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         int                     se_index;
  40         int                     se_stat;
  41 };
  42
  43 enum {
  44         SA_ENTRY_UNSTATED = 0,
  45         SA_ENTRY_STATED
  46 };
  47
  48 static struct ll_statahead_info *ll_sai_alloc(void)
  49 {
  50         struct ll_statahead_info *sai;
  51
  52         OBD_ALLOC_PTR(sai);
  53         if (!sai)
  54                 return NULL;
  55
  56         sai->sai_max = LL_STATAHEAD_MIN;
  57         cfs_waitq_init(&sai->sai_thread.t_ctl_waitq);
  58         CFS_INIT_LIST_HEAD(&sai->sai_entries);
  59         atomic_set(&sai->sai_refc, 1);
  60         return sai;
  61 }
  62
  63 static inline
  64 struct ll_statahead_info *ll_sai_get(struct ll_statahead_info *sai)
  65 {
  66         LASSERT(sai);
  67         atomic_inc(&sai->sai_refc);
  68         return sai;
  69 }
  70
  71 static void ll_sai_put(struct ll_statahead_info *sai)
  72 {
  73         struct inode *inode = sai->sai_inode;
  74         struct ll_inode_info *lli = ll_i2info(inode);
  75         ENTRY;
  76
  77         if (atomic_dec_and_lock(&sai->sai_refc, &lli->lli_lock)) {
  78                 struct ll_sai_entry  *entry, *next;
  79
  80                 list_for_each_entry_safe(entry, next, &sai->sai_entries,
  81                                          se_list) {
  82                         list_del(&entry->se_list);
  83                         OBD_FREE_PTR(entry);
  84                 }
  85                 OBD_FREE_PTR(sai);
  86                 lli->lli_sai = NULL;
  87                 spin_unlock(&lli->lli_lock);
  88                 iput(inode);
  89         }
  90         EXIT;
  91 }
  92
  93 static struct ll_sai_entry *ll_sai_entry_get(struct ll_statahead_info *sai,
  94                                              int index, int stat)
  95 {
  96         struct ll_inode_info *lli = ll_i2info(sai->sai_inode);
  97         struct ll_sb_info    *sbi = ll_i2sbi(sai->sai_inode);
  98         struct ll_sai_entry  *entry;
  99         ENTRY;
 100
 101         OBD_ALLOC_PTR(entry);
 102         if (entry == NULL)
 103                 RETURN(NULL);
 104
 105         CDEBUG(D_READA, "alloc sai entry %p index %d, stat %d\n",
 106                entry, index, stat);
 107         entry->se_index = index;
 108         entry->se_stat  = stat;
 109
 110         spin_lock(&lli->lli_lock);
 111         list_add_tail(&entry->se_list, &sai->sai_entries);
 112         sai->sai_entries_nr++;
 113         sbi->ll_sa_count = sai->sai_entries_nr;
 114         spin_unlock(&lli->lli_lock);
 115
 116         LASSERT(sai->sai_entries_nr <= sbi->ll_sa_max);
 117         RETURN(entry);
 118 }
 119
 120 /* inside lli_lock */
 121 static void ll_sai_entry_set(struct ll_statahead_info *sai, int index,
 122                              int stat)
 123 {
 124         struct ll_sai_entry *entry;
 125         ENTRY;
 126
 127         list_for_each_entry(entry, &sai->sai_entries, se_list) {
 128                 if (entry->se_index == index) {
 129                         LASSERT(entry->se_stat == SA_ENTRY_UNSTATED);
 130                         entry->se_stat = stat;
 131                         CDEBUG(D_READA, "set sai entry %p index %d stat %d\n",
 132                                entry, index, stat);
 133                         EXIT;
 134                         return;
 135                 }
 136         }
 137         /* Sometimes, this happens when entry has been put and freed */
 138         CDEBUG(D_READA, "can't find sai entry index %d\n", index);
 139         EXIT;
 140 }
 141
 142 /* check first entry was stated already */
 143 static int ll_sai_entry_stated(struct ll_statahead_info *sai)
 144 {
 145         struct ll_inode_info *lli = ll_i2info(sai->sai_inode);
 146         struct ll_sai_entry  *entry;
 147         int                   rc = 0;
 148         ENTRY;
 149
 150         spin_lock(&lli->lli_lock);
 151         if (!list_empty(&sai->sai_entries)) {
 152                 entry = list_entry(sai->sai_entries.next, struct ll_sai_entry,
 153                                    se_list);
 154                 CDEBUG(D_READA, "check sai entry %p index %d stat %d\n",
 155                        entry, entry->se_index, entry->se_stat);
 156                 rc = (entry->se_stat != SA_ENTRY_UNSTATED);
 157         }
 158         spin_unlock(&lli->lli_lock);
 159
 160         RETURN(rc);
 161 }
 162
 163 /* inside lli_lock */
 164 static void ll_sai_entry_put(struct ll_statahead_info *sai)
 165 {
 166         struct ll_sai_entry  *entry;
 167         ENTRY;
 168
 169         if (list_empty(&sai->sai_entries)) {
 170                 EXIT;
 171                 return;
 172         }
 173         LASSERT(sai->sai_entries_nr > 0);
 174
 175         entry = list_entry(sai->sai_entries.next, struct ll_sai_entry, se_list);
 176         list_del(&entry->se_list);
 177         sai->sai_entries_nr--;
 178
 179         CDEBUG(D_READA, "free sa entry %p index %d stat %d\n",
 180                entry, entry->se_index, entry->se_stat);
 181         OBD_FREE_PTR(entry);
 182         EXIT;
 183 }
 184
 185 /* finish lookup/revalidate */
 186 static int ll_statahead_interpret(struct obd_export *exp,
 187                                   struct ptlrpc_request *req,
 188                                   struct md_enqueue_info *minfo,
 189                                   int rc)
 190 {
 191         struct lookup_intent     *it = &minfo->mi_it;
 192         struct dentry            *dentry = minfo->mi_dentry;
 193         struct inode             *dir = dentry->d_parent->d_inode;
 194         struct ll_inode_info     *lli = ll_i2info(dir);
 195         struct ll_statahead_info *sai;
 196         ENTRY;
 197
 198         CDEBUG(D_READA, "interpret statahead %.*s rc %d\n",
 199                dentry->d_name.len, dentry->d_name.name, rc);
 200         if (rc || dir == NULL)
 201                 GOTO(out, rc);
 202
 203         if (dentry->d_inode == NULL) {
 204                 /* lookup */
 205                 struct dentry    *save = dentry;
 206                 struct it_cb_data icbd = {
 207                         .icbd_parent = dir,
 208                         .icbd_childp = &dentry
 209                 };
 210
 211                 rc = lookup_it_finish(req, DLM_REPLY_REC_OFF, it, &icbd);
 212                 if (!rc) {
 213                         /*
 214                          * Here dentry->d_inode might be NULL,
 215                          * because the entry may have been removed before
 216                          * we start doing stat ahead.
 217                          */
 218                         if (dentry != save)
 219                                 dput(save);
 220                         ll_lookup_finish_locks(it, dentry);
 221                 }
 222         } else {
 223                 /* revalidate */
 224                 struct mds_body *body;
 225
 226                 body = lustre_msg_buf(req->rq_repmsg, DLM_REPLY_REC_OFF,
 227                                       sizeof(*body));
 228                 if (memcmp(&minfo->mi_data.fid2, &body->fid1,
 229                            sizeof(body->fid1))) {
 230                         ll_unhash_aliases(dentry->d_inode);
 231                         GOTO(out, rc = -EAGAIN);
 232                 }
 233
 234                 rc = revalidate_it_finish(req, DLM_REPLY_REC_OFF, it, dentry);
 235                 if (rc) {
 236                         ll_unhash_aliases(dentry->d_inode);
 237                         GOTO(out, rc);
 238                 }
 239
 240                 spin_lock(&dcache_lock);
 241                 lock_dentry(dentry);
 242                 __d_drop(dentry);
 243 #ifdef DCACHE_LUSTRE_INVALID
 244                 dentry->d_flags &= ~DCACHE_LUSTRE_INVALID;
 245 #endif
 246                 unlock_dentry(dentry);
 247                 d_rehash_cond(dentry, 0);
 248                 spin_unlock(&dcache_lock);
 249
 250                 ll_lookup_finish_locks(it, dentry);
 251
 252         }
 253         EXIT;
 254 out:
 255         spin_lock(&lli->lli_lock);
 256         sai = lli->lli_sai;
 257         if (sai) {
 258                 lli->lli_sai->sai_replied++;
 259                 ll_sai_entry_set(lli->lli_sai, minfo->mi_cbdata,
 260                                  SA_ENTRY_STATED);
 261                 cfs_waitq_signal(&lli->lli_sai->sai_thread.t_ctl_waitq);
 262         }
 263         spin_unlock(&lli->lli_lock);
 264         ll_intent_release(it);
 265         OBD_FREE_PTR(minfo);
 266
 267         dput(dentry);
 268         return rc;
 269 }
 270
 271 static void sa_args_fini(struct md_enqueue_info *minfo,
 272                          struct ldlm_enqueue_info *einfo)
 273 {
 274         LASSERT(minfo && einfo);
 275         OBD_FREE_PTR(minfo);
 276         OBD_FREE_PTR(einfo);
 277 }
 278
 279 static int sa_args_prep(struct inode *dir, struct dentry *dentry,
 280                         struct md_enqueue_info **pmi,
 281                         struct ldlm_enqueue_info **pei)
 282 {
 283         struct ll_inode_info     *lli = ll_i2info(dir);
 284         struct md_enqueue_info   *minfo;
 285         struct ldlm_enqueue_info *einfo;
 286
 287         OBD_ALLOC_PTR(einfo);
 288         if (einfo == NULL)
 289                 return -ENOMEM;
 290
 291         OBD_ALLOC_PTR(minfo);
 292         if (minfo == NULL) {
 293                 OBD_FREE_PTR(einfo);
 294                 return -ENOMEM;
 295         }
 296
 297         minfo->mi_exp = ll_i2mdcexp(dir);
 298         minfo->mi_it.it_op = IT_GETATTR;
 299         minfo->mi_dentry = dentry;
 300         minfo->mi_cb = ll_statahead_interpret;
 301         minfo->mi_cbdata = lli->lli_sai->sai_sent;
 302
 303         einfo->ei_type   = LDLM_IBITS;
 304         einfo->ei_mode   = it_to_lock_mode(&minfo->mi_it);
 305         einfo->ei_cb_bl  = ll_mdc_blocking_ast;
 306         einfo->ei_cb_cp  = ldlm_completion_ast;
 307         einfo->ei_cb_gl  = NULL;
 308         einfo->ei_cbdata = NULL;
 309
 310         *pmi = minfo;
 311         *pei = einfo;
 312
 313         return 0;
 314 }
 315
 316 /* similar to ll_lookup_it(). */
 317 static int do_sa_lookup(struct inode *dir, struct dentry *dentry)
 318 {
 319         struct md_enqueue_info   *minfo;
 320         struct ldlm_enqueue_info *einfo;
 321         int                       rc;
 322         ENTRY;
 323
 324         rc = sa_args_prep(dir, dentry, &minfo, &einfo);
 325         if (rc)
 326                 RETURN(rc);
 327
 328         rc = ll_prepare_mdc_op_data(&minfo->mi_data, dir, NULL,
 329                                     dentry->d_name.name, dentry->d_name.len, 0,
 330                                     NULL);
 331         if (rc == 0)
 332                 rc = mdc_intent_getattr_async(minfo->mi_exp, minfo, einfo);
 333
 334         if (rc)
 335                 sa_args_fini(minfo, einfo);
 336
 337         RETURN(rc);
 338 }
 339
 340 /* similar to ll_revalidate_it().
 341  * return 1: dentry valid.
 342  *        0: will send stat-ahead request.
 343  *        -errno: prepare stat-ahead request failed. */
 344 static int do_sa_revalidate(struct dentry *dentry)
 345 {
 346         struct inode             *inode = dentry->d_inode;
 347         struct ll_inode_info     *lli = ll_i2info(dentry->d_parent->d_inode);
 348         struct ll_fid             fid;
 349         struct lookup_intent      it = { .it_op = IT_GETATTR };
 350         struct md_enqueue_info   *minfo;
 351         struct ldlm_enqueue_info *einfo;
 352         int rc;
 353         ENTRY;
 354
 355         if (inode == NULL)
 356                 RETURN(1);
 357
 358         if (d_mountpoint(dentry))
 359                 RETURN(1);
 360
 361         ll_inode2fid(&fid, inode);
 362
 363         rc = mdc_revalidate_lock(ll_i2mdcexp(inode), &it, &fid);
 364         if (rc == 1) {
 365                 ll_intent_release(&it);
 366                 lli->lli_sai->sai_cached++;
 367                 cfs_waitq_signal(&lli->lli_sai->sai_thread.t_ctl_waitq);
 368                 RETURN(1);
 369         }
 370
 371         rc = sa_args_prep(dentry->d_parent->d_inode, dentry, &minfo, &einfo);
 372         if (rc)
 373                 RETURN(rc);
 374
 375         rc = ll_prepare_mdc_op_data(&minfo->mi_data, dentry->d_parent->d_inode,
 376                                     inode, dentry->d_name.name,
 377                                     dentry->d_name.len, 0, NULL);
 378         if (rc == 0)
 379                 rc = mdc_intent_getattr_async(minfo->mi_exp, minfo, einfo);
 380
 381         if (rc)
 382                 sa_args_fini(minfo, einfo);
 383
 384         RETURN(rc);
 385 }
 386
 387 /* copied from kernel */
 388 static inline void name2qstr(struct qstr *this, const char *name, int namelen)
 389 {
 390         unsigned long        hash;
 391         const unsigned char *p = (const unsigned char *)name;
 392         int                  len;
 393         unsigned int         c;
 394
 395         hash = init_name_hash();
 396         for (len = 0; len < namelen; len++, p++) {
 397                 c = *p;
 398                 hash = partial_name_hash(c, hash);
 399         }
 400         this->name = name;
 401         this->len  = namelen;
 402         this->hash = end_name_hash(hash);
 403 }
 404
 405 static int ll_statahead_one(struct dentry *parent, ext2_dirent *de)
 406 {
 407         struct inode           *dir = parent->d_inode;
 408         struct ll_inode_info   *lli = ll_i2info(dir);
 409         struct qstr             name;
 410         struct dentry          *dentry;
 411         struct ll_sai_entry    *se;
 412         int                     rc;
 413         ENTRY;
 414
 415         name2qstr(&name, de->name, de->name_len);
 416
 417         se = ll_sai_entry_get(lli->lli_sai, lli->lli_sai->sai_sent,
 418                               SA_ENTRY_UNSTATED);
 419
 420 #ifdef DCACHE_LUSTRE_INVALID
 421         if (parent->d_flags & DCACHE_LUSTRE_INVALID) {
 422 #else
 423         if (d_unhashed(parent)) {
 424 #endif
 425                 CDEBUG(D_READA, "parent dentry@%p %.*s is "
 426                        "invalid, skip statahead\n",
 427                        parent, parent->d_name.len, parent->d_name.name);
 428                 GOTO(out, rc = -EINVAL);
 429         }
 430
 431         dentry = d_lookup(parent, &name);
 432         if (!dentry) {
 433                 struct dentry *dentry = d_alloc(parent, &name);
 434
 435                 rc = -ENOMEM;
 436                 if (dentry) {
 437                         rc = do_sa_lookup(dir, dentry);
 438                         if (rc)
 439                                 dput(dentry);
 440                 }
 441                 GOTO(out, rc);
 442         }
 443
 444         rc = do_sa_revalidate(dentry);
 445         if (rc)
 446                 dput(dentry);
 447         GOTO(out, rc);
 448 out:
 449         if (rc) {
 450                 CDEBUG(D_READA, "set sai entry %p index %d stat %d, rc %d\n",
 451                        se, se->se_index, se->se_stat, rc);
 452                 se->se_stat = rc;
 453                 cfs_waitq_signal(&lli->lli_sai->sai_thread.t_ctl_waitq);
 454         }
 455         lli->lli_sai->sai_sent++;
 456         return rc;
 457 }
 458
 459 static inline int sa_check_stop(struct ll_statahead_info *sai)
 460 {
 461         return !!(sai->sai_thread.t_flags & SVC_STOPPING);
 462 }
 463
 464 static inline int sa_not_full(struct ll_statahead_info *sai)
 465 {
 466         return sai->sai_sent - sai->sai_miss - sai->sai_hit < sai->sai_max;
 467 }
 468
 469 struct ll_sa_thread_args {
 470         struct dentry   *sta_parent;
 471         pid_t            sta_pid;
 472 };
 473
 474 static int ll_statahead_thread(void *arg)
 475 {
 476         struct ll_sa_thread_args *sta = arg;
 477         struct dentry            *parent = dget(sta->sta_parent);
 478         struct inode             *dir = parent->d_inode;
 479         struct ll_inode_info     *lli = ll_i2info(dir);
 480         struct ll_sb_info        *sbi = ll_i2sbi(dir);
 481         struct ll_statahead_info *sai = ll_sai_get(lli->lli_sai);
 482         struct ptlrpc_thread     *thread = &sai->sai_thread;
 483         struct l_wait_info        lwi = { 0 };
 484         unsigned long             index = 0;
 485         __u64                     offset = 0;
 486         int                       skip = 0;
 487         int                       rc = 0;
 488         char                      name[16] = "";
 489         ENTRY;
 490
 491         sbi->ll_sa_total++;
 492
 493         snprintf(name, 15, "ll_sa_%u", sta->sta_pid);
 494         cfs_daemonize(name);
 495         thread->t_flags = SVC_RUNNING;
 496         cfs_waitq_signal(&thread->t_ctl_waitq);
 497         CDEBUG(D_READA, "start doing statahead for %s\n", parent->d_name.name);
 498
 499         if (sai->sai_ls_all)
 500                 CDEBUG(D_READA, "do statahead for hidden files\n");
 501
 502         while (1) {
 503                 unsigned long npages = dir_pages(dir);
 504
 505                 /* hit ratio < 80% */
 506                 if ((sai->sai_hit < 4 * sai->sai_miss && sai->sai_hit > 7) ||
 507                      (sai->sai_consecutive_miss > 8)) {
 508                         sbi->ll_sa_wrong++;
 509                         CDEBUG(D_READA, "statahead for dir %.*s hit ratio too "
 510                                "low: hit/miss %u/%u, sent/replied %u/%u, "
 511                                "cached %u\n",
 512                                parent->d_name.len, parent->d_name.name,
 513                                sai->sai_hit, sai->sai_miss, sai->sai_sent,
 514                                sai->sai_replied, sai->sai_cached);
 515                         break;
 516                 }
 517
 518                 /* reach the end of dir */
 519                 if (index == npages) {
 520                         CDEBUG(D_READA, "reach end, index/npages %lu/%lu\n",
 521                                index, npages);
 522                         break;
 523                 }
 524
 525                 l_wait_event(thread->t_ctl_waitq,
 526                              sa_check_stop(sai) || sa_not_full(sai),
 527                              &lwi);
 528
 529                 if (sa_check_stop(sai))
 530                         break;
 531
 532                 for (; index < npages; index++, offset = 0) {
 533                         char *kaddr, *limit;
 534                         ext2_dirent *de;
 535                         struct page *page;
 536
 537                         CDEBUG(D_EXT2,"read %lu of dir %lu/%u page %lu"
 538                                "/%lu size %llu\n",
 539                                CFS_PAGE_SIZE, dir->i_ino, dir->i_generation,
 540                                index, npages, dir->i_size);
 541
 542                         page = ll_get_dir_page(dir, index);
 543                         npages = dir_pages(dir);
 544
 545                         if (IS_ERR(page)) {
 546                                 rc = PTR_ERR(page);
 547                                 CERROR("error reading dir %lu/%u page %lu: "
 548                                        "rc %d\n",
 549                                        dir->i_ino, dir->i_generation, index,
 550                                        rc);
 551                                 GOTO(out, rc);
 552                         }
 553
 554                         kaddr = page_address(page);
 555                         de = (ext2_dirent *)(kaddr + offset);
 556                         limit = kaddr + CFS_PAGE_SIZE - EXT2_DIR_REC_LEN(1);
 557                         for (; (char*)de <= limit && sa_not_full(sai);
 558                              de = ext2_next_entry(de)) {
 559                                 if (!de->inode)
 560                                         continue;
 561
 562                                 /* don't stat-ahead ".", ".." */
 563                                 if (skip < 2) {
 564                                         skip++;
 565                                         continue;
 566                                 }
 567
 568                                 /* don't stat-ahead for hidden files */
 569                                 if (de->name[0] == '.' && !sai->sai_ls_all)
 570                                         continue;
 571
 572                                 /* don't stat-ahead for the first de */
 573                                 if (skip < 3) {
 574                                         skip++;
 575                                         continue;
 576                                 }
 577
 578                                 rc = ll_statahead_one(parent, de);
 579                                 if (rc < 0) {
 580                                         ext2_put_page(page);
 581                                         GOTO(out, rc);
 582                                 }
 583                         }
 584                         offset = (char *)de - kaddr;
 585                         ext2_put_page(page);
 586
 587                         if ((char *)de <= limit)
 588                                 /* !sa_not_full() */
 589                                 break;
 590                 }
 591         }
 592         EXIT;
 593 out:
 594         spin_lock(&lli->lli_lock);
 595         thread->t_flags = SVC_STOPPED;
 596         cfs_waitq_signal(&thread->t_ctl_waitq);
 597         lli->lli_opendir_pid = 0; /* avoid statahead again */
 598         spin_unlock(&lli->lli_lock);
 599
 600         ll_sai_put(sai);
 601         dput(parent);
 602         CDEBUG(D_READA, "stopped statahead thread, pid %d for %s\n",
 603                current->pid, parent->d_name.name);
 604         return 0;
 605 }
 606
 607 /* called in ll_file_release */
 608 void ll_stop_statahead(struct inode *inode)
 609 {
 610         struct ll_inode_info *lli = ll_i2info(inode);
 611         struct ptlrpc_thread *thread;
 612
 613         spin_lock(&lli->lli_lock);
 614         /* don't check pid here. upon fork, if parent closedir before child,
 615          * child will not have chance to stop this thread. */
 616         lli->lli_opendir_pid = 0;
 617
 618         if (lli->lli_sai && (lli->lli_sai->sai_thread.t_flags & SVC_RUNNING)) {
 619                 struct l_wait_info lwi = { 0 };
 620                 ll_sai_get(lli->lli_sai);
 621                 thread = &lli->lli_sai->sai_thread;
 622                 thread->t_flags = SVC_STOPPING;
 623                 cfs_waitq_signal(&thread->t_ctl_waitq);
 624                 spin_unlock(&lli->lli_lock);
 625
 626                 CDEBUG(D_READA, "stopping statahead thread, pid %d\n",
 627                        current->pid);
 628                 l_wait_event(thread->t_ctl_waitq, thread->t_flags & SVC_STOPPED,
 629                              &lwi);
 630                 ll_sai_put(lli->lli_sai);
 631
 632                 return;
 633         }
 634         spin_unlock(&lli->lli_lock);
 635 }
 636
 637 enum {
 638         LS_NONE_FIRST_DE = 0,   /* not first dirent, or is "." */
 639         LS_FIRST_DE,            /* the first non-hidden dirent */
 640         LS_FIRST_DOT_DE         /* the first hidden dirent, that is ".xxx" */
 641 };
 642
 643 static int is_first_dirent(struct inode *dir, struct dentry *dentry)
 644 {
 645         struct qstr   *d_name = &dentry->d_name;
 646         unsigned long  npages = dir_pages(dir);
 647         struct page   *page;
 648         ext2_dirent   *de;
 649         unsigned long  index;
 650         __u64          offset = 0;
 651         char          *kaddr, *limit;
 652         int            dot_de = 1; /* dirent is dotfile till now */
 653         int            rc = LS_NONE_FIRST_DE;
 654         ENTRY;
 655
 656         page = ll_get_dir_page(dir, 0);
 657         if (IS_ERR(page)) {
 658                 CERROR("error reading dir %lu/%u page 0: rc %ld\n",
 659                        dir->i_ino, dir->i_generation, PTR_ERR(page));
 660                 RETURN(LS_NONE_FIRST_DE);
 661         }
 662
 663         kaddr = page_address(page);
 664         de = (ext2_dirent *)kaddr;
 665         if (!(de->name_len == 1 && strncmp(de->name, ".", 1) == 0))
 666                 CWARN("Maybe got bad on-disk dir:%lu\n", dir->i_ino);
 667         de = ext2_next_entry(de); /* skip ".", or ingore bad entry */
 668         if (!(de->name_len == 2 && strncmp(de->name, "..", 2) == 0))
 669                 CWARN("Maybe got bad on-disk dir:%lu\n", dir->i_ino);
 670         de = ext2_next_entry(de); /* skip "..", or ingore bad entry */
 671
 672         offset = (char *)de - kaddr;
 673
 674         for (index = 0; index < npages; offset = 0) {
 675                 de = (ext2_dirent *)(kaddr + offset);
 676                 limit = kaddr + CFS_PAGE_SIZE - EXT2_DIR_REC_LEN(1);
 677                 for (; (char*)de <= limit; de = ext2_next_entry(de)) {
 678                         if (!de->inode)
 679                                 continue;
 680
 681                         if (de->name[0] != '.')
 682                                 dot_de = 0;
 683
 684                         if (dot_de && d_name->name[0] != '.') {
 685                                 CDEBUG(D_READA, "%.*s skip hidden file %.*s\n",
 686                                        d_name->len, d_name->name,
 687                                        de->name_len, de->name);
 688                                 continue;
 689                         }
 690
 691                         if (d_name->len == de->name_len &&
 692                             !strncmp(d_name->name, de->name, d_name->len))
 693                                 rc = LS_FIRST_DE + dot_de;
 694                         else
 695                                 rc = LS_NONE_FIRST_DE;
 696                         GOTO(out, rc);
 697                 }
 698
 699                 if (++index >= npages)
 700                         break;
 701
 702                 ext2_put_page(page);
 703
 704                 page = ll_get_dir_page(dir, index);
 705                 if (IS_ERR(page)) {
 706                         CERROR("error reading dir %lu/%u page %lu: rc %ld\n",
 707                                dir->i_ino, dir->i_generation, index,
 708                                PTR_ERR(page));
 709                         RETURN(LS_NONE_FIRST_DE);
 710                 }
 711                 kaddr = page_address(page);
 712         }
 713         CERROR("%.*s not found in dir %.*s!\n", d_name->len, d_name->name,
 714                dentry->d_parent->d_name.len, dentry->d_parent->d_name.name);
 715         EXIT;
 716 out:
 717         ext2_put_page(page);
 718         return rc;
 719 }
 720
 721 /* start stat-ahead thread if this is the first dir entry, otherwise if a thread
 722  * is started already, wait until thread is ahead of me.
 723  * Return value:
 724  *    0 -- miss,
 725  *    1 -- hit,
 726  *    -EEXIST -- stat ahead thread started, and this is the first try.
 727  *    other negative value -- error.
 728  */
 729 int ll_statahead_enter(struct inode *dir, struct dentry **dentryp, int lookup)
 730 {
 731         struct ll_sb_info        *sbi = ll_i2sbi(dir);
 732         struct ll_inode_info     *lli = ll_i2info(dir);
 733         struct ll_statahead_info *sai;
 734         struct ll_sa_thread_args  sta;
 735         struct l_wait_info        lwi = { 0 };
 736         int                       rc;
 737         ENTRY;
 738
 739         if (sbi->ll_sa_max == 0)
 740                 RETURN(-ENOTSUPP);
 741
 742         /* not the same process, don't statahead */
 743         if (lli->lli_opendir_pid != current->pid)
 744                 RETURN(-EBADF);
 745
 746         spin_lock(&lli->lli_lock);
 747         if (lli->lli_sai) {
 748                 sai = ll_sai_get(lli->lli_sai);
 749                 spin_unlock(&lli->lli_lock);
 750
 751                 if (ll_sai_entry_stated(sai)) {
 752                         sbi->ll_sa_cached++;
 753                 } else {
 754                         struct l_wait_info lwi = { 0 };
 755
 756                         sbi->ll_sa_blocked++;
 757                         /* thread started already, avoid double-stat */
 758                         l_wait_event(sai->sai_thread.t_ctl_waitq,
 759                                      ll_sai_entry_stated(sai) ||
 760                                      sai->sai_thread.t_flags & SVC_STOPPED,
 761                                      &lwi);
 762                 }
 763
 764                 ll_sai_put(sai);
 765
 766                 if (lookup) {
 767                         struct dentry *result;
 768
 769                         result = d_lookup((*dentryp)->d_parent,
 770                                           &(*dentryp)->d_name);
 771                         if (result) {
 772                                 LASSERT(result != *dentryp);
 773                                 dput(*dentryp);
 774                                 *dentryp = result;
 775                         }
 776                         RETURN(result != NULL);
 777                 }
 778                 /* do nothing for revalidate */
 779                 RETURN(0);
 780         }
 781         spin_unlock(&lli->lli_lock);
 782
 783         rc = is_first_dirent(dir, *dentryp);
 784         if (!rc) {
 785                 /* optimization: don't statahead for this pid any longer */
 786                 spin_lock(&lli->lli_lock);
 787                 if (lli->lli_sai == NULL)
 788                         lli->lli_opendir_pid = 0;
 789                 spin_unlock(&lli->lli_lock);
 790                 RETURN(-EBADF);
 791         }
 792
 793         spin_lock(&lli->lli_lock);
 794         if (lli->lli_sai == NULL) {
 795                 lli->lli_sai = ll_sai_alloc();
 796                 if (lli->lli_sai == NULL) {
 797                         spin_unlock(&lli->lli_lock);
 798                         RETURN(-ENOMEM);
 799                 }
 800         } else {
 801                 /* sai is already there */
 802                 spin_unlock(&lli->lli_lock);
 803                 RETURN(-EBUSY);
 804         }
 805         spin_unlock(&lli->lli_lock);
 806
 807         sai = lli->lli_sai;
 808         sai->sai_inode = igrab(dir);
 809         sai->sai_ls_all = (rc == LS_FIRST_DOT_DE);
 810
 811         sta.sta_parent = (*dentryp)->d_parent;
 812         sta.sta_pid    = current->pid;
 813         rc = kernel_thread(ll_statahead_thread, &sta, 0);
 814         if (rc < 0) {
 815                 CERROR("can't start ll_sa thread, rc: %d\n", rc);
 816                 ll_sai_put(sai);
 817                 RETURN(rc);
 818         }
 819
 820         l_wait_event(sai->sai_thread.t_ctl_waitq,
 821                      sai->sai_thread.t_flags & (SVC_RUNNING | SVC_STOPPED),
 822                      &lwi);
 823         ll_sai_put(sai);
 824
 825         /* we don't stat-ahead for the first dirent since we are already in
 826          * lookup, and -EEXIST also indicates that this is the first dirent.
 827          */
 828         RETURN(-EEXIST);
 829 }
 830
 831 /* update hit/miss count */
 832 void ll_statahead_exit(struct dentry *dentry, int result)
 833 {
 834         struct ll_inode_info *lli = ll_i2info(dentry->d_parent->d_inode);
 835         struct ll_sb_info    *sbi = ll_i2sbi(dentry->d_parent->d_inode);
 836
 837         if (lli->lli_opendir_pid != current->pid)
 838                 return;
 839
 840         spin_lock(&lli->lli_lock);
 841         if (lli->lli_sai) {
 842                 struct ll_statahead_info *sai = lli->lli_sai;
 843
 844                 ll_sai_entry_put(sai);
 845                 if (result == 1) {
 846                         sai->sai_hit++;
 847                         sai->sai_consecutive_miss = 0;
 848                         sai->sai_max = min(2 * sai->sai_max, sbi->ll_sa_max);
 849                         CDEBUG(D_READA, "statahead %.*s hit(hit/miss %u/%u)\n",
 850                                dentry->d_name.len, dentry->d_name.name,
 851                                sai->sai_hit, sai->sai_miss);
 852                 } else {
 853                         sai->sai_miss++;
 854                         sai->sai_consecutive_miss++;
 855                         /* upon miss, it's always because some dentry is added
 856                          * by statahead thread, and at the mean time `ls`
 857                          * processs finds this dentry, but the d_op for this
 858                          * dentry is NULL, then revalidate is not done, and
 859                          * ll_statahead_exit() not called for this dentry,
 860                          * so statahead thread should be behind of `ls` process,
 861                          * put one entry to go ahead.
 862                          */
 863                         CDEBUG(D_READA, "statahead %.*s miss(hit/miss %u/%u)\n",
 864                                dentry->d_name.len, dentry->d_name.name,
 865                                sai->sai_hit, sai->sai_miss);
 866                         ll_sai_entry_put(sai);
 867                 }
 868                 cfs_waitq_signal(&sai->sai_thread.t_ctl_waitq);
 869         }
 870         spin_unlock(&lli->lli_lock);
 871 }