Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/fs/inode.c

  1 /*
  2  * (C) 1997 Linus Torvalds
  3  * (C) 1999 Andrea Arcangeli <andrea@suse.de> (dynamic inode allocation)
  4  */
  5 #include <linux/export.h>
  6 #include <linux/fs.h>
  7 #include <linux/mm.h>
  8 #include <linux/backing-dev.h>
  9 #include <linux/hash.h>
 10 #include <linux/swap.h>
 11 #include <linux/security.h>
 12 #include <linux/cdev.h>
 13 #include <linux/bootmem.h>
 14 #include <linux/fsnotify.h>
 15 #include <linux/mount.h>
 16 #include <linux/posix_acl.h>
 17 #include <linux/prefetch.h>
 18 #include <linux/buffer_head.h> /* for inode_has_buffers */
 19 #include <linux/ratelimit.h>
 20 #include <linux/list_lru.h>
 21 #include <trace/events/writeback.h>
 22 #include "internal.h"
 23 
 24 /*
 25  * Inode locking rules:
 26  *
 27  * inode->i_lock protects:
 28  *   inode->i_state, inode->i_hash, __iget()
 29  * Inode LRU list locks protect:
 30  *   inode->i_sb->s_inode_lru, inode->i_lru
 31  * inode->i_sb->s_inode_list_lock protects:
 32  *   inode->i_sb->s_inodes, inode->i_sb_list
 33  * bdi->wb.list_lock protects:
 34  *   bdi->wb.b_{dirty,io,more_io,dirty_time}, inode->i_io_list
 35  * inode_hash_lock protects:
 36  *   inode_hashtable, inode->i_hash
 37  *
 38  * Lock ordering:
 39  *
 40  * inode->i_sb->s_inode_list_lock
 41  *   inode->i_lock
 42  *     Inode LRU list locks
 43  *
 44  * bdi->wb.list_lock
 45  *   inode->i_lock
 46  *
 47  * inode_hash_lock
 48  *   inode->i_sb->s_inode_list_lock
 49  *   inode->i_lock
 50  *
 51  * iunique_lock
 52  *   inode_hash_lock
 53  */
 54 
 55 static unsigned int i_hash_mask __read_mostly;
 56 static unsigned int i_hash_shift __read_mostly;
 57 static struct hlist_head *inode_hashtable __read_mostly;
 58 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_hash_lock);
 59 
 60 /*
 61  * Empty aops. Can be used for the cases where the user does not
 62  * define any of the address_space operations.
 63  */
 64 const struct address_space_operations empty_aops = {
 65 };
 66 EXPORT_SYMBOL(empty_aops);
 67 
 68 /*
 69  * Statistics gathering..
 70  */
 71 struct inodes_stat_t inodes_stat;
 72 
 73 static DEFINE_PER_CPU(unsigned long, nr_inodes);
 74 static DEFINE_PER_CPU(unsigned long, nr_unused);
 75 
 76 static struct kmem_cache *inode_cachep __read_mostly;
 77 
 78 static long get_nr_inodes(void)
 79 {
 80         int i;
 81         long sum = 0;
 82         for_each_possible_cpu(i)
 83                 sum += per_cpu(nr_inodes, i);
 84         return sum < 0 ? 0 : sum;
 85 }
 86 
 87 static inline long get_nr_inodes_unused(void)
 88 {
 89         int i;
 90         long sum = 0;
 91         for_each_possible_cpu(i)
 92                 sum += per_cpu(nr_unused, i);
 93         return sum < 0 ? 0 : sum;
 94 }
 95 
 96 long get_nr_dirty_inodes(void)
 97 {
 98         /* not actually dirty inodes, but a wild approximation */
 99         long nr_dirty = get_nr_inodes() - get_nr_inodes_unused();
100         return nr_dirty > 0 ? nr_dirty : 0;
101 }
102 
103 /*
104  * Handle nr_inode sysctl
105  */
106 #ifdef CONFIG_SYSCTL
107 int proc_nr_inodes(struct ctl_table *table, int write,
108                    void __user *buffer, size_t *lenp, loff_t *ppos)
109 {
110         inodes_stat.nr_inodes = get_nr_inodes();
111         inodes_stat.nr_unused = get_nr_inodes_unused();
112         return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
113 }
114 #endif
115 
116 static int no_open(struct inode *inode, struct file *file)
117 {
118         return -ENXIO;
119 }
120 
121 /**
122  * inode_init_always - perform inode structure intialisation
123  * @sb: superblock inode belongs to
124  * @inode: inode to initialise
125  *
126  * These are initializations that need to be done on every inode
127  * allocation as the fields are not initialised by slab allocation.
128  */
129 int inode_init_always(struct super_block *sb, struct inode *inode)
130 {
131         static const struct inode_operations empty_iops;
132         static const struct file_operations no_open_fops = {.open = no_open};
133         struct address_space *const mapping = &inode->i_data;
134 
135         inode->i_sb = sb;
136         inode->i_blkbits = sb->s_blocksize_bits;
137         inode->i_flags = 0;
138         atomic_set(&inode->i_count, 1);
139         inode->i_op = &empty_iops;
140         inode->i_fop = &no_open_fops;
141         inode->__i_nlink = 1;
142         inode->i_opflags = 0;
143         if (sb->s_xattr)
144                 inode->i_opflags |= IOP_XATTR;
145         i_uid_write(inode, 0);
146         i_gid_write(inode, 0);
147         atomic_set(&inode->i_writecount, 0);
148         inode->i_size = 0;
149         inode->i_blocks = 0;
150         inode->i_bytes = 0;
151         inode->i_generation = 0;
152         inode->i_pipe = NULL;
153         inode->i_bdev = NULL;
154         inode->i_cdev = NULL;
155         inode->i_link = NULL;
156         inode->i_dir_seq = 0;
157         inode->i_rdev = 0;
158         inode->dirtied_when = 0;
159 
160 #ifdef CONFIG_CGROUP_WRITEBACK
161         inode->i_wb_frn_winner = 0;
162         inode->i_wb_frn_avg_time = 0;
163         inode->i_wb_frn_history = 0;
164 #endif
165 
166         if (security_inode_alloc(inode))
167                 goto out;
168         spin_lock_init(&inode->i_lock);
169         lockdep_set_class(&inode->i_lock, &sb->s_type->i_lock_key);
170 
171         init_rwsem(&inode->i_rwsem);
172         lockdep_set_class(&inode->i_rwsem, &sb->s_type->i_mutex_key);
173 
174         atomic_set(&inode->i_dio_count, 0);
175 
176         mapping->a_ops = &empty_aops;
177         mapping->host = inode;
178         mapping->flags = 0;
179         atomic_set(&mapping->i_mmap_writable, 0);
180         mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE);
181         mapping->private_data = NULL;
182         mapping->writeback_index = 0;
183         inode->i_private = NULL;
184         inode->i_mapping = mapping;
185         INIT_HLIST_HEAD(&inode->i_dentry);      /* buggered by rcu freeing */
186 #ifdef CONFIG_FS_POSIX_ACL
187         inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
188 #endif
189 
190 #ifdef CONFIG_FSNOTIFY
191         inode->i_fsnotify_mask = 0;
192 #endif
193         inode->i_flctx = NULL;
194         this_cpu_inc(nr_inodes);
195 
196         return 0;
197 out:
198         return -ENOMEM;
199 }
200 EXPORT_SYMBOL(inode_init_always);
201 
202 static struct inode *alloc_inode(struct super_block *sb)
203 {
204         struct inode *inode;
205 
206         if (sb->s_op->alloc_inode)
207                 inode = sb->s_op->alloc_inode(sb);
208         else
209                 inode = kmem_cache_alloc(inode_cachep, GFP_KERNEL);
210 
211         if (!inode)
212                 return NULL;
213 
214         if (unlikely(inode_init_always(sb, inode))) {
215                 if (inode->i_sb->s_op->destroy_inode)
216                         inode->i_sb->s_op->destroy_inode(inode);
217                 else
218                         kmem_cache_free(inode_cachep, inode);
219                 return NULL;
220         }
221 
222         return inode;
223 }
224 
225 void free_inode_nonrcu(struct inode *inode)
226 {
227         kmem_cache_free(inode_cachep, inode);
228 }
229 EXPORT_SYMBOL(free_inode_nonrcu);
230 
231 void __destroy_inode(struct inode *inode)
232 {
233         BUG_ON(inode_has_buffers(inode));
234         inode_detach_wb(inode);
235         security_inode_free(inode);
236         fsnotify_inode_delete(inode);
237         locks_free_lock_context(inode);
238         if (!inode->i_nlink) {
239                 WARN_ON(atomic_long_read(&inode->i_sb->s_remove_count) == 0);
240                 atomic_long_dec(&inode->i_sb->s_remove_count);
241         }
242 
243 #ifdef CONFIG_FS_POSIX_ACL
244         if (inode->i_acl && !is_uncached_acl(inode->i_acl))
245                 posix_acl_release(inode->i_acl);
246         if (inode->i_default_acl && !is_uncached_acl(inode->i_default_acl))
247                 posix_acl_release(inode->i_default_acl);
248 #endif
249         this_cpu_dec(nr_inodes);
250 }
251 EXPORT_SYMBOL(__destroy_inode);
252 
253 static void i_callback(struct rcu_head *head)
254 {
255         struct inode *inode = container_of(head, struct inode, i_rcu);
256         kmem_cache_free(inode_cachep, inode);
257 }
258 
259 static void destroy_inode(struct inode *inode)
260 {
261         BUG_ON(!list_empty(&inode->i_lru));
262         __destroy_inode(inode);
263         if (inode->i_sb->s_op->destroy_inode)
264                 inode->i_sb->s_op->destroy_inode(inode);
265         else
266                 call_rcu(&inode->i_rcu, i_callback);
267 }
268 
269 /**
270  * drop_nlink - directly drop an inode's link count
271  * @inode: inode
272  *
273  * This is a low-level filesystem helper to replace any
274  * direct filesystem manipulation of i_nlink.  In cases
275  * where we are attempting to track writes to the
276  * filesystem, a decrement to zero means an imminent
277  * write when the file is truncated and actually unlinked
278  * on the filesystem.
279  */
280 void drop_nlink(struct inode *inode)
281 {
282         WARN_ON(inode->i_nlink == 0);
283         inode->__i_nlink--;
284         if (!inode->i_nlink)
285                 atomic_long_inc(&inode->i_sb->s_remove_count);
286 }
287 EXPORT_SYMBOL(drop_nlink);
288 
289 /**
290  * clear_nlink - directly zero an inode's link count
291  * @inode: inode
292  *
293  * This is a low-level filesystem helper to replace any
294  * direct filesystem manipulation of i_nlink.  See
295  * drop_nlink() for why we care about i_nlink hitting zero.
296  */
297 void clear_nlink(struct inode *inode)
298 {
299         if (inode->i_nlink) {
300                 inode->__i_nlink = 0;
301                 atomic_long_inc(&inode->i_sb->s_remove_count);
302         }
303 }
304 EXPORT_SYMBOL(clear_nlink);
305 
306 /**
307  * set_nlink - directly set an inode's link count
308  * @inode: inode
309  * @nlink: new nlink (should be non-zero)
310  *
311  * This is a low-level filesystem helper to replace any
312  * direct filesystem manipulation of i_nlink.
313  */
314 void set_nlink(struct inode *inode, unsigned int nlink)
315 {
316         if (!nlink) {
317                 clear_nlink(inode);
318         } else {
319                 /* Yes, some filesystems do change nlink from zero to one */
320                 if (inode->i_nlink == 0)
321                         atomic_long_dec(&inode->i_sb->s_remove_count);
322 
323                 inode->__i_nlink = nlink;
324         }
325 }
326 EXPORT_SYMBOL(set_nlink);
327 
328 /**
329  * inc_nlink - directly increment an inode's link count
330  * @inode: inode
331  *
332  * This is a low-level filesystem helper to replace any
333  * direct filesystem manipulation of i_nlink.  Currently,
334  * it is only here for parity with dec_nlink().
335  */
336 void inc_nlink(struct inode *inode)
337 {
338         if (unlikely(inode->i_nlink == 0)) {
339                 WARN_ON(!(inode->i_state & I_LINKABLE));
340                 atomic_long_dec(&inode->i_sb->s_remove_count);
341         }
342 
343         inode->__i_nlink++;
344 }
345 EXPORT_SYMBOL(inc_nlink);
346 
347 void address_space_init_once(struct address_space *mapping)
348 {
349         memset(mapping, 0, sizeof(*mapping));
350         INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC | __GFP_ACCOUNT);
351         spin_lock_init(&mapping->tree_lock);
352         init_rwsem(&mapping->i_mmap_rwsem);
353         INIT_LIST_HEAD(&mapping->private_list);
354         spin_lock_init(&mapping->private_lock);
355         mapping->i_mmap = RB_ROOT;
356 }
357 EXPORT_SYMBOL(address_space_init_once);
358 
359 /*
360  * These are initializations that only need to be done
361  * once, because the fields are idempotent across use
362  * of the inode, so let the slab aware of that.
363  */
364 void inode_init_once(struct inode *inode)
365 {
366         memset(inode, 0, sizeof(*inode));
367         INIT_HLIST_NODE(&inode->i_hash);
368         INIT_LIST_HEAD(&inode->i_devices);
369         INIT_LIST_HEAD(&inode->i_io_list);
370         INIT_LIST_HEAD(&inode->i_wb_list);
371         INIT_LIST_HEAD(&inode->i_lru);
372         address_space_init_once(&inode->i_data);
373         i_size_ordered_init(inode);
374 #ifdef CONFIG_FSNOTIFY
375         INIT_HLIST_HEAD(&inode->i_fsnotify_marks);
376 #endif
377 }
378 EXPORT_SYMBOL(inode_init_once);
379 
380 static void init_once(void *foo)
381 {
382         struct inode *inode = (struct inode *) foo;
383 
384         inode_init_once(inode);
385 }
386 
387 /*
388  * inode->i_lock must be held
389  */
390 void __iget(struct inode *inode)
391 {
392         atomic_inc(&inode->i_count);
393 }
394 
395 /*
396  * get additional reference to inode; caller must already hold one.
397  */
398 void ihold(struct inode *inode)
399 {
400         WARN_ON(atomic_inc_return(&inode->i_count) < 2);
401 }
402 EXPORT_SYMBOL(ihold);
403 
404 static void inode_lru_list_add(struct inode *inode)
405 {
406         if (list_lru_add(&inode->i_sb->s_inode_lru, &inode->i_lru))
407                 this_cpu_inc(nr_unused);
408 }
409 
410 /*
411  * Add inode to LRU if needed (inode is unused and clean).
412  *
413  * Needs inode->i_lock held.
414  */
415 void inode_add_lru(struct inode *inode)
416 {
417         if (!(inode->i_state & (I_DIRTY_ALL | I_SYNC |
418                                 I_FREEING | I_WILL_FREE)) &&
419             !atomic_read(&inode->i_count) && inode->i_sb->s_flags & MS_ACTIVE)
420                 inode_lru_list_add(inode);
421 }
422 
423 
424 static void inode_lru_list_del(struct inode *inode)
425 {
426 
427         if (list_lru_del(&inode->i_sb->s_inode_lru, &inode->i_lru))
428                 this_cpu_dec(nr_unused);
429 }
430 
431 /**
432  * inode_sb_list_add - add inode to the superblock list of inodes
433  * @inode: inode to add
434  */
435 void inode_sb_list_add(struct inode *inode)
436 {
437         spin_lock(&inode->i_sb->s_inode_list_lock);
438         list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
439         spin_unlock(&inode->i_sb->s_inode_list_lock);
440 }
441 EXPORT_SYMBOL_GPL(inode_sb_list_add);
442 
443 static inline void inode_sb_list_del(struct inode *inode)
444 {
445         if (!list_empty(&inode->i_sb_list)) {
446                 spin_lock(&inode->i_sb->s_inode_list_lock);
447                 list_del_init(&inode->i_sb_list);
448                 spin_unlock(&inode->i_sb->s_inode_list_lock);
449         }
450 }
451 
452 static unsigned long hash(struct super_block *sb, unsigned long hashval)
453 {
454         unsigned long tmp;
455 
456         tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) /
457                         L1_CACHE_BYTES;
458         tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> i_hash_shift);
459         return tmp & i_hash_mask;
460 }
461 
462 /**
463  *      __insert_inode_hash - hash an inode
464  *      @inode: unhashed inode
465  *      @hashval: unsigned long value used to locate this object in the
466  *              inode_hashtable.
467  *
468  *      Add an inode to the inode hash for this superblock.
469  */
470 void __insert_inode_hash(struct inode *inode, unsigned long hashval)
471 {
472         struct hlist_head *b = inode_hashtable + hash(inode->i_sb, hashval);
473 
474         spin_lock(&inode_hash_lock);
475         spin_lock(&inode->i_lock);
476         hlist_add_head(&inode->i_hash, b);
477         spin_unlock(&inode->i_lock);
478         spin_unlock(&inode_hash_lock);
479 }
480 EXPORT_SYMBOL(__insert_inode_hash);
481 
482 /**
483  *      __remove_inode_hash - remove an inode from the hash
484  *      @inode: inode to unhash
485  *
486  *      Remove an inode from the superblock.
487  */
488 void __remove_inode_hash(struct inode *inode)
489 {
490         spin_lock(&inode_hash_lock);
491         spin_lock(&inode->i_lock);
492         hlist_del_init(&inode->i_hash);
493         spin_unlock(&inode->i_lock);
494         spin_unlock(&inode_hash_lock);
495 }
496 EXPORT_SYMBOL(__remove_inode_hash);
497 
498 void clear_inode(struct inode *inode)
499 {
500         might_sleep();
501         /*
502          * We have to cycle tree_lock here because reclaim can be still in the
503          * process of removing the last page (in __delete_from_page_cache())
504          * and we must not free mapping under it.
505          */
506         spin_lock_irq(&inode->i_data.tree_lock);
507         BUG_ON(inode->i_data.nrpages);
508         BUG_ON(inode->i_data.nrexceptional);
509         spin_unlock_irq(&inode->i_data.tree_lock);
510         BUG_ON(!list_empty(&inode->i_data.private_list));
511         BUG_ON(!(inode->i_state & I_FREEING));
512         BUG_ON(inode->i_state & I_CLEAR);
513         BUG_ON(!list_empty(&inode->i_wb_list));
514         /* don't need i_lock here, no concurrent mods to i_state */
515         inode->i_state = I_FREEING | I_CLEAR;
516 }
517 EXPORT_SYMBOL(clear_inode);
518 
519 /*
520  * Free the inode passed in, removing it from the lists it is still connected
521  * to. We remove any pages still attached to the inode and wait for any IO that
522  * is still in progress before finally destroying the inode.
523  *
524  * An inode must already be marked I_FREEING so that we avoid the inode being
525  * moved back onto lists if we race with other code that manipulates the lists
526  * (e.g. writeback_single_inode). The caller is responsible for setting this.
527  *
528  * An inode must already be removed from the LRU list before being evicted from
529  * the cache. This should occur atomically with setting the I_FREEING state
530  * flag, so no inodes here should ever be on the LRU when being evicted.
531  */
532 static void evict(struct inode *inode)
533 {
534         const struct super_operations *op = inode->i_sb->s_op;
535 
536         BUG_ON(!(inode->i_state & I_FREEING));
537         BUG_ON(!list_empty(&inode->i_lru));
538 
539         if (!list_empty(&inode->i_io_list))
540                 inode_io_list_del(inode);
541 
542         inode_sb_list_del(inode);
543 
544         /*
545          * Wait for flusher thread to be done with the inode so that filesystem
546          * does not start destroying it while writeback is still running. Since
547          * the inode has I_FREEING set, flusher thread won't start new work on
548          * the inode.  We just have to wait for running writeback to finish.
549          */
550         inode_wait_for_writeback(inode);
551 
552         if (op->evict_inode) {
553                 op->evict_inode(inode);
554         } else {
555                 truncate_inode_pages_final(&inode->i_data);
556                 clear_inode(inode);
557         }
558         if (S_ISBLK(inode->i_mode) && inode->i_bdev)
559                 bd_forget(inode);
560         if (S_ISCHR(inode->i_mode) && inode->i_cdev)
561                 cd_forget(inode);
562 
563         remove_inode_hash(inode);
564 
565         spin_lock(&inode->i_lock);
566         wake_up_bit(&inode->i_state, __I_NEW);
567         BUG_ON(inode->i_state != (I_FREEING | I_CLEAR));
568         spin_unlock(&inode->i_lock);
569 
570         destroy_inode(inode);
571 }
572 
573 /*
574  * dispose_list - dispose of the contents of a local list
575  * @head: the head of the list to free
576  *
577  * Dispose-list gets a local list with local inodes in it, so it doesn't
578  * need to worry about list corruption and SMP locks.
579  */
580 static void dispose_list(struct list_head *head)
581 {
582         while (!list_empty(head)) {
583                 struct inode *inode;
584 
585                 inode = list_first_entry(head, struct inode, i_lru);
586                 list_del_init(&inode->i_lru);
587 
588                 evict(inode);
589                 cond_resched();
590         }
591 }
592 
593 /**
594  * evict_inodes - evict all evictable inodes for a superblock
595  * @sb:         superblock to operate on
596  *
597  * Make sure that no inodes with zero refcount are retained.  This is
598  * called by superblock shutdown after having MS_ACTIVE flag removed,
599  * so any inode reaching zero refcount during or after that call will
600  * be immediately evicted.
601  */
602 void evict_inodes(struct super_block *sb)
603 {
604         struct inode *inode, *next;
605         LIST_HEAD(dispose);
606 
607 again:
608         spin_lock(&sb->s_inode_list_lock);
609         list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
610                 if (atomic_read(&inode->i_count))
611                         continue;
612 
613                 spin_lock(&inode->i_lock);
614                 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
615                         spin_unlock(&inode->i_lock);
616                         continue;
617                 }
618 
619                 inode->i_state |= I_FREEING;
620                 inode_lru_list_del(inode);
621                 spin_unlock(&inode->i_lock);
622                 list_add(&inode->i_lru, &dispose);
623 
624                 /*
625                  * We can have a ton of inodes to evict at unmount time given
626                  * enough memory, check to see if we need to go to sleep for a
627                  * bit so we don't livelock.
628                  */
629                 if (need_resched()) {
630                         spin_unlock(&sb->s_inode_list_lock);
631                         cond_resched();
632                         dispose_list(&dispose);
633                         goto again;
634                 }
635         }
636         spin_unlock(&sb->s_inode_list_lock);
637 
638         dispose_list(&dispose);
639 }
640 
641 /**
642  * invalidate_inodes    - attempt to free all inodes on a superblock
643  * @sb:         superblock to operate on
644  * @kill_dirty: flag to guide handling of dirty inodes
645  *
646  * Attempts to free all inodes for a given superblock.  If there were any
647  * busy inodes return a non-zero value, else zero.
648  * If @kill_dirty is set, discard dirty inodes too, otherwise treat
649  * them as busy.
650  */
651 int invalidate_inodes(struct super_block *sb, bool kill_dirty)
652 {
653         int busy = 0;
654         struct inode *inode, *next;
655         LIST_HEAD(dispose);
656 
657         spin_lock(&sb->s_inode_list_lock);
658         list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
659                 spin_lock(&inode->i_lock);
660                 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
661                         spin_unlock(&inode->i_lock);
662                         continue;
663                 }
664                 if (inode->i_state & I_DIRTY_ALL && !kill_dirty) {
665                         spin_unlock(&inode->i_lock);
666                         busy = 1;
667                         continue;
668                 }
669                 if (atomic_read(&inode->i_count)) {
670                         spin_unlock(&inode->i_lock);
671                         busy = 1;
672                         continue;
673                 }
674 
675                 inode->i_state |= I_FREEING;
676                 inode_lru_list_del(inode);
677                 spin_unlock(&inode->i_lock);
678                 list_add(&inode->i_lru, &dispose);
679         }
680         spin_unlock(&sb->s_inode_list_lock);
681 
682         dispose_list(&dispose);
683 
684         return busy;
685 }
686 
687 /*
688  * Isolate the inode from the LRU in preparation for freeing it.
689  *
690  * Any inodes which are pinned purely because of attached pagecache have their
691  * pagecache removed.  If the inode has metadata buffers attached to
692  * mapping->private_list then try to remove them.
693  *
694  * If the inode has the I_REFERENCED flag set, then it means that it has been
695  * used recently - the flag is set in iput_final(). When we encounter such an
696  * inode, clear the flag and move it to the back of the LRU so it gets another
697  * pass through the LRU before it gets reclaimed. This is necessary because of
698  * the fact we are doing lazy LRU updates to minimise lock contention so the
699  * LRU does not have strict ordering. Hence we don't want to reclaim inodes
700  * with this flag set because they are the inodes that are out of order.
701  */
702 static enum lru_status inode_lru_isolate(struct list_head *item,
703                 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
704 {
705         struct list_head *freeable = arg;
706         struct inode    *inode = container_of(item, struct inode, i_lru);
707 
708         /*
709          * we are inverting the lru lock/inode->i_lock here, so use a trylock.
710          * If we fail to get the lock, just skip it.
711          */
712         if (!spin_trylock(&inode->i_lock))
713                 return LRU_SKIP;
714 
715         /*
716          * Referenced or dirty inodes are still in use. Give them another pass
717          * through the LRU as we canot reclaim them now.
718          */
719         if (atomic_read(&inode->i_count) ||
720             (inode->i_state & ~I_REFERENCED)) {
721                 list_lru_isolate(lru, &inode->i_lru);
722                 spin_unlock(&inode->i_lock);
723                 this_cpu_dec(nr_unused);
724                 return LRU_REMOVED;
725         }
726 
727         /* recently referenced inodes get one more pass */
728         if (inode->i_state & I_REFERENCED) {
729                 inode->i_state &= ~I_REFERENCED;
730                 spin_unlock(&inode->i_lock);
731                 return LRU_ROTATE;
732         }
733 
734         if (inode_has_buffers(inode) || inode->i_data.nrpages) {
735                 __iget(inode);
736                 spin_unlock(&inode->i_lock);
737                 spin_unlock(lru_lock);
738                 if (remove_inode_buffers(inode)) {
739                         unsigned long reap;
740                         reap = invalidate_mapping_pages(&inode->i_data, 0, -1);
741                         if (current_is_kswapd())
742                                 __count_vm_events(KSWAPD_INODESTEAL, reap);
743                         else
744                                 __count_vm_events(PGINODESTEAL, reap);
745                         if (current->reclaim_state)
746                                 current->reclaim_state->reclaimed_slab += reap;
747                 }
748                 iput(inode);
749                 spin_lock(lru_lock);
750                 return LRU_RETRY;
751         }
752 
753         WARN_ON(inode->i_state & I_NEW);
754         inode->i_state |= I_FREEING;
755         list_lru_isolate_move(lru, &inode->i_lru, freeable);
756         spin_unlock(&inode->i_lock);
757 
758         this_cpu_dec(nr_unused);
759         return LRU_REMOVED;
760 }
761 
762 /*
763  * Walk the superblock inode LRU for freeable inodes and attempt to free them.
764  * This is called from the superblock shrinker function with a number of inodes
765  * to trim from the LRU. Inodes to be freed are moved to a temporary list and
766  * then are freed outside inode_lock by dispose_list().
767  */
768 long prune_icache_sb(struct super_block *sb, struct shrink_control *sc)
769 {
770         LIST_HEAD(freeable);
771         long freed;
772 
773         freed = list_lru_shrink_walk(&sb->s_inode_lru, sc,
774                                      inode_lru_isolate, &freeable);
775         dispose_list(&freeable);
776         return freed;
777 }
778 
779 static void __wait_on_freeing_inode(struct inode *inode);
780 /*
781  * Called with the inode lock held.
782  */
783 static struct inode *find_inode(struct super_block *sb,
784                                 struct hlist_head *head,
785                                 int (*test)(struct inode *, void *),
786                                 void *data)
787 {
788         struct inode *inode = NULL;
789 
790 repeat:
791         hlist_for_each_entry(inode, head, i_hash) {
792                 if (inode->i_sb != sb)
793                         continue;
794                 if (!test(inode, data))
795                         continue;
796                 spin_lock(&inode->i_lock);
797                 if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
798                         __wait_on_freeing_inode(inode);
799                         goto repeat;
800                 }
801                 __iget(inode);
802                 spin_unlock(&inode->i_lock);
803                 return inode;
804         }
805         return NULL;
806 }
807 
808 /*
809  * find_inode_fast is the fast path version of find_inode, see the comment at
810  * iget_locked for details.
811  */
812 static struct inode *find_inode_fast(struct super_block *sb,
813                                 struct hlist_head *head, unsigned long ino)
814 {
815         struct inode *inode = NULL;
816 
817 repeat:
818         hlist_for_each_entry(inode, head, i_hash) {
819                 if (inode->i_ino != ino)
820                         continue;
821                 if (inode->i_sb != sb)
822                         continue;
823                 spin_lock(&inode->i_lock);
824                 if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
825                         __wait_on_freeing_inode(inode);
826                         goto repeat;
827                 }
828                 __iget(inode);
829                 spin_unlock(&inode->i_lock);
830                 return inode;
831         }
832         return NULL;
833 }
834 
835 /*
836  * Each cpu owns a range of LAST_INO_BATCH numbers.
837  * 'shared_last_ino' is dirtied only once out of LAST_INO_BATCH allocations,
838  * to renew the exhausted range.
839  *
840  * This does not significantly increase overflow rate because every CPU can
841  * consume at most LAST_INO_BATCH-1 unused inode numbers. So there is
842  * NR_CPUS*(LAST_INO_BATCH-1) wastage. At 4096 and 1024, this is ~0.1% of the
843  * 2^32 range, and is a worst-case. Even a 50% wastage would only increase
844  * overflow rate by 2x, which does not seem too significant.
845  *
846  * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
847  * error if st_ino won't fit in target struct field. Use 32bit counter
848  * here to attempt to avoid that.
849  */
850 #define LAST_INO_BATCH 1024
851 static DEFINE_PER_CPU(unsigned int, last_ino);
852 
853 unsigned int get_next_ino(void)
854 {
855         unsigned int *p = &get_cpu_var(last_ino);
856         unsigned int res = *p;
857 
858 #ifdef CONFIG_SMP
859         if (unlikely((res & (LAST_INO_BATCH-1)) == 0)) {
860                 static atomic_t shared_last_ino;
861                 int next = atomic_add_return(LAST_INO_BATCH, &shared_last_ino);
862 
863                 res = next - LAST_INO_BATCH;
864         }
865 #endif
866 
867         res++;
868         /* get_next_ino should not provide a 0 inode number */
869         if (unlikely(!res))
870                 res++;
871         *p = res;
872         put_cpu_var(last_ino);
873         return res;
874 }
875 EXPORT_SYMBOL(get_next_ino);
876 
877 /**
878  *      new_inode_pseudo        - obtain an inode
879  *      @sb: superblock
880  *
881  *      Allocates a new inode for given superblock.
882  *      Inode wont be chained in superblock s_inodes list
883  *      This means :
884  *      - fs can't be unmount
885  *      - quotas, fsnotify, writeback can't work
886  */
887 struct inode *new_inode_pseudo(struct super_block *sb)
888 {
889         struct inode *inode = alloc_inode(sb);
890 
891         if (inode) {
892                 spin_lock(&inode->i_lock);
893                 inode->i_state = 0;
894                 spin_unlock(&inode->i_lock);
895                 INIT_LIST_HEAD(&inode->i_sb_list);
896         }
897         return inode;
898 }
899 
900 /**
901  *      new_inode       - obtain an inode
902  *      @sb: superblock
903  *
904  *      Allocates a new inode for given superblock. The default gfp_mask
905  *      for allocations related to inode->i_mapping is GFP_HIGHUSER_MOVABLE.
906  *      If HIGHMEM pages are unsuitable or it is known that pages allocated
907  *      for the page cache are not reclaimable or migratable,
908  *      mapping_set_gfp_mask() must be called with suitable flags on the
909  *      newly created inode's mapping
910  *
911  */
912 struct inode *new_inode(struct super_block *sb)
913 {
914         struct inode *inode;
915 
916         spin_lock_prefetch(&sb->s_inode_list_lock);
917 
918         inode = new_inode_pseudo(sb);
919         if (inode)
920                 inode_sb_list_add(inode);
921         return inode;
922 }
923 EXPORT_SYMBOL(new_inode);
924 
925 #ifdef CONFIG_DEBUG_LOCK_ALLOC
926 void lockdep_annotate_inode_mutex_key(struct inode *inode)
927 {
928         if (S_ISDIR(inode->i_mode)) {
929                 struct file_system_type *type = inode->i_sb->s_type;
930 
931                 /* Set new key only if filesystem hasn't already changed it */
932                 if (lockdep_match_class(&inode->i_rwsem, &type->i_mutex_key)) {
933                         /*
934                          * ensure nobody is actually holding i_mutex
935                          */
936                         // mutex_destroy(&inode->i_mutex);
937                         init_rwsem(&inode->i_rwsem);
938                         lockdep_set_class(&inode->i_rwsem,
939                                           &type->i_mutex_dir_key);
940                 }
941         }
942 }
943 EXPORT_SYMBOL(lockdep_annotate_inode_mutex_key);
944 #endif
945 
946 /**
947  * unlock_new_inode - clear the I_NEW state and wake up any waiters
948  * @inode:      new inode to unlock
949  *
950  * Called when the inode is fully initialised to clear the new state of the
951  * inode and wake up anyone waiting for the inode to finish initialisation.
952  */
953 void unlock_new_inode(struct inode *inode)
954 {
955         lockdep_annotate_inode_mutex_key(inode);
956         spin_lock(&inode->i_lock);
957         WARN_ON(!(inode->i_state & I_NEW));
958         inode->i_state &= ~I_NEW;
959         smp_mb();
960         wake_up_bit(&inode->i_state, __I_NEW);
961         spin_unlock(&inode->i_lock);
962 }
963 EXPORT_SYMBOL(unlock_new_inode);
964 
965 /**
966  * lock_two_nondirectories - take two i_mutexes on non-directory objects
967  *
968  * Lock any non-NULL argument that is not a directory.
969  * Zero, one or two objects may be locked by this function.
970  *
971  * @inode1: first inode to lock
972  * @inode2: second inode to lock
973  */
974 void lock_two_nondirectories(struct inode *inode1, struct inode *inode2)
975 {
976         if (inode1 > inode2)
977                 swap(inode1, inode2);
978 
979         if (inode1 && !S_ISDIR(inode1->i_mode))
980                 inode_lock(inode1);
981         if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1)
982                 inode_lock_nested(inode2, I_MUTEX_NONDIR2);
983 }
984 EXPORT_SYMBOL(lock_two_nondirectories);
985 
986 /**
987  * unlock_two_nondirectories - release locks from lock_two_nondirectories()
988  * @inode1: first inode to unlock
989  * @inode2: second inode to unlock
990  */
991 void unlock_two_nondirectories(struct inode *inode1, struct inode *inode2)
992 {
993         if (inode1 && !S_ISDIR(inode1->i_mode))
994                 inode_unlock(inode1);
995         if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1)
996                 inode_unlock(inode2);
997 }
998 EXPORT_SYMBOL(unlock_two_nondirectories);
999 
1000 /**
1001  * iget5_locked - obtain an inode from a mounted file system
1002  * @sb:         super block of file system
1003  * @hashval:    hash value (usually inode number) to get
1004  * @test:       callback used for comparisons between inodes
1005  * @set:        callback used to initialize a new struct inode
1006  * @data:       opaque data pointer to pass to @test and @set
1007  *
1008  * Search for the inode specified by @hashval and @data in the inode cache,
1009  * and if present it is return it with an increased reference count. This is
1010  * a generalized version of iget_locked() for file systems where the inode
1011  * number is not sufficient for unique identification of an inode.
1012  *
1013  * If the inode is not in cache, allocate a new inode and return it locked,
1014  * hashed, and with the I_NEW flag set. The file system gets to fill it in
1015  * before unlocking it via unlock_new_inode().
1016  *
1017  * Note both @test and @set are called with the inode_hash_lock held, so can't
1018  * sleep.
1019  */
1020 struct inode *iget5_locked(struct super_block *sb, unsigned long hashval,
1021                 int (*test)(struct inode *, void *),
1022                 int (*set)(struct inode *, void *), void *data)
1023 {
1024         struct hlist_head *head = inode_hashtable + hash(sb, hashval);
1025         struct inode *inode;
1026 again:
1027         spin_lock(&inode_hash_lock);
1028         inode = find_inode(sb, head, test, data);
1029         spin_unlock(&inode_hash_lock);
1030 
1031         if (inode) {
1032                 wait_on_inode(inode);
1033                 if (unlikely(inode_unhashed(inode))) {
1034                         iput(inode);
1035                         goto again;
1036                 }
1037                 return inode;
1038         }
1039 
1040         inode = alloc_inode(sb);
1041         if (inode) {
1042                 struct inode *old;
1043 
1044                 spin_lock(&inode_hash_lock);
1045                 /* We released the lock, so.. */
1046                 old = find_inode(sb, head, test, data);
1047                 if (!old) {
1048                         if (set(inode, data))
1049                                 goto set_failed;
1050 
1051                         spin_lock(&inode->i_lock);
1052                         inode->i_state = I_NEW;
1053                         hlist_add_head(&inode->i_hash, head);
1054                         spin_unlock(&inode->i_lock);
1055                         inode_sb_list_add(inode);
1056                         spin_unlock(&inode_hash_lock);
1057 
1058                         /* Return the locked inode with I_NEW set, the
1059                          * caller is responsible for filling in the contents
1060                          */
1061                         return inode;
1062                 }
1063 
1064                 /*
1065                  * Uhhuh, somebody else created the same inode under
1066                  * us. Use the old inode instead of the one we just
1067                  * allocated.
1068                  */
1069                 spin_unlock(&inode_hash_lock);
1070                 destroy_inode(inode);
1071                 inode = old;
1072                 wait_on_inode(inode);
1073                 if (unlikely(inode_unhashed(inode))) {
1074                         iput(inode);
1075                         goto again;
1076                 }
1077         }
1078         return inode;
1079 
1080 set_failed:
1081         spin_unlock(&inode_hash_lock);
1082         destroy_inode(inode);
1083         return NULL;
1084 }
1085 EXPORT_SYMBOL(iget5_locked);
1086 
1087 /**
1088  * iget_locked - obtain an inode from a mounted file system
1089  * @sb:         super block of file system
1090  * @ino:        inode number to get
1091  *
1092  * Search for the inode specified by @ino in the inode cache and if present
1093  * return it with an increased reference count. This is for file systems
1094  * where the inode number is sufficient for unique identification of an inode.
1095  *
1096  * If the inode is not in cache, allocate a new inode and return it locked,
1097  * hashed, and with the I_NEW flag set.  The file system gets to fill it in
1098  * before unlocking it via unlock_new_inode().
1099  */
1100 struct inode *iget_locked(struct super_block *sb, unsigned long ino)
1101 {
1102         struct hlist_head *head = inode_hashtable + hash(sb, ino);
1103         struct inode *inode;
1104 again:
1105         spin_lock(&inode_hash_lock);
1106         inode = find_inode_fast(sb, head, ino);
1107         spin_unlock(&inode_hash_lock);
1108         if (inode) {
1109                 wait_on_inode(inode);
1110                 if (unlikely(inode_unhashed(inode))) {
1111                         iput(inode);
1112                         goto again;
1113                 }
1114                 return inode;
1115         }
1116 
1117         inode = alloc_inode(sb);
1118         if (inode) {
1119                 struct inode *old;
1120 
1121                 spin_lock(&inode_hash_lock);
1122                 /* We released the lock, so.. */
1123                 old = find_inode_fast(sb, head, ino);
1124                 if (!old) {
1125                         inode->i_ino = ino;
1126                         spin_lock(&inode->i_lock);
1127                         inode->i_state = I_NEW;
1128                         hlist_add_head(&inode->i_hash, head);
1129                         spin_unlock(&inode->i_lock);
1130                         inode_sb_list_add(inode);
1131                         spin_unlock(&inode_hash_lock);
1132 
1133                         /* Return the locked inode with I_NEW set, the
1134                          * caller is responsible for filling in the contents
1135                          */
1136                         return inode;
1137                 }
1138 
1139                 /*
1140                  * Uhhuh, somebody else created the same inode under
1141                  * us. Use the old inode instead of the one we just
1142                  * allocated.
1143                  */
1144                 spin_unlock(&inode_hash_lock);
1145                 destroy_inode(inode);
1146                 inode = old;
1147                 wait_on_inode(inode);
1148                 if (unlikely(inode_unhashed(inode))) {
1149                         iput(inode);
1150                         goto again;
1151                 }
1152         }
1153         return inode;
1154 }
1155 EXPORT_SYMBOL(iget_locked);
1156 
1157 /*
1158  * search the inode cache for a matching inode number.
1159  * If we find one, then the inode number we are trying to
1160  * allocate is not unique and so we should not use it.
1161  *
1162  * Returns 1 if the inode number is unique, 0 if it is not.
1163  */
1164 static int test_inode_iunique(struct super_block *sb, unsigned long ino)
1165 {
1166         struct hlist_head *b = inode_hashtable + hash(sb, ino);
1167         struct inode *inode;
1168 
1169         spin_lock(&inode_hash_lock);
1170         hlist_for_each_entry(inode, b, i_hash) {
1171                 if (inode->i_ino == ino && inode->i_sb == sb) {
1172                         spin_unlock(&inode_hash_lock);
1173                         return 0;
1174                 }
1175         }
1176         spin_unlock(&inode_hash_lock);
1177 
1178         return 1;
1179 }
1180 
1181 /**
1182  *      iunique - get a unique inode number
1183  *      @sb: superblock
1184  *      @max_reserved: highest reserved inode number
1185  *
1186  *      Obtain an inode number that is unique on the system for a given
1187  *      superblock. This is used by file systems that have no natural
1188  *      permanent inode numbering system. An inode number is returned that
1189  *      is higher than the reserved limit but unique.
1190  *
1191  *      BUGS:
1192  *      With a large number of inodes live on the file system this function
1193  *      currently becomes quite slow.
1194  */
1195 ino_t iunique(struct super_block *sb, ino_t max_reserved)
1196 {
1197         /*
1198          * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
1199          * error if st_ino won't fit in target struct field. Use 32bit counter
1200          * here to attempt to avoid that.
1201          */
1202         static DEFINE_SPINLOCK(iunique_lock);
1203         static unsigned int counter;
1204         ino_t res;
1205 
1206         spin_lock(&iunique_lock);
1207         do {
1208                 if (counter <= max_reserved)
1209                         counter = max_reserved + 1;
1210                 res = counter++;
1211         } while (!test_inode_iunique(sb, res));
1212         spin_unlock(&iunique_lock);
1213 
1214         return res;
1215 }
1216 EXPORT_SYMBOL(iunique);
1217 
1218 struct inode *igrab(struct inode *inode)
1219 {
1220         spin_lock(&inode->i_lock);
1221         if (!(inode->i_state & (I_FREEING|I_WILL_FREE))) {
1222                 __iget(inode);
1223                 spin_unlock(&inode->i_lock);
1224         } else {
1225                 spin_unlock(&inode->i_lock);
1226                 /*
1227                  * Handle the case where s_op->clear_inode is not been
1228                  * called yet, and somebody is calling igrab
1229                  * while the inode is getting freed.
1230                  */
1231                 inode = NULL;
1232         }
1233         return inode;
1234 }
1235 EXPORT_SYMBOL(igrab);
1236 
1237 /**
1238  * ilookup5_nowait - search for an inode in the inode cache
1239  * @sb:         super block of file system to search
1240  * @hashval:    hash value (usually inode number) to search for
1241  * @test:       callback used for comparisons between inodes
1242  * @data:       opaque data pointer to pass to @test
1243  *
1244  * Search for the inode specified by @hashval and @data in the inode cache.
1245  * If the inode is in the cache, the inode is returned with an incremented
1246  * reference count.
1247  *
1248  * Note: I_NEW is not waited upon so you have to be very careful what you do
1249  * with the returned inode.  You probably should be using ilookup5() instead.
1250  *
1251  * Note2: @test is called with the inode_hash_lock held, so can't sleep.
1252  */
1253 struct inode *ilookup5_nowait(struct super_block *sb, unsigned long hashval,
1254                 int (*test)(struct inode *, void *), void *data)
1255 {
1256         struct hlist_head *head = inode_hashtable + hash(sb, hashval);
1257         struct inode *inode;
1258 
1259         spin_lock(&inode_hash_lock);
1260         inode = find_inode(sb, head, test, data);
1261         spin_unlock(&inode_hash_lock);
1262 
1263         return inode;
1264 }
1265 EXPORT_SYMBOL(ilookup5_nowait);
1266 
1267 /**
1268  * ilookup5 - search for an inode in the inode cache
1269  * @sb:         super block of file system to search
1270  * @hashval:    hash value (usually inode number) to search for
1271  * @test:       callback used for comparisons between inodes
1272  * @data:       opaque data pointer to pass to @test
1273  *
1274  * Search for the inode specified by @hashval and @data in the inode cache,
1275  * and if the inode is in the cache, return the inode with an incremented
1276  * reference count.  Waits on I_NEW before returning the inode.
1277  * returned with an incremented reference count.
1278  *
1279  * This is a generalized version of ilookup() for file systems where the
1280  * inode number is not sufficient for unique identification of an inode.
1281  *
1282  * Note: @test is called with the inode_hash_lock held, so can't sleep.
1283  */
1284 struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
1285                 int (*test)(struct inode *, void *), void *data)
1286 {
1287         struct inode *inode;
1288 again:
1289         inode = ilookup5_nowait(sb, hashval, test, data);
1290         if (inode) {
1291                 wait_on_inode(inode);
1292                 if (unlikely(inode_unhashed(inode))) {
1293                         iput(inode);
1294                         goto again;
1295                 }
1296         }
1297         return inode;
1298 }
1299 EXPORT_SYMBOL(ilookup5);
1300 
1301 /**
1302  * ilookup - search for an inode in the inode cache
1303  * @sb:         super block of file system to search
1304  * @ino:        inode number to search for
1305  *
1306  * Search for the inode @ino in the inode cache, and if the inode is in the
1307  * cache, the inode is returned with an incremented reference count.
1308  */
1309 struct inode *ilookup(struct super_block *sb, unsigned long ino)
1310 {
1311         struct hlist_head *head = inode_hashtable + hash(sb, ino);
1312         struct inode *inode;
1313 again:
1314         spin_lock(&inode_hash_lock);
1315         inode = find_inode_fast(sb, head, ino);
1316         spin_unlock(&inode_hash_lock);
1317 
1318         if (inode) {
1319                 wait_on_inode(inode);
1320                 if (unlikely(inode_unhashed(inode))) {
1321                         iput(inode);
1322                         goto again;
1323                 }
1324         }
1325         return inode;
1326 }
1327 EXPORT_SYMBOL(ilookup);
1328 
1329 /**
1330  * find_inode_nowait - find an inode in the inode cache
1331  * @sb:         super block of file system to search
1332  * @hashval:    hash value (usually inode number) to search for
1333  * @match:      callback used for comparisons between inodes
1334  * @data:       opaque data pointer to pass to @match
1335  *
1336  * Search for the inode specified by @hashval and @data in the inode
1337  * cache, where the helper function @match will return 0 if the inode
1338  * does not match, 1 if the inode does match, and -1 if the search
1339  * should be stopped.  The @match function must be responsible for
1340  * taking the i_lock spin_lock and checking i_state for an inode being
1341  * freed or being initialized, and incrementing the reference count
1342  * before returning 1.  It also must not sleep, since it is called with
1343  * the inode_hash_lock spinlock held.
1344  *
1345  * This is a even more generalized version of ilookup5() when the
1346  * function must never block --- find_inode() can block in
1347  * __wait_on_freeing_inode() --- or when the caller can not increment
1348  * the reference count because the resulting iput() might cause an
1349  * inode eviction.  The tradeoff is that the @match funtion must be
1350  * very carefully implemented.
1351  */
1352 struct inode *find_inode_nowait(struct super_block *sb,
1353                                 unsigned long hashval,
1354                                 int (*match)(struct inode *, unsigned long,
1355                                              void *),
1356                                 void *data)
1357 {
1358         struct hlist_head *head = inode_hashtable + hash(sb, hashval);
1359         struct inode *inode, *ret_inode = NULL;
1360         int mval;
1361 
1362         spin_lock(&inode_hash_lock);
1363         hlist_for_each_entry(inode, head, i_hash) {
1364                 if (inode->i_sb != sb)
1365                         continue;
1366                 mval = match(inode, hashval, data);
1367                 if (mval == 0)
1368                         continue;
1369                 if (mval == 1)
1370                         ret_inode = inode;
1371                 goto out;
1372         }
1373 out:
1374         spin_unlock(&inode_hash_lock);
1375         return ret_inode;
1376 }
1377 EXPORT_SYMBOL(find_inode_nowait);
1378 
1379 int insert_inode_locked(struct inode *inode)
1380 {
1381         struct super_block *sb = inode->i_sb;
1382         ino_t ino = inode->i_ino;
1383         struct hlist_head *head = inode_hashtable + hash(sb, ino);
1384 
1385         while (1) {
1386                 struct inode *old = NULL;
1387                 spin_lock(&inode_hash_lock);
1388                 hlist_for_each_entry(old, head, i_hash) {
1389                         if (old->i_ino != ino)
1390                                 continue;
1391                         if (old->i_sb != sb)
1392                                 continue;
1393                         spin_lock(&old->i_lock);
1394                         if (old->i_state & (I_FREEING|I_WILL_FREE)) {
1395                                 spin_unlock(&old->i_lock);
1396                                 continue;
1397                         }
1398                         break;
1399                 }
1400                 if (likely(!old)) {
1401                         spin_lock(&inode->i_lock);
1402                         inode->i_state |= I_NEW;
1403                         hlist_add_head(&inode->i_hash, head);
1404                         spin_unlock(&inode->i_lock);
1405                         spin_unlock(&inode_hash_lock);
1406                         return 0;
1407                 }
1408                 __iget(old);
1409                 spin_unlock(&old->i_lock);
1410                 spin_unlock(&inode_hash_lock);
1411                 wait_on_inode(old);
1412                 if (unlikely(!inode_unhashed(old))) {
1413                         iput(old);
1414                         return -EBUSY;
1415                 }
1416                 iput(old);
1417         }
1418 }
1419 EXPORT_SYMBOL(insert_inode_locked);
1420 
1421 int insert_inode_locked4(struct inode *inode, unsigned long hashval,
1422                 int (*test)(struct inode *, void *), void *data)
1423 {
1424         struct super_block *sb = inode->i_sb;
1425         struct hlist_head *head = inode_hashtable + hash(sb, hashval);
1426 
1427         while (1) {
1428                 struct inode *old = NULL;
1429 
1430                 spin_lock(&inode_hash_lock);
1431                 hlist_for_each_entry(old, head, i_hash) {
1432                         if (old->i_sb != sb)
1433                                 continue;
1434                         if (!test(old, data))
1435                                 continue;
1436                         spin_lock(&old->i_lock);
1437                         if (old->i_state & (I_FREEING|I_WILL_FREE)) {
1438                                 spin_unlock(&old->i_lock);
1439                                 continue;
1440                         }
1441                         break;
1442                 }
1443                 if (likely(!old)) {
1444                         spin_lock(&inode->i_lock);
1445                         inode->i_state |= I_NEW;
1446                         hlist_add_head(&inode->i_hash, head);
1447                         spin_unlock(&inode->i_lock);
1448                         spin_unlock(&inode_hash_lock);
1449                         return 0;
1450                 }
1451                 __iget(old);
1452                 spin_unlock(&old->i_lock);
1453                 spin_unlock(&inode_hash_lock);
1454                 wait_on_inode(old);
1455                 if (unlikely(!inode_unhashed(old))) {
1456                         iput(old);
1457                         return -EBUSY;
1458                 }
1459                 iput(old);
1460         }
1461 }
1462 EXPORT_SYMBOL(insert_inode_locked4);
1463 
1464 
1465 int generic_delete_inode(struct inode *inode)
1466 {
1467         return 1;
1468 }
1469 EXPORT_SYMBOL(generic_delete_inode);
1470 
1471 /*
1472  * Called when we're dropping the last reference
1473  * to an inode.
1474  *
1475  * Call the FS "drop_inode()" function, defaulting to
1476  * the legacy UNIX filesystem behaviour.  If it tells
1477  * us to evict inode, do so.  Otherwise, retain inode
1478  * in cache if fs is alive, sync and evict if fs is
1479  * shutting down.
1480  */
1481 static void iput_final(struct inode *inode)
1482 {
1483         struct super_block *sb = inode->i_sb;
1484         const struct super_operations *op = inode->i_sb->s_op;
1485         int drop;
1486 
1487         WARN_ON(inode->i_state & I_NEW);
1488 
1489         if (op->drop_inode)
1490                 drop = op->drop_inode(inode);
1491         else
1492                 drop = generic_drop_inode(inode);
1493 
1494         if (!drop && (sb->s_flags & MS_ACTIVE)) {
1495                 inode->i_state |= I_REFERENCED;
1496                 inode_add_lru(inode);
1497                 spin_unlock(&inode->i_lock);
1498                 return;
1499         }
1500 
1501         if (!drop) {
1502                 inode->i_state |= I_WILL_FREE;
1503                 spin_unlock(&inode->i_lock);
1504                 write_inode_now(inode, 1);
1505                 spin_lock(&inode->i_lock);
1506                 WARN_ON(inode->i_state & I_NEW);
1507                 inode->i_state &= ~I_WILL_FREE;
1508         }
1509 
1510         inode->i_state |= I_FREEING;
1511         if (!list_empty(&inode->i_lru))
1512                 inode_lru_list_del(inode);
1513         spin_unlock(&inode->i_lock);
1514 
1515         evict(inode);
1516 }
1517 
1518 /**
1519  *      iput    - put an inode
1520  *      @inode: inode to put
1521  *
1522  *      Puts an inode, dropping its usage count. If the inode use count hits
1523  *      zero, the inode is then freed and may also be destroyed.
1524  *
1525  *      Consequently, iput() can sleep.
1526  */
1527 void iput(struct inode *inode)
1528 {
1529         if (!inode)
1530                 return;
1531         BUG_ON(inode->i_state & I_CLEAR);
1532 retry:
1533         if (atomic_dec_and_lock(&inode->i_count, &inode->i_lock)) {
1534                 if (inode->i_nlink && (inode->i_state & I_DIRTY_TIME)) {
1535                         atomic_inc(&inode->i_count);
1536                         inode->i_state &= ~I_DIRTY_TIME;
1537                         spin_unlock(&inode->i_lock);
1538                         trace_writeback_lazytime_iput(inode);
1539                         mark_inode_dirty_sync(inode);
1540                         goto retry;
1541                 }
1542                 iput_final(inode);
1543         }
1544 }
1545 EXPORT_SYMBOL(iput);
1546 
1547 /**
1548  *      bmap    - find a block number in a file
1549  *      @inode: inode of file
1550  *      @block: block to find
1551  *
1552  *      Returns the block number on the device holding the inode that
1553  *      is the disk block number for the block of the file requested.
1554  *      That is, asked for block 4 of inode 1 the function will return the
1555  *      disk block relative to the disk start that holds that block of the
1556  *      file.
1557  */
1558 sector_t bmap(struct inode *inode, sector_t block)
1559 {
1560         sector_t res = 0;
1561         if (inode->i_mapping->a_ops->bmap)
1562                 res = inode->i_mapping->a_ops->bmap(inode->i_mapping, block);
1563         return res;
1564 }
1565 EXPORT_SYMBOL(bmap);
1566 
1567 /*
1568  * Update times in overlayed inode from underlying real inode
1569  */
1570 static void update_ovl_inode_times(struct dentry *dentry, struct inode *inode,
1571                                bool rcu)
1572 {
1573         if (!rcu) {
1574                 struct inode *realinode = d_real_inode(dentry);
1575 
1576                 if (unlikely(inode != realinode) &&
1577                     (!timespec_equal(&inode->i_mtime, &realinode->i_mtime) ||
1578                      !timespec_equal(&inode->i_ctime, &realinode->i_ctime))) {
1579                         inode->i_mtime = realinode->i_mtime;
1580                         inode->i_ctime = realinode->i_ctime;
1581                 }
1582         }
1583 }
1584 
1585 /*
1586  * With relative atime, only update atime if the previous atime is
1587  * earlier than either the ctime or mtime or if at least a day has
1588  * passed since the last atime update.
1589  */
1590 static int relatime_need_update(const struct path *path, struct inode *inode,
1591                                 struct timespec now, bool rcu)
1592 {
1593 
1594         if (!(path->mnt->mnt_flags & MNT_RELATIME))
1595                 return 1;
1596 
1597         update_ovl_inode_times(path->dentry, inode, rcu);
1598         /*
1599          * Is mtime younger than atime? If yes, update atime:
1600          */
1601         if (timespec_compare(&inode->i_mtime, &inode->i_atime) >= 0)
1602                 return 1;
1603         /*
1604          * Is ctime younger than atime? If yes, update atime:
1605          */
1606         if (timespec_compare(&inode->i_ctime, &inode->i_atime) >= 0)
1607                 return 1;
1608 
1609         /*
1610          * Is the previous atime value older than a day? If yes,
1611          * update atime:
1612          */
1613         if ((long)(now.tv_sec - inode->i_atime.tv_sec) >= 24*60*60)
1614                 return 1;
1615         /*
1616          * Good, we can skip the atime update:
1617          */
1618         return 0;
1619 }
1620 
1621 int generic_update_time(struct inode *inode, struct timespec *time, int flags)
1622 {
1623         int iflags = I_DIRTY_TIME;
1624 
1625         if (flags & S_ATIME)
1626                 inode->i_atime = *time;
1627         if (flags & S_VERSION)
1628                 inode_inc_iversion(inode);
1629         if (flags & S_CTIME)
1630                 inode->i_ctime = *time;
1631         if (flags & S_MTIME)
1632                 inode->i_mtime = *time;
1633 
1634         if (!(inode->i_sb->s_flags & MS_LAZYTIME) || (flags & S_VERSION))
1635                 iflags |= I_DIRTY_SYNC;
1636         __mark_inode_dirty(inode, iflags);
1637         return 0;
1638 }
1639 EXPORT_SYMBOL(generic_update_time);
1640 
1641 /*
1642  * This does the actual work of updating an inodes time or version.  Must have
1643  * had called mnt_want_write() before calling this.
1644  */
1645 static int update_time(struct inode *inode, struct timespec *time, int flags)
1646 {
1647         int (*update_time)(struct inode *, struct timespec *, int);
1648 
1649         update_time = inode->i_op->update_time ? inode->i_op->update_time :
1650                 generic_update_time;
1651 
1652         return update_time(inode, time, flags);
1653 }
1654 
1655 /**
1656  *      touch_atime     -       update the access time
1657  *      @path: the &struct path to update
1658  *      @inode: inode to update
1659  *
1660  *      Update the accessed time on an inode and mark it for writeback.
1661  *      This function automatically handles read only file systems and media,
1662  *      as well as the "noatime" flag and inode specific "noatime" markers.
1663  */
1664 bool __atime_needs_update(const struct path *path, struct inode *inode,
1665                           bool rcu)
1666 {
1667         struct vfsmount *mnt = path->mnt;
1668         struct timespec now;
1669 
1670         if (inode->i_flags & S_NOATIME)
1671                 return false;
1672 
1673         /* Atime updates will likely cause i_uid and i_gid to be written
1674          * back improprely if their true value is unknown to the vfs.
1675          */
1676         if (HAS_UNMAPPED_ID(inode))
1677                 return false;
1678 
1679         if (IS_NOATIME(inode))
1680                 return false;
1681         if ((inode->i_sb->s_flags & MS_NODIRATIME) && S_ISDIR(inode->i_mode))
1682                 return false;
1683 
1684         if (mnt->mnt_flags & MNT_NOATIME)
1685                 return false;
1686         if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))
1687                 return false;
1688 
1689         now = current_time(inode);
1690 
1691         if (!relatime_need_update(path, inode, now, rcu))
1692                 return false;
1693 
1694         if (timespec_equal(&inode->i_atime, &now))
1695                 return false;
1696 
1697         return true;
1698 }
1699 
1700 void touch_atime(const struct path *path)
1701 {
1702         struct vfsmount *mnt = path->mnt;
1703         struct inode *inode = d_inode(path->dentry);
1704         struct timespec now;
1705 
1706         if (!__atime_needs_update(path, inode, false))
1707                 return;
1708 
1709         if (!sb_start_write_trylock(inode->i_sb))
1710                 return;
1711 
1712         if (__mnt_want_write(mnt) != 0)
1713                 goto skip_update;
1714         /*
1715          * File systems can error out when updating inodes if they need to
1716          * allocate new space to modify an inode (such is the case for
1717          * Btrfs), but since we touch atime while walking down the path we
1718          * really don't care if we failed to update the atime of the file,
1719          * so just ignore the return value.
1720          * We may also fail on filesystems that have the ability to make parts
1721          * of the fs read only, e.g. subvolumes in Btrfs.
1722          */
1723         now = current_time(inode);
1724         update_time(inode, &now, S_ATIME);
1725         __mnt_drop_write(mnt);
1726 skip_update:
1727         sb_end_write(inode->i_sb);
1728 }
1729 EXPORT_SYMBOL(touch_atime);
1730 
1731 /*
1732  * The logic we want is
1733  *
1734  *      if suid or (sgid and xgrp)
1735  *              remove privs
1736  */
1737 int should_remove_suid(struct dentry *dentry)
1738 {
1739         umode_t mode = d_inode(dentry)->i_mode;
1740         int kill = 0;
1741 
1742         /* suid always must be killed */
1743         if (unlikely(mode & S_ISUID))
1744                 kill = ATTR_KILL_SUID;
1745 
1746         /*
1747          * sgid without any exec bits is just a mandatory locking mark; leave
1748          * it alone.  If some exec bits are set, it's a real sgid; kill it.
1749          */
1750         if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1751                 kill |= ATTR_KILL_SGID;
1752 
1753         if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1754                 return kill;
1755 
1756         return 0;
1757 }
1758 EXPORT_SYMBOL(should_remove_suid);
1759 
1760 /*
1761  * Return mask of changes for notify_change() that need to be done as a
1762  * response to write or truncate. Return 0 if nothing has to be changed.
1763  * Negative value on error (change should be denied).
1764  */
1765 int dentry_needs_remove_privs(struct dentry *dentry)
1766 {
1767         struct inode *inode = d_inode(dentry);
1768         int mask = 0;
1769         int ret;
1770 
1771         if (IS_NOSEC(inode))
1772                 return 0;
1773 
1774         mask = should_remove_suid(dentry);
1775         ret = security_inode_need_killpriv(dentry);
1776         if (ret < 0)
1777                 return ret;
1778         if (ret)
1779                 mask |= ATTR_KILL_PRIV;
1780         return mask;
1781 }
1782 
1783 static int __remove_privs(struct dentry *dentry, int kill)
1784 {
1785         struct iattr newattrs;
1786 
1787         newattrs.ia_valid = ATTR_FORCE | kill;
1788         /*
1789          * Note we call this on write, so notify_change will not
1790          * encounter any conflicting delegations:
1791          */
1792         return notify_change(dentry, &newattrs, NULL);
1793 }
1794 
1795 /*
1796  * Remove special file priviledges (suid, capabilities) when file is written
1797  * to or truncated.
1798  */
1799 int file_remove_privs(struct file *file)
1800 {
1801         struct dentry *dentry = file_dentry(file);
1802         struct inode *inode = file_inode(file);
1803         int kill;
1804         int error = 0;
1805 
1806         /* Fast path for nothing security related */
1807         if (IS_NOSEC(inode))
1808                 return 0;
1809 
1810         kill = dentry_needs_remove_privs(dentry);
1811         if (kill < 0)
1812                 return kill;
1813         if (kill)
1814                 error = __remove_privs(dentry, kill);
1815         if (!error)
1816                 inode_has_no_xattr(inode);
1817 
1818         return error;
1819 }
1820 EXPORT_SYMBOL(file_remove_privs);
1821 
1822 /**
1823  *      file_update_time        -       update mtime and ctime time
1824  *      @file: file accessed
1825  *
1826  *      Update the mtime and ctime members of an inode and mark the inode
1827  *      for writeback.  Note that this function is meant exclusively for
1828  *      usage in the file write path of filesystems, and filesystems may
1829  *      choose to explicitly ignore update via this function with the
1830  *      S_NOCMTIME inode flag, e.g. for network filesystem where these
1831  *      timestamps are handled by the server.  This can return an error for
1832  *      file systems who need to allocate space in order to update an inode.
1833  */
1834 
1835 int file_update_time(struct file *file)
1836 {
1837         struct inode *inode = file_inode(file);
1838         struct timespec now;
1839         int sync_it = 0;
1840         int ret;
1841 
1842         /* First try to exhaust all avenues to not sync */
1843         if (IS_NOCMTIME(inode))
1844                 return 0;
1845 
1846         now = current_time(inode);
1847         if (!timespec_equal(&inode->i_mtime, &now))
1848                 sync_it = S_MTIME;
1849 
1850         if (!timespec_equal(&inode->i_ctime, &now))
1851                 sync_it |= S_CTIME;
1852 
1853         if (IS_I_VERSION(inode))
1854                 sync_it |= S_VERSION;
1855 
1856         if (!sync_it)
1857                 return 0;
1858 
1859         /* Finally allowed to write? Takes lock. */
1860         if (__mnt_want_write_file(file))
1861                 return 0;
1862 
1863         ret = update_time(inode, &now, sync_it);
1864         __mnt_drop_write_file(file);
1865 
1866         return ret;
1867 }
1868 EXPORT_SYMBOL(file_update_time);
1869 
1870 int inode_needs_sync(struct inode *inode)
1871 {
1872         if (IS_SYNC(inode))
1873                 return 1;
1874         if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode))
1875                 return 1;
1876         return 0;
1877 }
1878 EXPORT_SYMBOL(inode_needs_sync);
1879 
1880 /*
1881  * If we try to find an inode in the inode hash while it is being
1882  * deleted, we have to wait until the filesystem completes its
1883  * deletion before reporting that it isn't found.  This function waits
1884  * until the deletion _might_ have completed.  Callers are responsible
1885  * to recheck inode state.
1886  *
1887  * It doesn't matter if I_NEW is not set initially, a call to
1888  * wake_up_bit(&inode->i_state, __I_NEW) after removing from the hash list
1889  * will DTRT.
1890  */
1891 static void __wait_on_freeing_inode(struct inode *inode)
1892 {
1893         wait_queue_head_t *wq;
1894         DEFINE_WAIT_BIT(wait, &inode->i_state, __I_NEW);
1895         wq = bit_waitqueue(&inode->i_state, __I_NEW);
1896         prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
1897         spin_unlock(&inode->i_lock);
1898         spin_unlock(&inode_hash_lock);
1899         schedule();
1900         finish_wait(wq, &wait.wait);
1901         spin_lock(&inode_hash_lock);
1902 }
1903 
1904 static __initdata unsigned long ihash_entries;
1905 static int __init set_ihash_entries(char *str)
1906 {
1907         if (!str)
1908                 return 0;
1909         ihash_entries = simple_strtoul(str, &str, 0);
1910         return 1;
1911 }
1912 __setup("ihash_entries=", set_ihash_entries);
1913 
1914 /*
1915  * Initialize the waitqueues and inode hash table.
1916  */
1917 void __init inode_init_early(void)
1918 {
1919         unsigned int loop;
1920 
1921         /* If hashes are distributed across NUMA nodes, defer
1922          * hash allocation until vmalloc space is available.
1923          */
1924         if (hashdist)
1925                 return;
1926 
1927         inode_hashtable =
1928                 alloc_large_system_hash("Inode-cache",
1929                                         sizeof(struct hlist_head),
1930                                         ihash_entries,
1931                                         14,
1932                                         HASH_EARLY,
1933                                         &i_hash_shift,
1934                                         &i_hash_mask,
1935                                         0,
1936                                         0);
1937 
1938         for (loop = 0; loop < (1U << i_hash_shift); loop++)
1939                 INIT_HLIST_HEAD(&inode_hashtable[loop]);
1940 }
1941 
1942 void __init inode_init(void)
1943 {
1944         unsigned int loop;
1945 
1946         /* inode slab cache */
1947         inode_cachep = kmem_cache_create("inode_cache",
1948                                          sizeof(struct inode),
1949                                          0,
1950                                          (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
1951                                          SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1952                                          init_once);
1953 
1954         /* Hash may have been set up in inode_init_early */
1955         if (!hashdist)
1956                 return;
1957 
1958         inode_hashtable =
1959                 alloc_large_system_hash("Inode-cache",
1960                                         sizeof(struct hlist_head),
1961                                         ihash_entries,
1962                                         14,
1963                                         0,
1964                                         &i_hash_shift,
1965                                         &i_hash_mask,
1966                                         0,
1967                                         0);
1968 
1969         for (loop = 0; loop < (1U << i_hash_shift); loop++)
1970                 INIT_HLIST_HEAD(&inode_hashtable[loop]);
1971 }
1972 
1973 void init_special_inode(struct inode *inode, umode_t mode, dev_t rdev)
1974 {
1975         inode->i_mode = mode;
1976         if (S_ISCHR(mode)) {
1977                 inode->i_fop = &def_chr_fops;
1978                 inode->i_rdev = rdev;
1979         } else if (S_ISBLK(mode)) {
1980                 inode->i_fop = &def_blk_fops;
1981                 inode->i_rdev = rdev;
1982         } else if (S_ISFIFO(mode))
1983                 inode->i_fop = &pipefifo_fops;
1984         else if (S_ISSOCK(mode))
1985                 ;       /* leave it no_open_fops */
1986         else
1987                 printk(KERN_DEBUG "init_special_inode: bogus i_mode (%o) for"
1988                                   " inode %s:%lu\n", mode, inode->i_sb->s_id,
1989                                   inode->i_ino);
1990 }
1991 EXPORT_SYMBOL(init_special_inode);
1992 
1993 /**
1994  * inode_init_owner - Init uid,gid,mode for new inode according to posix standards
1995  * @inode: New inode
1996  * @dir: Directory inode
1997  * @mode: mode of the new inode
1998  */
1999 void inode_init_owner(struct inode *inode, const struct inode *dir,
2000                         umode_t mode)
2001 {
2002         inode->i_uid = current_fsuid();
2003         if (dir && dir->i_mode & S_ISGID) {
2004                 inode->i_gid = dir->i_gid;
2005                 if (S_ISDIR(mode))
2006                         mode |= S_ISGID;
2007         } else
2008                 inode->i_gid = current_fsgid();
2009         inode->i_mode = mode;
2010 }
2011 EXPORT_SYMBOL(inode_init_owner);
2012 
2013 /**
2014  * inode_owner_or_capable - check current task permissions to inode
2015  * @inode: inode being checked
2016  *
2017  * Return true if current either has CAP_FOWNER in a namespace with the
2018  * inode owner uid mapped, or owns the file.
2019  */
2020 bool inode_owner_or_capable(const struct inode *inode)
2021 {
2022         struct user_namespace *ns;
2023 
2024         if (uid_eq(current_fsuid(), inode->i_uid))
2025                 return true;
2026 
2027         ns = current_user_ns();
2028         if (ns_capable(ns, CAP_FOWNER) && kuid_has_mapping(ns, inode->i_uid))
2029                 return true;
2030         return false;
2031 }
2032 EXPORT_SYMBOL(inode_owner_or_capable);
2033 
2034 /*
2035  * Direct i/o helper functions
2036  */
2037 static void __inode_dio_wait(struct inode *inode)
2038 {
2039         wait_queue_head_t *wq = bit_waitqueue(&inode->i_state, __I_DIO_WAKEUP);
2040         DEFINE_WAIT_BIT(q, &inode->i_state, __I_DIO_WAKEUP);
2041 
2042         do {
2043                 prepare_to_wait(wq, &q.wait, TASK_UNINTERRUPTIBLE);
2044                 if (atomic_read(&inode->i_dio_count))
2045                         schedule();
2046         } while (atomic_read(&inode->i_dio_count));
2047         finish_wait(wq, &q.wait);
2048 }
2049 
2050 /**
2051  * inode_dio_wait - wait for outstanding DIO requests to finish
2052  * @inode: inode to wait for
2053  *
2054  * Waits for all pending direct I/O requests to finish so that we can
2055  * proceed with a truncate or equivalent operation.
2056  *
2057  * Must be called under a lock that serializes taking new references
2058  * to i_dio_count, usually by inode->i_mutex.
2059  */
2060 void inode_dio_wait(struct inode *inode)
2061 {
2062         if (atomic_read(&inode->i_dio_count))
2063                 __inode_dio_wait(inode);
2064 }
2065 EXPORT_SYMBOL(inode_dio_wait);
2066 
2067 /*
2068  * inode_set_flags - atomically set some inode flags
2069  *
2070  * Note: the caller should be holding i_mutex, or else be sure that
2071  * they have exclusive access to the inode structure (i.e., while the
2072  * inode is being instantiated).  The reason for the cmpxchg() loop
2073  * --- which wouldn't be necessary if all code paths which modify
2074  * i_flags actually followed this rule, is that there is at least one
2075  * code path which doesn't today so we use cmpxchg() out of an abundance
2076  * of caution.
2077  *
2078  * In the long run, i_mutex is overkill, and we should probably look
2079  * at using the i_lock spinlock to protect i_flags, and then make sure
2080  * it is so documented in include/linux/fs.h and that all code follows
2081  * the locking convention!!
2082  */
2083 void inode_set_flags(struct inode *inode, unsigned int flags,
2084                      unsigned int mask)
2085 {
2086         unsigned int old_flags, new_flags;
2087 
2088         WARN_ON_ONCE(flags & ~mask);
2089         do {
2090                 old_flags = ACCESS_ONCE(inode->i_flags);
2091                 new_flags = (old_flags & ~mask) | flags;
2092         } while (unlikely(cmpxchg(&inode->i_flags, old_flags,
2093                                   new_flags) != old_flags));
2094 }
2095 EXPORT_SYMBOL(inode_set_flags);
2096 
2097 void inode_nohighmem(struct inode *inode)
2098 {
2099         mapping_set_gfp_mask(inode->i_mapping, GFP_USER);
2100 }
2101 EXPORT_SYMBOL(inode_nohighmem);
2102 
2103 /**
2104  * current_time - Return FS time
2105  * @inode: inode.
2106  *
2107  * Return the current time truncated to the time granularity supported by
2108  * the fs.
2109  *
2110  * Note that inode and inode->sb cannot be NULL.
2111  * Otherwise, the function warns and returns time without truncation.
2112  */
2113 struct timespec current_time(struct inode *inode)
2114 {
2115         struct timespec now = current_kernel_time();
2116 
2117         if (unlikely(!inode->i_sb)) {
2118                 WARN(1, "current_time() called with uninitialized super_block in the inode");
2119                 return now;
2120         }
2121 
2122         return timespec_trunc(now, inode->i_sb->s_time_gran);
2123 }
2124 EXPORT_SYMBOL(current_time);
2125 

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