lustre/llite/statahead.c

   1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
   2  * vim:expandtab:shiftwidth=8:tabstop=8:
   3  *
   4  *  Copyright (c) 2007 Cluster File Systems, Inc.
   5  *
   6  *   This file is part of Lustre, http://www.lustre.org.
   7  *
   8  *   Lustre is free software; you can redistribute it and/or
   9  *   modify it under the terms of version 2 of the GNU General Public
  10  *   License as published by the Free Software Foundation.
  11  *
  12  *   Lustre is distributed in the hope that it will be useful,
  13  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *   GNU General Public License for more details.
  16  *
  17  *   You should have received a copy of the GNU General Public License
  18  *   along with Lustre; if not, write to the Free Software
  19  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22 #include <linux/fs.h>
  23 #include <linux/sched.h>
  24 #include <linux/mm.h>
  25 #include <linux/smp_lock.h>
  26 #include <linux/highmem.h>
  27 #include <linux/pagemap.h>
  28
  29 #define DEBUG_SUBSYSTEM S_LLITE
  30
  31 #include <obd_support.h>
  32 #include <lustre_lite.h>
  33 #include <lustre_dlm.h>
  34 #include <linux/lustre_version.h>
  35 #include "llite_internal.h"
  36
  37 struct ll_sai_entry {
  38         struct list_head        se_list;
  39         unsigned int            se_index;
  40         int                     se_stat;
  41 };
  42
  43 enum {
  44         SA_ENTRY_UNSTATED = 0,
  45         SA_ENTRY_STATED
  46 };
  47
  48 static unsigned int sai_generation = 0;
  49 static spinlock_t sai_generation_lock = SPIN_LOCK_UNLOCKED;
  50
  51 static struct ll_statahead_info *ll_sai_alloc(void)
  52 {
  53         struct ll_statahead_info *sai;
  54
  55         OBD_ALLOC_PTR(sai);
  56         if (!sai)
  57                 return NULL;
  58
  59         spin_lock(&sai_generation_lock);
  60         sai->sai_generation = ++sai_generation;
  61         if (unlikely(sai_generation == 0))
  62                 sai->sai_generation = ++sai_generation;
  63         spin_unlock(&sai_generation_lock);
  64         atomic_set(&sai->sai_refcount, 1);
  65         sai->sai_max = LL_SA_RPC_MIN;
  66         cfs_waitq_init(&sai->sai_waitq);
  67         cfs_waitq_init(&sai->sai_thread.t_ctl_waitq);
  68         CFS_INIT_LIST_HEAD(&sai->sai_entries);
  69         return sai;
  70 }
  71
  72 static inline
  73 struct ll_statahead_info *ll_sai_get(struct ll_statahead_info *sai)
  74 {
  75         LASSERT(sai);
  76         atomic_inc(&sai->sai_refcount);
  77         return sai;
  78 }
  79
  80 static void ll_sai_put(struct ll_statahead_info *sai)
  81 {
  82         struct inode         *inode = sai->sai_inode;
  83         struct ll_inode_info *lli = ll_i2info(inode);
  84         ENTRY;
  85
  86         if (atomic_dec_and_lock(&sai->sai_refcount, &lli->lli_lock)) {
  87                 struct ll_sai_entry *entry, *next;
  88
  89                 lli->lli_sai = NULL;
  90                 spin_unlock(&lli->lli_lock);
  91
  92                 LASSERT(sai->sai_thread.t_flags & SVC_STOPPED);
  93
  94                 if (sai->sai_sent > sai->sai_replied)
  95                         CDEBUG(D_READA,"statahead for dir %lu/%u does not "
  96                               "finish: [sent:%u] [replied:%u]\n",
  97                               inode->i_ino, inode->i_generation,
  98                               sai->sai_sent, sai->sai_replied);
  99
 100                 list_for_each_entry_safe(entry, next, &sai->sai_entries,
 101                                          se_list) {
 102                         list_del(&entry->se_list);
 103                         OBD_FREE_PTR(entry);
 104                 }
 105                 OBD_FREE_PTR(sai);
 106                 iput(inode);
 107         }
 108         EXIT;
 109 }
 110
 111 static struct ll_sai_entry *
 112 ll_sai_entry_get(struct ll_statahead_info *sai, unsigned int index, int stat)
 113 {
 114         struct ll_inode_info *lli = ll_i2info(sai->sai_inode);
 115         struct ll_sai_entry  *entry;
 116         ENTRY;
 117
 118         OBD_ALLOC_PTR(entry);
 119         if (entry == NULL)
 120                 RETURN(ERR_PTR(-ENOMEM));
 121
 122         CDEBUG(D_READA, "alloc sai entry %p index %u, stat %d\n",
 123                entry, index, stat);
 124         entry->se_index = index;
 125         entry->se_stat  = stat;
 126
 127         spin_lock(&lli->lli_lock);
 128         list_add_tail(&entry->se_list, &sai->sai_entries);
 129         spin_unlock(&lli->lli_lock);
 130
 131         RETURN(entry);
 132 }
 133
 134 /*
 135  * inside lli_lock
 136  * return value:
 137  *  0: can not find the entry with the index
 138  *  1: it is the first entry
 139  *  2: it is not the first entry
 140  */
 141 static int
 142 ll_sai_entry_set(struct ll_statahead_info *sai, unsigned int index, int stat)
 143 {
 144         struct ll_sai_entry *entry;
 145         int                  rc = 0;
 146         ENTRY;
 147
 148         if (list_empty(&sai->sai_entries))
 149                 RETURN(0);
 150
 151         entry = list_entry(sai->sai_entries.next, struct ll_sai_entry, se_list);
 152         if (entry->se_index == index)
 153                 GOTO(out, rc = 1);
 154
 155         while (entry->se_list.next != &sai->sai_entries &&
 156                entry->se_index < index) {
 157                 entry = list_entry(entry->se_list.next, struct ll_sai_entry,
 158                                    se_list);
 159                 if (entry->se_index == index)
 160                         GOTO(out, rc = 2);
 161         }
 162
 163         EXIT;
 164
 165 out:
 166         if (rc) {
 167                 LASSERT(entry->se_stat == SA_ENTRY_UNSTATED);
 168                 entry->se_stat = stat;
 169         }
 170
 171         return rc;
 172 }
 173
 174 /*
 175  * Check whether first entry was stated already or not.
 176  * No need to hold lli_lock, for:
 177  * (1) it is me that remove entry from the list
 178  * (2) the statahead thread only add new entry to the list tail
 179  */
 180 static int ll_sai_entry_stated(struct ll_statahead_info *sai)
 181 {
 182         struct ll_sai_entry  *entry;
 183         int                   rc = 0;
 184         ENTRY;
 185
 186         if (!list_empty(&sai->sai_entries)) {
 187                 entry = list_entry(sai->sai_entries.next, struct ll_sai_entry,
 188                                    se_list);
 189                 rc = (entry->se_stat != SA_ENTRY_UNSTATED);
 190         }
 191
 192         RETURN(rc);
 193 }
 194
 195 static void ll_sai_entry_put(struct ll_statahead_info *sai)
 196 {
 197         struct ll_inode_info *lli = ll_i2info(sai->sai_inode);
 198         struct ll_sai_entry  *entry;
 199         ENTRY;
 200
 201         spin_lock(&lli->lli_lock);
 202         if (!list_empty(&sai->sai_entries)) {
 203                 entry = list_entry(sai->sai_entries.next,
 204                                    struct ll_sai_entry, se_list);
 205                 list_del(&entry->se_list);
 206                 OBD_FREE_PTR(entry);
 207         }
 208         spin_unlock(&lli->lli_lock);
 209
 210         EXIT;
 211 }
 212
 213 /* finish lookup/revalidate */
 214 static int ll_statahead_interpret(struct obd_export *exp,
 215                                   struct ptlrpc_request *req,
 216                                   struct md_enqueue_info *minfo,
 217                                   int rc)
 218 {
 219         struct lookup_intent     *it = &minfo->mi_it;
 220         struct dentry            *dentry = minfo->mi_dentry;
 221         struct inode             *dir = dentry->d_parent->d_inode;
 222         struct ll_inode_info     *lli = ll_i2info(dir);
 223         struct ll_statahead_info *sai = NULL;
 224         ENTRY;
 225
 226         CDEBUG(D_READA, "interpret statahead %.*s rc %d\n",
 227                dentry->d_name.len, dentry->d_name.name, rc);
 228
 229         spin_lock(&lli->lli_lock);
 230         if (unlikely(lli->lli_sai == NULL ||
 231             lli->lli_sai->sai_generation != minfo->mi_generation)) {
 232                 spin_unlock(&lli->lli_lock);
 233                 GOTO(out_free, rc = -ESTALE);
 234         } else {
 235                 sai = ll_sai_get(lli->lli_sai);
 236                 spin_unlock(&lli->lli_lock);
 237         }
 238
 239         if (rc || dir == NULL)
 240                 GOTO(out, rc);
 241
 242         if (dentry->d_inode == NULL) {
 243                 /* lookup */
 244                 struct dentry    *save = dentry;
 245                 struct it_cb_data icbd = {
 246                         .icbd_parent   = dir,
 247                         .icbd_childp   = &dentry
 248                 };
 249
 250                 rc = lookup_it_finish(req, DLM_REPLY_REC_OFF, it, &icbd);
 251                 if (!rc)
 252                         /*
 253                          * Here dentry->d_inode might be NULL,
 254                          * because the entry may have been removed before
 255                          * we start doing stat ahead.
 256                          */
 257                         ll_lookup_finish_locks(it, dentry);
 258
 259                 if (dentry != save)
 260                         dput(save);
 261         } else {
 262                 /* revalidate */
 263                 struct mds_body *body;
 264
 265                 body = lustre_msg_buf(req->rq_repmsg, DLM_REPLY_REC_OFF,
 266                                       sizeof(*body));
 267                 if (memcmp(&minfo->mi_data.fid2, &body->fid1,
 268                            sizeof(body->fid1))) {
 269                         ll_unhash_aliases(dentry->d_inode);
 270                         GOTO(out, rc = -EAGAIN);
 271                 }
 272
 273                 rc = revalidate_it_finish(req, DLM_REPLY_REC_OFF, it, dentry);
 274                 if (rc) {
 275                         ll_unhash_aliases(dentry->d_inode);
 276                         GOTO(out, rc);
 277                 }
 278
 279                 spin_lock(&dcache_lock);
 280                 lock_dentry(dentry);
 281                 __d_drop(dentry);
 282 #ifdef DCACHE_LUSTRE_INVALID
 283                 dentry->d_flags &= ~DCACHE_LUSTRE_INVALID;
 284 #endif
 285                 unlock_dentry(dentry);
 286                 d_rehash_cond(dentry, 0);
 287                 spin_unlock(&dcache_lock);
 288
 289                 ll_lookup_finish_locks(it, dentry);
 290         }
 291         EXIT;
 292
 293 out:
 294         if (sai != NULL) {
 295                 int first;
 296
 297                 sai->sai_replied++;
 298                 spin_lock(&lli->lli_lock);
 299                 first = ll_sai_entry_set(sai,
 300                                          (unsigned int)(long)minfo->mi_cbdata,
 301                                          SA_ENTRY_STATED);
 302                 /*
 303                  * wake up the "ls -l" process only when the first entry
 304                  * returned.
 305                  */
 306                 spin_unlock(&lli->lli_lock);
 307                 if (first == 1)
 308                         cfs_waitq_signal(&sai->sai_waitq);
 309                 else if (first == 0)
 310                         CDEBUG(D_READA, "can't find sai entry for dir "
 311                                "%lu/%u generation %u index %d\n",
 312                                dir->i_ino, dir->i_generation,
 313                                minfo->mi_generation,
 314                                (unsigned int)(long)minfo->mi_cbdata);
 315
 316                 ll_sai_put(sai);
 317         }
 318 out_free:
 319         ll_intent_release(it);
 320         OBD_FREE_PTR(minfo);
 321
 322         dput(dentry);
 323         return rc;
 324 }
 325
 326 static void sa_args_fini(struct md_enqueue_info *minfo,
 327                          struct ldlm_enqueue_info *einfo)
 328 {
 329         LASSERT(minfo && einfo);
 330         OBD_FREE_PTR(minfo);
 331         OBD_FREE_PTR(einfo);
 332 }
 333
 334 static int sa_args_prep(struct inode *dir, struct dentry *dentry,
 335                         struct md_enqueue_info **pmi,
 336                         struct ldlm_enqueue_info **pei)
 337 {
 338         struct ll_inode_info     *lli = ll_i2info(dir);
 339         struct md_enqueue_info   *minfo;
 340         struct ldlm_enqueue_info *einfo;
 341
 342         OBD_ALLOC_PTR(einfo);
 343         if (einfo == NULL)
 344                 return -ENOMEM;
 345
 346         OBD_ALLOC_PTR(minfo);
 347         if (minfo == NULL) {
 348                 OBD_FREE_PTR(einfo);
 349                 return -ENOMEM;
 350         }
 351
 352         minfo->mi_exp = ll_i2mdcexp(dir);
 353         minfo->mi_it.it_op = IT_GETATTR;
 354         minfo->mi_dentry = dentry;
 355         minfo->mi_cb = ll_statahead_interpret;
 356         minfo->mi_generation = lli->lli_sai->sai_generation;
 357         minfo->mi_cbdata = (void *)(long)lli->lli_sai->sai_index;
 358
 359         einfo->ei_type   = LDLM_IBITS;
 360         einfo->ei_mode   = it_to_lock_mode(&minfo->mi_it);
 361         einfo->ei_cb_bl  = ll_mdc_blocking_ast;
 362         einfo->ei_cb_cp  = ldlm_completion_ast;
 363         einfo->ei_cb_gl  = NULL;
 364         einfo->ei_cbdata = NULL;
 365
 366         *pmi = minfo;
 367         *pei = einfo;
 368
 369         return 0;
 370 }
 371
 372 /* similar to ll_lookup_it(). */
 373 static int do_sa_lookup(struct inode *dir, struct dentry *dentry)
 374 {
 375         struct md_enqueue_info   *minfo;
 376         struct ldlm_enqueue_info *einfo;
 377         int                       rc;
 378         ENTRY;
 379
 380         rc = sa_args_prep(dir, dentry, &minfo, &einfo);
 381         if (rc)
 382                 RETURN(rc);
 383
 384         rc = ll_prepare_mdc_op_data(&minfo->mi_data, dir, NULL,
 385                                     dentry->d_name.name, dentry->d_name.len, 0,
 386                                     NULL);
 387         if (rc == 0)
 388                 rc = mdc_intent_getattr_async(minfo->mi_exp, minfo, einfo);
 389
 390         if (rc)
 391                 sa_args_fini(minfo, einfo);
 392
 393         RETURN(rc);
 394 }
 395
 396 /*
 397  * similar to ll_revalidate_it().
 398  * return value:
 399  *  1      -- dentry valid
 400  *  0      -- will send stat-ahead request
 401  *  others -- prepare stat-ahead request failed
 402  */
 403 static int do_sa_revalidate(struct dentry *dentry)
 404 {
 405         struct inode             *inode = dentry->d_inode;
 406         struct ll_fid             fid;
 407         struct lookup_intent      it = { .it_op = IT_GETATTR };
 408         struct md_enqueue_info   *minfo;
 409         struct ldlm_enqueue_info *einfo;
 410         int rc;
 411         ENTRY;
 412
 413         if (inode == NULL)
 414                 RETURN(1);
 415
 416         if (d_mountpoint(dentry))
 417                 RETURN(1);
 418
 419         if (dentry == dentry->d_sb->s_root)
 420                 RETURN(1);
 421
 422         ll_inode2fid(&fid, inode);
 423
 424         rc = mdc_revalidate_lock(ll_i2mdcexp(inode), &it, &fid);
 425         if (rc == 1) {
 426                 ll_intent_release(&it);
 427                 RETURN(1);
 428         }
 429
 430         rc = sa_args_prep(dentry->d_parent->d_inode, dentry, &minfo, &einfo);
 431         if (rc)
 432                 RETURN(rc);
 433
 434         rc = ll_prepare_mdc_op_data(&minfo->mi_data, dentry->d_parent->d_inode,
 435                                     inode, dentry->d_name.name,
 436                                     dentry->d_name.len, 0, NULL);
 437         if (rc == 0)
 438                 rc = mdc_intent_getattr_async(minfo->mi_exp, minfo, einfo);
 439
 440         if (rc)
 441                 sa_args_fini(minfo, einfo);
 442
 443         RETURN(rc);
 444 }
 445
 446 static inline void ll_name2qstr(struct qstr *this, const char *name, int namelen)
 447 {
 448         unsigned long hash = init_name_hash();
 449         unsigned int  c;
 450
 451         this->name = name;
 452         this->len  = namelen;
 453         for (; namelen > 0; namelen--, name++) {
 454                 c = *(const unsigned char *)name;
 455                 hash = partial_name_hash(c, hash);
 456         }
 457         this->hash = end_name_hash(hash);
 458 }
 459
 460 static int ll_statahead_one(struct dentry *parent, ext2_dirent *de)
 461 {
 462         struct inode           *dir = parent->d_inode;
 463         struct ll_inode_info   *lli = ll_i2info(dir);
 464         struct qstr             name;
 465         struct dentry          *dentry;
 466         struct ll_sai_entry    *se;
 467         int                     rc;
 468         ENTRY;
 469
 470 #ifdef DCACHE_LUSTRE_INVALID
 471         if (parent->d_flags & DCACHE_LUSTRE_INVALID) {
 472 #else
 473         if (d_unhashed(parent)) {
 474 #endif
 475                 CDEBUG(D_READA, "parent dentry@%p %.*s is "
 476                        "invalid, skip statahead\n",
 477                        parent, parent->d_name.len, parent->d_name.name);
 478                 RETURN(-EINVAL);
 479         }
 480
 481         se = ll_sai_entry_get(lli->lli_sai, lli->lli_sai->sai_index,
 482                               SA_ENTRY_UNSTATED);
 483         if (IS_ERR(se))
 484                 RETURN(PTR_ERR(se));
 485
 486         ll_name2qstr(&name, de->name, de->name_len);
 487         dentry = d_lookup(parent, &name);
 488         if (!dentry) {
 489                 dentry = d_alloc(parent, &name);
 490                 if (dentry) {
 491                         rc = do_sa_lookup(dir, dentry);
 492                         if (rc)
 493                                 dput(dentry);
 494                 } else {
 495                         GOTO(out, rc = -ENOMEM);
 496                 }
 497         } else {
 498                 rc = do_sa_revalidate(dentry);
 499                 if (rc)
 500                         dput(dentry);
 501         }
 502
 503         EXIT;
 504
 505 out:
 506         if (rc) {
 507                 CDEBUG(D_READA, "set sai entry %p index %u stat %d rc %d\n",
 508                        se, se->se_index, se->se_stat, rc);
 509                 se->se_stat = rc;
 510                 cfs_waitq_signal(&lli->lli_sai->sai_waitq);
 511         } else {
 512                 lli->lli_sai->sai_sent++;
 513         }
 514
 515         lli->lli_sai->sai_index++;
 516         return rc;
 517 }
 518
 519 static inline int sa_check_stop(struct ll_statahead_info *sai)
 520 {
 521         return !!(sai->sai_thread.t_flags & SVC_STOPPING);
 522 }
 523
 524 static inline int sa_not_full(struct ll_statahead_info *sai)
 525 {
 526         return sai->sai_index < sai->sai_hit + sai->sai_miss + sai->sai_max;
 527 }
 528
 529 /* (1) hit ratio less than 80%
 530  * or
 531  * (2) consecutive miss more than 8
 532  */
 533 static inline int sa_low_hit(struct ll_statahead_info *sai)
 534 {
 535         return ((sai->sai_hit < 4 * sai->sai_miss && sai->sai_hit > 7) ||
 536                 (sai->sai_consecutive_miss > 8));
 537 }
 538
 539 struct ll_sa_thread_args {
 540         struct dentry   *sta_parent;
 541         pid_t            sta_pid;
 542 };
 543
 544 static int ll_statahead_thread(void *arg)
 545 {
 546         struct ll_sa_thread_args *sta = arg;
 547         struct dentry            *parent = dget(sta->sta_parent);
 548         struct inode             *dir = parent->d_inode;
 549         struct ll_inode_info     *lli = ll_i2info(dir);
 550         struct ll_sb_info        *sbi = ll_i2sbi(dir);
 551         struct ll_statahead_info *sai = ll_sai_get(lli->lli_sai);
 552         struct ptlrpc_thread     *thread = &sai->sai_thread;
 553         unsigned long             index = 0;
 554         int                       first = 0;
 555         int                       rc = 0;
 556         char                      name[16] = "";
 557         ENTRY;
 558
 559         sbi->ll_sa_total++;
 560         snprintf(name, 15, "ll_sa_%u", sta->sta_pid);
 561         cfs_daemonize(name);
 562         spin_lock(&lli->lli_lock);
 563         thread->t_flags = SVC_RUNNING;
 564         spin_unlock(&lli->lli_lock);
 565         cfs_waitq_signal(&thread->t_ctl_waitq);
 566         CDEBUG(D_READA, "start doing statahead for %s\n", parent->d_name.name);
 567
 568         while (1) {
 569                 struct l_wait_info lwi = { 0 };
 570                 unsigned long npages;
 571                 char *kaddr, *limit;
 572                 ext2_dirent *de;
 573                 struct page *page;
 574
 575                 npages = dir_pages(dir);
 576                 /* reach the end of dir */
 577                 if (index >= npages) {
 578                         CDEBUG(D_READA, "reach end, index/npages %lu/%lu\n",
 579                                index, npages);
 580                         break;
 581                 }
 582
 583                 page = ll_get_dir_page(dir, index);
 584                 if (IS_ERR(page)) {
 585                         rc = PTR_ERR(page);
 586                         CERROR("error reading dir %lu/%u page %lu/%u: rc %d\n",
 587                                dir->i_ino, dir->i_generation, index,
 588                                sai->sai_index, rc);
 589                         break;
 590                 }
 591
 592                 kaddr = page_address(page);
 593                 limit = kaddr + CFS_PAGE_SIZE - EXT2_DIR_REC_LEN(1);
 594                 de = (ext2_dirent *)kaddr;
 595                 if (!index) {
 596                         de = ext2_next_entry(de); /* skip "." */
 597                         de = ext2_next_entry(de); /* skip ".." */
 598                 }
 599
 600                 for (; (char*)de <= limit; de = ext2_next_entry(de)) {
 601                         if (!de->inode)
 602                                 continue;
 603
 604                         if (de->name[0] == '.' && !sai->sai_ls_all) {
 605                                 /* skip hidden files */
 606                                 sai->sai_skip_hidden++;
 607                                 continue;
 608                         }
 609
 610                         /* don't stat-ahead first entry */
 611                         if (unlikely(!first)) {
 612                                 first++;
 613                                 continue;
 614                         }
 615
 616                         l_wait_event(thread->t_ctl_waitq,
 617                                      sa_check_stop(sai) || sa_not_full(sai),
 618                                      &lwi);
 619
 620                         if (unlikely(sa_check_stop(sai))) {
 621                                 ext2_put_page(page);
 622                                 GOTO(out, rc);
 623                         }
 624
 625                         rc = ll_statahead_one(parent, de);
 626                         if (rc < 0) {
 627                                 ext2_put_page(page);
 628                                 GOTO(out, rc);
 629                         }
 630                 }
 631                 ext2_put_page(page);
 632                 index++;
 633         }
 634         EXIT;
 635 out:
 636         spin_lock(&lli->lli_lock);
 637         thread->t_flags = SVC_STOPPED;
 638         spin_unlock(&lli->lli_lock);
 639         cfs_waitq_signal(&sai->sai_waitq);
 640         cfs_waitq_signal(&thread->t_ctl_waitq);
 641         ll_sai_put(sai);
 642         dput(parent);
 643         CDEBUG(D_READA, "statahead thread stopped, pid %d\n",
 644                cfs_curproc_pid());
 645         return rc;
 646 }
 647
 648 /* called in ll_file_release() */
 649 void ll_stop_statahead(struct inode *inode, void *key)
 650 {
 651         struct ll_inode_info *lli = ll_i2info(inode);
 652         struct ptlrpc_thread *thread;
 653
 654         spin_lock(&lli->lli_lock);
 655         if (lli->lli_opendir_pid == 0 ||
 656             unlikely(lli->lli_opendir_key != key)) {
 657                 spin_unlock(&lli->lli_lock);
 658                 return;
 659         }
 660
 661         lli->lli_opendir_key = NULL;
 662         lli->lli_opendir_pid = 0;
 663
 664         if (lli->lli_sai) {
 665                 struct l_wait_info lwi = { 0 };
 666
 667                 thread = &lli->lli_sai->sai_thread;
 668                 if (!(thread->t_flags & SVC_STOPPED)) {
 669                         thread->t_flags = SVC_STOPPING;
 670                         spin_unlock(&lli->lli_lock);
 671                         cfs_waitq_signal(&thread->t_ctl_waitq);
 672
 673                         CDEBUG(D_READA, "stopping statahead thread, pid %d\n",
 674                                cfs_curproc_pid());
 675                         l_wait_event(thread->t_ctl_waitq,
 676                                      thread->t_flags & SVC_STOPPED,
 677                                      &lwi);
 678                 } else {
 679                         spin_unlock(&lli->lli_lock);
 680                 }
 681
 682                 /*
 683                  * Put the ref which was held when first statahead_enter.
 684                  * It maybe not the last ref for some statahead requests
 685                  * maybe inflight.
 686                  */
 687                 ll_sai_put(lli->lli_sai);
 688                 return;
 689         }
 690         spin_unlock(&lli->lli_lock);
 691 }
 692
 693 enum {
 694         LS_NONE_FIRST_DE = 0,   /* not first dirent, or is "." */
 695         LS_FIRST_DE,            /* the first non-hidden dirent */
 696         LS_FIRST_DOT_DE         /* the first hidden dirent, that is ".xxx" */
 697 };
 698
 699 static int is_first_dirent(struct inode *dir, struct dentry *dentry)
 700 {
 701         struct qstr   *d_name = &dentry->d_name;
 702         unsigned long  npages, index = 0;
 703         struct page   *page;
 704         ext2_dirent   *de;
 705         char          *kaddr, *limit;
 706         int            rc = LS_NONE_FIRST_DE, dot_de;
 707         ENTRY;
 708
 709         while (1) {
 710                 npages = dir_pages(dir);
 711                 /* reach the end of dir */
 712                 if (index >= npages) {
 713                         CDEBUG(D_READA, "reach end, index/npages %lu/%lu\n",
 714                                index, npages);
 715                         break;
 716                 }
 717
 718                 page = ll_get_dir_page(dir, index);
 719                 if (IS_ERR(page)) {
 720                         rc = PTR_ERR(page);
 721                         CERROR("error reading dir %lu/%u page %lu: rc %d\n",
 722                                dir->i_ino, dir->i_generation, index, rc);
 723                         break;
 724                 }
 725
 726                 kaddr = page_address(page);
 727                 limit = kaddr + CFS_PAGE_SIZE - EXT2_DIR_REC_LEN(1);
 728                 de = (ext2_dirent *)kaddr;
 729                 if (!index) {
 730                         de = ext2_next_entry(de); /* skip "." */
 731                         de = ext2_next_entry(de); /* skip ".." */
 732                 }
 733
 734                 for (; (char*)de <= limit; de = ext2_next_entry(de)) {
 735                         if (!de->inode)
 736                                 continue;
 737
 738                         if (de->name[0] == '.')
 739                                 dot_de = 1;
 740                         else
 741                                 dot_de = 0;
 742
 743                         if (dot_de && d_name->name[0] != '.') {
 744                                 CDEBUG(D_READA, "%.*s skip hidden file %.*s\n",
 745                                        d_name->len, d_name->name,
 746                                        de->name_len, de->name);
 747                                 continue;
 748                         }
 749
 750                         if (d_name->len == de->name_len &&
 751                             !strncmp(d_name->name, de->name, d_name->len))
 752                                 rc = LS_FIRST_DE + dot_de;
 753                         else
 754                                 rc = LS_NONE_FIRST_DE;
 755                         ext2_put_page(page);
 756                         RETURN(rc);
 757                 }
 758                 ext2_put_page(page);
 759                 index++;
 760         }
 761         RETURN(rc);
 762 }
 763
 764 /* Start statahead thread if this is the first dir entry.
 765  * Otherwise if a thread is started already, wait it until it is ahead of me.
 766  * Return value:
 767  *  0       -- miss
 768  *  1       -- hit
 769  *  -EEXIST -- stat ahead thread started, and this is the first dentry
 770  *  -EBADFD -- statahead thread exit and not dentry available
 771  *  others  -- error
 772  */
 773 int do_statahead_enter(struct inode *dir, struct dentry **dentryp, int lookup)
 774 {
 775         struct ll_sb_info        *sbi = ll_i2sbi(dir);
 776         struct ll_inode_info     *lli = ll_i2info(dir);
 777         struct ll_statahead_info *sai = lli->lli_sai;
 778         struct ll_sa_thread_args  sta;
 779         struct l_wait_info        lwi = { 0 };
 780         int                       rc;
 781         ENTRY;
 782
 783         LASSERT(lli->lli_opendir_pid == cfs_curproc_pid());
 784
 785         if (sai) {
 786                 if (unlikely(sai->sai_thread.t_flags & SVC_STOPPED &&
 787                              list_empty(&sai->sai_entries)))
 788                         RETURN(-EBADFD);
 789
 790                 if ((*dentryp)->d_name.name[0] == '.') {
 791                         if (likely(sai->sai_ls_all ||
 792                             sai->sai_miss_hidden >= sai->sai_skip_hidden)) {
 793                                 /*
 794                                  * Hidden dentry is the first one, or statahead
 795                                  * thread does not skip so many hidden dentries
 796                                  * before "sai_ls_all" enabled as below.
 797                                  */
 798                         } else {
 799                                 if (!sai->sai_ls_all)
 800                                         /*
 801                                          * It maybe because hidden dentry is not
 802                                          * the first one, "sai_ls_all" was not
 803                                          * set, then "ls -al" missed. Enable
 804                                          * "sai_ls_all" for such case.
 805                                          */
 806                                         sai->sai_ls_all = 1;
 807
 808                                 /*
 809                                  * Such "getattr" has been skipped before
 810                                  * "sai_ls_all" enabled as above.
 811                                  */
 812                                 sai->sai_miss_hidden++;
 813                                 RETURN(-ENOENT);
 814                         }
 815                 }
 816
 817                 if (ll_sai_entry_stated(sai)) {
 818                         sbi->ll_sa_cached++;
 819                 } else {
 820                         sbi->ll_sa_blocked++;
 821                         /* thread started already, avoid double-stat */
 822                         l_wait_event(sai->sai_waitq,
 823                                      ll_sai_entry_stated(sai) ||
 824                                      sai->sai_thread.t_flags & SVC_STOPPED,
 825                                      &lwi);
 826                 }
 827
 828                 if (lookup) {
 829                         struct dentry *result;
 830
 831                         result = d_lookup((*dentryp)->d_parent,
 832                                           &(*dentryp)->d_name);
 833                         if (result) {
 834                                 LASSERT(result != *dentryp);
 835                                 dput(*dentryp);
 836                                 *dentryp = result;
 837                                 RETURN(1);
 838                         }
 839                 }
 840                 /* do nothing for revalidate */
 841                 RETURN(0);
 842         }
 843
 844          /* I am the "lli_opendir_pid" owner, only me can set "lli_sai". */
 845         LASSERT(lli->lli_sai == NULL);
 846
 847         rc = is_first_dirent(dir, *dentryp);
 848         if (rc == LS_NONE_FIRST_DE) {
 849                 /* It is not "ls -{a}l" operation, no need statahead for it */
 850                 spin_lock(&lli->lli_lock);
 851                 lli->lli_opendir_key = NULL;
 852                 lli->lli_opendir_pid = 0;
 853                 spin_unlock(&lli->lli_lock);
 854                 RETURN(-EBADF);
 855         }
 856
 857         sai = ll_sai_alloc();
 858         if (sai == NULL)
 859                 RETURN(-ENOMEM);
 860
 861         sai->sai_inode  = igrab(dir);
 862         sai->sai_ls_all = (rc == LS_FIRST_DOT_DE);
 863
 864         sta.sta_parent = (*dentryp)->d_parent;
 865         sta.sta_pid    = cfs_curproc_pid();
 866
 867         lli->lli_sai = sai;
 868         rc = cfs_kernel_thread(ll_statahead_thread, &sta, 0);
 869         if (rc < 0) {
 870                 CERROR("can't start ll_sa thread, rc: %d\n", rc);
 871                 sai->sai_thread.t_flags = SVC_STOPPED;
 872                 ll_sai_put(sai);
 873                 LASSERT(lli->lli_sai == NULL);
 874                 RETURN(rc);
 875         }
 876
 877         l_wait_event(sai->sai_thread.t_ctl_waitq,
 878                      sai->sai_thread.t_flags & (SVC_RUNNING | SVC_STOPPED),
 879                      &lwi);
 880
 881         /*
 882          * We don't stat-ahead for the first dirent since we are already in
 883          * lookup, and -EEXIST also indicates that this is the first dirent.
 884          */
 885         RETURN(-EEXIST);
 886 }
 887
 888 /* update hit/miss count */
 889 void ll_statahead_exit(struct dentry *dentry, int result)
 890 {
 891         struct dentry         *parent = dentry->d_parent;
 892         struct ll_inode_info  *lli = ll_i2info(parent->d_inode);
 893         struct ll_sb_info     *sbi = ll_i2sbi(parent->d_inode);
 894         struct ll_dentry_data *ldd = ll_d2d(dentry);
 895
 896         if (lli->lli_opendir_pid != cfs_curproc_pid())
 897                 return;
 898
 899         if (lli->lli_sai) {
 900                 struct ll_statahead_info *sai = lli->lli_sai;
 901
 902                 if (result == 1) {
 903                         sbi->ll_sa_hit++;
 904                         sai->sai_hit++;
 905                         sai->sai_consecutive_miss = 0;
 906                         sai->sai_max = min(2 * sai->sai_max, sbi->ll_sa_max);
 907                 } else {
 908                         sbi->ll_sa_miss++;
 909                         sai->sai_miss++;
 910                         sai->sai_consecutive_miss++;
 911                         if (sa_low_hit(sai)) {
 912                                 sbi->ll_sa_wrong++;
 913                                 CDEBUG(D_READA, "statahead for dir %.*s hit "
 914                                        "ratio too low: hit/miss %u/%u, "
 915                                        "sent/replied %u/%u. stopping statahead "
 916                                        "thread: pid %d\n",
 917                                        parent->d_name.len, parent->d_name.name,
 918                                        sai->sai_hit, sai->sai_miss,
 919                                        sai->sai_sent, sai->sai_replied,
 920                                        cfs_curproc_pid());
 921                                 spin_lock(&lli->lli_lock);
 922                                 if (!(sai->sai_thread.t_flags & SVC_STOPPED))
 923                                         sai->sai_thread.t_flags = SVC_STOPPING;
 924                                 spin_unlock(&lli->lli_lock);
 925                         }
 926                 }
 927
 928                 cfs_waitq_signal(&sai->sai_thread.t_ctl_waitq);
 929                 ll_sai_entry_put(sai);
 930
 931                 if (likely(ldd != NULL))
 932                         ldd->lld_sa_generation = sai->sai_generation;
 933         }
 934 }