fs/nfsd/filecache.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * The NFSD open file cache.
   4  *
   5  * (c) 2015 - Jeff Layton <jeff.layton@primarydata.com>
   6  *
   7  * An nfsd_file object is a per-file collection of open state that binds
   8  * together:
   9  *   - a struct file *
  10  *   - a user credential
  11  *   - a network namespace
  12  *   - a read-ahead context
  13  *   - monitoring for writeback errors
  14  *
  15  * nfsd_file objects are reference-counted. Consumers acquire a new
  16  * object via the nfsd_file_acquire API. They manage their interest in
  17  * the acquired object, and hence the object's reference count, via
  18  * nfsd_file_get and nfsd_file_put. There are two varieties of nfsd_file
  19  * object:
  20  *
  21  *  * non-garbage-collected: When a consumer wants to precisely control
  22  *    the lifetime of a file's open state, it acquires a non-garbage-
  23  *    collected nfsd_file. The final nfsd_file_put releases the open
  24  *    state immediately.
  25  *
  26  *  * garbage-collected: When a consumer does not control the lifetime
  27  *    of open state, it acquires a garbage-collected nfsd_file. The
  28  *    final nfsd_file_put allows the open state to linger for a period
  29  *    during which it may be re-used.
  30  */
  31
  32 #include <linux/hash.h>
  33 #include <linux/slab.h>
  34 #include <linux/file.h>
  35 #include <linux/pagemap.h>
  36 #include <linux/sched.h>
  37 #include <linux/list_lru.h>
  38 #include <linux/fsnotify_backend.h>
  39 #include <linux/fsnotify.h>
  40 #include <linux/seq_file.h>
  41 #include <linux/rhashtable.h>
  42
  43 #include "vfs.h"
  44 #include "nfsd.h"
  45 #include "nfsfh.h"
  46 #include "netns.h"
  47 #include "filecache.h"
  48 #include "trace.h"
  49
  50 #define NFSD_LAUNDRETTE_DELAY                (2 * HZ)
  51
  52 #define NFSD_FILE_CACHE_UP                   (0)
  53
  54 /* We only care about NFSD_MAY_READ/WRITE for this cache */
  55 #define NFSD_FILE_MAY_MASK      (NFSD_MAY_READ|NFSD_MAY_WRITE)
  56
  57 static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits);
  58 static DEFINE_PER_CPU(unsigned long, nfsd_file_acquisitions);
  59 static DEFINE_PER_CPU(unsigned long, nfsd_file_releases);
  60 static DEFINE_PER_CPU(unsigned long, nfsd_file_total_age);
  61 static DEFINE_PER_CPU(unsigned long, nfsd_file_evictions);
  62
  63 struct nfsd_fcache_disposal {
  64         spinlock_t lock;
  65         struct list_head freeme;
  66 };
  67
  68 static struct kmem_cache                *nfsd_file_slab;
  69 static struct kmem_cache                *nfsd_file_mark_slab;
  70 static struct list_lru                  nfsd_file_lru;
  71 static unsigned long                    nfsd_file_flags;
  72 static struct fsnotify_group            *nfsd_file_fsnotify_group;
  73 static struct delayed_work              nfsd_filecache_laundrette;
  74 static struct rhltable                  nfsd_file_rhltable
  75                                                 ____cacheline_aligned_in_smp;
  76
  77 static bool
  78 nfsd_match_cred(const struct cred *c1, const struct cred *c2)
  79 {
  80         int i;
  81
  82         if (!uid_eq(c1->fsuid, c2->fsuid))
  83                 return false;
  84         if (!gid_eq(c1->fsgid, c2->fsgid))
  85                 return false;
  86         if (c1->group_info == NULL || c2->group_info == NULL)
  87                 return c1->group_info == c2->group_info;
  88         if (c1->group_info->ngroups != c2->group_info->ngroups)
  89                 return false;
  90         for (i = 0; i < c1->group_info->ngroups; i++) {
  91                 if (!gid_eq(c1->group_info->gid[i], c2->group_info->gid[i]))
  92                         return false;
  93         }
  94         return true;
  95 }
  96
  97 static const struct rhashtable_params nfsd_file_rhash_params = {
  98         .key_len                = sizeof_field(struct nfsd_file, nf_inode),
  99         .key_offset             = offsetof(struct nfsd_file, nf_inode),
 100         .head_offset            = offsetof(struct nfsd_file, nf_rlist),
 101
 102         /*
 103          * Start with a single page hash table to reduce resizing churn
 104          * on light workloads.
 105          */
 106         .min_size               = 256,
 107         .automatic_shrinking    = true,
 108 };
 109
 110 static void
 111 nfsd_file_schedule_laundrette(void)
 112 {
 113         if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags))
 114                 queue_delayed_work(system_wq, &nfsd_filecache_laundrette,
 115                                    NFSD_LAUNDRETTE_DELAY);
 116 }
 117
 118 static void
 119 nfsd_file_slab_free(struct rcu_head *rcu)
 120 {
 121         struct nfsd_file *nf = container_of(rcu, struct nfsd_file, nf_rcu);
 122
 123         put_cred(nf->nf_cred);
 124         kmem_cache_free(nfsd_file_slab, nf);
 125 }
 126
 127 static void
 128 nfsd_file_mark_free(struct fsnotify_mark *mark)
 129 {
 130         struct nfsd_file_mark *nfm = container_of(mark, struct nfsd_file_mark,
 131                                                   nfm_mark);
 132
 133         kmem_cache_free(nfsd_file_mark_slab, nfm);
 134 }
 135
 136 static struct nfsd_file_mark *
 137 nfsd_file_mark_get(struct nfsd_file_mark *nfm)
 138 {
 139         if (!refcount_inc_not_zero(&nfm->nfm_ref))
 140                 return NULL;
 141         return nfm;
 142 }
 143
 144 static void
 145 nfsd_file_mark_put(struct nfsd_file_mark *nfm)
 146 {
 147         if (refcount_dec_and_test(&nfm->nfm_ref)) {
 148                 fsnotify_destroy_mark(&nfm->nfm_mark, nfsd_file_fsnotify_group);
 149                 fsnotify_put_mark(&nfm->nfm_mark);
 150         }
 151 }
 152
 153 static struct nfsd_file_mark *
 154 nfsd_file_mark_find_or_create(struct nfsd_file *nf, struct inode *inode)
 155 {
 156         int                     err;
 157         struct fsnotify_mark    *mark;
 158         struct nfsd_file_mark   *nfm = NULL, *new;
 159
 160         do {
 161                 fsnotify_group_lock(nfsd_file_fsnotify_group);
 162                 mark = fsnotify_find_mark(&inode->i_fsnotify_marks,
 163                                           nfsd_file_fsnotify_group);
 164                 if (mark) {
 165                         nfm = nfsd_file_mark_get(container_of(mark,
 166                                                  struct nfsd_file_mark,
 167                                                  nfm_mark));
 168                         fsnotify_group_unlock(nfsd_file_fsnotify_group);
 169                         if (nfm) {
 170                                 fsnotify_put_mark(mark);
 171                                 break;
 172                         }
 173                         /* Avoid soft lockup race with nfsd_file_mark_put() */
 174                         fsnotify_destroy_mark(mark, nfsd_file_fsnotify_group);
 175                         fsnotify_put_mark(mark);
 176                 } else {
 177                         fsnotify_group_unlock(nfsd_file_fsnotify_group);
 178                 }
 179
 180                 /* allocate a new nfm */
 181                 new = kmem_cache_alloc(nfsd_file_mark_slab, GFP_KERNEL);
 182                 if (!new)
 183                         return NULL;
 184                 fsnotify_init_mark(&new->nfm_mark, nfsd_file_fsnotify_group);
 185                 new->nfm_mark.mask = FS_ATTRIB|FS_DELETE_SELF;
 186                 refcount_set(&new->nfm_ref, 1);
 187
 188                 err = fsnotify_add_inode_mark(&new->nfm_mark, inode, 0);
 189
 190                 /*
 191                  * If the add was successful, then return the object.
 192                  * Otherwise, we need to put the reference we hold on the
 193                  * nfm_mark. The fsnotify code will take a reference and put
 194                  * it on failure, so we can't just free it directly. It's also
 195                  * not safe to call fsnotify_destroy_mark on it as the
 196                  * mark->group will be NULL. Thus, we can't let the nfm_ref
 197                  * counter drive the destruction at this point.
 198                  */
 199                 if (likely(!err))
 200                         nfm = new;
 201                 else
 202                         fsnotify_put_mark(&new->nfm_mark);
 203         } while (unlikely(err == -EEXIST));
 204
 205         return nfm;
 206 }
 207
 208 static struct nfsd_file *
 209 nfsd_file_alloc(struct net *net, struct inode *inode, unsigned char need,
 210                 bool want_gc)
 211 {
 212         struct nfsd_file *nf;
 213
 214         nf = kmem_cache_alloc(nfsd_file_slab, GFP_KERNEL);
 215         if (unlikely(!nf))
 216                 return NULL;
 217
 218         INIT_LIST_HEAD(&nf->nf_lru);
 219         nf->nf_birthtime = ktime_get();
 220         nf->nf_file = NULL;
 221         nf->nf_cred = get_current_cred();
 222         nf->nf_net = net;
 223         nf->nf_flags = want_gc ?
 224                 BIT(NFSD_FILE_HASHED) | BIT(NFSD_FILE_PENDING) | BIT(NFSD_FILE_GC) :
 225                 BIT(NFSD_FILE_HASHED) | BIT(NFSD_FILE_PENDING);
 226         nf->nf_inode = inode;
 227         refcount_set(&nf->nf_ref, 1);
 228         nf->nf_may = need;
 229         nf->nf_mark = NULL;
 230         return nf;
 231 }
 232
 233 /**
 234  * nfsd_file_check_write_error - check for writeback errors on a file
 235  * @nf: nfsd_file to check for writeback errors
 236  *
 237  * Check whether a nfsd_file has an unseen error. Reset the write
 238  * verifier if so.
 239  */
 240 static void
 241 nfsd_file_check_write_error(struct nfsd_file *nf)
 242 {
 243         struct file *file = nf->nf_file;
 244
 245         if ((file->f_mode & FMODE_WRITE) &&
 246             filemap_check_wb_err(file->f_mapping, READ_ONCE(file->f_wb_err)))
 247                 nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id));
 248 }
 249
 250 static void
 251 nfsd_file_hash_remove(struct nfsd_file *nf)
 252 {
 253         trace_nfsd_file_unhash(nf);
 254         rhltable_remove(&nfsd_file_rhltable, &nf->nf_rlist,
 255                         nfsd_file_rhash_params);
 256 }
 257
 258 static bool
 259 nfsd_file_unhash(struct nfsd_file *nf)
 260 {
 261         if (test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
 262                 nfsd_file_hash_remove(nf);
 263                 return true;
 264         }
 265         return false;
 266 }
 267
 268 static void
 269 nfsd_file_free(struct nfsd_file *nf)
 270 {
 271         s64 age = ktime_to_ms(ktime_sub(ktime_get(), nf->nf_birthtime));
 272
 273         trace_nfsd_file_free(nf);
 274
 275         this_cpu_inc(nfsd_file_releases);
 276         this_cpu_add(nfsd_file_total_age, age);
 277
 278         nfsd_file_unhash(nf);
 279         if (nf->nf_mark)
 280                 nfsd_file_mark_put(nf->nf_mark);
 281         if (nf->nf_file) {
 282                 nfsd_file_check_write_error(nf);
 283                 nfsd_filp_close(nf->nf_file);
 284         }
 285
 286         /*
 287          * If this item is still linked via nf_lru, that's a bug.
 288          * WARN and leak it to preserve system stability.
 289          */
 290         if (WARN_ON_ONCE(!list_empty(&nf->nf_lru)))
 291                 return;
 292
 293         call_rcu(&nf->nf_rcu, nfsd_file_slab_free);
 294 }
 295
 296 static bool
 297 nfsd_file_check_writeback(struct nfsd_file *nf)
 298 {
 299         struct file *file = nf->nf_file;
 300         struct address_space *mapping;
 301
 302         /* File not open for write? */
 303         if (!(file->f_mode & FMODE_WRITE))
 304                 return false;
 305
 306         /*
 307          * Some filesystems (e.g. NFS) flush all dirty data on close.
 308          * On others, there is no need to wait for writeback.
 309          */
 310         if (!(file_inode(file)->i_sb->s_export_op->flags & EXPORT_OP_FLUSH_ON_CLOSE))
 311                 return false;
 312
 313         mapping = file->f_mapping;
 314         return mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) ||
 315                 mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK);
 316 }
 317
 318
 319 static bool nfsd_file_lru_add(struct nfsd_file *nf)
 320 {
 321         set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags);
 322         if (list_lru_add_obj(&nfsd_file_lru, &nf->nf_lru)) {
 323                 trace_nfsd_file_lru_add(nf);
 324                 return true;
 325         }
 326         return false;
 327 }
 328
 329 static bool nfsd_file_lru_remove(struct nfsd_file *nf)
 330 {
 331         if (list_lru_del_obj(&nfsd_file_lru, &nf->nf_lru)) {
 332                 trace_nfsd_file_lru_del(nf);
 333                 return true;
 334         }
 335         return false;
 336 }
 337
 338 struct nfsd_file *
 339 nfsd_file_get(struct nfsd_file *nf)
 340 {
 341         if (nf && refcount_inc_not_zero(&nf->nf_ref))
 342                 return nf;
 343         return NULL;
 344 }
 345
 346 /**
 347  * nfsd_file_put - put the reference to a nfsd_file
 348  * @nf: nfsd_file of which to put the reference
 349  *
 350  * Put a reference to a nfsd_file. In the non-GC case, we just put the
 351  * reference immediately. In the GC case, if the reference would be
 352  * the last one, the put it on the LRU instead to be cleaned up later.
 353  */
 354 void
 355 nfsd_file_put(struct nfsd_file *nf)
 356 {
 357         might_sleep();
 358         trace_nfsd_file_put(nf);
 359
 360         if (test_bit(NFSD_FILE_GC, &nf->nf_flags) &&
 361             test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
 362                 /*
 363                  * If this is the last reference (nf_ref == 1), then try to
 364                  * transfer it to the LRU.
 365                  */
 366                 if (refcount_dec_not_one(&nf->nf_ref))
 367                         return;
 368
 369                 /* Try to add it to the LRU.  If that fails, decrement. */
 370                 if (nfsd_file_lru_add(nf)) {
 371                         /* If it's still hashed, we're done */
 372                         if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
 373                                 nfsd_file_schedule_laundrette();
 374                                 return;
 375                         }
 376
 377                         /*
 378                          * We're racing with unhashing, so try to remove it from
 379                          * the LRU. If removal fails, then someone else already
 380                          * has our reference.
 381                          */
 382                         if (!nfsd_file_lru_remove(nf))
 383                                 return;
 384                 }
 385         }
 386         if (refcount_dec_and_test(&nf->nf_ref))
 387                 nfsd_file_free(nf);
 388 }
 389
 390 static void
 391 nfsd_file_dispose_list(struct list_head *dispose)
 392 {
 393         struct nfsd_file *nf;
 394
 395         while (!list_empty(dispose)) {
 396                 nf = list_first_entry(dispose, struct nfsd_file, nf_lru);
 397                 list_del_init(&nf->nf_lru);
 398                 nfsd_file_free(nf);
 399         }
 400 }
 401
 402 /**
 403  * nfsd_file_dispose_list_delayed - move list of dead files to net's freeme list
 404  * @dispose: list of nfsd_files to be disposed
 405  *
 406  * Transfers each file to the "freeme" list for its nfsd_net, to eventually
 407  * be disposed of by the per-net garbage collector.
 408  */
 409 static void
 410 nfsd_file_dispose_list_delayed(struct list_head *dispose)
 411 {
 412         while(!list_empty(dispose)) {
 413                 struct nfsd_file *nf = list_first_entry(dispose,
 414                                                 struct nfsd_file, nf_lru);
 415                 struct nfsd_net *nn = net_generic(nf->nf_net, nfsd_net_id);
 416                 struct nfsd_fcache_disposal *l = nn->fcache_disposal;
 417
 418                 spin_lock(&l->lock);
 419                 list_move_tail(&nf->nf_lru, &l->freeme);
 420                 spin_unlock(&l->lock);
 421                 svc_wake_up(nn->nfsd_serv);
 422         }
 423 }
 424
 425 /**
 426  * nfsd_file_net_dispose - deal with nfsd_files waiting to be disposed.
 427  * @nn: nfsd_net in which to find files to be disposed.
 428  *
 429  * When files held open for nfsv3 are removed from the filecache, whether
 430  * due to memory pressure or garbage collection, they are queued to
 431  * a per-net-ns queue.  This function completes the disposal, either
 432  * directly or by waking another nfsd thread to help with the work.
 433  */
 434 void nfsd_file_net_dispose(struct nfsd_net *nn)
 435 {
 436         struct nfsd_fcache_disposal *l = nn->fcache_disposal;
 437
 438         if (!list_empty(&l->freeme)) {
 439                 LIST_HEAD(dispose);
 440                 int i;
 441
 442                 spin_lock(&l->lock);
 443                 for (i = 0; i < 8 && !list_empty(&l->freeme); i++)
 444                         list_move(l->freeme.next, &dispose);
 445                 spin_unlock(&l->lock);
 446                 if (!list_empty(&l->freeme))
 447                         /* Wake up another thread to share the work
 448                          * *before* doing any actual disposing.
 449                          */
 450                         svc_wake_up(nn->nfsd_serv);
 451                 nfsd_file_dispose_list(&dispose);
 452         }
 453 }
 454
 455 /**
 456  * nfsd_file_lru_cb - Examine an entry on the LRU list
 457  * @item: LRU entry to examine
 458  * @lru: controlling LRU
 459  * @lock: LRU list lock (unused)
 460  * @arg: dispose list
 461  *
 462  * Return values:
 463  *   %LRU_REMOVED: @item was removed from the LRU
 464  *   %LRU_ROTATE: @item is to be moved to the LRU tail
 465  *   %LRU_SKIP: @item cannot be evicted
 466  */
 467 static enum lru_status
 468 nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru,
 469                  spinlock_t *lock, void *arg)
 470         __releases(lock)
 471         __acquires(lock)
 472 {
 473         struct list_head *head = arg;
 474         struct nfsd_file *nf = list_entry(item, struct nfsd_file, nf_lru);
 475
 476         /* We should only be dealing with GC entries here */
 477         WARN_ON_ONCE(!test_bit(NFSD_FILE_GC, &nf->nf_flags));
 478
 479         /*
 480          * Don't throw out files that are still undergoing I/O or
 481          * that have uncleared errors pending.
 482          */
 483         if (nfsd_file_check_writeback(nf)) {
 484                 trace_nfsd_file_gc_writeback(nf);
 485                 return LRU_SKIP;
 486         }
 487
 488         /* If it was recently added to the list, skip it */
 489         if (test_and_clear_bit(NFSD_FILE_REFERENCED, &nf->nf_flags)) {
 490                 trace_nfsd_file_gc_referenced(nf);
 491                 return LRU_ROTATE;
 492         }
 493
 494         /*
 495          * Put the reference held on behalf of the LRU. If it wasn't the last
 496          * one, then just remove it from the LRU and ignore it.
 497          */
 498         if (!refcount_dec_and_test(&nf->nf_ref)) {
 499                 trace_nfsd_file_gc_in_use(nf);
 500                 list_lru_isolate(lru, &nf->nf_lru);
 501                 return LRU_REMOVED;
 502         }
 503
 504         /* Refcount went to zero. Unhash it and queue it to the dispose list */
 505         nfsd_file_unhash(nf);
 506         list_lru_isolate_move(lru, &nf->nf_lru, head);
 507         this_cpu_inc(nfsd_file_evictions);
 508         trace_nfsd_file_gc_disposed(nf);
 509         return LRU_REMOVED;
 510 }
 511
 512 static void
 513 nfsd_file_gc(void)
 514 {
 515         LIST_HEAD(dispose);
 516         unsigned long ret;
 517
 518         ret = list_lru_walk(&nfsd_file_lru, nfsd_file_lru_cb,
 519                             &dispose, list_lru_count(&nfsd_file_lru));
 520         trace_nfsd_file_gc_removed(ret, list_lru_count(&nfsd_file_lru));
 521         nfsd_file_dispose_list_delayed(&dispose);
 522 }
 523
 524 static void
 525 nfsd_file_gc_worker(struct work_struct *work)
 526 {
 527         nfsd_file_gc();
 528         if (list_lru_count(&nfsd_file_lru))
 529                 nfsd_file_schedule_laundrette();
 530 }
 531
 532 static unsigned long
 533 nfsd_file_lru_count(struct shrinker *s, struct shrink_control *sc)
 534 {
 535         return list_lru_count(&nfsd_file_lru);
 536 }
 537
 538 static unsigned long
 539 nfsd_file_lru_scan(struct shrinker *s, struct shrink_control *sc)
 540 {
 541         LIST_HEAD(dispose);
 542         unsigned long ret;
 543
 544         ret = list_lru_shrink_walk(&nfsd_file_lru, sc,
 545                                    nfsd_file_lru_cb, &dispose);
 546         trace_nfsd_file_shrinker_removed(ret, list_lru_count(&nfsd_file_lru));
 547         nfsd_file_dispose_list_delayed(&dispose);
 548         return ret;
 549 }
 550
 551 static struct shrinker *nfsd_file_shrinker;
 552
 553 /**
 554  * nfsd_file_cond_queue - conditionally unhash and queue a nfsd_file
 555  * @nf: nfsd_file to attempt to queue
 556  * @dispose: private list to queue successfully-put objects
 557  *
 558  * Unhash an nfsd_file, try to get a reference to it, and then put that
 559  * reference. If it's the last reference, queue it to the dispose list.
 560  */
 561 static void
 562 nfsd_file_cond_queue(struct nfsd_file *nf, struct list_head *dispose)
 563         __must_hold(RCU)
 564 {
 565         int decrement = 1;
 566
 567         /* If we raced with someone else unhashing, ignore it */
 568         if (!nfsd_file_unhash(nf))
 569                 return;
 570
 571         /* If we can't get a reference, ignore it */
 572         if (!nfsd_file_get(nf))
 573                 return;
 574
 575         /* Extra decrement if we remove from the LRU */
 576         if (nfsd_file_lru_remove(nf))
 577                 ++decrement;
 578
 579         /* If refcount goes to 0, then put on the dispose list */
 580         if (refcount_sub_and_test(decrement, &nf->nf_ref)) {
 581                 list_add(&nf->nf_lru, dispose);
 582                 trace_nfsd_file_closing(nf);
 583         }
 584 }
 585
 586 /**
 587  * nfsd_file_queue_for_close: try to close out any open nfsd_files for an inode
 588  * @inode:   inode on which to close out nfsd_files
 589  * @dispose: list on which to gather nfsd_files to close out
 590  *
 591  * An nfsd_file represents a struct file being held open on behalf of nfsd.
 592  * An open file however can block other activity (such as leases), or cause
 593  * undesirable behavior (e.g. spurious silly-renames when reexporting NFS).
 594  *
 595  * This function is intended to find open nfsd_files when this sort of
 596  * conflicting access occurs and then attempt to close those files out.
 597  *
 598  * Populates the dispose list with entries that have already had their
 599  * refcounts go to zero. The actual free of an nfsd_file can be expensive,
 600  * so we leave it up to the caller whether it wants to wait or not.
 601  */
 602 static void
 603 nfsd_file_queue_for_close(struct inode *inode, struct list_head *dispose)
 604 {
 605         struct rhlist_head *tmp, *list;
 606         struct nfsd_file *nf;
 607
 608         rcu_read_lock();
 609         list = rhltable_lookup(&nfsd_file_rhltable, &inode,
 610                                nfsd_file_rhash_params);
 611         rhl_for_each_entry_rcu(nf, tmp, list, nf_rlist) {
 612                 if (!test_bit(NFSD_FILE_GC, &nf->nf_flags))
 613                         continue;
 614                 nfsd_file_cond_queue(nf, dispose);
 615         }
 616         rcu_read_unlock();
 617 }
 618
 619 /**
 620  * nfsd_file_close_inode - attempt a delayed close of a nfsd_file
 621  * @inode: inode of the file to attempt to remove
 622  *
 623  * Close out any open nfsd_files that can be reaped for @inode. The
 624  * actual freeing is deferred to the dispose_list_delayed infrastructure.
 625  *
 626  * This is used by the fsnotify callbacks and setlease notifier.
 627  */
 628 static void
 629 nfsd_file_close_inode(struct inode *inode)
 630 {
 631         LIST_HEAD(dispose);
 632
 633         nfsd_file_queue_for_close(inode, &dispose);
 634         nfsd_file_dispose_list_delayed(&dispose);
 635 }
 636
 637 /**
 638  * nfsd_file_close_inode_sync - attempt to forcibly close a nfsd_file
 639  * @inode: inode of the file to attempt to remove
 640  *
 641  * Close out any open nfsd_files that can be reaped for @inode. The
 642  * nfsd_files are closed out synchronously.
 643  *
 644  * This is called from nfsd_rename and nfsd_unlink to avoid silly-renames
 645  * when reexporting NFS.
 646  */
 647 void
 648 nfsd_file_close_inode_sync(struct inode *inode)
 649 {
 650         struct nfsd_file *nf;
 651         LIST_HEAD(dispose);
 652
 653         trace_nfsd_file_close(inode);
 654
 655         nfsd_file_queue_for_close(inode, &dispose);
 656         while (!list_empty(&dispose)) {
 657                 nf = list_first_entry(&dispose, struct nfsd_file, nf_lru);
 658                 list_del_init(&nf->nf_lru);
 659                 nfsd_file_free(nf);
 660         }
 661 }
 662
 663 static int
 664 nfsd_file_lease_notifier_call(struct notifier_block *nb, unsigned long arg,
 665                             void *data)
 666 {
 667         struct file_lock *fl = data;
 668
 669         /* Only close files for F_SETLEASE leases */
 670         if (fl->c.flc_flags & FL_LEASE)
 671                 nfsd_file_close_inode(file_inode(fl->c.flc_file));
 672         return 0;
 673 }
 674
 675 static struct notifier_block nfsd_file_lease_notifier = {
 676         .notifier_call = nfsd_file_lease_notifier_call,
 677 };
 678
 679 static int
 680 nfsd_file_fsnotify_handle_event(struct fsnotify_mark *mark, u32 mask,
 681                                 struct inode *inode, struct inode *dir,
 682                                 const struct qstr *name, u32 cookie)
 683 {
 684         if (WARN_ON_ONCE(!inode))
 685                 return 0;
 686
 687         trace_nfsd_file_fsnotify_handle_event(inode, mask);
 688
 689         /* Should be no marks on non-regular files */
 690         if (!S_ISREG(inode->i_mode)) {
 691                 WARN_ON_ONCE(1);
 692                 return 0;
 693         }
 694
 695         /* don't close files if this was not the last link */
 696         if (mask & FS_ATTRIB) {
 697                 if (inode->i_nlink)
 698                         return 0;
 699         }
 700
 701         nfsd_file_close_inode(inode);
 702         return 0;
 703 }
 704
 705
 706 static const struct fsnotify_ops nfsd_file_fsnotify_ops = {
 707         .handle_inode_event = nfsd_file_fsnotify_handle_event,
 708         .free_mark = nfsd_file_mark_free,
 709 };
 710
 711 int
 712 nfsd_file_cache_init(void)
 713 {
 714         int ret;
 715
 716         lockdep_assert_held(&nfsd_mutex);
 717         if (test_and_set_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 1)
 718                 return 0;
 719
 720         ret = rhltable_init(&nfsd_file_rhltable, &nfsd_file_rhash_params);
 721         if (ret)
 722                 return ret;
 723
 724         ret = -ENOMEM;
 725         nfsd_file_slab = KMEM_CACHE(nfsd_file, 0);
 726         if (!nfsd_file_slab) {
 727                 pr_err("nfsd: unable to create nfsd_file_slab\n");
 728                 goto out_err;
 729         }
 730
 731         nfsd_file_mark_slab = KMEM_CACHE(nfsd_file_mark, 0);
 732         if (!nfsd_file_mark_slab) {
 733                 pr_err("nfsd: unable to create nfsd_file_mark_slab\n");
 734                 goto out_err;
 735         }
 736
 737         ret = list_lru_init(&nfsd_file_lru);
 738         if (ret) {
 739                 pr_err("nfsd: failed to init nfsd_file_lru: %d\n", ret);
 740                 goto out_err;
 741         }
 742
 743         nfsd_file_shrinker = shrinker_alloc(0, "nfsd-filecache");
 744         if (!nfsd_file_shrinker) {
 745                 ret = -ENOMEM;
 746                 pr_err("nfsd: failed to allocate nfsd_file_shrinker\n");
 747                 goto out_lru;
 748         }
 749
 750         nfsd_file_shrinker->count_objects = nfsd_file_lru_count;
 751         nfsd_file_shrinker->scan_objects = nfsd_file_lru_scan;
 752         nfsd_file_shrinker->seeks = 1;
 753
 754         shrinker_register(nfsd_file_shrinker);
 755
 756         ret = lease_register_notifier(&nfsd_file_lease_notifier);
 757         if (ret) {
 758                 pr_err("nfsd: unable to register lease notifier: %d\n", ret);
 759                 goto out_shrinker;
 760         }
 761
 762         nfsd_file_fsnotify_group = fsnotify_alloc_group(&nfsd_file_fsnotify_ops,
 763                                                         FSNOTIFY_GROUP_NOFS);
 764         if (IS_ERR(nfsd_file_fsnotify_group)) {
 765                 pr_err("nfsd: unable to create fsnotify group: %ld\n",
 766                         PTR_ERR(nfsd_file_fsnotify_group));
 767                 ret = PTR_ERR(nfsd_file_fsnotify_group);
 768                 nfsd_file_fsnotify_group = NULL;
 769                 goto out_notifier;
 770         }
 771
 772         INIT_DELAYED_WORK(&nfsd_filecache_laundrette, nfsd_file_gc_worker);
 773 out:
 774         return ret;
 775 out_notifier:
 776         lease_unregister_notifier(&nfsd_file_lease_notifier);
 777 out_shrinker:
 778         shrinker_free(nfsd_file_shrinker);
 779 out_lru:
 780         list_lru_destroy(&nfsd_file_lru);
 781 out_err:
 782         kmem_cache_destroy(nfsd_file_slab);
 783         nfsd_file_slab = NULL;
 784         kmem_cache_destroy(nfsd_file_mark_slab);
 785         nfsd_file_mark_slab = NULL;
 786         rhltable_destroy(&nfsd_file_rhltable);
 787         goto out;
 788 }
 789
 790 /**
 791  * __nfsd_file_cache_purge: clean out the cache for shutdown
 792  * @net: net-namespace to shut down the cache (may be NULL)
 793  *
 794  * Walk the nfsd_file cache and close out any that match @net. If @net is NULL,
 795  * then close out everything. Called when an nfsd instance is being shut down,
 796  * and when the exports table is flushed.
 797  */
 798 static void
 799 __nfsd_file_cache_purge(struct net *net)
 800 {
 801         struct rhashtable_iter iter;
 802         struct nfsd_file *nf;
 803         LIST_HEAD(dispose);
 804
 805         rhltable_walk_enter(&nfsd_file_rhltable, &iter);
 806         do {
 807                 rhashtable_walk_start(&iter);
 808
 809                 nf = rhashtable_walk_next(&iter);
 810                 while (!IS_ERR_OR_NULL(nf)) {
 811                         if (!net || nf->nf_net == net)
 812                                 nfsd_file_cond_queue(nf, &dispose);
 813                         nf = rhashtable_walk_next(&iter);
 814                 }
 815
 816                 rhashtable_walk_stop(&iter);
 817         } while (nf == ERR_PTR(-EAGAIN));
 818         rhashtable_walk_exit(&iter);
 819
 820         nfsd_file_dispose_list(&dispose);
 821 }
 822
 823 static struct nfsd_fcache_disposal *
 824 nfsd_alloc_fcache_disposal(void)
 825 {
 826         struct nfsd_fcache_disposal *l;
 827
 828         l = kmalloc(sizeof(*l), GFP_KERNEL);
 829         if (!l)
 830                 return NULL;
 831         spin_lock_init(&l->lock);
 832         INIT_LIST_HEAD(&l->freeme);
 833         return l;
 834 }
 835
 836 static void
 837 nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l)
 838 {
 839         nfsd_file_dispose_list(&l->freeme);
 840         kfree(l);
 841 }
 842
 843 static void
 844 nfsd_free_fcache_disposal_net(struct net *net)
 845 {
 846         struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 847         struct nfsd_fcache_disposal *l = nn->fcache_disposal;
 848
 849         nfsd_free_fcache_disposal(l);
 850 }
 851
 852 int
 853 nfsd_file_cache_start_net(struct net *net)
 854 {
 855         struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 856
 857         nn->fcache_disposal = nfsd_alloc_fcache_disposal();
 858         return nn->fcache_disposal ? 0 : -ENOMEM;
 859 }
 860
 861 /**
 862  * nfsd_file_cache_purge - Remove all cache items associated with @net
 863  * @net: target net namespace
 864  *
 865  */
 866 void
 867 nfsd_file_cache_purge(struct net *net)
 868 {
 869         lockdep_assert_held(&nfsd_mutex);
 870         if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 1)
 871                 __nfsd_file_cache_purge(net);
 872 }
 873
 874 void
 875 nfsd_file_cache_shutdown_net(struct net *net)
 876 {
 877         nfsd_file_cache_purge(net);
 878         nfsd_free_fcache_disposal_net(net);
 879 }
 880
 881 void
 882 nfsd_file_cache_shutdown(void)
 883 {
 884         int i;
 885
 886         lockdep_assert_held(&nfsd_mutex);
 887         if (test_and_clear_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 0)
 888                 return;
 889
 890         lease_unregister_notifier(&nfsd_file_lease_notifier);
 891         shrinker_free(nfsd_file_shrinker);
 892         /*
 893          * make sure all callers of nfsd_file_lru_cb are done before
 894          * calling nfsd_file_cache_purge
 895          */
 896         cancel_delayed_work_sync(&nfsd_filecache_laundrette);
 897         __nfsd_file_cache_purge(NULL);
 898         list_lru_destroy(&nfsd_file_lru);
 899         rcu_barrier();
 900         fsnotify_put_group(nfsd_file_fsnotify_group);
 901         nfsd_file_fsnotify_group = NULL;
 902         kmem_cache_destroy(nfsd_file_slab);
 903         nfsd_file_slab = NULL;
 904         fsnotify_wait_marks_destroyed();
 905         kmem_cache_destroy(nfsd_file_mark_slab);
 906         nfsd_file_mark_slab = NULL;
 907         rhltable_destroy(&nfsd_file_rhltable);
 908
 909         for_each_possible_cpu(i) {
 910                 per_cpu(nfsd_file_cache_hits, i) = 0;
 911                 per_cpu(nfsd_file_acquisitions, i) = 0;
 912                 per_cpu(nfsd_file_releases, i) = 0;
 913                 per_cpu(nfsd_file_total_age, i) = 0;
 914                 per_cpu(nfsd_file_evictions, i) = 0;
 915         }
 916 }
 917
 918 static struct nfsd_file *
 919 nfsd_file_lookup_locked(const struct net *net, const struct cred *cred,
 920                         struct inode *inode, unsigned char need,
 921                         bool want_gc)
 922 {
 923         struct rhlist_head *tmp, *list;
 924         struct nfsd_file *nf;
 925
 926         list = rhltable_lookup(&nfsd_file_rhltable, &inode,
 927                                nfsd_file_rhash_params);
 928         rhl_for_each_entry_rcu(nf, tmp, list, nf_rlist) {
 929                 if (nf->nf_may != need)
 930                         continue;
 931                 if (nf->nf_net != net)
 932                         continue;
 933                 if (!nfsd_match_cred(nf->nf_cred, cred))
 934                         continue;
 935                 if (test_bit(NFSD_FILE_GC, &nf->nf_flags) != want_gc)
 936                         continue;
 937                 if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags) == 0)
 938                         continue;
 939
 940                 if (!nfsd_file_get(nf))
 941                         continue;
 942                 return nf;
 943         }
 944         return NULL;
 945 }
 946
 947 /**
 948  * nfsd_file_is_cached - are there any cached open files for this inode?
 949  * @inode: inode to check
 950  *
 951  * The lookup matches inodes in all net namespaces and is atomic wrt
 952  * nfsd_file_acquire().
 953  *
 954  * Return values:
 955  *   %true: filecache contains at least one file matching this inode
 956  *   %false: filecache contains no files matching this inode
 957  */
 958 bool
 959 nfsd_file_is_cached(struct inode *inode)
 960 {
 961         struct rhlist_head *tmp, *list;
 962         struct nfsd_file *nf;
 963         bool ret = false;
 964
 965         rcu_read_lock();
 966         list = rhltable_lookup(&nfsd_file_rhltable, &inode,
 967                                nfsd_file_rhash_params);
 968         rhl_for_each_entry_rcu(nf, tmp, list, nf_rlist)
 969                 if (test_bit(NFSD_FILE_GC, &nf->nf_flags)) {
 970                         ret = true;
 971                         break;
 972                 }
 973         rcu_read_unlock();
 974
 975         trace_nfsd_file_is_cached(inode, (int)ret);
 976         return ret;
 977 }
 978
 979 static __be32
 980 nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
 981                      unsigned int may_flags, struct file *file,
 982                      struct nfsd_file **pnf, bool want_gc)
 983 {
 984         unsigned char need = may_flags & NFSD_FILE_MAY_MASK;
 985         struct net *net = SVC_NET(rqstp);
 986         struct nfsd_file *new, *nf;
 987         bool stale_retry = true;
 988         bool open_retry = true;
 989         struct inode *inode;
 990         __be32 status;
 991         int ret;
 992
 993 retry:
 994         status = fh_verify(rqstp, fhp, S_IFREG,
 995                                 may_flags|NFSD_MAY_OWNER_OVERRIDE);
 996         if (status != nfs_ok)
 997                 return status;
 998         inode = d_inode(fhp->fh_dentry);
 999
1000         rcu_read_lock();
1001         nf = nfsd_file_lookup_locked(net, current_cred(), inode, need, want_gc);
1002         rcu_read_unlock();
1003
1004         if (nf) {
1005                 /*
1006                  * If the nf is on the LRU then it holds an extra reference
1007                  * that must be put if it's removed. It had better not be
1008                  * the last one however, since we should hold another.
1009                  */
1010                 if (nfsd_file_lru_remove(nf))
1011                         WARN_ON_ONCE(refcount_dec_and_test(&nf->nf_ref));
1012                 goto wait_for_construction;
1013         }
1014
1015         new = nfsd_file_alloc(net, inode, need, want_gc);
1016         if (!new) {
1017                 status = nfserr_jukebox;
1018                 goto out;
1019         }
1020
1021         rcu_read_lock();
1022         spin_lock(&inode->i_lock);
1023         nf = nfsd_file_lookup_locked(net, current_cred(), inode, need, want_gc);
1024         if (unlikely(nf)) {
1025                 spin_unlock(&inode->i_lock);
1026                 rcu_read_unlock();
1027                 nfsd_file_slab_free(&new->nf_rcu);
1028                 goto wait_for_construction;
1029         }
1030         nf = new;
1031         ret = rhltable_insert(&nfsd_file_rhltable, &nf->nf_rlist,
1032                               nfsd_file_rhash_params);
1033         spin_unlock(&inode->i_lock);
1034         rcu_read_unlock();
1035         if (likely(ret == 0))
1036                 goto open_file;
1037
1038         if (ret == -EEXIST)
1039                 goto retry;
1040         trace_nfsd_file_insert_err(rqstp, inode, may_flags, ret);
1041         status = nfserr_jukebox;
1042         goto construction_err;
1043
1044 wait_for_construction:
1045         wait_on_bit(&nf->nf_flags, NFSD_FILE_PENDING, TASK_UNINTERRUPTIBLE);
1046
1047         /* Did construction of this file fail? */
1048         if (!test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
1049                 trace_nfsd_file_cons_err(rqstp, inode, may_flags, nf);
1050                 if (!open_retry) {
1051                         status = nfserr_jukebox;
1052                         goto construction_err;
1053                 }
1054                 open_retry = false;
1055                 fh_put(fhp);
1056                 goto retry;
1057         }
1058         this_cpu_inc(nfsd_file_cache_hits);
1059
1060         status = nfserrno(nfsd_open_break_lease(file_inode(nf->nf_file), may_flags));
1061         if (status != nfs_ok) {
1062                 nfsd_file_put(nf);
1063                 nf = NULL;
1064         }
1065
1066 out:
1067         if (status == nfs_ok) {
1068                 this_cpu_inc(nfsd_file_acquisitions);
1069                 nfsd_file_check_write_error(nf);
1070                 *pnf = nf;
1071         }
1072         trace_nfsd_file_acquire(rqstp, inode, may_flags, nf, status);
1073         return status;
1074
1075 open_file:
1076         trace_nfsd_file_alloc(nf);
1077         nf->nf_mark = nfsd_file_mark_find_or_create(nf, inode);
1078         if (nf->nf_mark) {
1079                 if (file) {
1080                         get_file(file);
1081                         nf->nf_file = file;
1082                         status = nfs_ok;
1083                         trace_nfsd_file_opened(nf, status);
1084                 } else {
1085                         ret = nfsd_open_verified(rqstp, fhp, may_flags,
1086                                                  &nf->nf_file);
1087                         if (ret == -EOPENSTALE && stale_retry) {
1088                                 stale_retry = false;
1089                                 nfsd_file_unhash(nf);
1090                                 clear_and_wake_up_bit(NFSD_FILE_PENDING,
1091                                                       &nf->nf_flags);
1092                                 if (refcount_dec_and_test(&nf->nf_ref))
1093                                         nfsd_file_free(nf);
1094                                 nf = NULL;
1095                                 fh_put(fhp);
1096                                 goto retry;
1097                         }
1098                         status = nfserrno(ret);
1099                         trace_nfsd_file_open(nf, status);
1100                 }
1101         } else
1102                 status = nfserr_jukebox;
1103         /*
1104          * If construction failed, or we raced with a call to unlink()
1105          * then unhash.
1106          */
1107         if (status != nfs_ok || inode->i_nlink == 0)
1108                 nfsd_file_unhash(nf);
1109         clear_and_wake_up_bit(NFSD_FILE_PENDING, &nf->nf_flags);
1110         if (status == nfs_ok)
1111                 goto out;
1112
1113 construction_err:
1114         if (refcount_dec_and_test(&nf->nf_ref))
1115                 nfsd_file_free(nf);
1116         nf = NULL;
1117         goto out;
1118 }
1119
1120 /**
1121  * nfsd_file_acquire_gc - Get a struct nfsd_file with an open file
1122  * @rqstp: the RPC transaction being executed
1123  * @fhp: the NFS filehandle of the file to be opened
1124  * @may_flags: NFSD_MAY_ settings for the file
1125  * @pnf: OUT: new or found "struct nfsd_file" object
1126  *
1127  * The nfsd_file object returned by this API is reference-counted
1128  * and garbage-collected. The object is retained for a few
1129  * seconds after the final nfsd_file_put() in case the caller
1130  * wants to re-use it.
1131  *
1132  * Return values:
1133  *   %nfs_ok - @pnf points to an nfsd_file with its reference
1134  *   count boosted.
1135  *
1136  * On error, an nfsstat value in network byte order is returned.
1137  */
1138 __be32
1139 nfsd_file_acquire_gc(struct svc_rqst *rqstp, struct svc_fh *fhp,
1140                      unsigned int may_flags, struct nfsd_file **pnf)
1141 {
1142         return nfsd_file_do_acquire(rqstp, fhp, may_flags, NULL, pnf, true);
1143 }
1144
1145 /**
1146  * nfsd_file_acquire - Get a struct nfsd_file with an open file
1147  * @rqstp: the RPC transaction being executed
1148  * @fhp: the NFS filehandle of the file to be opened
1149  * @may_flags: NFSD_MAY_ settings for the file
1150  * @pnf: OUT: new or found "struct nfsd_file" object
1151  *
1152  * The nfsd_file_object returned by this API is reference-counted
1153  * but not garbage-collected. The object is unhashed after the
1154  * final nfsd_file_put().
1155  *
1156  * Return values:
1157  *   %nfs_ok - @pnf points to an nfsd_file with its reference
1158  *   count boosted.
1159  *
1160  * On error, an nfsstat value in network byte order is returned.
1161  */
1162 __be32
1163 nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
1164                   unsigned int may_flags, struct nfsd_file **pnf)
1165 {
1166         return nfsd_file_do_acquire(rqstp, fhp, may_flags, NULL, pnf, false);
1167 }
1168
1169 /**
1170  * nfsd_file_acquire_opened - Get a struct nfsd_file using existing open file
1171  * @rqstp: the RPC transaction being executed
1172  * @fhp: the NFS filehandle of the file just created
1173  * @may_flags: NFSD_MAY_ settings for the file
1174  * @file: cached, already-open file (may be NULL)
1175  * @pnf: OUT: new or found "struct nfsd_file" object
1176  *
1177  * Acquire a nfsd_file object that is not GC'ed. If one doesn't already exist,
1178  * and @file is non-NULL, use it to instantiate a new nfsd_file instead of
1179  * opening a new one.
1180  *
1181  * Return values:
1182  *   %nfs_ok - @pnf points to an nfsd_file with its reference
1183  *   count boosted.
1184  *
1185  * On error, an nfsstat value in network byte order is returned.
1186  */
1187 __be32
1188 nfsd_file_acquire_opened(struct svc_rqst *rqstp, struct svc_fh *fhp,
1189                          unsigned int may_flags, struct file *file,
1190                          struct nfsd_file **pnf)
1191 {
1192         return nfsd_file_do_acquire(rqstp, fhp, may_flags, file, pnf, false);
1193 }
1194
1195 /*
1196  * Note that fields may be added, removed or reordered in the future. Programs
1197  * scraping this file for info should test the labels to ensure they're
1198  * getting the correct field.
1199  */
1200 int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
1201 {
1202         unsigned long releases = 0, evictions = 0;
1203         unsigned long hits = 0, acquisitions = 0;
1204         unsigned int i, count = 0, buckets = 0;
1205         unsigned long lru = 0, total_age = 0;
1206
1207         /* Serialize with server shutdown */
1208         mutex_lock(&nfsd_mutex);
1209         if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 1) {
1210                 struct bucket_table *tbl;
1211                 struct rhashtable *ht;
1212
1213                 lru = list_lru_count(&nfsd_file_lru);
1214
1215                 rcu_read_lock();
1216                 ht = &nfsd_file_rhltable.ht;
1217                 count = atomic_read(&ht->nelems);
1218                 tbl = rht_dereference_rcu(ht->tbl, ht);
1219                 buckets = tbl->size;
1220                 rcu_read_unlock();
1221         }
1222         mutex_unlock(&nfsd_mutex);
1223
1224         for_each_possible_cpu(i) {
1225                 hits += per_cpu(nfsd_file_cache_hits, i);
1226                 acquisitions += per_cpu(nfsd_file_acquisitions, i);
1227                 releases += per_cpu(nfsd_file_releases, i);
1228                 total_age += per_cpu(nfsd_file_total_age, i);
1229                 evictions += per_cpu(nfsd_file_evictions, i);
1230         }
1231
1232         seq_printf(m, "total inodes:  %u\n", count);
1233         seq_printf(m, "hash buckets:  %u\n", buckets);
1234         seq_printf(m, "lru entries:   %lu\n", lru);
1235         seq_printf(m, "cache hits:    %lu\n", hits);
1236         seq_printf(m, "acquisitions:  %lu\n", acquisitions);
1237         seq_printf(m, "releases:      %lu\n", releases);
1238         seq_printf(m, "evictions:     %lu\n", evictions);
1239         if (releases)
1240                 seq_printf(m, "mean age (ms): %ld\n", total_age / releases);
1241         else
1242                 seq_printf(m, "mean age (ms): -\n");
1243         return 0;
1244 }