z_EROFS_INLINE_BVECS, fe->pcl->vcnt);
 878         /* since file-backed online pages are traversed in reverse order */
 879         fe->icur = z_erofs_pclusterpages(fe->pcl);
 880         return 0;
 881 }
 882
 883 /*
 884  * keep in mind that no referenced pclusters will be freed
 885  * only after a RCU grace period.
 886  */
 887 static void z_erofs_rcu_callback(struct rcu_head *head)
 888 {
 889         z_erofs_free_pcluster(container_of(head,
 890                         struct z_erofs_pcluster, rcu));
 891 }
 892
 893 void erofs_workgroup_free_rcu(struct erofs_workgroup *grp)
 894 {
 895         struct z_erofs_pcluster *const pcl =
 896                 container_of(grp, struct z_erofs_pcluster, obj);
 897
 898         call_rcu(&pcl->rcu, z_erofs_rcu_callback);
 899 }
 900
 901 static bool z_erofs_collector_end(struct z_erofs_decompress_frontend *fe)
 902 {
 903         struct z_erofs_pcluster *pcl = fe->pcl;
 904
 905         if (!pcl)
 906                 return false;
 907
 908         z_erofs_bvec_iter_end(&fe->biter);
 909         mutex_unlock(&pcl->lock);
 910
 911         if (fe->candidate_bvpage) {
 912                 DBG_BUGON(z_erofs_is_shortlived_page(fe->candidate_bvpage));
 913                 fe->candidate_bvpage = NULL;
 914         }
 915
 916         /*
 917          * if all pending pages are added, don't hold its reference
 918          * any longer if the pcluster isn't hosted by ourselves.
 919          */
 920         if (fe->mode < Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE)
 921                 erofs_workgroup_put(&pcl->obj);
 922
 923         fe->pcl = NULL;
 924         return true;
 925 }
 926
 927 static int z_erofs_read_fragment(struct inode *inode, erofs_off_t pos,
 928                                  struct page *page, unsigned int pageofs,
 929                                  unsigned int len)
 930 {
 931         struct super_block *sb = inode->i_sb;
 932         struct inode *packed_inode = EROFS_I_SB(inode)->packed_inode;
 933         struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
 934         u8 *src, *dst;
 935         unsigned int i, cnt;
 936
 937         if (!packed_inode)
 938                 return -EFSCORRUPTED;
 939
 940         buf.inode = packed_inode;
 941         pos += EROFS_I(inode)->z_fragmentoff;
 942         for (i = 0; i < len; i += cnt) {
 943                 cnt = min_t(unsigned int, len - i,
 944                             sb->s_blocksize - erofs_blkoff(sb, pos));
 945                 src = erofs_bread(&buf, erofs_blknr(sb, pos), EROFS_KMAP);
 946                 if (IS_ERR(src)) {
 947                         erofs_put_metabuf(&buf);
 948                         return PTR_ERR(src);
 949                 }
 950
 951                 dst = kmap_local_page(page);
 952                 memcpy(dst + pageofs + i, src + erofs_blkoff(sb, pos), cnt);
 953                 kunmap_local(dst);
 954                 pos += cnt;
 955         }
 956         erofs_put_metabuf(&buf);
 957         return 0;
 958 }
 959
 960 static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 961                                 struct page *page, struct page **pagepool)
 962 {
 963         struct inode *const inode = fe->inode;
 964         struct erofs_map_blocks *const map = &fe->map;
 965         const loff_t offset = page_offset(page);
 966         bool tight = true, exclusive;
 967         unsigned int cur, end, spiltted;
 968         int err = 0;
 969
 970         /* register locked file pages as online pages in pack */
 971         z_erofs_onlinepage_init(page);
 972
 973         spiltted = 0;
 974         end = PAGE_SIZE;
 975 repeat:
 976         cur = end - 1;
 977
 978         if (offset + cur < map->m_la ||
 979             offset + cur >= map->m_la + map->m_llen) {
 980                 if (z_erofs_collector_end(fe))
 981                         fe->backmost = false;
 982                 map->m_la = offset + cur;
 983                 map->m_llen = 0;
 984                 err = z_erofs_map_blocks_iter(inode, map, 0);
 985                 if (err)
 986                         goto out;
 987         } else {
 988                 if (fe->pcl)
 989                         goto hitted;
 990                 /* didn't get a valid pcluster previously (very rare) */
 991         }
 992
 993         if (!(map->m_flags & EROFS_MAP_MAPPED) ||
 994             map->m_flags & EROFS_MAP_FRAGMENT)
 995                 goto hitted;
 996
 997         err = z_erofs_collector_begin(fe);
 998         if (err)
 999                 goto out;
1000
1001         if (z_erofs_is_inline_pcluster(fe->pcl)) {
1002                 void *mp;
1003
1004                 mp = erofs_read_metabuf(&fe->map.buf, inode->i_sb,
1005                                         erofs_blknr(inode->i_sb, map->m_pa),
1006                                         EROFS_NO_KMAP);
1007                 if (IS_ERR(mp)) {
1008                         err = PTR_ERR(mp);
1009                         erofs_err(inode->i_sb,
1010                                   "failed to get inline page, err %d", err);
1011                         goto out;
1012                 }
1013                 get_page(fe->map.buf.page);
1014                 WRITE_ONCE(fe->pcl->compressed_bvecs[0].page,
1015                            fe->map.buf.page);
1016                 fe->mode = Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE;
1017         } else {
1018                 /* bind cache first when cached decompression is preferred */
1019                 z_erofs_bind_cache(fe, pagepool);
1020         }
1021 hitted:
1022         /*
1023          * Ensure the current partial page belongs to this submit chain rather
1024          * than other concurrent submit chains or the noio(bypass) chain since
1025          * those chains are handled asynchronously thus the page cannot be used
1026          * for inplace I/O or bvpage (should be processed in a strict order.)
1027          */
1028         tight &= (fe->mode >= Z_EROFS_PCLUSTER_HOOKED &&
1029                   fe->mode != Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE);
1030
1031         cur = end - min_t(unsigned int, offset + end - map->m_la, end);
1032         if (!(map->m_flags & EROFS_MAP_MAPPED)) {
1033                 zero_user_segment(page, cur, end);
1034                 goto next_part;
1035         }
1036         if (map->m_flags & EROFS_MAP_FRAGMENT) {
1037                 unsigned int pageofs, skip, len;
1038
1039                 if (offset > map->m_la) {
1040                         pageofs = 0;
1041                         skip = offset - map->m_la;
1042                 } else {
1043                         pageofs = map->m_la & ~PAGE_MASK;
1044                         skip = 0;
1045                 }
1046                 len = min_t(unsigned int, map->m_llen - skip, end - cur);
1047                 err = z_erofs_read_fragment(inode, skip, page, pageofs, len);
1048                 if (err)
1049                         goto out;
1050                 ++spiltted;
1051                 tight = false;
1052                 goto next_part;
1053         }
1054
1055         exclusive = (!cur && (!spiltted || tight));
1056         if (cur)
1057                 tight &= (fe->mode >= Z_EROFS_PCLUSTER_FOLLOWED);
1058
1059 retry:
1060         err = z_erofs_attach_page(fe, &((struct z_erofs_bvec) {
1061                                         .page = page,
1062                                         .offset = offset - map->m_la,
1063                                         .end = end,
1064                                   }), exclusive);
1065         /* should allocate an additional short-lived page for bvset */
1066         if (err == -EAGAIN && !fe->candidate_bvpage) {
1067                 fe->candidate_bvpage = alloc_page(GFP_NOFS | __GFP_NOFAIL);
1068                 set_page_private(fe->candidate_bvpage,
1069                                  Z_EROFS_SHORTLIVED_PAGE);
1070                 goto retry;
1071         }
1072
1073         if (err) {
1074                 DBG_BUGON(err == -EAGAIN && fe->candidate_bvpage);
1075                 goto out;
1076         }
1077
1078         z_erofs_onlinepage_split(page);
1079         /* bump up the number of spiltted parts of a page */
1080         ++spiltted;
1081         if (fe->pcl->pageofs_out != (map->m_la & ~PAGE_MASK))
1082                 fe->pcl->multibases = true;
1083         if (fe->pcl->length < offset + end - map->m_la) {
1084                 fe->pcl->length = offset + end - map->m_la;
1085                 fe->pcl->pageofs_out = map->m_la & ~PAGE_MASK;
1086         }
1087         if ((map->m_flags & EROFS_MAP_FULL_MAPPED) &&
1088             !(map->m_flags & EROFS_MAP_PARTIAL_REF) &&
1089             fe->pcl->length == map->m_llen)
1090                 fe->pcl->partial = false;
1091 next_part:
1092         /* shorten the remaining extent to update progress */
1093         map->m_llen = offset + cur - map->m_la;
1094         map->m_flags &= ~EROFS_MAP_FULL_MAPPED;
1095
1096         end = cur;
1097         if (end > 0)
1098                 goto repeat;
1099
1100 out:
1101         if (err)
1102                 z_erofs_page_mark_eio(page);
1103         z_erofs_onlinepage_endio(page);
1104         return err;
1105 }
1106
1107 static bool z_erofs_get_sync_decompress_policy(struct erofs_sb_info *sbi,
1108                                        unsigned int readahead_pages)
1109 {
1110         /* auto: enable for read_folio, disable for readahead */
1111         if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO) &&
1112             !readahead_pages)
1113                 return true;
1114
1115         if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_FORCE_ON) &&
1116             (readahead_pages <= sbi->opt.max_sync_decompress_pages))
1117                 return true;
1118
1119         return false;
1120 }
1121
1122 static bool z_erofs_page_is_invalidated(struct page *page)
1123 {
1124         return !page->mapping && !z_erofs_is_shortlived_page(page);
1125 }
1126
1127 struct z_erofs_decompress_backend {
1128         struct page *onstack_pages[Z_EROFS_ONSTACK_PAGES];
1129         struct super_block *sb;
1130         struct z_erofs_pcluster *pcl;
1131
1132         /* pages with the longest decompressed length for deduplication */
1133         struct page **decompressed_pages;
1134         /* pages to keep the compressed data */
1135         struct page **compressed_pages;
1136
1137         struct list_head decompressed_secondary_bvecs;
1138         struct page **pagepool;
1139         unsigned int onstack_used, nr_pages;
1140 };
1141
1142 struct z_erofs_bvec_item {
1143         struct z_erofs_bvec bvec;
1144         struct list_head list;
1145 };
1146
1147 static void z_erofs_do_decompressed_bvec(struct z_erofs_decompress_backend *be,
1148                                          struct z_erofs_bvec *bvec)
1149 {
1150         struct z_erofs_bvec_item *item;
1151
1152         if (!((bvec->offset + be->pcl->pageofs_out) & ~PAGE_MASK)) {
1153                 unsigned int pgnr;
1154
1155                 pgnr = (bvec->offset + be->pcl->pageofs_out) >> PAGE_SHIFT;
1156                 DBG_BUGON(pgnr >= be->nr_pages);
1157                 if (!be->decompressed_pages[pgnr]) {
1158                         be->decompressed_pages[pgnr] = bvec->page;
1159                         return;
1160                 }
1161         }
1162
1163         /* (cold path) one pcluster is requested multiple times */
1164         item = kmalloc(sizeof(*item), GFP_KERNEL | __GFP_NOFAIL);
1165         item->bvec = *bvec;
1166         list_add(&item->list, &be->decompressed_secondary_bvecs);
1167 }
1168
1169 static void z_erofs_fill_other_copies(struct z_erofs_decompress_backend *be,
1170                                       int err)
1171 {
1172         unsigned int off0 = be->pcl->pageofs_out;
1173         struct list_head *p, *n;
1174
1175         list_for_each_safe(p, n, &be->decompressed_secondary_bvecs) {
1176                 struct z_erofs_bvec_item *bvi;
1177                 unsigned int end, cur;
1178                 void *dst, *src;
1179
1180                 bvi = container_of(p, struct z_erofs_bvec_item, list);
1181                 cur = bvi->bvec.offset < 0 ? -bvi->bvec.offset : 0;
1182                 end = min_t(unsigned int, be->pcl->length - bvi->bvec.offset,
1183                             bvi->bvec.end);
1184                 dst = kmap_local_page(bvi->bvec.page);
1185                 while (cur < end) {
1186                         unsigned int pgnr, scur, len;
1187
1188                         pgnr = (bvi->bvec.offset + cur + off0) >> PAGE_SHIFT;
1189                         DBG_BUGON(pgnr >= be->nr_pages);
1190
1191                         scur = bvi->bvec.offset + cur -
1192                                         ((pgnr << PAGE_SHIFT) - off0);
1193                         len = min_t(unsigned int, end - cur, PAGE_SIZE - scur);
1194                         if (!be->decompressed_pages[pgnr]) {
1195                                 err = -EFSCORRUPTED;
1196                                 cur += len;
1197                                 continue;
1198                         }
1199                         src = kmap_local_page(be->decompressed_pages[pgnr]);
1200                         memcpy(dst + cur, src + scur, len);
1201                         kunmap_local(src);
1202                         cur += len;
1203                 }
1204                 kunmap_local(dst);
1205                 if (err)
1206                         z_erofs_page_mark_eio(bvi->bvec.page);
1207                 z_erofs_onlinepage_endio(bvi->bvec.page);
1208                 list_del(p);
1209                 kfree(bvi);
1210         }
1211 }
1212
1213 static void z_erofs_parse_out_bvecs(struct z_erofs_decompress_backend *be)
1214 {
1215         struct z_erofs_pcluster *pcl = be->pcl;
1216         struct z_erofs_bvec_iter biter;
1217         struct page *old_bvpage;
1218         int i;
1219
1220         z_erofs_bvec_iter_begin(&biter, &pcl->bvset, Z_EROFS_INLINE_BVECS, 0);
1221         for (i = 0; i < pcl->vcnt; ++i) {
1222                 struct z_erofs_bvec bvec;
1223
1224                 z_erofs_bvec_dequeue(&biter, &bvec, &old_bvpage);
1225
1226                 if (old_bvpage)
1227                         z_erofs_put_shortlivedpage(be->pagepool, old_bvpage);
1228
1229                 DBG_BUGON(z_erofs_page_is_invalidated(bvec.page));
1230                 z_erofs_do_decompressed_bvec(be, &bvec);
1231         }
1232
1233         old_bvpage = z_erofs_bvec_iter_end(&biter);
1234         if (old_bvpage)
1235                 z_erofs_put_shortlivedpage(be->pagepool, old_bvpage);
1236 }
1237
1238 static int z_erofs_parse_in_bvecs(struct z_erofs_decompress_backend *be,
1239                                   bool *overlapped)
1240 {
1241         struct z_erofs_pcluster *pcl = be->pcl;
1242         unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
1243         int i, err = 0;
1244
1245         *overlapped = false;
1246         for (i = 0; i < pclusterpages; ++i) {
1247                 struct z_erofs_bvec *bvec = &pcl->compressed_bvecs[i];
1248                 struct page *page = bvec->page;
1249
1250                 /* compressed pages ought to be present before decompressing */
1251                 if (!page) {
1252                         DBG_BUGON(1);
1253                         continue;
1254                 }
1255                 be->compressed_pages[i] = page;
1256
1257                 if (z_erofs_is_inline_pcluster(pcl)) {
1258                         if (!PageUptodate(page))
1259                                 err = -EIO;
1260                         continue;
1261                 }
1262
1263                 DBG_BUGON(z_erofs_page_is_invalidated(page));
1264                 if (!z_erofs_is_shortlived_page(page)) {
1265                         if (erofs_page_is_managed(EROFS_SB(be->sb), page)) {
1266                                 if (!PageUptodate(page))
1267                                         err = -EIO;
1268                                 continue;
1269                         }
1270                         z_erofs_do_decompressed_bvec(be, bvec);
1271                         *overlapped = true;
1272                 }
1273         }
1274
1275         if (err)
1276                 return err;
1277         return 0;
1278 }
1279
1280 static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
1281                                        int err)
1282 {
1283         struct erofs_sb_info *const sbi = EROFS_SB(be->sb);
1284         struct z_erofs_pcluster *pcl = be->pcl;
1285         unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
1286         unsigned int i, inputsize;
1287         int err2;
1288         struct page *page;
1289         bool overlapped;
1290
1291         mutex_lock(&pcl->lock);
1292         be->nr_pages = PAGE_ALIGN(pcl->length + pcl->pageofs_out) >> PAGE_SHIFT;
1293
1294         /* allocate (de)compressed page arrays if cannot be kept on stack */
1295         be->decompressed_pages = NULL;
1296         be->compressed_pages = NULL;
1297         be->onstack_used = 0;
1298         if (be->nr_pages <= Z_EROFS_ONSTACK_PAGES) {
1299                 be->decompressed_pages = be->onstack_pages;
1300                 be->onstack_used = be->nr_pages;
1301                 memset(be->decompressed_pages, 0,
1302                        sizeof(struct page *) * be->nr_pages);
1303         }
1304
1305         if (pclusterpages + be->onstack_used <= Z_EROFS_ONSTACK_PAGES)
1306                 be->compressed_pages = be->onstack_pages + be->onstack_used;
1307
1308         if (!be->decompressed_pages)
1309                 be->decompressed_pages =
1310                         kvcalloc(be->nr_pages, sizeof(struct page *),
1311                                  GFP_KERNEL | __GFP_NOFAIL);
1312         if (!be->compressed_pages)
1313                 be->compressed_pages =
1314                         kvcalloc(pclusterpages, sizeof(struct page *),
1315                                  GFP_KERNEL | __GFP_NOFAIL);
1316
1317         z_erofs_parse_out_bvecs(be);
1318         err2 = z_erofs_parse_in_bvecs(be, &overlapped);
1319         if (err2)
1320                 err = err2;
1321         if (err)
1322                 goto out;
1323
1324         if (z_erofs_is_inline_pcluster(pcl))
1325                 inputsize = pcl->tailpacking_size;
1326         else
1327                 inputsize = pclusterpages * PAGE_SIZE;
1328
1329         err = z_erofs_decompress(&(struct z_erofs_decompress_req) {
1330                                         .sb = be->sb,
1331                                         .in = be->compressed_pages,
1332                                         .out = be->decompressed_pages,
1333                                         .pageofs_in = pcl->pageofs_in,
1334                                         .pageofs_out = pcl->pageofs_out,
1335                                         .inputsize = inputsize,
1336                                         .outputsize = pcl->length,
1337                                         .alg = pcl->algorithmformat,
1338                                         .inplace_io = overlapped,
1339                                         .partial_decoding = pcl->partial,
1340                                         .fillgaps = pcl->multibases,
1341                                  }, be->pagepool);
1342
1343 out:
1344         /* must handle all compressed pages before actual file pages */
1345         if (z_erofs_is_inline_pcluster(pcl)) {
1346                 page = pcl->compressed_bvecs[0].page;
1347                 WRITE_ONCE(pcl->compressed_bvecs[0].page, NULL);
1348                 put_page(page);
1349         } else {
1350                 for (i = 0; i < pclusterpages; ++i) {
1351                         page = pcl->compressed_bvecs[i].page;
1352
1353                         if (erofs_page_is_managed(sbi, page))
1354                                 continue;
1355
1356                         /* recycle all individual short-lived pages */
1357                         (void)z_erofs_put_shortlivedpage(be->pagepool, page);
1358                         WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
1359                 }
1360         }
1361         if (be->compressed_pages < be->onstack_pages ||
1362             be->compressed_pages >= be->onstack_pages + Z_EROFS_ONSTACK_PAGES)
1363                 kvfree(be->compressed_pages);
1364         z_erofs_fill_other_copies(be, err);
1365
1366         for (i = 0; i < be->nr_pages; ++i) {
1367                 page = be->decompressed_pages[i];
1368                 if (!page)
1369                         continue;
1370
1371                 DBG_BUGON(z_erofs_page_is_invalidated(page));
1372
1373                 /* recycle all individual short-lived pages */
1374                 if (z_erofs_put_shortlivedpage(be->pagepool, page))
1375                         continue;
1376                 if (err)
1377                         z_erofs_page_mark_eio(page);
1378                 z_erofs_onlinepage_endio(page);
1379         }
1380
1381         if (be->decompressed_pages != be->onstack_pages)
1382                 kvfree(be->decompressed_pages);
1383
1384         pcl->length = 0;
1385         pcl->partial = true;
1386         pcl->multibases = false;
1387         pcl->bvset.nextpage = NULL;
1388         pcl->vcnt = 0;
1389
1390         /* pcluster lock MUST be taken before the following line */
1391         WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_NIL);
1392         mutex_unlock(&pcl->lock);
1393         return err;
1394 }
1395
1396 static void z_erofs_decompress_queue(const struct z_erofs_decompressqueue *io,
1397                                      struct page **pagepool)
1398 {
1399         struct z_erofs_decompress_backend be = {
1400                 .sb = io->sb,
1401                 .pagepool = pagepool,
1402                 .decompressed_secondary_bvecs =
1403                         LIST_HEAD_INIT(be.decompressed_secondary_bvecs),
1404         };
1405         z_erofs_next_pcluster_t owned = io->head;
1406
1407         while (owned != Z_EROFS_PCLUSTER_TAIL_CLOSED) {
1408                 /* impossible that 'owned' equals Z_EROFS_WORK_TPTR_TAIL */
1409                 DBG_BUGON(owned == Z_EROFS_PCLUSTER_TAIL);
1410                 /* impossible that 'owned' equals Z_EROFS_PCLUSTER_NIL */
1411                 DBG_BUGON(owned == Z_EROFS_PCLUSTER_NIL);
1412
1413                 be.pcl = container_of(owned, struct z_erofs_pcluster, next);
1414                 owned = READ_ONCE(be.pcl->next);
1415
1416                 z_erofs_decompress_pcluster(&be, io->eio ? -EIO : 0);
1417                 erofs_workgroup_put(&be.pcl->obj);
1418         }
1419 }
1420
1421 static void z_erofs_decompressqueue_work(struct work_struct *work)
1422 {
1423         struct z_erofs_decompressqueue *bgq =
1424                 container_of(work, struct z_erofs_decompressqueue, u.work);
1425         struct page *pagepool = NULL;
1426
1427         DBG_BUGON(bgq->head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
1428         z_erofs_decompress_queue(bgq, &pagepool);
1429         erofs_release_pages(&pagepool);
1430         kvfree(bgq);
1431 }
1432
1433 #ifdef CONFIG_EROFS_FS_PCPU_KTHREAD
1434 static void z_erofs_decompressqueue_kthread_work(struct kthread_work *work)
1435 {
1436         z_erofs_decompressqueue_work((struct work_struct *)work);
1437 }
1438 #endif
1439
1440 static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
1441                                        int bios)
1442 {
1443         struct erofs_sb_info *const sbi = EROFS_SB(io->sb);
1444
1445         /* wake up the caller thread for sync decompression */
1446         if (io->sync) {
1447                 if (!atomic_add_return(bios, &io->pending_bios))
1448                         complete(&io->u.done);
1449                 return;
1450         }
1451
1452         if (atomic_add_return(bios, &io->pending_bios))
1453                 return;
1454         /* Use (kthread_)work and sync decompression for atomic contexts only */
1455         if (in_atomic() || irqs_disabled()) {
1456 #ifdef CONFIG_EROFS_FS_PCPU_KTHREAD
1457                 struct kthread_worker *worker;
1458
1459                 rcu_read_lock();
1460                 worker = rcu_dereference(
1461                                 z_erofs_pcpu_workers[raw_smp_processor_id()]);
1462                 if (!worker) {
1463                         INIT_WORK(&io->u.work, z_erofs_decompressqueue_work);
1464                         queue_work(z_erofs_workqueue, &io->u.work);
1465                 } else {
1466                         kthread_queue_work(worker, &io->u.kthread_work);
1467                 }
1468                 rcu_read_unlock();
1469 #else
1470                 queue_work(z_erofs_workqueue, &io->u.work);
1471 #endif
1472                 /* enable sync decompression for readahead */
1473                 if (sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO)
1474                         sbi->opt.sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON;
1475                 return;
1476         }
1477         z_erofs_decompressqueue_work(&io->u.work);
1478 }
1479
1480 static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
1481                                                unsigned int nr,
1482                                                struct page **pagepool,
1483                                                struct address_space *mc)
1484 {
1485         const pgoff_t index = pcl->obj.index;
1486         gfp_t gfp = mapping_gfp_mask(mc);
1487         bool tocache = false;
1488
1489         struct address_space *mapping;
1490         struct page *oldpage, *page;
1491         int justfound;
1492
1493 repeat:
1494         page = READ_ONCE(pcl->compressed_bvecs[nr].page);
1495         oldpage = page;
1496
1497         if (!page)
1498                 goto out_allocpage;
1499
1500         justfound = (unsigned long)page & 1UL;
1501         page = (struct page *)((unsigned long)page & ~1UL);
1502
1503         /*
1504          * preallocated cached pages, which is used to avoid direct reclaim
1505          * otherwise, it will go inplace I/O path instead.
1506          */
1507         if (page->private == Z_EROFS_PREALLOCATED_PAGE) {
1508                 WRITE_ONCE(pcl->compressed_bvecs[nr].page, page);
1509                 set_page_private(page, 0);
1510                 tocache = true;
1511                 goto out_tocache;
1512         }
1513         mapping = READ_ONCE(page->mapping);
1514
1515         /*
1516          * file-backed online pages in plcuster are all locked steady,
1517          * therefore it is impossible for `mapping' to be NULL.
1518          */
1519         if (mapping && mapping != mc)
1520                 /* ought to be unmanaged pages */
1521                 goto out;
1522
1523         /* directly return for shortlived page as well */
1524         if (z_erofs_is_shortlived_page(page))
1525                 goto out;
1526
1527         lock_page(page);
1528
1529         /* only true if page reclaim goes wrong, should never happen */
1530         DBG_BUGON(justfound && PagePrivate(page));
1531
1532         /* the page is still in manage cache */
1533         if (page->mapping == mc) {
1534                 WRITE_ONCE(pcl->compressed_bvecs[nr].page, page);
1535
1536                 if (!PagePrivate(page)) {
1537                         /*
1538                          * impossible to be !PagePrivate(page) for
1539                          * the current restriction as well if
1540                          * the page is already in compressed_bvecs[].
1541                          */
1542                         DBG_BUGON(!justfound);
1543
1544                         justfound = 0;
1545                         set_page_private(page, (unsigned long)pcl);
1546                         SetPagePrivate(page);
1547                 }
1548
1549                 /* no need to submit io if it is already up-to-date */
1550                 if (PageUptodate(page)) {
1551                         unlock_page(page);
1552                         page = NULL;
1553                 }
1554                 goto out;
1555         }
1556
1557         /*
1558          * the managed page has been truncated, it's unsafe to
1559          * reuse this one, let's allocate a new cache-managed page.
1560          */
1561         DBG_BUGON(page->mapping);
1562         DBG_BUGON(!justfound);
1563
1564         tocache = true;
1565         unlock_page(page);
1566         put_page(page);
1567 out_allocpage:
1568         page = erofs_allocpage(pagepool, gfp | __GFP_NOFAIL);
1569         if (oldpage != cmpxchg(&pcl->compressed_bvecs[nr].page,
1570                                oldpage, page)) {
1571                 erofs_pagepool_add(pagepool, page);
1572                 cond_resched();
1573                 goto repeat;
1574         }
1575 out_tocache:
1576         if (!tocache || add_to_page_cache_lru(page, mc, index + nr, gfp)) {
1577                 /* turn into temporary page if fails (1 ref) */
1578                 set_page_private(page, Z_EROFS_SHORTLIVED_PAGE);
1579                 goto out;
1580         }
1581         attach_page_private(page, pcl);
1582         /* drop a refcount added by allocpage (then we have 2 refs here) */
1583         put_page(page);
1584
1585 out:    /* the only exit (for tracing and debugging) */
1586         return page;
1587 }
1588
1589 static struct z_erofs_decompressqueue *jobqueue_init(struct super_block *sb,
1590                               struct z_erofs_decompressqueue *fgq, bool *fg)
1591 {
1592         struct z_erofs_decompressqueue *q;
1593
1594         if (fg && !*fg) {
1595                 q = kvzalloc(sizeof(*q), GFP_KERNEL | __GFP_NOWARN);
1596                 if (!q) {
1597                         *fg = true;
1598                         goto fg_out;
1599                 }
1600 #ifdef CONFIG_EROFS_FS_PCPU_KTHREAD
1601                 kthread_init_work(&q->u.kthread_work,
1602                                   z_erofs_decompressqueue_kthread_work);
1603 #else
1604                 INIT_WORK(&q->u.work, z_erofs_decompressqueue_work);
1605 #endif
1606         } else {
1607 fg_out:
1608                 q = fgq;
1609                 init_completion(&fgq->u.done);
1610                 atomic_set(&fgq->pending_bios, 0);
1611                 q->eio = false;
1612                 q->sync = true;
1613         }
1614         q->sb = sb;
1615         q->head = Z_EROFS_PCLUSTER_TAIL_CLOSED;
1616         return q;
1617 }
1618
1619 /* define decompression jobqueue types */
1620 enum {
1621         JQ_BYPASS,
1622         JQ_SUBMIT,
1623         NR_JOBQUEUES,
1624 };
1625
1626 static void move_to_bypass_jobqueue(struct z_erofs_pcluster *pcl,
1627                                     z_erofs_next_pcluster_t qtail[],
1628                                     z_erofs_next_pcluster_t owned_head)
1629 {
1630         z_erofs_next_pcluster_t *const submit_qtail = qtail[JQ_SUBMIT];
1631         z_erofs_next_pcluster_t *const bypass_qtail = qtail[JQ_BYPASS];
1632
1633         DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
1634         if (owned_head == Z_EROFS_PCLUSTER_TAIL)
1635                 owned_head = Z_EROFS_PCLUSTER_TAIL_CLOSED;
1636
1637         WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_TAIL_CLOSED);
1638
1639         WRITE_ONCE(*submit_qtail, owned_head);
1640         WRITE_ONCE(*bypass_qtail, &pcl->next);
1641
1642         qtail[JQ_BYPASS] = &pcl->next;
1643 }
1644
1645 static void z_erofs_decompressqueue_endio(struct bio *bio)
1646 {
1647         struct z_erofs_decompressqueue *q = bio->bi_private;
1648         blk_status_t err = bio->bi_status;
1649         struct bio_vec *bvec;
1650         struct bvec_iter_all iter_all;
1651
1652         bio_for_each_segment_all(bvec, bio, iter_all) {
1653                 struct page *page = bvec->bv_page;
1654
1655                 DBG_BUGON(PageUptodate(page));
1656                 DBG_BUGON(z_erofs_page_is_invalidated(page));
1657
1658                 if (erofs_page_is_managed(EROFS_SB(q->sb), page)) {
1659                         if (!err)
1660                                 SetPageUptodate(page);
1661                         unlock_page(page);
1662                 }
1663         }
1664         if (err)
1665                 q->eio = true;
1666         z_erofs_decompress_kickoff(q, -1);
1667         bio_put(bio);
1668 }
1669
1670 static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f,
1671                                  struct page **pagepool,
1672                                  struct z_erofs_decompressqueue *fgq,
1673                                  bool *force_fg)
1674 {
1675         struct super_block *sb = f->inode->i_sb;
1676         struct address_space *mc = MNGD_MAPPING(EROFS_SB(sb));
1677         z_erofs_next_pcluster_t qtail[NR_JOBQUEUES];
1678         struct z_erofs_decompressqueue *q[NR_JOBQUEUES];
1679         z_erofs_next_pcluster_t owned_head = f->owned_head;
1680         /* bio is NULL initially, so no need to initialize last_{index,bdev} */
1681         pgoff_t last_index;
1682         struct block_device *last_bdev;
1683         unsigned int nr_bios = 0;
1684         struct bio *bio = NULL;
1685         unsigned long pflags;
1686         int memstall = 0;
1687
1688         /*
1689          * if managed cache is enabled, bypass jobqueue is needed,
1690          * no need to read from device for all pclusters in this queue.
1691          */
1692         q[JQ_BYPASS] = jobqueue_init(sb, fgq + JQ_BYPASS, NULL);
1693         q[JQ_SUBMIT] = jobqueue_init(sb, fgq + JQ_SUBMIT, force_fg);
1694
1695         qtail[JQ_BYPASS] = &q[JQ_BYPASS]->head;
1696         qtail[JQ_SUBMIT] = &q[JQ_SUBMIT]->head;
1697
1698         /* by default, all need io submission */
1699         q[JQ_SUBMIT]->head = owned_head;
1700
1701         do {
1702                 struct erofs_map_dev mdev;
1703                 struct z_erofs_pcluster *pcl;
1704                 pgoff_t cur, end;
1705                 unsigned int i = 0;
1706                 bool bypass = true;
1707
1708                 /* no possible 'owned_head' equals the following */
1709                 DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
1710                 DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_NIL);
1711
1712                 pcl = container_of(owned_head, struct z_erofs_pcluster, next);
1713
1714                 /* close the main owned chain at first */
1715                 owned_head = cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_TAIL,
1716                                      Z_EROFS_PCLUSTER_TAIL_CLOSED);
1717                 if (z_erofs_is_inline_pcluster(pcl)) {
1718                         move_to_bypass_jobqueue(pcl, qtail, owned_head);
1719                         continue;
1720                 }
1721
1722                 /* no device id here, thus it will always succeed */
1723                 mdev = (struct erofs_map_dev) {
1724                         .m_pa = erofs_pos(sb, pcl->obj.index),
1725                 };
1726                 (void)erofs_map_dev(sb, &mdev);
1727
1728                 cur = erofs_blknr(sb, mdev.m_pa);
1729                 end = cur + pcl->pclusterpages;
1730
1731                 do {
1732                         struct page *page;
1733
1734                         page = pickup_page_for_submission(pcl, i++, pagepool,
1735                                                           mc);
1736                         if (!page)
1737                                 continue;
1738
1739                         if (bio && (cur != last_index + 1 ||
1740                                     last_bdev != mdev.m_bdev)) {
1741 submit_bio_retry:
1742                                 submit_bio(bio);
1743                                 if (memstall) {
1744                                         psi_memstall_leave(&pflags);
1745                                         memstall = 0;
1746                                 }
1747                                 bio = NULL;
1748                         }
1749
1750                         if (unlikely(PageWorkingset(page)) && !memstall) {
1751                                 psi_memstall_enter(&pflags);
1752                                 memstall = 1;
1753                         }
1754
1755                         if (!bio) {
1756                                 bio = bio_alloc(mdev.m_bdev, BIO_MAX_VECS,
1757                                                 REQ_OP_READ, GFP_NOIO);
1758                                 bio->bi_end_io = z_erofs_decompressqueue_endio;
1759
1760                                 last_bdev = mdev.m_bdev;
1761                                 bio->bi_iter.bi_sector = (sector_t)cur <<
1762                                         (sb->s_blocksize_bits - 9);
1763                                 bio->bi_private = q[JQ_SUBMIT];
1764                                 if (f->readahead)
1765                                         bio->bi_opf |= REQ_RAHEAD;
1766                                 ++nr_bios;
1767                         }
1768
1769                         if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE)
1770                                 goto submit_bio_retry;
1771
1772                         last_index = cur;
1773                         bypass = false;
1774                 } while (++cur < end);
1775
1776                 if (!bypass)
1777                         qtail[JQ_SUBMIT] = &pcl->next;
1778                 else
1779                         move_to_bypass_jobqueue(pcl, qtail, owned_head);
1780         } while (owned_head != Z_EROFS_PCLUSTER_TAIL);
1781
1782         if (bio) {
1783                 submit_bio(bio);
1784                 if (memstall)
1785                         psi_memstall_leave(&pflags);
1786         }
1787
1788         /*
1789          * although background is preferred, no one is pending for submission.
1790          * don't issue decompression but drop it directly instead.
1791          */
1792         if (!*force_fg && !nr_bios) {
1793                 kvfree(q[JQ_SUBMIT]);
1794                 return;
1795         }
1796         z_erofs_decompress_kickoff(q[JQ_SUBMIT], nr_bios);
1797 }
1798
1799 static void z_erofs_runqueue(struct z_erofs_decompress_frontend *f,
1800                              struct page **pagepool, bool force_fg)
1801 {
1802         struct z_erofs_decompressqueue io[NR_JOBQUEUES];
1803
1804         if (f->owned_head == Z_EROFS_PCLUSTER_TAIL)
1805                 return;
1806         z_erofs_submit_queue(f, pagepool, io, &force_fg);
1807
1808         /* handle bypass queue (no i/o pclusters) immediately */
1809         z_erofs_decompress_queue(&io[JQ_BYPASS], pagepool);
1810
1811         if (!force_fg)
1812                 return;
1813
1814         /* wait until all bios are completed */
1815         wait_for_completion_io(&io[JQ_SUBMIT].u.done);
1816
1817         /* handle synchronous decompress queue in the caller context */
1818         z_erofs_decompress_queue(&io[JQ_SUBMIT], pagepool);
1819 }
1820
1821 /*
1822  * Since partial uptodate is still unimplemented for now, we have to use
1823  * approximate readmore strategies as a start.
1824  */
1825 static void z_erofs_pcluster_readmore(struct z_erofs_decompress_frontend *f,
1826                                       struct readahead_control *rac,
1827                                       erofs_off_t end,
1828                                       struct page **pagepool,
1829                                       bool backmost)
1830 {
1831         struct inode *inode = f->inode;
1832         struct erofs_map_blocks *map = &f->map;
1833         erofs_off_t cur;
1834         int err;
1835
1836         if (backmost) {
1837                 map->m_la = end;
1838                 err = z_erofs_map_blocks_iter(inode, map,
1839                                               EROFS_GET_BLOCKS_READMORE);
1840                 if (err)
1841                         return;
1842
1843                 /* expend ra for the trailing edge if readahead */
1844                 if (rac) {
1845                         loff_t newstart = readahead_pos(rac);
1846
1847                         cur = round_up(map->m_la + map->m_llen, PAGE_SIZE);
1848                         readahead_expand(rac, newstart, cur - newstart);
1849                         return;
1850                 }
1851                 end = round_up(end, PAGE_SIZE);
1852         } else {
1853                 end = round_up(map->m_la, PAGE_SIZE);
1854
1855                 if (!map->m_llen)
1856                         return;
1857         }
1858
1859         cur = map->m_la + map->m_llen - 1;
1860         while (cur >= end) {
1861                 pgoff_t index = cur >> PAGE_SHIFT;
1862                 struct page *page;
1863
1864                 page = erofs_grab_cache_page_nowait(inode->i_mapping, index);
1865                 if (page) {
1866                         if (PageUptodate(page)) {
1867                                 unlock_page(page);
1868                         } else {
1869                                 err = z_erofs_do_read_page(f, page, pagepool);
1870                                 if (err)
1871                                         erofs_err(inode->i_sb,
1872                                                   "readmore error at page %lu @ nid %llu",
1873                                                   index, EROFS_I(inode)->nid);
1874                         }
1875                         put_page(page);
1876                 }
1877
1878                 if (cur < PAGE_SIZE)
1879                         break;
1880                 cur = (index << PAGE_SHIFT) - 1;
1881         }
1882 }
1883
1884 static int z_erofs_read_folio(struct file *file, struct folio *folio)
1885 {
1886         struct page *page = &folio->page;
1887         struct inode *const inode = page->mapping->host;
1888         struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
1889         struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
1890         struct page *pagepool = NULL;
1891         int err;
1892
1893         trace_erofs_readpage(page, false);
1894         f.headoffset = (erofs_off_t)page->index << PAGE_SHIFT;
1895
1896         z_erofs_pcluster_readmore(&f, NULL, f.headoffset + PAGE_SIZE - 1,
1897                                   &pagepool, true);
1898         err = z_erofs_do_read_page(&f, page, &pagepool);
1899         z_erofs_pcluster_readmore(&f, NULL, 0, &pagepool, false);
1900
1901         (void)z_erofs_collector_end(&f);
1902
1903         /* if some compressed cluster ready, need submit them anyway */
1904         z_erofs_runqueue(&f, &pagepool,
1905                          z_erofs_get_sync_decompress_policy(sbi, 0));
1906
1907         if (err)
1908                 erofs_err(inode->i_sb, "failed to read, err [%d]", err);
1909
1910         erofs_put_metabuf(&f.map.buf);
1911         erofs_release_pages(&pagepool);
1912         return err;
1913 }
1914
1915 static void z_erofs_readahead(struct readahead_control *rac)
1916 {
1917         struct inode *const inode = rac->mapping->host;
1918         struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
1919         struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
1920         struct page *pagepool = NULL, *head = NULL, *page;
1921         unsigned int nr_pages;
1922
1923         f.readahead = true;
1924         f.headoffset = readahead_pos(rac);
1925
1926         z_erofs_pcluster_readmore(&f, rac, f.headoffset +
1927                                   readahead_length(rac) - 1, &pagepool, true);
1928         nr_pages = readahead_count(rac);
1929         trace_erofs_readpages(inode, readahead_index(rac), nr_pages, false);
1930
1931         while ((page = readahead_page(rac))) {
1932                 set_page_private(page, (unsigned long)head);
1933                 head = page;
1934         }
1935
1936         while (head) {
1937                 struct page *page = head;
1938                 int err;
1939
1940                 /* traversal in reverse order */
1941                 head = (void *)page_private(page);
1942
1943                 err = z_erofs_do_read_page(&f, page, &pagepool);
1944                 if (err)
1945                         erofs_err(inode->i_sb,
1946                                   "readahead error at page %lu @ nid %llu",
1947                                   page->index, EROFS_I(inode)->nid);
1948                 put_page(page);
1949         }
1950         z_erofs_pcluster_readmore(&f, rac, 0, &pagepool, false);
1951         (void)z_erofs_collector_end(&f);
1952
1953         z_erofs_runqueue(&f, &pagepool,
1954                          z_erofs_get_sync_decompress_policy(sbi, nr_pages));
1955         erofs_put_metabuf(&f.map.buf);
1956         erofs_release_pages(&pagepool);
1957 }
1958
1959 const struct address_space_operations z_erofs_aops = {
1960         .read_folio = z_erofs_read_folio,
1961         .readahead = z_erofs_readahead,
1962 };