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         struct work_struct work;
  65         spinlock_t lock;
  66         struct list_head freeme;
  67 };
  68
  69 static struct workqueue_struct *nfsd_filecache_wq __read_mostly;
  70
  71 static struct kmem_cache                *nfsd_file_slab;
  72 static struct kmem_cache                *nfsd_file_mark_slab;
  73 static struct list_lru                  nfsd_file_lru;
  74 static unsigned long                    nfsd_file_flags;
  75 static struct fsnotify_group            *nfsd_file_fsnotify_group;
  76 static struct delayed_work              nfsd_filecache_laundrette;
  77 static struct rhltable                  nfsd_file_rhltable
  78                                                 ____cacheline_aligned_in_smp;
  79
  80 static bool
  81 nfsd_match_cred(const struct cred *c1, const struct cred *c2)
  82 {
  83         int i;
  84
  85         if (!uid_eq(c1->fsuid, c2->fsuid))
  86                 return false;
  87         if (!gid_eq(c1->fsgid, c2->fsgid))
  88                 return false;
  89         if (c1->group_info == NULL || c2->group_info == NULL)
  90                 return c1->group_info == c2->group_info;
  91         if (c1->group_info->ngroups != c2->group_info->ngroups)
  92                 return false;
  93         for (i = 0; i < c1->group_info->ngroups; i++) {
  94                 if (!gid_eq(c1->group_info->gid[i], c2->group_info->gid[i]))
  95                         return false;
  96         }
  97         return true;
  98 }
  99
 100 static const struct rhashtable_params nfsd_file_rhash_params = {
 101         .key_len                = sizeof_field(struct nfsd_file, nf_inode),
 102         .key_offset             = offsetof(struct nfsd_file, nf_inode),
 103         .head_offset            = offsetof(struct nfsd_file, nf_rlist),
 104
 105         /*
 106          * Start with a single page hash table to reduce resizing churn
 107          * on light workloads.
 108          */
 109         .min_size               = 256,
 110         .automatic_shrinking    = true,
 111 };
 112
 113 static void
 114 nfsd_file_schedule_laundrette(void)
 115 {
 116         if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags))
 117                 queue_delayed_work(system_wq, &nfsd_filecache_laundrette,
 118                                    NFSD_LAUNDRETTE_DELAY);
 119 }
 120
 121 static void
 122 nfsd_file_slab_free(struct rcu_head *rcu)
 123 {
 124         struct nfsd_file *nf = container_of(rcu, struct nfsd_file, nf_rcu);
 125
 126         put_cred(nf->nf_cred);
 127         kmem_cache_free(nfsd_file_slab, nf);
 128 }
 129
 130 static void
 131 nfsd_file_mark_free(struct fsnotify_mark *mark)
 132 {
 133         struct nfsd_file_mark *nfm = container_of(mark, struct nfsd_file_mark,
 134                                                   nfm_mark);
 135
 136         kmem_cache_free(nfsd_file_mark_slab, nfm);
 137 }
 138
 139 static struct nfsd_file_mark *
 140 nfsd_file_mark_get(struct nfsd_file_mark *nfm)
 141 {
 142         if (!refcount_inc_not_zero(&nfm->nfm_ref))
 143                 return NULL;
 144         return nfm;
 145 }
 146
 147 static void
 148 nfsd_file_mark_put(struct nfsd_file_mark *nfm)
 149 {
 150         if (refcount_dec_and_test(&nfm->nfm_ref)) {
 151                 fsnotify_destroy_mark(&nfm->nfm_mark, nfsd_file_fsnotify_group);
 152                 fsnotify_put_mark(&nfm->nfm_mark);
 153         }
 154 }
 155
 156 static struct nfsd_file_mark *
 157 nfsd_file_mark_find_or_create(struct nfsd_file *nf, struct inode *inode)
 158 {
 159         int                     err;
 160         struct fsnotify_mark    *mark;
 161         struct nfsd_file_mark   *nfm = NULL, *new;
 162
 163         do {
 164                 fsnotify_group_lock(nfsd_file_fsnotify_group);
 165                 mark = fsnotify_find_mark(&inode->i_fsnotify_marks,
 166                                           nfsd_file_fsnotify_group);
 167                 if (mark) {
 168                         nfm = nfsd_file_mark_get(container_of(mark,
 169                                                  struct nfsd_file_mark,
 170                                                  nfm_mark));
 171                         fsnotify_group_unlock(nfsd_file_fsnotify_group);
 172                         if (nfm) {
 173                                 fsnotify_put_mark(mark);
 174                                 break;
 175                         }
 176                         /* Avoid soft lockup race with nfsd_file_mark_put() */
 177                         fsnotify_destroy_mark(mark, nfsd_file_fsnotify_group);
 178                         fsnotify_put_mark(mark);
 179                 } else {
 180                         fsnotify_group_unlock(nfsd_file_fsnotify_group);
 181                 }
 182
 183                 /* allocate a new nfm */
 184                 new = kmem_cache_alloc(nfsd_file_mark_slab, GFP_KERNEL);
 185                 if (!new)
 186                         return NULL;
 187                 fsnotify_init_mark(&new->nfm_mark, nfsd_file_fsnotify_group);
 188                 new->nfm_mark.mask = FS_ATTRIB|FS_DELETE_SELF;
 189                 refcount_set(&new->nfm_ref, 1);
 190
 191                 err = fsnotify_add_inode_mark(&new->nfm_mark, inode, 0);
 192
 193                 /*
 194                  * If the add was successful, then return the object.
 195                  * Otherwise, we need to put the reference we hold on the
 196                  * nfm_mark. The fsnotify code will take a reference and put
 197                  * it on failure, so we can't just free it directly. It's also
 198                  * not safe to call fsnotify_destroy_mark on it as the
 199                  * mark->group will be NULL. Thus, we can't let the nfm_ref
 200                  * counter drive the destruction at this point.
 201                  */
 202                 if (likely(!err))
 203                         nfm = new;
 204                 else
 205                         fsnotify_put_mark(&new->nfm_mark);
 206         } while (unlikely(err == -EEXIST));
 207
 208         return nfm;
 209 }
 210
 211 static struct nfsd_file *
 212 nfsd_file_alloc(struct net *net, struct inode *inode, unsigned char need,
 213                 bool want_gc)
 214 {
 215         struct nfsd_file *nf;
 216
 217         nf = kmem_cache_alloc(nfsd_file_slab, GFP_KERNEL);
 218         if (unlikely(!nf))
 219                 return NULL;
 220
 221         INIT_LIST_HEAD(&nf->nf_lru);
 222         nf->nf_birthtime = ktime_get();
 223         nf->nf_file = NULL;
 224         nf->nf_cred = get_current_cred();
 225         nf->nf_net = net;
 226         nf->nf_flags = want_gc ?
 227                 BIT(NFSD_FILE_HASHED) | BIT(NFSD_FILE_PENDING) | BIT(NFSD_FILE_GC) :
 228                 BIT(NFSD_FILE_HASHED) | BIT(NFSD_FILE_PENDING);
 229         nf->nf_inode = inode;
 230         refcount_set(&nf->nf_ref, 1);
 231         nf->nf_may = need;
 232         nf->nf_mark = NULL;
 233         return nf;
 234 }
 235
 236 /**
 237  * nfsd_file_check_write_error - check for writeback errors on a file
 238  * @nf: nfsd_file to check for writeback errors
 239  *
 240  * Check whether a nfsd_file has an unseen error. Reset the write
 241  * verifier if so.
 242  */
 243 static void
 244 nfsd_file_check_write_error(struct nfsd_file *nf)
 245 {
 246         struct file *file = nf->nf_file;
 247
 248         if ((file->f_mode & FMODE_WRITE) &&
 249             filemap_check_wb_err(file->f_mapping, READ_ONCE(file->f_wb_err)))
 250                 nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id));
 251 }
 252
 253 static void
 254 nfsd_file_hash_remove(struct nfsd_file *nf)
 255 {
 256         trace_nfsd_file_unhash(nf);
 257         rhltable_remove(&nfsd_file_rhltable, &nf->nf_rlist,
 258                         nfsd_file_rhash_params);
 259 }
 260
 261 static bool
 262 nfsd_file_unhash(struct nfsd_file *nf)
 263 {
 264         if (test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
 265                 nfsd_file_hash_remove(nf);
 266                 return true;
 267         }
 268         return false;
 269 }
 270
 271 static void
 272 nfsd_file_free(struct nfsd_file *nf)
 273 {
 274         s64 age = ktime_to_ms(ktime_sub(ktime_get(), nf->nf_birthtime));
 275
 276         trace_nfsd_file_free(nf);
 277
 278         this_cpu_inc(nfsd_file_releases);
 279         this_cpu_add(nfsd_file_total_age, age);
 280
 281         nfsd_file_unhash(nf);
 282         if (nf->nf_mark)
 283                 nfsd_file_mark_put(nf->nf_mark);
 284         if (nf->nf_file) {
 285                 nfsd_file_check_write_error(nf);
 286                 filp_close(nf->nf_file, NULL);
 287         }
 288
 289         /*
 290          * If this item is still linked via nf_lru, that's a bug.
 291          * WARN and leak it to preserve system stability.
 292          */
 293         if (WARN_ON_ONCE(!list_empty(&nf->nf_lru)))
 294                 return;
 295
 296         call_rcu(&nf->nf_rcu, nfsd_file_slab_free);
 297 }
 298
 299 static bool
 300 nfsd_file_check_writeback(struct nfsd_file *nf)
 301 {
 302         struct file *file = nf->nf_file;
 303         struct address_space *mapping;
 304
 305         /* File not open for write? */
 306         if (!(file->f_mode & FMODE_WRITE))
 307                 return false;
 308
 309         /*
 310          * Some filesystems (e.g. NFS) flush all dirty data on close.
 311          * On others, there is no need to wait for writeback.
 312          */
 313         if (!(file_inode(file)->i_sb->s_export_op->flags & EXPORT_OP_FLUSH_ON_CLOSE))
 314                 return false;
 315
 316         mapping = file->f_mapping;
 317         return mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) ||
 318                 mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK);
 319 }
 320
 321
 322 static bool nfsd_file_lru_add(struct nfsd_file *nf)
 323 {
 324         set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags);
 325         if (list_lru_add(&nfsd_file_lru, &nf->nf_lru)) {
 326                 trace_nfsd_file_lru_add(nf);
 327                 return true;
 328         }
 329         return false;
 330 }
 331
 332 static bool nfsd_file_lru_remove(struct nfsd_file *nf)
 333 {
 334         if (list_lru_del(&nfsd_file_lru, &nf->nf_lru)) {
 335                 trace_nfsd_file_lru_del(nf);
 336                 return true;
 337         }
 338         return false;
 339 }
 340
 341 struct nfsd_file *
 342 nfsd_file_get(struct nfsd_file *nf)
 343 {
 344         if (nf && refcount_inc_not_zero(&nf->nf_ref))
 345                 return nf;
 346         return NULL;
 347 }
 348
 349 /**
 350  * nfsd_file_put - put the reference to a nfsd_file
 351  * @nf: nfsd_file of which to put the reference
 352  *
 353  * Put a reference to a nfsd_file. In the non-GC case, we just put the
 354  * reference immediately. In the GC case, if the reference would be
 355  * the last one, the put it on the LRU instead to be cleaned up later.
 356  */
 357 void
 358 nfsd_file_put(struct nfsd_file *nf)
 359 {
 360         might_sleep();
 361         trace_nfsd_file_put(nf);
 362
 363         if (test_bit(NFSD_FILE_GC, &nf->nf_flags) &&
 364             test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
 365                 /*
 366                  * If this is the last reference (nf_ref == 1), then try to
 367                  * transfer it to the LRU.
 368                  */
 369                 if (refcount_dec_not_one(&nf->nf_ref))
 370                         return;
 371
 372                 /* Try to add it to the LRU.  If that fails, decrement. */
 373                 if (nfsd_file_lru_add(nf)) {
 374                         /* If it's still hashed, we're done */
 375                         if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
 376                                 nfsd_file_schedule_laundrette();
 377                                 return;
 378                         }
 379
 380                         /*
 381                          * We're racing with unhashing, so try to remove it from
 382                          * the LRU. If removal fails, then someone else already
 383                          * has our reference.
 384                          */
 385                         if (!nfsd_file_lru_remove(nf))
 386                                 return;
 387                 }
 388         }
 389         if (refcount_dec_and_test(&nf->nf_ref))
 390                 nfsd_file_free(nf);
 391 }
 392
 393 static void
 394 nfsd_file_dispose_list(struct list_head *dispose)
 395 {
 396         struct nfsd_file *nf;
 397
 398         while (!list_empty(dispose)) {
 399                 nf = list_first_entry(dispose, struct nfsd_file, nf_lru);
 400                 list_del_init(&nf->nf_lru);
 401                 nfsd_file_free(nf);
 402         }
 403 }
 404
 405 /**
 406  * nfsd_file_dispose_list_delayed - move list of dead files to net's freeme list
 407  * @dispose: list of nfsd_files to be disposed
 408  *
 409  * Transfers each file to the "freeme" list for its nfsd_net, to eventually
 410  * be disposed of by the per-net garbage collector.
 411  */
 412 static void
 413 nfsd_file_dispose_list_delayed(struct list_head *dispose)
 414 {
 415         while(!list_empty(dispose)) {
 416                 struct nfsd_file *nf = list_first_entry(dispose,
 417                                                 struct nfsd_file, nf_lru);
 418                 struct nfsd_net *nn = net_generic(nf->nf_net, nfsd_net_id);
 419                 struct nfsd_fcache_disposal *l = nn->fcache_disposal;
 420
 421                 spin_lock(&l->lock);
 422                 list_move_tail(&nf->nf_lru, &l->freeme);
 423                 spin_unlock(&l->lock);
 424                 queue_work(nfsd_filecache_wq, &l->work);
 425         }
 426 }
 427
 428 /**
 429  * nfsd_file_lru_cb - Examine an entry on the LRU list
 430  * @item: LRU entry to examine
 431  * @lru: controlling LRU
 432  * @lock: LRU list lock (unused)
 433  * @arg: dispose list
 434  *
 435  * Return values:
 436  *   %LRU_REMOVED: @item was removed from the LRU
 437  *   %LRU_ROTATE: @item is to be moved to the LRU tail
 438  *   %LRU_SKIP: @item cannot be evicted
 439  */
 440 static enum lru_status
 441 nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru,
 442                  spinlock_t *lock, void *arg)
 443         __releases(lock)
 444         __acquires(lock)
 445 {
 446         struct list_head *head = arg;
 447         struct nfsd_file *nf = list_entry(item, struct nfsd_file, nf_lru);
 448
 449         /* We should only be dealing with GC entries here */
 450         WARN_ON_ONCE(!test_bit(NFSD_FILE_GC, &nf->nf_flags));
 451
 452         /*
 453          * Don't throw out files that are still undergoing I/O or
 454          * that have uncleared errors pending.
 455          */
 456         if (nfsd_file_check_writeback(nf)) {
 457                 trace_nfsd_file_gc_writeback(nf);
 458                 return LRU_SKIP;
 459         }
 460
 461         /* If it was recently added to the list, skip it */
 462         if (test_and_clear_bit(NFSD_FILE_REFERENCED, &nf->nf_flags)) {
 463                 trace_nfsd_file_gc_referenced(nf);
 464                 return LRU_ROTATE;
 465         }
 466
 467         /*
 468          * Put the reference held on behalf of the LRU. If it wasn't the last
 469          * one, then just remove it from the LRU and ignore it.
 470          */
 471         if (!refcount_dec_and_test(&nf->nf_ref)) {
 472                 trace_nfsd_file_gc_in_use(nf);
 473                 list_lru_isolate(lru, &nf->nf_lru);
 474                 return LRU_REMOVED;
 475         }
 476
 477         /* Refcount went to zero. Unhash it and queue it to the dispose list */
 478         nfsd_file_unhash(nf);
 479         list_lru_isolate_move(lru, &nf->nf_lru, head);
 480         this_cpu_inc(nfsd_file_evictions);
 481         trace_nfsd_file_gc_disposed(nf);
 482         return LRU_REMOVED;
 483 }
 484
 485 static void
 486 nfsd_file_gc(void)
 487 {
 488         LIST_HEAD(dispose);
 489         unsigned long ret;
 490
 491         ret = list_lru_walk(&nfsd_file_lru, nfsd_file_lru_cb,
 492                             &dispose, list_lru_count(&nfsd_file_lru));
 493         trace_nfsd_file_gc_removed(ret, list_lru_count(&nfsd_file_lru));
 494         nfsd_file_dispose_list_delayed(&dispose);
 495 }
 496
 497 static void
 498 nfsd_file_gc_worker(struct work_struct *work)
 499 {
 500         nfsd_file_gc();
 501         if (list_lru_count(&nfsd_file_lru))
 502                 nfsd_file_schedule_laundrette();
 503 }
 504
 505 static unsigned long
 506 nfsd_file_lru_count(struct shrinker *s, struct shrink_control *sc)
 507 {
 508         return list_lru_count(&nfsd_file_lru);
 509 }
 510
 511 static unsigned long
 512 nfsd_file_lru_scan(struct shrinker *s, struct shrink_control *sc)
 513 {
 514         LIST_HEAD(dispose);
 515         unsigned long ret;
 516
 517         ret = list_lru_shrink_walk(&nfsd_file_lru, sc,
 518                                    nfsd_file_lru_cb, &dispose);
 519         trace_nfsd_file_shrinker_removed(ret, list_lru_count(&nfsd_file_lru));
 520         nfsd_file_dispose_list_delayed(&dispose);
 521         return ret;
 522 }
 523
 524 static struct shrinker *nfsd_file_shrinker;
 525
 526 /**
 527  * nfsd_file_cond_queue - conditionally unhash and queue a nfsd_file
 528  * @nf: nfsd_file to attempt to queue
 529  * @dispose: private list to queue successfully-put objects
 530  *
 531  * Unhash an nfsd_file, try to get a reference to it, and then put that
 532  * reference. If it's the last reference, queue it to the dispose list.
 533  */
 534 static void
 535 nfsd_file_cond_queue(struct nfsd_file *nf, struct list_head *dispose)
 536         __must_hold(RCU)
 537 {
 538         int decrement = 1;
 539
 540         /* If we raced with someone else unhashing, ignore it */
 541         if (!nfsd_file_unhash(nf))
 542                 return;
 543
 544         /* If we can't get a reference, ignore it */
 545         if (!nfsd_file_get(nf))
 546                 return;
 547
 548         /* Extra decrement if we remove from the LRU */
 549         if (nfsd_file_lru_remove(nf))
 550                 ++decrement;
 551
 552         /* If refcount goes to 0, then put on the dispose list */
 553         if (refcount_sub_and_test(decrement, &nf->nf_ref)) {
 554                 list_add(&nf->nf_lru, dispose);
 555                 trace_nfsd_file_closing(nf);
 556         }
 557 }
 558
 559 /**
 560  * nfsd_file_queue_for_close: try to close out any open nfsd_files for an inode
 561  * @inode:   inode on which to close out nfsd_files
 562  * @dispose: list on which to gather nfsd_files to close out
 563  *
 564  * An nfsd_file represents a struct file being held open on behalf of nfsd.
 565  * An open file however can block other activity (such as leases), or cause
 566  * undesirable behavior (e.g. spurious silly-renames when reexporting NFS).
 567  *
 568  * This function is intended to find open nfsd_files when this sort of
 569  * conflicting access occurs and then attempt to close those files out.
 570  *
 571  * Populates the dispose list with entries that have already had their
 572  * refcounts go to zero. The actual free of an nfsd_file can be expensive,
 573  * so we leave it up to the caller whether it wants to wait or not.
 574  */
 575 static void
 576 nfsd_file_queue_for_close(struct inode *inode, struct list_head *dispose)
 577 {
 578         struct rhlist_head *tmp, *list;
 579         struct nfsd_file *nf;
 580
 581         rcu_read_lock();
 582         list = rhltable_lookup(&nfsd_file_rhltable, &inode,
 583                                nfsd_file_rhash_params);
 584         rhl_for_each_entry_rcu(nf, tmp, list, nf_rlist) {
 585                 if (!test_bit(NFSD_FILE_GC, &nf->nf_flags))
 586                         continue;
 587                 nfsd_file_cond_queue(nf, dispose);
 588         }
 589         rcu_read_unlock();
 590 }
 591
 592 /**
 593  * nfsd_file_close_inode - attempt a delayed close of a nfsd_file
 594  * @inode: inode of the file to attempt to remove
 595  *
 596  * Close out any open nfsd_files that can be reaped for @inode. The
 597  * actual freeing is deferred to the dispose_list_delayed infrastructure.
 598  *
 599  * This is used by the fsnotify callbacks and setlease notifier.
 600  */
 601 static void
 602 nfsd_file_close_inode(struct inode *inode)
 603 {
 604         LIST_HEAD(dispose);
 605
 606         nfsd_file_queue_for_close(inode, &dispose);
 607         nfsd_file_dispose_list_delayed(&dispose);
 608 }
 609
 610 /**
 611  * nfsd_file_close_inode_sync - attempt to forcibly close a nfsd_file
 612  * @inode: inode of the file to attempt to remove
 613  *
 614  * Close out any open nfsd_files that can be reaped for @inode. The
 615  * nfsd_files are closed out synchronously.
 616  *
 617  * This is called from nfsd_rename and nfsd_unlink to avoid silly-renames
 618  * when reexporting NFS.
 619  */
 620 void
 621 nfsd_file_close_inode_sync(struct inode *inode)
 622 {
 623         struct nfsd_file *nf;
 624         LIST_HEAD(dispose);
 625
 626         trace_nfsd_file_close(inode);
 627
 628         nfsd_file_queue_for_close(inode, &dispose);
 629         while (!list_empty(&dispose)) {
 630                 nf = list_first_entry(&dispose, struct nfsd_file, nf_lru);
 631                 list_del_init(&nf->nf_lru);
 632                 nfsd_file_free(nf);
 633         }
 634         flush_delayed_fput();
 635 }
 636
 637 /**
 638  * nfsd_file_delayed_close - close unused nfsd_files
 639  * @work: dummy
 640  *
 641  * Scrape the freeme list for this nfsd_net, and then dispose of them
 642  * all.
 643  */
 644 static void
 645 nfsd_file_delayed_close(struct work_struct *work)
 646 {
 647         LIST_HEAD(head);
 648         struct nfsd_fcache_disposal *l = container_of(work,
 649                         struct nfsd_fcache_disposal, work);
 650
 651         spin_lock(&l->lock);
 652         list_splice_init(&l->freeme, &head);
 653         spin_unlock(&l->lock);
 654
 655         nfsd_file_dispose_list(&head);
 656 }
 657
 658 static int
 659 nfsd_file_lease_notifier_call(struct notifier_block *nb, unsigned long arg,
 660                             void *data)
 661 {
 662         struct file_lock *fl = data;
 663
 664         /* Only close files for F_SETLEASE leases */
 665         if (fl->fl_flags & FL_LEASE)
 666                 nfsd_file_close_inode(file_inode(fl->fl_file));
 667         return 0;
 668 }
 669
 670 static struct notifier_block nfsd_file_lease_notifier = {
 671         .notifier_call = nfsd_file_lease_notifier_call,
 672 };
 673
 674 static int
 675 nfsd_file_fsnotify_handle_event(struct fsnotify_mark *mark, u32 mask,
 676                                 struct inode *inode, struct inode *dir,
 677                                 const struct qstr *name, u32 cookie)
 678 {
 679         if (WARN_ON_ONCE(!inode))
 680                 return 0;
 681
 682         trace_nfsd_file_fsnotify_handle_event(inode, mask);
 683
 684         /* Should be no marks on non-regular files */
 685         if (!S_ISREG(inode->i_mode)) {
 686                 WARN_ON_ONCE(1);
 687                 return 0;
 688         }
 689
 690         /* don't close files if this was not the last link */
 691         if (mask & FS_ATTRIB) {
 692                 if (inode->i_nlink)
 693                         return 0;
 694         }
 695
 696         nfsd_file_close_inode(inode);
 697         return 0;
 698 }
 699
 700
 701 static const struct fsnotify_ops nfsd_file_fsnotify_ops = {
 702         .handle_inode_event = nfsd_file_fsnotify_handle_event,
 703         .free_mark = nfsd_file_mark_free,
 704 };
 705
 706 int
 707 nfsd_file_cache_init(void)
 708 {
 709         int ret;
 710
 711         lockdep_assert_held(&nfsd_mutex);
 712         if (test_and_set_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 1)
 713                 return 0;
 714
 715         ret = rhltable_init(&nfsd_file_rhltable, &nfsd_file_rhash_params);
 716         if (ret)
 717                 return ret;
 718
 719         ret = -ENOMEM;
 720         nfsd_filecache_wq = alloc_workqueue("nfsd_filecache", 0, 0);
 721         if (!nfsd_filecache_wq)
 722                 goto out;
 723
 724         nfsd_file_slab = kmem_cache_create("nfsd_file",
 725                                 sizeof(struct nfsd_file), 0, 0, NULL);
 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_create("nfsd_file_mark",
 732                                         sizeof(struct nfsd_file_mark), 0, 0, NULL);
 733         if (!nfsd_file_mark_slab) {
 734                 pr_err("nfsd: unable to create nfsd_file_mark_slab\n");
 735                 goto out_err;
 736         }
 737
 738
 739         ret = list_lru_init(&nfsd_file_lru);
 740         if (ret) {
 741                 pr_err("nfsd: failed to init nfsd_file_lru: %d\n", ret);
 742                 goto out_err;
 743         }
 744
 745         nfsd_file_shrinker = shrinker_alloc(0, "nfsd-filecache");
 746         if (!nfsd_file_shrinker) {
 747                 ret = -ENOMEM;
 748                 pr_err("nfsd: failed to allocate nfsd_file_shrinker\n");
 749                 goto out_lru;
 750         }
 751
 752         nfsd_file_shrinker->count_objects = nfsd_file_lru_count;
 753         nfsd_file_shrinker->scan_objects = nfsd_file_lru_scan;
 754         nfsd_file_shrinker->seeks = 1;
 755
 756         shrinker_register(nfsd_file_shrinker);
 757
 758         ret = lease_register_notifier(&nfsd_file_lease_notifier);
 759         if (ret) {
 760                 pr_err("nfsd: unable to register lease notifier: %d\n", ret);
 761                 goto out_shrinker;
 762         }
 763
 764         nfsd_file_fsnotify_group = fsnotify_alloc_group(&nfsd_file_fsnotify_ops,
 765                                                         FSNOTIFY_GROUP_NOFS);
 766         if (IS_ERR(nfsd_file_fsnotify_group)) {
 767                 pr_err("nfsd: unable to create fsnotify group: %ld\n",
 768                         PTR_ERR(nfsd_file_fsnotify_group));
 769                 ret = PTR_ERR(nfsd_file_fsnotify_group);
 770                 nfsd_file_fsnotify_group = NULL;
 771                 goto out_notifier;
 772         }
 773
 774         INIT_DELAYED_WORK(&nfsd_filecache_laundrette, nfsd_file_gc_worker);
 775 out:
 776         return ret;
 777 out_notifier:
 778         lease_unregister_notifier(&nfsd_file_lease_notifier);
 779 out_shrinker:
 780         shrinker_free(nfsd_file_shrinker);
 781 out_lru:
 782         list_lru_destroy(&nfsd_file_lru);
 783 out_err:
 784         kmem_cache_destroy(nfsd_file_slab);
 785         nfsd_file_slab = NULL;
 786         kmem_cache_destroy(nfsd_file_mark_slab);
 787         nfsd_file_mark_slab = NULL;
 788         destroy_workqueue(nfsd_filecache_wq);
 789         nfsd_filecache_wq = NULL;
 790         rhltable_destroy(&nfsd_file_rhltable);
 791         goto out;
 792 }
 793
 794 /**
 795  * __nfsd_file_cache_purge: clean out the cache for shutdown
 796  * @net: net-namespace to shut down the cache (may be NULL)
 797  *
 798  * Walk the nfsd_file cache and close out any that match @net. If @net is NULL,
 799  * then close out everything. Called when an nfsd instance is being shut down,
 800  * and when the exports table is flushed.
 801  */
 802 static void
 803 __nfsd_file_cache_purge(struct net *net)
 804 {
 805         struct rhashtable_iter iter;
 806         struct nfsd_file *nf;
 807         LIST_HEAD(dispose);
 808
 809         rhltable_walk_enter(&nfsd_file_rhltable, &iter);
 810         do {
 811                 rhashtable_walk_start(&iter);
 812
 813                 nf = rhashtable_walk_next(&iter);
 814                 while (!IS_ERR_OR_NULL(nf)) {
 815                         if (!net || nf->nf_net == net)
 816                                 nfsd_file_cond_queue(nf, &dispose);
 817                         nf = rhashtable_walk_next(&iter);
 818                 }
 819
 820                 rhashtable_walk_stop(&iter);
 821         } while (nf == ERR_PTR(-EAGAIN));
 822         rhashtable_walk_exit(&iter);
 823
 824         nfsd_file_dispose_list(&dispose);
 825 }
 826
 827 static struct nfsd_fcache_disposal *
 828 nfsd_alloc_fcache_disposal(void)
 829 {
 830         struct nfsd_fcache_disposal *l;
 831
 832         l = kmalloc(sizeof(*l), GFP_KERNEL);
 833         if (!l)
 834                 return NULL;
 835         INIT_WORK(&l->work, nfsd_file_delayed_close);
 836         spin_lock_init(&l->lock);
 837         INIT_LIST_HEAD(&l->freeme);
 838         return l;
 839 }
 840
 841 static void
 842 nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l)
 843 {
 844         cancel_work_sync(&l->work);
 845         nfsd_file_dispose_list(&l->freeme);
 846         kfree(l);
 847 }
 848
 849 static void
 850 nfsd_free_fcache_disposal_net(struct net *net)
 851 {
 852         struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 853         struct nfsd_fcache_disposal *l = nn->fcache_disposal;
 854
 855         nfsd_free_fcache_disposal(l);
 856 }
 857
 858 int
 859 nfsd_file_cache_start_net(struct net *net)
 860 {
 861         struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 862
 863         nn->fcache_disposal = nfsd_alloc_fcache_disposal();
 864         return nn->fcache_disposal ? 0 : -ENOMEM;
 865 }
 866
 867 /**
 868  * nfsd_file_cache_purge - Remove all cache items associated with @net
 869  * @net: target net namespace
 870  *
 871  */
 872 void
 873 nfsd_file_cache_purge(struct net *net)
 874 {
 875         lockdep_assert_held(&nfsd_mutex);
 876         if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 1)
 877                 __nfsd_file_cache_purge(net);
 878 }
 879
 880 void
 881 nfsd_file_cache_shutdown_net(struct net *net)
 882 {
 883         nfsd_file_cache_purge(net);
 884         nfsd_free_fcache_disposal_net(net);
 885 }
 886
 887 void
 888 nfsd_file_cache_shutdown(void)
 889 {
 890         int i;
 891
 892         lockdep_assert_held(&nfsd_mutex);
 893         if (test_and_clear_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 0)
 894                 return;
 895
 896         lease_unregister_notifier(&nfsd_file_lease_notifier);
 897         shrinker_free(nfsd_file_shrinker);
 898         /*
 899          * make sure all callers of nfsd_file_lru_cb are done before
 900          * calling nfsd_file_cache_purge
 901          */
 902         cancel_delayed_work_sync(&nfsd_filecache_laundrette);
 903         __nfsd_file_cache_purge(NULL);
 904         list_lru_destroy(&nfsd_file_lru);
 905         rcu_barrier();
 906         fsnotify_put_group(nfsd_file_fsnotify_group);
 907         nfsd_file_fsnotify_group = NULL;
 908         kmem_cache_destroy(nfsd_file_slab);
 909         nfsd_file_slab = NULL;
 910         fsnotify_wait_marks_destroyed();
 911         kmem_cache_destroy(nfsd_file_mark_slab);
 912         nfsd_file_mark_slab = NULL;
 913         destroy_workqueue(nfsd_filecache_wq);
 914         nfsd_filecache_wq = NULL;
 915         rhltable_destroy(&nfsd_file_rhltable);
 916
 917         for_each_possible_cpu(i) {
 918                 per_cpu(nfsd_file_cache_hits, i) = 0;
 919                 per_cpu(nfsd_file_acquisitions, i) = 0;
 920                 per_cpu(nfsd_file_releases, i) = 0;
 921                 per_cpu(nfsd_file_total_age, i) = 0;
 922                 per_cpu(nfsd_file_evictions, i) = 0;
 923         }
 924 }
 925
 926 static struct nfsd_file *
 927 nfsd_file_lookup_locked(const struct net *net, const struct cred *cred,
 928                         struct inode *inode, unsigned char need,
 929                         bool want_gc)
 930 {
 931         struct rhlist_head *tmp, *list;
 932         struct nfsd_file *nf;
 933
 934         list = rhltable_lookup(&nfsd_file_rhltable, &inode,
 935                                nfsd_file_rhash_params);
 936         rhl_for_each_entry_rcu(nf, tmp, list, nf_rlist) {
 937                 if (nf->nf_may != need)
 938                         continue;
 939                 if (nf->nf_net != net)
 940                         continue;
 941                 if (!nfsd_match_cred(nf->nf_cred, cred))
 942                         continue;
 943                 if (test_bit(NFSD_FILE_GC, &nf->nf_flags) != want_gc)
 944                         continue;
 945                 if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags) == 0)
 946                         continue;
 947
 948                 if (!nfsd_file_get(nf))
 949                         continue;
 950                 return nf;
 951         }
 952         return NULL;
 953 }
 954
 955 /**
 956  * nfsd_file_is_cached - are there any cached open files for this inode?
 957  * @inode: inode to check
 958  *
 959  * The lookup matches inodes in all net namespaces and is atomic wrt
 960  * nfsd_file_acquire().
 961  *
 962  * Return values:
 963  *   %true: filecache contains at least one file matching this inode
 964  *   %false: filecache contains no files matching this inode
 965  */
 966 bool
 967 nfsd_file_is_cached(struct inode *inode)
 968 {
 969         struct rhlist_head *tmp, *list;
 970         struct nfsd_file *nf;
 971         bool ret = false;
 972
 973         rcu_read_lock();
 974         list = rhltable_lookup(&nfsd_file_rhltable, &inode,
 975                                nfsd_file_rhash_params);
 976         rhl_for_each_entry_rcu(nf, tmp, list, nf_rlist)
 977                 if (test_bit(NFSD_FILE_GC, &nf->nf_flags)) {
 978                         ret = true;
 979                         break;
 980                 }
 981         rcu_read_unlock();
 982
 983         trace_nfsd_file_is_cached(inode, (int)ret);
 984         return ret;
 985 }
 986
 987 static __be32
 988 nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
 989                      unsigned int may_flags, struct file *file,
 990                      struct nfsd_file **pnf, bool want_gc)
 991 {
 992         unsigned char need = may_flags & NFSD_FILE_MAY_MASK;
 993         struct net *net = SVC_NET(rqstp);
 994         struct nfsd_file *new, *nf;
 995         bool stale_retry = true;
 996         bool open_retry = true;
 997         struct inode *inode;
 998         __be32 status;
 999         int ret;
1000
1001 retry:
1002         status = fh_verify(rqstp, fhp, S_IFREG,
1003                                 may_flags|NFSD_MAY_OWNER_OVERRIDE);
1004         if (status != nfs_ok)
1005                 return status;
1006         inode = d_inode(fhp->fh_dentry);
1007
1008         rcu_read_lock();
1009         nf = nfsd_file_lookup_locked(net, current_cred(), inode, need, want_gc);
1010         rcu_read_unlock();
1011
1012         if (nf) {
1013                 /*
1014                  * If the nf is on the LRU then it holds an extra reference
1015                  * that must be put if it's removed. It had better not be
1016                  * the last one however, since we should hold another.
1017                  */
1018                 if (nfsd_file_lru_remove(nf))
1019                         WARN_ON_ONCE(refcount_dec_and_test(&nf->nf_ref));
1020                 goto wait_for_construction;
1021         }
1022
1023         new = nfsd_file_alloc(net, inode, need, want_gc);
1024         if (!new) {
1025                 status = nfserr_jukebox;
1026                 goto out;
1027         }
1028
1029         rcu_read_lock();
1030         spin_lock(&inode->i_lock);
1031         nf = nfsd_file_lookup_locked(net, current_cred(), inode, need, want_gc);
1032         if (unlikely(nf)) {
1033                 spin_unlock(&inode->i_lock);
1034                 rcu_read_unlock();
1035                 nfsd_file_slab_free(&new->nf_rcu);
1036                 goto wait_for_construction;
1037         }
1038         nf = new;
1039         ret = rhltable_insert(&nfsd_file_rhltable, &nf->nf_rlist,
1040                               nfsd_file_rhash_params);
1041         spin_unlock(&inode->i_lock);
1042         rcu_read_unlock();
1043         if (likely(ret == 0))
1044                 goto open_file;
1045
1046         if (ret == -EEXIST)
1047                 goto retry;
1048         trace_nfsd_file_insert_err(rqstp, inode, may_flags, ret);
1049         status = nfserr_jukebox;
1050         goto construction_err;
1051
1052 wait_for_construction:
1053         wait_on_bit(&nf->nf_flags, NFSD_FILE_PENDING, TASK_UNINTERRUPTIBLE);
1054
1055         /* Did construction of this file fail? */
1056         if (!test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
1057                 trace_nfsd_file_cons_err(rqstp, inode, may_flags, nf);
1058                 if (!open_retry) {
1059                         status = nfserr_jukebox;
1060                         goto construction_err;
1061                 }
1062                 open_retry = false;
1063                 fh_put(fhp);
1064                 goto retry;
1065         }
1066         this_cpu_inc(nfsd_file_cache_hits);
1067
1068         status = nfserrno(nfsd_open_break_lease(file_inode(nf->nf_file), may_flags));
1069         if (status != nfs_ok) {
1070                 nfsd_file_put(nf);
1071                 nf = NULL;
1072         }
1073
1074 out:
1075         if (status == nfs_ok) {
1076                 this_cpu_inc(nfsd_file_acquisitions);
1077                 nfsd_file_check_write_error(nf);
1078                 *pnf = nf;
1079         }
1080         trace_nfsd_file_acquire(rqstp, inode, may_flags, nf, status);
1081         return status;
1082
1083 open_file:
1084         trace_nfsd_file_alloc(nf);
1085         nf->nf_mark = nfsd_file_mark_find_or_create(nf, inode);
1086         if (nf->nf_mark) {
1087                 if (file) {
1088                         get_file(file);
1089                         nf->nf_file = file;
1090                         status = nfs_ok;
1091                         trace_nfsd_file_opened(nf, status);
1092                 } else {
1093                         ret = nfsd_open_verified(rqstp, fhp, may_flags,
1094                                                  &nf->nf_file);
1095                         if (ret == -EOPENSTALE && stale_retry) {
1096                                 stale_retry = false;
1097                                 nfsd_file_unhash(nf);
1098                                 clear_and_wake_up_bit(NFSD_FILE_PENDING,
1099                                                       &nf->nf_flags);
1100                                 if (refcount_dec_and_test(&nf->nf_ref))
1101                                         nfsd_file_free(nf);
1102                                 nf = NULL;
1103                                 fh_put(fhp);
1104                                 goto retry;
1105                         }
1106                         status = nfserrno(ret);
1107                         trace_nfsd_file_open(nf, status);
1108                 }
1109         } else
1110                 status = nfserr_jukebox;
1111         /*
1112          * If construction failed, or we raced with a call to unlink()
1113          * then unhash.
1114          */
1115         if (status != nfs_ok || inode->i_nlink == 0)
1116                 nfsd_file_unhash(nf);
1117         clear_and_wake_up_bit(NFSD_FILE_PENDING, &nf->nf_flags);
1118         if (status == nfs_ok)
1119                 goto out;
1120
1121 construction_err:
1122         if (refcount_dec_and_test(&nf->nf_ref))
1123                 nfsd_file_free(nf);
1124         nf = NULL;
1125         goto out;
1126 }
1127
1128 /**
1129  * nfsd_file_acquire_gc - Get a struct nfsd_file with an open file
1130  * @rqstp: the RPC transaction being executed
1131  * @fhp: the NFS filehandle of the file to be opened
1132  * @may_flags: NFSD_MAY_ settings for the file
1133  * @pnf: OUT: new or found "struct nfsd_file" object
1134  *
1135  * The nfsd_file object returned by this API is reference-counted
1136  * and garbage-collected. The object is retained for a few
1137  * seconds after the final nfsd_file_put() in case the caller
1138  * wants to re-use it.
1139  *
1140  * Return values:
1141  *   %nfs_ok - @pnf points to an nfsd_file with its reference
1142  *   count boosted.
1143  *
1144  * On error, an nfsstat value in network byte order is returned.
1145  */
1146 __be32
1147 nfsd_file_acquire_gc(struct svc_rqst *rqstp, struct svc_fh *fhp,
1148                      unsigned int may_flags, struct nfsd_file **pnf)
1149 {
1150         return nfsd_file_do_acquire(rqstp, fhp, may_flags, NULL, pnf, true);
1151 }
1152
1153 /**
1154  * nfsd_file_acquire - Get a struct nfsd_file with an open file
1155  * @rqstp: the RPC transaction being executed
1156  * @fhp: the NFS filehandle of the file to be opened
1157  * @may_flags: NFSD_MAY_ settings for the file
1158  * @pnf: OUT: new or found "struct nfsd_file" object
1159  *
1160  * The nfsd_file_object returned by this API is reference-counted
1161  * but not garbage-collected. The object is unhashed after the
1162  * final nfsd_file_put().
1163  *
1164  * Return values:
1165  *   %nfs_ok - @pnf points to an nfsd_file with its reference
1166  *   count boosted.
1167  *
1168  * On error, an nfsstat value in network byte order is returned.
1169  */
1170 __be32
1171 nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
1172                   unsigned int may_flags, struct nfsd_file **pnf)
1173 {
1174         return nfsd_file_do_acquire(rqstp, fhp, may_flags, NULL, pnf, false);
1175 }
1176
1177 /**
1178  * nfsd_file_acquire_opened - Get a struct nfsd_file using existing open file
1179  * @rqstp: the RPC transaction being executed
1180  * @fhp: the NFS filehandle of the file just created
1181  * @may_flags: NFSD_MAY_ settings for the file
1182  * @file: cached, already-open file (may be NULL)
1183  * @pnf: OUT: new or found "struct nfsd_file" object
1184  *
1185  * Acquire a nfsd_file object that is not GC'ed. If one doesn't already exist,
1186  * and @file is non-NULL, use it to instantiate a new nfsd_file instead of
1187  * opening a new one.
1188  *
1189  * Return values:
1190  *   %nfs_ok - @pnf points to an nfsd_file with its reference
1191  *   count boosted.
1192  *
1193  * On error, an nfsstat value in network byte order is returned.
1194  */
1195 __be32
1196 nfsd_file_acquire_opened(struct svc_rqst *rqstp, struct svc_fh *fhp,
1197                          unsigned int may_flags, struct file *file,
1198                          struct nfsd_file **pnf)
1199 {
1200         return nfsd_file_do_acquire(rqstp, fhp, may_flags, file, pnf, false);
1201 }
1202
1203 /*
1204  * Note that fields may be added, removed or reordered in the future. Programs
1205  * scraping this file for info should test the labels to ensure they're
1206  * getting the correct field.
1207  */
1208 int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
1209 {
1210         unsigned long releases = 0, evictions = 0;
1211         unsigned long hits = 0, acquisitions = 0;
1212         unsigned int i, count = 0, buckets = 0;
1213         unsigned long lru = 0, total_age = 0;
1214
1215         /* Serialize with server shutdown */
1216         mutex_lock(&nfsd_mutex);
1217         if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 1) {
1218                 struct bucket_table *tbl;
1219                 struct rhashtable *ht;
1220
1221                 lru = list_lru_count(&nfsd_file_lru);
1222
1223                 rcu_read_lock();
1224                 ht = &nfsd_file_rhltable.ht;
1225                 count = atomic_read(&ht->nelems);
1226                 tbl = rht_dereference_rcu(ht->tbl, ht);
1227                 buckets = tbl->size;
1228                 rcu_read_unlock();
1229         }
1230         mutex_unlock(&nfsd_mutex);
1231
1232         for_each_possible_cpu(i) {
1233                 hits += per_cpu(nfsd_file_cache_hits, i);
1234                 acquisitions += per_cpu(nfsd_file_acquisitions, i);
1235                 releases += per_cpu(nfsd_file_releases, i);
1236                 total_age += per_cpu(nfsd_file_total_age, i);
1237                 evictions += per_cpu(nfsd_file_evictions, i);
1238         }
1239
1240         seq_printf(m, "total inodes:  %u\n", count);
1241         seq_printf(m, "hash buckets:  %u\n", buckets);
1242         seq_printf(m, "lru entries:   %lu\n", lru);
1243         seq_printf(m, "cache hits:    %lu\n", hits);
1244         seq_printf(m, "acquisitions:  %lu\n", acquisitions);
1245         seq_printf(m, "releases:      %lu\n", releases);
1246         seq_printf(m, "evictions:     %lu\n", evictions);
1247         if (releases)
1248                 seq_printf(m, "mean age (ms): %ld\n", total_age / releases);
1249         else
1250                 seq_printf(m, "mean age (ms): -\n");
1251         return 0;
1252 }