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 "zdata.h"
   8 #include "compress.h"
   9 #include <linux/prefetch.h>
  10 #include <linux/psi.h>
  11
  12 #include <trace/events/erofs.h>
  13
  14 /*
  15  * since pclustersize is variable for big pcluster feature, introduce slab
  16  * pools implementation for different pcluster sizes.
  17  */
  18 struct z_erofs_pcluster_slab {
  19         struct kmem_cache *slab;
  20         unsigned int maxpages;
  21         char name[48];
  22 };
  23
  24 #define _PCLP(n) { .maxpages = n }
  25
  26 static struct z_erofs_pcluster_slab pcluster_pool[] __read_mostly = {
  27         _PCLP(1), _PCLP(4), _PCLP(16), _PCLP(64), _PCLP(128),
  28         _PCLP(Z_EROFS_PCLUSTER_MAX_PAGES)
  29 };
  30
  31 struct z_erofs_bvec_iter {
  32         struct page *bvpage;
  33         struct z_erofs_bvset *bvset;
  34         unsigned int nr, cur;
  35 };
  36
  37 static struct page *z_erofs_bvec_iter_end(struct z_erofs_bvec_iter *iter)
  38 {
  39         if (iter->bvpage)
  40                 kunmap_local(iter->bvset);
  41         return iter->bvpage;
  42 }
  43
  44 static struct page *z_erofs_bvset_flip(struct z_erofs_bvec_iter *iter)
  45 {
  46         unsigned long base = (unsigned long)((struct z_erofs_bvset *)0)->bvec;
  47         /* have to access nextpage in advance, otherwise it will be unmapped */
  48         struct page *nextpage = iter->bvset->nextpage;
  49         struct page *oldpage;
  50
  51         DBG_BUGON(!nextpage);
  52         oldpage = z_erofs_bvec_iter_end(iter);
  53         iter->bvpage = nextpage;
  54         iter->bvset = kmap_local_page(nextpage);
  55         iter->nr = (PAGE_SIZE - base) / sizeof(struct z_erofs_bvec);
  56         iter->cur = 0;
  57         return oldpage;
  58 }
  59
  60 static void z_erofs_bvec_iter_begin(struct z_erofs_bvec_iter *iter,
  61                                     struct z_erofs_bvset_inline *bvset,
  62                                     unsigned int bootstrap_nr,
  63                                     unsigned int cur)
  64 {
  65         *iter = (struct z_erofs_bvec_iter) {
  66                 .nr = bootstrap_nr,
  67                 .bvset = (struct z_erofs_bvset *)bvset,
  68         };
  69
  70         while (cur > iter->nr) {
  71                 cur -= iter->nr;
  72                 z_erofs_bvset_flip(iter);
  73         }
  74         iter->cur = cur;
  75 }
  76
  77 static int z_erofs_bvec_enqueue(struct z_erofs_bvec_iter *iter,
  78                                 struct z_erofs_bvec *bvec,
  79                                 struct page **candidate_bvpage)
  80 {
  81         if (iter->cur == iter->nr) {
  82                 if (!*candidate_bvpage)
  83                         return -EAGAIN;
  84
  85                 DBG_BUGON(iter->bvset->nextpage);
  86                 iter->bvset->nextpage = *candidate_bvpage;
  87                 z_erofs_bvset_flip(iter);
  88
  89                 iter->bvset->nextpage = NULL;
  90                 *candidate_bvpage = NULL;
  91         }
  92         iter->bvset->bvec[iter->cur++] = *bvec;
  93         return 0;
  94 }
  95
  96 static void z_erofs_bvec_dequeue(struct z_erofs_bvec_iter *iter,
  97                                  struct z_erofs_bvec *bvec,
  98                                  struct page **old_bvpage)
  99 {
 100         if (iter->cur == iter->nr)
 101                 *old_bvpage = z_erofs_bvset_flip(iter);
 102         else
 103                 *old_bvpage = NULL;
 104         *bvec = iter->bvset->bvec[iter->cur++];
 105 }
 106
 107 static void z_erofs_destroy_pcluster_pool(void)
 108 {
 109         int i;
 110
 111         for (i = 0; i < ARRAY_SIZE(pcluster_pool); ++i) {
 112                 if (!pcluster_pool[i].slab)
 113                         continue;
 114                 kmem_cache_destroy(pcluster_pool[i].slab);
 115                 pcluster_pool[i].slab = NULL;
 116         }
 117 }
 118
 119 static int z_erofs_create_pcluster_pool(void)
 120 {
 121         struct z_erofs_pcluster_slab *pcs;
 122         struct z_erofs_pcluster *a;
 123         unsigned int size;
 124
 125         for (pcs = pcluster_pool;
 126              pcs < pcluster_pool + ARRAY_SIZE(pcluster_pool); ++pcs) {
 127                 size = struct_size(a, compressed_bvecs, pcs->maxpages);
 128
 129                 sprintf(pcs->name, "erofs_pcluster-%u", pcs->maxpages);
 130                 pcs->slab = kmem_cache_create(pcs->name, size, 0,
 131                                               SLAB_RECLAIM_ACCOUNT, NULL);
 132                 if (pcs->slab)
 133                         continue;
 134
 135                 z_erofs_destroy_pcluster_pool();
 136                 return -ENOMEM;
 137         }
 138         return 0;
 139 }
 140
 141 static struct z_erofs_pcluster *z_erofs_alloc_pcluster(unsigned int nrpages)
 142 {
 143         int i;
 144
 145         for (i = 0; i < ARRAY_SIZE(pcluster_pool); ++i) {
 146                 struct z_erofs_pcluster_slab *pcs = pcluster_pool + i;
 147                 struct z_erofs_pcluster *pcl;
 148
 149                 if (nrpages > pcs->maxpages)
 150                         continue;
 151
 152                 pcl = kmem_cache_zalloc(pcs->slab, GFP_NOFS);
 153                 if (!pcl)
 154                         return ERR_PTR(-ENOMEM);
 155                 pcl->pclusterpages = nrpages;
 156                 return pcl;
 157         }
 158         return ERR_PTR(-EINVAL);
 159 }
 160
 161 static void z_erofs_free_pcluster(struct z_erofs_pcluster *pcl)
 162 {
 163         unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
 164         int i;
 165
 166         for (i = 0; i < ARRAY_SIZE(pcluster_pool); ++i) {
 167                 struct z_erofs_pcluster_slab *pcs = pcluster_pool + i;
 168
 169                 if (pclusterpages > pcs->maxpages)
 170                         continue;
 171
 172                 kmem_cache_free(pcs->slab, pcl);
 173                 return;
 174         }
 175         DBG_BUGON(1);
 176 }
 177
 178 /* how to allocate cached pages for a pcluster */
 179 enum z_erofs_cache_alloctype {
 180         DONTALLOC,      /* don't allocate any cached pages */
 181         /*
 182          * try to use cached I/O if page allocation succeeds or fallback
 183          * to in-place I/O instead to avoid any direct reclaim.
 184          */
 185         TRYALLOC,
 186 };
 187
 188 /*
 189  * tagged pointer with 1-bit tag for all compressed pages
 190  * tag 0 - the page is just found with an extra page reference
 191  */
 192 typedef tagptr1_t compressed_page_t;
 193
 194 #define tag_compressed_page_justfound(page) \
 195         tagptr_fold(compressed_page_t, page, 1)
 196
 197 static struct workqueue_struct *z_erofs_workqueue __read_mostly;
 198
 199 void z_erofs_exit_zip_subsystem(void)
 200 {
 201         destroy_workqueue(z_erofs_workqueue);
 202         z_erofs_destroy_pcluster_pool();
 203 }
 204
 205 static inline int z_erofs_init_workqueue(void)
 206 {
 207         const unsigned int onlinecpus = num_possible_cpus();
 208
 209         /*
 210          * no need to spawn too many threads, limiting threads could minimum
 211          * scheduling overhead, perhaps per-CPU threads should be better?
 212          */
 213         z_erofs_workqueue = alloc_workqueue("erofs_unzipd",
 214                                             WQ_UNBOUND | WQ_HIGHPRI,
 215                                             onlinecpus + onlinecpus / 4);
 216         return z_erofs_workqueue ? 0 : -ENOMEM;
 217 }
 218
 219 int __init z_erofs_init_zip_subsystem(void)
 220 {
 221         int err = z_erofs_create_pcluster_pool();
 222
 223         if (err)
 224                 return err;
 225         err = z_erofs_init_workqueue();
 226         if (err)
 227                 z_erofs_destroy_pcluster_pool();
 228         return err;
 229 }
 230
 231 enum z_erofs_pclustermode {
 232         Z_EROFS_PCLUSTER_INFLIGHT,
 233         /*
 234          * The current pclusters was the tail of an exist chain, in addition
 235          * that the previous processed chained pclusters are all decided to
 236          * be hooked up to it.
 237          * A new chain will be created for the remaining pclusters which are
 238          * not processed yet, so different from Z_EROFS_PCLUSTER_FOLLOWED,
 239          * the next pcluster cannot reuse the whole page safely for inplace I/O
 240          * in the following scenario:
 241          *  ________________________________________________________________
 242          * |      tail (partial) page     |       head (partial) page       |
 243          * |   (belongs to the next pcl)  |   (belongs to the current pcl)  |
 244          * |_______PCLUSTER_FOLLOWED______|________PCLUSTER_HOOKED__________|
 245          */
 246         Z_EROFS_PCLUSTER_HOOKED,
 247         /*
 248          * a weak form of Z_EROFS_PCLUSTER_FOLLOWED, the difference is that it
 249          * could be dispatched into bypass queue later due to uptodated managed
 250          * pages. All related online pages cannot be reused for inplace I/O (or
 251          * bvpage) since it can be directly decoded without I/O submission.
 252          */
 253         Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE,
 254         /*
 255          * The current collection has been linked with the owned chain, and
 256          * could also be linked with the remaining collections, which means
 257          * if the processing page is the tail page of the collection, thus
 258          * the current collection can safely use the whole page (since
 259          * the previous collection is under control) for in-place I/O, as
 260          * illustrated below:
 261          *  ________________________________________________________________
 262          * |  tail (partial) page |          head (partial) page           |
 263          * |  (of the current cl) |      (of the previous collection)      |
 264          * | PCLUSTER_FOLLOWED or |                                        |
 265          * |_____PCLUSTER_HOOKED__|___________PCLUSTER_FOLLOWED____________|
 266          *
 267          * [  (*) the above page can be used as inplace I/O.               ]
 268          */
 269         Z_EROFS_PCLUSTER_FOLLOWED,
 270 };
 271
 272 struct z_erofs_decompress_frontend {
 273         struct inode *const inode;
 274         struct erofs_map_blocks map;
 275         struct z_erofs_bvec_iter biter;
 276
 277         struct page *candidate_bvpage;
 278         struct z_erofs_pcluster *pcl, *tailpcl;
 279         z_erofs_next_pcluster_t owned_head;
 280         enum z_erofs_pclustermode mode;
 281
 282         bool readahead;
 283         /* used for applying cache strategy on the fly */
 284         bool backmost;
 285         erofs_off_t headoffset;
 286
 287         /* a pointer used to pick up inplace I/O pages */
 288         unsigned int icur;
 289 };
 290
 291 #define DECOMPRESS_FRONTEND_INIT(__i) { \
 292         .inode = __i, .owned_head = Z_EROFS_PCLUSTER_TAIL, \
 293         .mode = Z_EROFS_PCLUSTER_FOLLOWED, .backmost = true }
 294
 295 static void z_erofs_bind_cache(struct z_erofs_decompress_frontend *fe,
 296                                enum z_erofs_cache_alloctype type,
 297                                struct page **pagepool)
 298 {
 299         struct address_space *mc = MNGD_MAPPING(EROFS_I_SB(fe->inode));
 300         struct z_erofs_pcluster *pcl = fe->pcl;
 301         bool standalone = true;
 302         /*
 303          * optimistic allocation without direct reclaim since inplace I/O
 304          * can be used if low memory otherwise.
 305          */
 306         gfp_t gfp = (mapping_gfp_mask(mc) & ~__GFP_DIRECT_RECLAIM) |
 307                         __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
 308         unsigned int i;
 309
 310         if (fe->mode < Z_EROFS_PCLUSTER_FOLLOWED)
 311                 return;
 312
 313         for (i = 0; i < pcl->pclusterpages; ++i) {
 314                 struct page *page;
 315                 compressed_page_t t;
 316                 struct page *newpage = NULL;
 317
 318                 /* the compressed page was loaded before */
 319                 if (READ_ONCE(pcl->compressed_bvecs[i].page))
 320                         continue;
 321
 322                 page = find_get_page(mc, pcl->obj.index + i);
 323
 324                 if (page) {
 325                         t = tag_compressed_page_justfound(page);
 326                 } else {
 327                         /* I/O is needed, no possible to decompress directly */
 328                         standalone = false;
 329                         switch (type) {
 330                         case TRYALLOC:
 331                                 newpage = erofs_allocpage(pagepool, gfp);
 332                                 if (!newpage)
 333                                         continue;
 334                                 set_page_private(newpage,
 335                                                  Z_EROFS_PREALLOCATED_PAGE);
 336                                 t = tag_compressed_page_justfound(newpage);
 337                                 break;
 338                         default:        /* DONTALLOC */
 339                                 continue;
 340                         }
 341                 }
 342
 343                 if (!cmpxchg_relaxed(&pcl->compressed_bvecs[i].page, NULL,
 344                                      tagptr_cast_ptr(t)))
 345                         continue;
 346
 347                 if (page)
 348                         put_page(page);
 349                 else if (newpage)
 350                         erofs_pagepool_add(pagepool, newpage);
 351         }
 352
 353         /*
 354          * don't do inplace I/O if all compressed pages are available in
 355          * managed cache since it can be moved to the bypass queue instead.
 356          */
 357         if (standalone)
 358                 fe->mode = Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE;
 359 }
 360
 361 /* called by erofs_shrinker to get rid of all compressed_pages */
 362 int erofs_try_to_free_all_cached_pages(struct erofs_sb_info *sbi,
 363                                        struct erofs_workgroup *grp)
 364 {
 365         struct z_erofs_pcluster *const pcl =
 366                 container_of(grp, struct z_erofs_pcluster, obj);
 367         int i;
 368
 369         DBG_BUGON(z_erofs_is_inline_pcluster(pcl));
 370         /*
 371          * refcount of workgroup is now freezed as 1,
 372          * therefore no need to worry about available decompression users.
 373          */
 374         for (i = 0; i < pcl->pclusterpages; ++i) {
 375                 struct page *page = pcl->compressed_bvecs[i].page;
 376
 377                 if (!page)
 378                         continue;
 379
 380                 /* block other users from reclaiming or migrating the page */
 381                 if (!trylock_page(page))
 382                         return -EBUSY;
 383
 384                 if (!erofs_page_is_managed(sbi, page))
 385                         continue;
 386
 387                 /* barrier is implied in the following 'unlock_page' */
 388                 WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
 389                 detach_page_private(page);
 390                 unlock_page(page);
 391         }
 392         return 0;
 393 }
 394
 395 int erofs_try_to_free_cached_page(struct page *page)
 396 {
 397         struct z_erofs_pcluster *const pcl = (void *)page_private(page);
 398         int ret, i;
 399
 400         if (!erofs_workgroup_try_to_freeze(&pcl->obj, 1))
 401                 return 0;
 402
 403         ret = 0;
 404         DBG_BUGON(z_erofs_is_inline_pcluster(pcl));
 405         for (i = 0; i < pcl->pclusterpages; ++i) {
 406                 if (pcl->compressed_bvecs[i].page == page) {
 407                         WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
 408                         ret = 1;
 409                         break;
 410                 }
 411         }
 412         erofs_workgroup_unfreeze(&pcl->obj, 1);
 413         if (ret)
 414                 detach_page_private(page);
 415         return ret;
 416 }
 417
 418 static bool z_erofs_try_inplace_io(struct z_erofs_decompress_frontend *fe,
 419                                    struct z_erofs_bvec *bvec)
 420 {
 421         struct z_erofs_pcluster *const pcl = fe->pcl;
 422
 423         while (fe->icur > 0) {
 424                 if (!cmpxchg(&pcl->compressed_bvecs[--fe->icur].page,
 425                              NULL, bvec->page)) {
 426                         pcl->compressed_bvecs[fe->icur] = *bvec;
 427                         return true;
 428                 }
 429         }
 430         return false;
 431 }
 432
 433 /* callers must be with pcluster lock held */
 434 static int z_erofs_attach_page(struct z_erofs_decompress_frontend *fe,
 435                                struct z_erofs_bvec *bvec, bool exclusive)
 436 {
 437         int ret;
 438
 439         if (exclusive) {
 440                 /* give priority for inplaceio to use file pages first */
 441                 if (z_erofs_try_inplace_io(fe, bvec))
 442                         return 0;
 443                 /* otherwise, check if it can be used as a bvpage */
 444                 if (fe->mode >= Z_EROFS_PCLUSTER_FOLLOWED &&
 445                     !fe->candidate_bvpage)
 446                         fe->candidate_bvpage = bvec->page;
 447         }
 448         ret = z_erofs_bvec_enqueue(&fe->biter, bvec, &fe->candidate_bvpage);
 449         fe->pcl->vcnt += (ret >= 0);
 450         return ret;
 451 }
 452
 453 static void z_erofs_try_to_claim_pcluster(struct z_erofs_decompress_frontend *f)
 454 {
 455         struct z_erofs_pcluster *pcl = f->pcl;
 456         z_erofs_next_pcluster_t *owned_head = &f->owned_head;
 457
 458         /* type 1, nil pcluster (this pcluster doesn't belong to any chain.) */
 459         if (cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_NIL,
 460                     *owned_head) == Z_EROFS_PCLUSTER_NIL) {
 461                 *owned_head = &pcl->next;
 462                 /* so we can attach this pcluster to our submission chain. */
 463                 f->mode = Z_EROFS_PCLUSTER_FOLLOWED;
 464                 return;
 465         }
 466
 467         /*
 468          * type 2, link to the end of an existing open chain, be careful
 469          * that its submission is controlled by the original attached chain.
 470          */
 471         if (*owned_head != &pcl->next && pcl != f->tailpcl &&
 472             cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_TAIL,
 473                     *owned_head) == Z_EROFS_PCLUSTER_TAIL) {
 474                 *owned_head = Z_EROFS_PCLUSTER_TAIL;
 475                 f->mode = Z_EROFS_PCLUSTER_HOOKED;
 476                 f->tailpcl = NULL;
 477                 return;
 478         }
 479         /* type 3, it belongs to a chain, but it isn't the end of the chain */
 480         f->mode = Z_EROFS_PCLUSTER_INFLIGHT;
 481 }
 482
 483 static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
 484 {
 485         struct erofs_map_blocks *map = &fe->map;
 486         bool ztailpacking = map->m_flags & EROFS_MAP_META;
 487         struct z_erofs_pcluster *pcl;
 488         struct erofs_workgroup *grp;
 489         int err;
 490
 491         if (!(map->m_flags & EROFS_MAP_ENCODED)) {
 492                 DBG_BUGON(1);
 493                 return -EFSCORRUPTED;
 494         }
 495
 496         /* no available pcluster, let's allocate one */
 497         pcl = z_erofs_alloc_pcluster(ztailpacking ? 1 :
 498                                      map->m_plen >> PAGE_SHIFT);
 499         if (IS_ERR(pcl))
 500                 return PTR_ERR(pcl);
 501
 502         atomic_set(&pcl->obj.refcount, 1);
 503         pcl->algorithmformat = map->m_algorithmformat;
 504         pcl->length = 0;
 505         pcl->partial = true;
 506
 507         /* new pclusters should be claimed as type 1, primary and followed */
 508         pcl->next = fe->owned_head;
 509         pcl->pageofs_out = map->m_la & ~PAGE_MASK;
 510         fe->mode = Z_EROFS_PCLUSTER_FOLLOWED;
 511
 512         /*
 513          * lock all primary followed works before visible to others
 514          * and mutex_trylock *never* fails for a new pcluster.
 515          */
 516         mutex_init(&pcl->lock);
 517         DBG_BUGON(!mutex_trylock(&pcl->lock));
 518
 519         if (ztailpacking) {
 520                 pcl->obj.index = 0;     /* which indicates ztailpacking */
 521                 pcl->pageofs_in = erofs_blkoff(map->m_pa);
 522                 pcl->tailpacking_size = map->m_plen;
 523         } else {
 524                 pcl->obj.index = map->m_pa >> PAGE_SHIFT;
 525
 526                 grp = erofs_insert_workgroup(fe->inode->i_sb, &pcl->obj);
 527                 if (IS_ERR(grp)) {
 528                         err = PTR_ERR(grp);
 529                         goto err_out;
 530                 }
 531
 532                 if (grp != &pcl->obj) {
 533                         fe->pcl = container_of(grp,
 534                                         struct z_erofs_pcluster, obj);
 535                         err = -EEXIST;
 536                         goto err_out;
 537                 }
 538         }
 539         /* used to check tail merging loop due to corrupted images */
 540         if (fe->owned_head == Z_EROFS_PCLUSTER_TAIL)
 541                 fe->tailpcl = pcl;
 542         fe->owned_head = &pcl->next;
 543         fe->pcl = pcl;
 544         return 0;
 545
 546 err_out:
 547         mutex_unlock(&pcl->lock);
 548         z_erofs_free_pcluster(pcl);
 549         return err;
 550 }
 551
 552 static int z_erofs_collector_begin(struct z_erofs_decompress_frontend *fe)
 553 {
 554         struct erofs_map_blocks *map = &fe->map;
 555         struct erofs_workgroup *grp = NULL;
 556         int ret;
 557
 558         DBG_BUGON(fe->pcl);
 559
 560         /* must be Z_EROFS_PCLUSTER_TAIL or pointed to previous pcluster */
 561         DBG_BUGON(fe->owned_head == Z_EROFS_PCLUSTER_NIL);
 562         DBG_BUGON(fe->owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
 563
 564         if (!(map->m_flags & EROFS_MAP_META)) {
 565                 grp = erofs_find_workgroup(fe->inode->i_sb,
 566                                            map->m_pa >> PAGE_SHIFT);
 567         } else if ((map->m_pa & ~PAGE_MASK) + map->m_plen > PAGE_SIZE) {
 568                 DBG_BUGON(1);
 569                 return -EFSCORRUPTED;
 570         }
 571
 572         if (grp) {
 573                 fe->pcl = container_of(grp, struct z_erofs_pcluster, obj);
 574                 ret = -EEXIST;
 575         } else {
 576                 ret = z_erofs_register_pcluster(fe);
 577         }
 578
 579         if (ret == -EEXIST) {
 580                 mutex_lock(&fe->pcl->lock);
 581                 /* used to check tail merging loop due to corrupted images */
 582                 if (fe->owned_head == Z_EROFS_PCLUSTER_TAIL)
 583                         fe->tailpcl = fe->pcl;
 584
 585                 z_erofs_try_to_claim_pcluster(fe);
 586         } else if (ret) {
 587                 return ret;
 588         }
 589         z_erofs_bvec_iter_begin(&fe->biter, &fe->pcl->bvset,
 590                                 Z_EROFS_INLINE_BVECS, fe->pcl->vcnt);
 591         /* since file-backed online pages are traversed in reverse order */
 592         fe->icur = z_erofs_pclusterpages(fe->pcl);
 593         return 0;
 594 }
 595
 596 /*
 597  * keep in mind that no referenced pclusters will be freed
 598  * only after a RCU grace period.
 599  */
 600 static void z_erofs_rcu_callback(struct rcu_head *head)
 601 {
 602         z_erofs_free_pcluster(container_of(head,
 603                         struct z_erofs_pcluster, rcu));
 604 }
 605
 606 void erofs_workgroup_free_rcu(struct erofs_workgroup *grp)
 607 {
 608         struct z_erofs_pcluster *const pcl =
 609                 container_of(grp, struct z_erofs_pcluster, obj);
 610
 611         call_rcu(&pcl->rcu, z_erofs_rcu_callback);
 612 }
 613
 614 static bool z_erofs_collector_end(struct z_erofs_decompress_frontend *fe)
 615 {
 616         struct z_erofs_pcluster *pcl = fe->pcl;
 617
 618         if (!pcl)
 619                 return false;
 620
 621         z_erofs_bvec_iter_end(&fe->biter);
 622         mutex_unlock(&pcl->lock);
 623
 624         if (fe->candidate_bvpage) {
 625                 DBG_BUGON(z_erofs_is_shortlived_page(fe->candidate_bvpage));
 626                 fe->candidate_bvpage = NULL;
 627         }
 628
 629         /*
 630          * if all pending pages are added, don't hold its reference
 631          * any longer if the pcluster isn't hosted by ourselves.
 632          */
 633         if (fe->mode < Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE)
 634                 erofs_workgroup_put(&pcl->obj);
 635
 636         fe->pcl = NULL;
 637         return true;
 638 }
 639
 640 static bool should_alloc_managed_pages(struct z_erofs_decompress_frontend *fe,
 641                                        unsigned int cachestrategy,
 642                                        erofs_off_t la)
 643 {
 644         if (cachestrategy <= EROFS_ZIP_CACHE_DISABLED)
 645                 return false;
 646
 647         if (fe->backmost)
 648                 return true;
 649
 650         return cachestrategy >= EROFS_ZIP_CACHE_READAROUND &&
 651                 la < fe->headoffset;
 652 }
 653
 654 static int z_erofs_read_fragment(struct inode *inode, erofs_off_t pos,
 655                                  struct page *page, unsigned int pageofs,
 656                                  unsigned int len)
 657 {
 658         struct inode *packed_inode = EROFS_I_SB(inode)->packed_inode;
 659         struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
 660         u8 *src, *dst;
 661         unsigned int i, cnt;
 662
 663         if (!packed_inode)
 664                 return -EFSCORRUPTED;
 665
 666         pos += EROFS_I(inode)->z_fragmentoff;
 667         for (i = 0; i < len; i += cnt) {
 668                 cnt = min_t(unsigned int, len - i,
 669                             EROFS_BLKSIZ - erofs_blkoff(pos));
 670                 src = erofs_bread(&buf, packed_inode,
 671                                   erofs_blknr(pos), EROFS_KMAP);
 672                 if (IS_ERR(src)) {
 673                         erofs_put_metabuf(&buf);
 674                         return PTR_ERR(src);
 675                 }
 676
 677                 dst = kmap_local_page(page);
 678                 memcpy(dst + pageofs + i, src + erofs_blkoff(pos), cnt);
 679                 kunmap_local(dst);
 680                 pos += cnt;
 681         }
 682         erofs_put_metabuf(&buf);
 683         return 0;
 684 }
 685
 686 static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 687                                 struct page *page, struct page **pagepool)
 688 {
 689         struct inode *const inode = fe->inode;
 690         struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
 691         struct erofs_map_blocks *const map = &fe->map;
 692         const loff_t offset = page_offset(page);
 693         bool tight = true, exclusive;
 694
 695         enum z_erofs_cache_alloctype cache_strategy;
 696         unsigned int cur, end, spiltted;
 697         int err = 0;
 698
 699         /* register locked file pages as online pages in pack */
 700         z_erofs_onlinepage_init(page);
 701
 702         spiltted = 0;
 703         end = PAGE_SIZE;
 704 repeat:
 705         cur = end - 1;
 706
 707         if (offset + cur < map->m_la ||
 708             offset + cur >= map->m_la + map->m_llen) {
 709                 erofs_dbg("out-of-range map @ pos %llu", offset + cur);
 710
 711                 if (z_erofs_collector_end(fe))
 712                         fe->backmost = false;
 713                 map->m_la = offset + cur;
 714                 map->m_llen = 0;
 715                 err = z_erofs_map_blocks_iter(inode, map, 0);
 716                 if (err)
 717                         goto out;
 718         } else {
 719                 if (fe->pcl)
 720                         goto hitted;
 721                 /* didn't get a valid pcluster previously (very rare) */
 722         }
 723
 724         if (!(map->m_flags & EROFS_MAP_MAPPED) ||
 725             map->m_flags & EROFS_MAP_FRAGMENT)
 726                 goto hitted;
 727
 728         err = z_erofs_collector_begin(fe);
 729         if (err)
 730                 goto out;
 731
 732         if (z_erofs_is_inline_pcluster(fe->pcl)) {
 733                 void *mp;
 734
 735                 mp = erofs_read_metabuf(&fe->map.buf, inode->i_sb,
 736                                         erofs_blknr(map->m_pa), EROFS_NO_KMAP);
 737                 if (IS_ERR(mp)) {
 738                         err = PTR_ERR(mp);
 739                         erofs_err(inode->i_sb,
 740                                   "failed to get inline page, err %d", err);
 741                         goto out;
 742                 }
 743                 get_page(fe->map.buf.page);
 744                 WRITE_ONCE(fe->pcl->compressed_bvecs[0].page,
 745                            fe->map.buf.page);
 746                 fe->mode = Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE;
 747         } else {
 748                 /* bind cache first when cached decompression is preferred */
 749                 if (should_alloc_managed_pages(fe, sbi->opt.cache_strategy,
 750                                                map->m_la))
 751                         cache_strategy = TRYALLOC;
 752                 else
 753                         cache_strategy = DONTALLOC;
 754
 755                 z_erofs_bind_cache(fe, cache_strategy, pagepool);
 756         }
 757 hitted:
 758         /*
 759          * Ensure the current partial page belongs to this submit chain rather
 760          * than other concurrent submit chains or the noio(bypass) chain since
 761          * those chains are handled asynchronously thus the page cannot be used
 762          * for inplace I/O or bvpage (should be processed in a strict order.)
 763          */
 764         tight &= (fe->mode >= Z_EROFS_PCLUSTER_HOOKED &&
 765                   fe->mode != Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE);
 766
 767         cur = end - min_t(unsigned int, offset + end - map->m_la, end);
 768         if (!(map->m_flags & EROFS_MAP_MAPPED)) {
 769                 zero_user_segment(page, cur, end);
 770                 goto next_part;
 771         }
 772         if (map->m_flags & EROFS_MAP_FRAGMENT) {
 773                 unsigned int pageofs, skip, len;
 774
 775                 if (offset > map->m_la) {
 776                         pageofs = 0;
 777                         skip = offset - map->m_la;
 778                 } else {
 779                         pageofs = map->m_la & ~PAGE_MASK;
 780                         skip = 0;
 781                 }
 782                 len = min_t(unsigned int, map->m_llen - skip, end - cur);
 783                 err = z_erofs_read_fragment(inode, skip, page, pageofs, len);
 784                 if (err)
 785                         goto out;
 786                 ++spiltted;
 787                 tight = false;
 788                 goto next_part;
 789         }
 790
 791         exclusive = (!cur && (!spiltted || tight));
 792         if (cur)
 793                 tight &= (fe->mode >= Z_EROFS_PCLUSTER_FOLLOWED);
 794
 795 retry:
 796         err = z_erofs_attach_page(fe, &((struct z_erofs_bvec) {
 797                                         .page = page,
 798                                         .offset = offset - map->m_la,
 799                                         .end = end,
 800                                   }), exclusive);
 801         /* should allocate an additional short-lived page for bvset */
 802         if (err == -EAGAIN && !fe->candidate_bvpage) {
 803                 fe->candidate_bvpage = alloc_page(GFP_NOFS | __GFP_NOFAIL);
 804                 set_page_private(fe->candidate_bvpage,
 805                                  Z_EROFS_SHORTLIVED_PAGE);
 806                 goto retry;
 807         }
 808
 809         if (err) {
 810                 DBG_BUGON(err == -EAGAIN && fe->candidate_bvpage);
 811                 goto out;
 812         }
 813
 814         z_erofs_onlinepage_split(page);
 815         /* bump up the number of spiltted parts of a page */
 816         ++spiltted;
 817         if (fe->pcl->pageofs_out != (map->m_la & ~PAGE_MASK))
 818                 fe->pcl->multibases = true;
 819         if (fe->pcl->length < offset + end - map->m_la) {
 820                 fe->pcl->length = offset + end - map->m_la;
 821                 fe->pcl->pageofs_out = map->m_la & ~PAGE_MASK;
 822         }
 823         if ((map->m_flags & EROFS_MAP_FULL_MAPPED) &&
 824             !(map->m_flags & EROFS_MAP_PARTIAL_REF) &&
 825             fe->pcl->length == map->m_llen)
 826                 fe->pcl->partial = false;
 827 next_part:
 828         /* shorten the remaining extent to update progress */
 829         map->m_llen = offset + cur - map->m_la;
 830         map->m_flags &= ~EROFS_MAP_FULL_MAPPED;
 831
 832         end = cur;
 833         if (end > 0)
 834                 goto repeat;
 835
 836 out:
 837         if (err)
 838                 z_erofs_page_mark_eio(page);
 839         z_erofs_onlinepage_endio(page);
 840
 841         erofs_dbg("%s, finish page: %pK spiltted: %u map->m_llen %llu",
 842                   __func__, page, spiltted, map->m_llen);
 843         return err;
 844 }
 845
 846 static bool z_erofs_get_sync_decompress_policy(struct erofs_sb_info *sbi,
 847                                        unsigned int readahead_pages)
 848 {
 849         /* auto: enable for read_folio, disable for readahead */
 850         if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO) &&
 851             !readahead_pages)
 852                 return true;
 853
 854         if ((sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_FORCE_ON) &&
 855             (readahead_pages <= sbi->opt.max_sync_decompress_pages))
 856                 return true;
 857
 858         return false;
 859 }
 860
 861 static bool z_erofs_page_is_invalidated(struct page *page)
 862 {
 863         return !page->mapping && !z_erofs_is_shortlived_page(page);
 864 }
 865
 866 struct z_erofs_decompress_backend {
 867         struct page *onstack_pages[Z_EROFS_ONSTACK_PAGES];
 868         struct super_block *sb;
 869         struct z_erofs_pcluster *pcl;
 870
 871         /* pages with the longest decompressed length for deduplication */
 872         struct page **decompressed_pages;
 873         /* pages to keep the compressed data */
 874         struct page **compressed_pages;
 875
 876         struct list_head decompressed_secondary_bvecs;
 877         struct page **pagepool;
 878         unsigned int onstack_used, nr_pages;
 879 };
 880
 881 struct z_erofs_bvec_item {
 882         struct z_erofs_bvec bvec;
 883         struct list_head list;
 884 };
 885
 886 static void z_erofs_do_decompressed_bvec(struct z_erofs_decompress_backend *be,
 887                                          struct z_erofs_bvec *bvec)
 888 {
 889         struct z_erofs_bvec_item *item;
 890
 891         if (!((bvec->offset + be->pcl->pageofs_out) & ~PAGE_MASK)) {
 892                 unsigned int pgnr;
 893
 894                 pgnr = (bvec->offset + be->pcl->pageofs_out) >> PAGE_SHIFT;
 895                 DBG_BUGON(pgnr >= be->nr_pages);
 896                 if (!be->decompressed_pages[pgnr]) {
 897                         be->decompressed_pages[pgnr] = bvec->page;
 898                         return;
 899                 }
 900         }
 901
 902         /* (cold path) one pcluster is requested multiple times */
 903         item = kmalloc(sizeof(*item), GFP_KERNEL | __GFP_NOFAIL);
 904         item->bvec = *bvec;
 905         list_add(&item->list, &be->decompressed_secondary_bvecs);
 906 }
 907
 908 static void z_erofs_fill_other_copies(struct z_erofs_decompress_backend *be,
 909                                       int err)
 910 {
 911         unsigned int off0 = be->pcl->pageofs_out;
 912         struct list_head *p, *n;
 913
 914         list_for_each_safe(p, n, &be->decompressed_secondary_bvecs) {
 915                 struct z_erofs_bvec_item *bvi;
 916                 unsigned int end, cur;
 917                 void *dst, *src;
 918
 919                 bvi = container_of(p, struct z_erofs_bvec_item, list);
 920                 cur = bvi->bvec.offset < 0 ? -bvi->bvec.offset : 0;
 921                 end = min_t(unsigned int, be->pcl->length - bvi->bvec.offset,
 922                             bvi->bvec.end);
 923                 dst = kmap_local_page(bvi->bvec.page);
 924                 while (cur < end) {
 925                         unsigned int pgnr, scur, len;
 926
 927                         pgnr = (bvi->bvec.offset + cur + off0) >> PAGE_SHIFT;
 928                         DBG_BUGON(pgnr >= be->nr_pages);
 929
 930                         scur = bvi->bvec.offset + cur -
 931                                         ((pgnr << PAGE_SHIFT) - off0);
 932                         len = min_t(unsigned int, end - cur, PAGE_SIZE - scur);
 933                         if (!be->decompressed_pages[pgnr]) {
 934                                 err = -EFSCORRUPTED;
 935                                 cur += len;
 936                                 continue;
 937                         }
 938                         src = kmap_local_page(be->decompressed_pages[pgnr]);
 939                         memcpy(dst + cur, src + scur, len);
 940                         kunmap_local(src);
 941                         cur += len;
 942                 }
 943                 kunmap_local(dst);
 944                 if (err)
 945                         z_erofs_page_mark_eio(bvi->bvec.page);
 946                 z_erofs_onlinepage_endio(bvi->bvec.page);
 947                 list_del(p);
 948                 kfree(bvi);
 949         }
 950 }
 951
 952 static void z_erofs_parse_out_bvecs(struct z_erofs_decompress_backend *be)
 953 {
 954         struct z_erofs_pcluster *pcl = be->pcl;
 955         struct z_erofs_bvec_iter biter;
 956         struct page *old_bvpage;
 957         int i;
 958
 959         z_erofs_bvec_iter_begin(&biter, &pcl->bvset, Z_EROFS_INLINE_BVECS, 0);
 960         for (i = 0; i < pcl->vcnt; ++i) {
 961                 struct z_erofs_bvec bvec;
 962
 963                 z_erofs_bvec_dequeue(&biter, &bvec, &old_bvpage);
 964
 965                 if (old_bvpage)
 966                         z_erofs_put_shortlivedpage(be->pagepool, old_bvpage);
 967
 968                 DBG_BUGON(z_erofs_page_is_invalidated(bvec.page));
 969                 z_erofs_do_decompressed_bvec(be, &bvec);
 970         }
 971
 972         old_bvpage = z_erofs_bvec_iter_end(&biter);
 973         if (old_bvpage)
 974                 z_erofs_put_shortlivedpage(be->pagepool, old_bvpage);
 975 }
 976
 977 static int z_erofs_parse_in_bvecs(struct z_erofs_decompress_backend *be,
 978                                   bool *overlapped)
 979 {
 980         struct z_erofs_pcluster *pcl = be->pcl;
 981         unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
 982         int i, err = 0;
 983
 984         *overlapped = false;
 985         for (i = 0; i < pclusterpages; ++i) {
 986                 struct z_erofs_bvec *bvec = &pcl->compressed_bvecs[i];
 987                 struct page *page = bvec->page;
 988
 989                 /* compressed pages ought to be present before decompressing */
 990                 if (!page) {
 991                         DBG_BUGON(1);
 992                         continue;
 993                 }
 994                 be->compressed_pages[i] = page;
 995
 996                 if (z_erofs_is_inline_pcluster(pcl)) {
 997                         if (!PageUptodate(page))
 998                                 err = -EIO;
 999                         continue;
1000                 }
1001
1002                 DBG_BUGON(z_erofs_page_is_invalidated(page));
1003                 if (!z_erofs_is_shortlived_page(page)) {
1004                         if (erofs_page_is_managed(EROFS_SB(be->sb), page)) {
1005                                 if (!PageUptodate(page))
1006                                         err = -EIO;
1007                                 continue;
1008                         }
1009                         z_erofs_do_decompressed_bvec(be, bvec);
1010                         *overlapped = true;
1011                 }
1012         }
1013
1014         if (err)
1015                 return err;
1016         return 0;
1017 }
1018
1019 static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
1020                                        int err)
1021 {
1022         struct erofs_sb_info *const sbi = EROFS_SB(be->sb);
1023         struct z_erofs_pcluster *pcl = be->pcl;
1024         unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
1025         unsigned int i, inputsize;
1026         int err2;
1027         struct page *page;
1028         bool overlapped;
1029
1030         mutex_lock(&pcl->lock);
1031         be->nr_pages = PAGE_ALIGN(pcl->length + pcl->pageofs_out) >> PAGE_SHIFT;
1032
1033         /* allocate (de)compressed page arrays if cannot be kept on stack */
1034         be->decompressed_pages = NULL;
1035         be->compressed_pages = NULL;
1036         be->onstack_used = 0;
1037         if (be->nr_pages <= Z_EROFS_ONSTACK_PAGES) {
1038                 be->decompressed_pages = be->onstack_pages;
1039                 be->onstack_used = be->nr_pages;
1040                 memset(be->decompressed_pages, 0,
1041                        sizeof(struct page *) * be->nr_pages);
1042         }
1043
1044         if (pclusterpages + be->onstack_used <= Z_EROFS_ONSTACK_PAGES)
1045                 be->compressed_pages = be->onstack_pages + be->onstack_used;
1046
1047         if (!be->decompressed_pages)
1048                 be->decompressed_pages =
1049                         kvcalloc(be->nr_pages, sizeof(struct page *),
1050                                  GFP_KERNEL | __GFP_NOFAIL);
1051         if (!be->compressed_pages)
1052                 be->compressed_pages =
1053                         kvcalloc(pclusterpages, sizeof(struct page *),
1054                                  GFP_KERNEL | __GFP_NOFAIL);
1055
1056         z_erofs_parse_out_bvecs(be);
1057         err2 = z_erofs_parse_in_bvecs(be, &overlapped);
1058         if (err2)
1059                 err = err2;
1060         if (err)
1061                 goto out;
1062
1063         if (z_erofs_is_inline_pcluster(pcl))
1064                 inputsize = pcl->tailpacking_size;
1065         else
1066                 inputsize = pclusterpages * PAGE_SIZE;
1067
1068         err = z_erofs_decompress(&(struct z_erofs_decompress_req) {
1069                                         .sb = be->sb,
1070                                         .in = be->compressed_pages,
1071                                         .out = be->decompressed_pages,
1072                                         .pageofs_in = pcl->pageofs_in,
1073                                         .pageofs_out = pcl->pageofs_out,
1074                                         .inputsize = inputsize,
1075                                         .outputsize = pcl->length,
1076                                         .alg = pcl->algorithmformat,
1077                                         .inplace_io = overlapped,
1078                                         .partial_decoding = pcl->partial,
1079                                         .fillgaps = pcl->multibases,
1080                                  }, be->pagepool);
1081
1082 out:
1083         /* must handle all compressed pages before actual file pages */
1084         if (z_erofs_is_inline_pcluster(pcl)) {
1085                 page = pcl->compressed_bvecs[0].page;
1086                 WRITE_ONCE(pcl->compressed_bvecs[0].page, NULL);
1087                 put_page(page);
1088         } else {
1089                 for (i = 0; i < pclusterpages; ++i) {
1090                         page = pcl->compressed_bvecs[i].page;
1091
1092                         if (erofs_page_is_managed(sbi, page))
1093                                 continue;
1094
1095                         /* recycle all individual short-lived pages */
1096                         (void)z_erofs_put_shortlivedpage(be->pagepool, page);
1097                         WRITE_ONCE(pcl->compressed_bvecs[i].page, NULL);
1098                 }
1099         }
1100         if (be->compressed_pages < be->onstack_pages ||
1101             be->compressed_pages >= be->onstack_pages + Z_EROFS_ONSTACK_PAGES)
1102                 kvfree(be->compressed_pages);
1103         z_erofs_fill_other_copies(be, err);
1104
1105         for (i = 0; i < be->nr_pages; ++i) {
1106                 page = be->decompressed_pages[i];
1107                 if (!page)
1108                         continue;
1109
1110                 DBG_BUGON(z_erofs_page_is_invalidated(page));
1111
1112                 /* recycle all individual short-lived pages */
1113                 if (z_erofs_put_shortlivedpage(be->pagepool, page))
1114                         continue;
1115                 if (err)
1116                         z_erofs_page_mark_eio(page);
1117                 z_erofs_onlinepage_endio(page);
1118         }
1119
1120         if (be->decompressed_pages != be->onstack_pages)
1121                 kvfree(be->decompressed_pages);
1122
1123         pcl->length = 0;
1124         pcl->partial = true;
1125         pcl->multibases = false;
1126         pcl->bvset.nextpage = NULL;
1127         pcl->vcnt = 0;
1128
1129         /* pcluster lock MUST be taken before the following line */
1130         WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_NIL);
1131         mutex_unlock(&pcl->lock);
1132         return err;
1133 }
1134
1135 static void z_erofs_decompress_queue(const struct z_erofs_decompressqueue *io,
1136                                      struct page **pagepool)
1137 {
1138         struct z_erofs_decompress_backend be = {
1139                 .sb = io->sb,
1140                 .pagepool = pagepool,
1141                 .decompressed_secondary_bvecs =
1142                         LIST_HEAD_INIT(be.decompressed_secondary_bvecs),
1143         };
1144         z_erofs_next_pcluster_t owned = io->head;
1145
1146         while (owned != Z_EROFS_PCLUSTER_TAIL_CLOSED) {
1147                 /* impossible that 'owned' equals Z_EROFS_WORK_TPTR_TAIL */
1148                 DBG_BUGON(owned == Z_EROFS_PCLUSTER_TAIL);
1149                 /* impossible that 'owned' equals Z_EROFS_PCLUSTER_NIL */
1150                 DBG_BUGON(owned == Z_EROFS_PCLUSTER_NIL);
1151
1152                 be.pcl = container_of(owned, struct z_erofs_pcluster, next);
1153                 owned = READ_ONCE(be.pcl->next);
1154
1155                 z_erofs_decompress_pcluster(&be, io->eio ? -EIO : 0);
1156                 erofs_workgroup_put(&be.pcl->obj);
1157         }
1158 }
1159
1160 static void z_erofs_decompressqueue_work(struct work_struct *work)
1161 {
1162         struct z_erofs_decompressqueue *bgq =
1163                 container_of(work, struct z_erofs_decompressqueue, u.work);
1164         struct page *pagepool = NULL;
1165
1166         DBG_BUGON(bgq->head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
1167         z_erofs_decompress_queue(bgq, &pagepool);
1168
1169         erofs_release_pages(&pagepool);
1170         kvfree(bgq);
1171 }
1172
1173 static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
1174                                        bool sync, int bios)
1175 {
1176         struct erofs_sb_info *const sbi = EROFS_SB(io->sb);
1177
1178         /* wake up the caller thread for sync decompression */
1179         if (sync) {
1180                 if (!atomic_add_return(bios, &io->pending_bios))
1181                         complete(&io->u.done);
1182                 return;
1183         }
1184
1185         if (atomic_add_return(bios, &io->pending_bios))
1186                 return;
1187         /* Use workqueue and sync decompression for atomic contexts only */
1188         if (in_atomic() || irqs_disabled()) {
1189                 queue_work(z_erofs_workqueue, &io->u.work);
1190                 /* enable sync decompression for readahead */
1191                 if (sbi->opt.sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO)
1192                         sbi->opt.sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON;
1193                 return;
1194         }
1195         z_erofs_decompressqueue_work(&io->u.work);
1196 }
1197
1198 static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl,
1199                                                unsigned int nr,
1200                                                struct page **pagepool,
1201                                                struct address_space *mc)
1202 {
1203         const pgoff_t index = pcl->obj.index;
1204         gfp_t gfp = mapping_gfp_mask(mc);
1205         bool tocache = false;
1206
1207         struct address_space *mapping;
1208         struct page *oldpage, *page;
1209
1210         compressed_page_t t;
1211         int justfound;
1212
1213 repeat:
1214         page = READ_ONCE(pcl->compressed_bvecs[nr].page);
1215         oldpage = page;
1216
1217         if (!page)
1218                 goto out_allocpage;
1219
1220         /* process the target tagged pointer */
1221         t = tagptr_init(compressed_page_t, page);
1222         justfound = tagptr_unfold_tags(t);
1223         page = tagptr_unfold_ptr(t);
1224
1225         /*
1226          * preallocated cached pages, which is used to avoid direct reclaim
1227          * otherwise, it will go inplace I/O path instead.
1228          */
1229         if (page->private == Z_EROFS_PREALLOCATED_PAGE) {
1230                 WRITE_ONCE(pcl->compressed_bvecs[nr].page, page);
1231                 set_page_private(page, 0);
1232                 tocache = true;
1233                 goto out_tocache;
1234         }
1235         mapping = READ_ONCE(page->mapping);
1236
1237         /*
1238          * file-backed online pages in plcuster are all locked steady,
1239          * therefore it is impossible for `mapping' to be NULL.
1240          */
1241         if (mapping && mapping != mc)
1242                 /* ought to be unmanaged pages */
1243                 goto out;
1244
1245         /* directly return for shortlived page as well */
1246         if (z_erofs_is_shortlived_page(page))
1247                 goto out;
1248
1249         lock_page(page);
1250
1251         /* only true if page reclaim goes wrong, should never happen */
1252         DBG_BUGON(justfound && PagePrivate(page));
1253
1254         /* the page is still in manage cache */
1255         if (page->mapping == mc) {
1256                 WRITE_ONCE(pcl->compressed_bvecs[nr].page, page);
1257
1258                 if (!PagePrivate(page)) {
1259                         /*
1260                          * impossible to be !PagePrivate(page) for
1261                          * the current restriction as well if
1262                          * the page is already in compressed_bvecs[].
1263                          */
1264                         DBG_BUGON(!justfound);
1265
1266                         justfound = 0;
1267                         set_page_private(page, (unsigned long)pcl);
1268                         SetPagePrivate(page);
1269                 }
1270
1271                 /* no need to submit io if it is already up-to-date */
1272                 if (PageUptodate(page)) {
1273                         unlock_page(page);
1274                         page = NULL;
1275                 }
1276                 goto out;
1277         }
1278
1279         /*
1280          * the managed page has been truncated, it's unsafe to
1281          * reuse this one, let's allocate a new cache-managed page.
1282          */
1283         DBG_BUGON(page->mapping);
1284         DBG_BUGON(!justfound);
1285
1286         tocache = true;
1287         unlock_page(page);
1288         put_page(page);
1289 out_allocpage:
1290         page = erofs_allocpage(pagepool, gfp | __GFP_NOFAIL);
1291         if (oldpage != cmpxchg(&pcl->compressed_bvecs[nr].page,
1292                                oldpage, page)) {
1293                 erofs_pagepool_add(pagepool, page);
1294                 cond_resched();
1295                 goto repeat;
1296         }
1297 out_tocache:
1298         if (!tocache || add_to_page_cache_lru(page, mc, index + nr, gfp)) {
1299                 /* turn into temporary page if fails (1 ref) */
1300                 set_page_private(page, Z_EROFS_SHORTLIVED_PAGE);
1301                 goto out;
1302         }
1303         attach_page_private(page, pcl);
1304         /* drop a refcount added by allocpage (then we have 2 refs here) */
1305         put_page(page);
1306
1307 out:    /* the only exit (for tracing and debugging) */
1308         return page;
1309 }
1310
1311 static struct z_erofs_decompressqueue *
1312 jobqueue_init(struct super_block *sb,
1313               struct z_erofs_decompressqueue *fgq, bool *fg)
1314 {
1315         struct z_erofs_decompressqueue *q;
1316
1317         if (fg && !*fg) {
1318                 q = kvzalloc(sizeof(*q), GFP_KERNEL | __GFP_NOWARN);
1319                 if (!q) {
1320                         *fg = true;
1321                         goto fg_out;
1322                 }
1323                 INIT_WORK(&q->u.work, z_erofs_decompressqueue_work);
1324         } else {
1325 fg_out:
1326                 q = fgq;
1327                 init_completion(&fgq->u.done);
1328                 atomic_set(&fgq->pending_bios, 0);
1329                 q->eio = false;
1330         }
1331         q->sb = sb;
1332         q->head = Z_EROFS_PCLUSTER_TAIL_CLOSED;
1333         return q;
1334 }
1335
1336 /* define decompression jobqueue types */
1337 enum {
1338         JQ_BYPASS,
1339         JQ_SUBMIT,
1340         NR_JOBQUEUES,
1341 };
1342
1343 static void *jobqueueset_init(struct super_block *sb,
1344                               struct z_erofs_decompressqueue *q[],
1345                               struct z_erofs_decompressqueue *fgq, bool *fg)
1346 {
1347         /*
1348          * if managed cache is enabled, bypass jobqueue is needed,
1349          * no need to read from device for all pclusters in this queue.
1350          */
1351         q[JQ_BYPASS] = jobqueue_init(sb, fgq + JQ_BYPASS, NULL);
1352         q[JQ_SUBMIT] = jobqueue_init(sb, fgq + JQ_SUBMIT, fg);
1353
1354         return tagptr_cast_ptr(tagptr_fold(tagptr1_t, q[JQ_SUBMIT], *fg));
1355 }
1356
1357 static void move_to_bypass_jobqueue(struct z_erofs_pcluster *pcl,
1358                                     z_erofs_next_pcluster_t qtail[],
1359                                     z_erofs_next_pcluster_t owned_head)
1360 {
1361         z_erofs_next_pcluster_t *const submit_qtail = qtail[JQ_SUBMIT];
1362         z_erofs_next_pcluster_t *const bypass_qtail = qtail[JQ_BYPASS];
1363
1364         DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
1365         if (owned_head == Z_EROFS_PCLUSTER_TAIL)
1366                 owned_head = Z_EROFS_PCLUSTER_TAIL_CLOSED;
1367
1368         WRITE_ONCE(pcl->next, Z_EROFS_PCLUSTER_TAIL_CLOSED);
1369
1370         WRITE_ONCE(*submit_qtail, owned_head);
1371         WRITE_ONCE(*bypass_qtail, &pcl->next);
1372
1373         qtail[JQ_BYPASS] = &pcl->next;
1374 }
1375
1376 static void z_erofs_decompressqueue_endio(struct bio *bio)
1377 {
1378         tagptr1_t t = tagptr_init(tagptr1_t, bio->bi_private);
1379         struct z_erofs_decompressqueue *q = tagptr_unfold_ptr(t);
1380         blk_status_t err = bio->bi_status;
1381         struct bio_vec *bvec;
1382         struct bvec_iter_all iter_all;
1383
1384         bio_for_each_segment_all(bvec, bio, iter_all) {
1385                 struct page *page = bvec->bv_page;
1386
1387                 DBG_BUGON(PageUptodate(page));
1388                 DBG_BUGON(z_erofs_page_is_invalidated(page));
1389
1390                 if (erofs_page_is_managed(EROFS_SB(q->sb), page)) {
1391                         if (!err)
1392                                 SetPageUptodate(page);
1393                         unlock_page(page);
1394                 }
1395         }
1396         if (err)
1397                 q->eio = true;
1398         z_erofs_decompress_kickoff(q, tagptr_unfold_tags(t), -1);
1399         bio_put(bio);
1400 }
1401
1402 static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f,
1403                                  struct page **pagepool,
1404                                  struct z_erofs_decompressqueue *fgq,
1405                                  bool *force_fg)
1406 {
1407         struct super_block *sb = f->inode->i_sb;
1408         struct address_space *mc = MNGD_MAPPING(EROFS_SB(sb));
1409         z_erofs_next_pcluster_t qtail[NR_JOBQUEUES];
1410         struct z_erofs_decompressqueue *q[NR_JOBQUEUES];
1411         void *bi_private;
1412         z_erofs_next_pcluster_t owned_head = f->owned_head;
1413         /* bio is NULL initially, so no need to initialize last_{index,bdev} */
1414         pgoff_t last_index;
1415         struct block_device *last_bdev;
1416         unsigned int nr_bios = 0;
1417         struct bio *bio = NULL;
1418         unsigned long pflags;
1419         int memstall = 0;
1420
1421         bi_private = jobqueueset_init(sb, q, fgq, force_fg);
1422         qtail[JQ_BYPASS] = &q[JQ_BYPASS]->head;
1423         qtail[JQ_SUBMIT] = &q[JQ_SUBMIT]->head;
1424
1425         /* by default, all need io submission */
1426         q[JQ_SUBMIT]->head = owned_head;
1427
1428         do {
1429                 struct erofs_map_dev mdev;
1430                 struct z_erofs_pcluster *pcl;
1431                 pgoff_t cur, end;
1432                 unsigned int i = 0;
1433                 bool bypass = true;
1434
1435                 /* no possible 'owned_head' equals the following */
1436                 DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
1437                 DBG_BUGON(owned_head == Z_EROFS_PCLUSTER_NIL);
1438
1439                 pcl = container_of(owned_head, struct z_erofs_pcluster, next);
1440
1441                 /* close the main owned chain at first */
1442                 owned_head = cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_TAIL,
1443                                      Z_EROFS_PCLUSTER_TAIL_CLOSED);
1444                 if (z_erofs_is_inline_pcluster(pcl)) {
1445                         move_to_bypass_jobqueue(pcl, qtail, owned_head);
1446                         continue;
1447                 }
1448
1449                 /* no device id here, thus it will always succeed */
1450                 mdev = (struct erofs_map_dev) {
1451                         .m_pa = blknr_to_addr(pcl->obj.index),
1452                 };
1453                 (void)erofs_map_dev(sb, &mdev);
1454
1455                 cur = erofs_blknr(mdev.m_pa);
1456                 end = cur + pcl->pclusterpages;
1457
1458                 do {
1459                         struct page *page;
1460
1461                         page = pickup_page_for_submission(pcl, i++, pagepool,
1462                                                           mc);
1463                         if (!page)
1464                                 continue;
1465
1466                         if (bio && (cur != last_index + 1 ||
1467                                     last_bdev != mdev.m_bdev)) {
1468 submit_bio_retry:
1469                                 submit_bio(bio);
1470                                 if (memstall) {
1471                                         psi_memstall_leave(&pflags);
1472                                         memstall = 0;
1473                                 }
1474                                 bio = NULL;
1475                         }
1476
1477                         if (unlikely(PageWorkingset(page)) && !memstall) {
1478                                 psi_memstall_enter(&pflags);
1479                                 memstall = 1;
1480                         }
1481
1482                         if (!bio) {
1483                                 bio = bio_alloc(mdev.m_bdev, BIO_MAX_VECS,
1484                                                 REQ_OP_READ, GFP_NOIO);
1485                                 bio->bi_end_io = z_erofs_decompressqueue_endio;
1486
1487                                 last_bdev = mdev.m_bdev;
1488                                 bio->bi_iter.bi_sector = (sector_t)cur <<
1489                                         LOG_SECTORS_PER_BLOCK;
1490                                 bio->bi_private = bi_private;
1491                                 if (f->readahead)
1492                                         bio->bi_opf |= REQ_RAHEAD;
1493                                 ++nr_bios;
1494                         }
1495
1496                         if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE)
1497                                 goto submit_bio_retry;
1498
1499                         last_index = cur;
1500                         bypass = false;
1501                 } while (++cur < end);
1502
1503                 if (!bypass)
1504                         qtail[JQ_SUBMIT] = &pcl->next;
1505                 else
1506                         move_to_bypass_jobqueue(pcl, qtail, owned_head);
1507         } while (owned_head != Z_EROFS_PCLUSTER_TAIL);
1508
1509         if (bio) {
1510                 submit_bio(bio);
1511                 if (memstall)
1512                         psi_memstall_leave(&pflags);
1513         }
1514
1515         /*
1516          * although background is preferred, no one is pending for submission.
1517          * don't issue workqueue for decompression but drop it directly instead.
1518          */
1519         if (!*force_fg && !nr_bios) {
1520                 kvfree(q[JQ_SUBMIT]);
1521                 return;
1522         }
1523         z_erofs_decompress_kickoff(q[JQ_SUBMIT], *force_fg, nr_bios);
1524 }
1525
1526 static void z_erofs_runqueue(struct z_erofs_decompress_frontend *f,
1527                              struct page **pagepool, bool force_fg)
1528 {
1529         struct z_erofs_decompressqueue io[NR_JOBQUEUES];
1530
1531         if (f->owned_head == Z_EROFS_PCLUSTER_TAIL)
1532                 return;
1533         z_erofs_submit_queue(f, pagepool, io, &force_fg);
1534
1535         /* handle bypass queue (no i/o pclusters) immediately */
1536         z_erofs_decompress_queue(&io[JQ_BYPASS], pagepool);
1537
1538         if (!force_fg)
1539                 return;
1540
1541         /* wait until all bios are completed */
1542         wait_for_completion_io(&io[JQ_SUBMIT].u.done);
1543
1544         /* handle synchronous decompress queue in the caller context */
1545         z_erofs_decompress_queue(&io[JQ_SUBMIT], pagepool);
1546 }
1547
1548 /*
1549  * Since partial uptodate is still unimplemented for now, we have to use
1550  * approximate readmore strategies as a start.
1551  */
1552 static void z_erofs_pcluster_readmore(struct z_erofs_decompress_frontend *f,
1553                                       struct readahead_control *rac,
1554                                       erofs_off_t end,
1555                                       struct page **pagepool,
1556                                       bool backmost)
1557 {
1558         struct inode *inode = f->inode;
1559         struct erofs_map_blocks *map = &f->map;
1560         erofs_off_t cur;
1561         int err;
1562
1563         if (backmost) {
1564                 map->m_la = end;
1565                 err = z_erofs_map_blocks_iter(inode, map,
1566                                               EROFS_GET_BLOCKS_READMORE);
1567                 if (err)
1568                         return;
1569
1570                 /* expend ra for the trailing edge if readahead */
1571                 if (rac) {
1572                         loff_t newstart = readahead_pos(rac);
1573
1574                         cur = round_up(map->m_la + map->m_llen, PAGE_SIZE);
1575                         readahead_expand(rac, newstart, cur - newstart);
1576                         return;
1577                 }
1578                 end = round_up(end, PAGE_SIZE);
1579         } else {
1580                 end = round_up(map->m_la, PAGE_SIZE);
1581
1582                 if (!map->m_llen)
1583                         return;
1584         }
1585
1586         cur = map->m_la + map->m_llen - 1;
1587         while (cur >= end) {
1588                 pgoff_t index = cur >> PAGE_SHIFT;
1589                 struct page *page;
1590
1591                 page = erofs_grab_cache_page_nowait(inode->i_mapping, index);
1592                 if (page) {
1593                         if (PageUptodate(page)) {
1594                                 unlock_page(page);
1595                         } else {
1596                                 err = z_erofs_do_read_page(f, page, pagepool);
1597                                 if (err)
1598                                         erofs_err(inode->i_sb,
1599                                                   "readmore error at page %lu @ nid %llu",
1600                                                   index, EROFS_I(inode)->nid);
1601                         }
1602                         put_page(page);
1603                 }
1604
1605                 if (cur < PAGE_SIZE)
1606                         break;
1607                 cur = (index << PAGE_SHIFT) - 1;
1608         }
1609 }
1610
1611 static int z_erofs_read_folio(struct file *file, struct folio *folio)
1612 {
1613         struct page *page = &folio->page;
1614         struct inode *const inode = page->mapping->host;
1615         struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
1616         struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
1617         struct page *pagepool = NULL;
1618         int err;
1619
1620         trace_erofs_readpage(page, false);
1621         f.headoffset = (erofs_off_t)page->index << PAGE_SHIFT;
1622
1623         z_erofs_pcluster_readmore(&f, NULL, f.headoffset + PAGE_SIZE - 1,
1624                                   &pagepool, true);
1625         err = z_erofs_do_read_page(&f, page, &pagepool);
1626         z_erofs_pcluster_readmore(&f, NULL, 0, &pagepool, false);
1627
1628         (void)z_erofs_collector_end(&f);
1629
1630         /* if some compressed cluster ready, need submit them anyway */
1631         z_erofs_runqueue(&f, &pagepool,
1632                          z_erofs_get_sync_decompress_policy(sbi, 0));
1633
1634         if (err)
1635                 erofs_err(inode->i_sb, "failed to read, err [%d]", err);
1636
1637         erofs_put_metabuf(&f.map.buf);
1638         erofs_release_pages(&pagepool);
1639         return err;
1640 }
1641
1642 static void z_erofs_readahead(struct readahead_control *rac)
1643 {
1644         struct inode *const inode = rac->mapping->host;
1645         struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
1646         struct z_erofs_decompress_frontend f = DECOMPRESS_FRONTEND_INIT(inode);
1647         struct page *pagepool = NULL, *head = NULL, *page;
1648         unsigned int nr_pages;
1649
1650         f.readahead = true;
1651         f.headoffset = readahead_pos(rac);
1652
1653         z_erofs_pcluster_readmore(&f, rac, f.headoffset +
1654                                   readahead_length(rac) - 1, &pagepool, true);
1655         nr_pages = readahead_count(rac);
1656         trace_erofs_readpages(inode, readahead_index(rac), nr_pages, false);
1657
1658         while ((page = readahead_page(rac))) {
1659                 set_page_private(page, (unsigned long)head);
1660                 head = page;
1661         }
1662
1663         while (head) {
1664                 struct page *page = head;
1665                 int err;
1666
1667                 /* traversal in reverse order */
1668                 head = (void *)page_private(page);
1669
1670                 err = z_erofs_do_read_page(&f, page, &pagepool);
1671                 if (err)
1672                         erofs_err(inode->i_sb,
1673                                   "readahead error at page %lu @ nid %llu",
1674                                   page->index, EROFS_I(inode)->nid);
1675                 put_page(page);
1676         }
1677         z_erofs_pcluster_readmore(&f, rac, 0, &pagepool, false);
1678         (void)z_erofs_collector_end(&f);
1679
1680         z_erofs_runqueue(&f, &pagepool,
1681                          z_erofs_get_sync_decompress_policy(sbi, nr_pages));
1682         erofs_put_metabuf(&f.map.buf);
1683         erofs_release_pages(&pagepool);
1684 }
1685
1686 const struct address_space_operations z_erofs_aops = {
1687         .read_folio = z_erofs_read_folio,
1688         .readahead = z_erofs_readahead,
1689 };