Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1#ifndef __LINUX_DCACHE_H
2#define __LINUX_DCACHE_H
3
4#include <linux/atomic.h>
5#include <linux/list.h>
6#include <linux/rculist.h>
7#include <linux/rculist_bl.h>
8#include <linux/spinlock.h>
9#include <linux/seqlock.h>
10#include <linux/cache.h>
11#include <linux/rcupdate.h>
12
13struct nameidata;
14struct path;
15struct vfsmount;
16
17/*
18 * linux/include/linux/dcache.h
19 *
20 * Dirent cache data structures
21 *
22 * (C) Copyright 1997 Thomas Schoebel-Theuer,
23 * with heavy changes by Linus Torvalds
24 */
25
26#define IS_ROOT(x) ((x) == (x)->d_parent)
27
28/*
29 * "quick string" -- eases parameter passing, but more importantly
30 * saves "metadata" about the string (ie length and the hash).
31 *
32 * hash comes first so it snuggles against d_parent in the
33 * dentry.
34 */
35struct qstr {
36 unsigned int hash;
37 unsigned int len;
38 const unsigned char *name;
39};
40
41struct dentry_stat_t {
42 int nr_dentry;
43 int nr_unused;
44 int age_limit; /* age in seconds */
45 int want_pages; /* pages requested by system */
46 int dummy[2];
47};
48extern struct dentry_stat_t dentry_stat;
49
50/*
51 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
52 * The strings are both count bytes long, and count is non-zero.
53 */
54static inline int dentry_cmp(const unsigned char *cs, size_t scount,
55 const unsigned char *ct, size_t tcount)
56{
57 if (scount != tcount)
58 return 1;
59
60 do {
61 if (*cs != *ct)
62 return 1;
63 cs++;
64 ct++;
65 tcount--;
66 } while (tcount);
67 return 0;
68}
69
70/* Name hashing routines. Initial hash value */
71/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
72#define init_name_hash() 0
73
74/* partial hash update function. Assume roughly 4 bits per character */
75static inline unsigned long
76partial_name_hash(unsigned long c, unsigned long prevhash)
77{
78 return (prevhash + (c << 4) + (c >> 4)) * 11;
79}
80
81/*
82 * Finally: cut down the number of bits to a int value (and try to avoid
83 * losing bits)
84 */
85static inline unsigned long end_name_hash(unsigned long hash)
86{
87 return (unsigned int) hash;
88}
89
90/* Compute the hash for a name string. */
91extern unsigned int full_name_hash(const unsigned char *, unsigned int);
92
93/*
94 * Try to keep struct dentry aligned on 64 byte cachelines (this will
95 * give reasonable cacheline footprint with larger lines without the
96 * large memory footprint increase).
97 */
98#ifdef CONFIG_64BIT
99# define DNAME_INLINE_LEN 32 /* 192 bytes */
100#else
101# ifdef CONFIG_SMP
102# define DNAME_INLINE_LEN 36 /* 128 bytes */
103# else
104# define DNAME_INLINE_LEN 40 /* 128 bytes */
105# endif
106#endif
107
108struct dentry {
109 /* RCU lookup touched fields */
110 unsigned int d_flags; /* protected by d_lock */
111 seqcount_t d_seq; /* per dentry seqlock */
112 struct hlist_bl_node d_hash; /* lookup hash list */
113 struct dentry *d_parent; /* parent directory */
114 struct qstr d_name;
115 struct inode *d_inode; /* Where the name belongs to - NULL is
116 * negative */
117 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
118
119 /* Ref lookup also touches following */
120 unsigned int d_count; /* protected by d_lock */
121 spinlock_t d_lock; /* per dentry lock */
122 const struct dentry_operations *d_op;
123 struct super_block *d_sb; /* The root of the dentry tree */
124 unsigned long d_time; /* used by d_revalidate */
125 void *d_fsdata; /* fs-specific data */
126
127 struct list_head d_lru; /* LRU list */
128 /*
129 * d_child and d_rcu can share memory
130 */
131 union {
132 struct list_head d_child; /* child of parent list */
133 struct rcu_head d_rcu;
134 } d_u;
135 struct list_head d_subdirs; /* our children */
136 struct list_head d_alias; /* inode alias list */
137};
138
139/*
140 * dentry->d_lock spinlock nesting subclasses:
141 *
142 * 0: normal
143 * 1: nested
144 */
145enum dentry_d_lock_class
146{
147 DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
148 DENTRY_D_LOCK_NESTED
149};
150
151struct dentry_operations {
152 int (*d_revalidate)(struct dentry *, struct nameidata *);
153 int (*d_hash)(const struct dentry *, const struct inode *,
154 struct qstr *);
155 int (*d_compare)(const struct dentry *, const struct inode *,
156 const struct dentry *, const struct inode *,
157 unsigned int, const char *, const struct qstr *);
158 int (*d_delete)(const struct dentry *);
159 void (*d_release)(struct dentry *);
160 void (*d_prune)(struct dentry *);
161 void (*d_iput)(struct dentry *, struct inode *);
162 char *(*d_dname)(struct dentry *, char *, int);
163 struct vfsmount *(*d_automount)(struct path *);
164 int (*d_manage)(struct dentry *, bool);
165} ____cacheline_aligned;
166
167/*
168 * Locking rules for dentry_operations callbacks are to be found in
169 * Documentation/filesystems/Locking. Keep it updated!
170 *
171 * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
172 * Keep it updated too!
173 */
174
175/* d_flags entries */
176#define DCACHE_OP_HASH 0x0001
177#define DCACHE_OP_COMPARE 0x0002
178#define DCACHE_OP_REVALIDATE 0x0004
179#define DCACHE_OP_DELETE 0x0008
180#define DCACHE_OP_PRUNE 0x0010
181
182#define DCACHE_DISCONNECTED 0x0020
183 /* This dentry is possibly not currently connected to the dcache tree, in
184 * which case its parent will either be itself, or will have this flag as
185 * well. nfsd will not use a dentry with this bit set, but will first
186 * endeavour to clear the bit either by discovering that it is connected,
187 * or by performing lookup operations. Any filesystem which supports
188 * nfsd_operations MUST have a lookup function which, if it finds a
189 * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
190 * dentry into place and return that dentry rather than the passed one,
191 * typically using d_splice_alias. */
192
193#define DCACHE_REFERENCED 0x0040 /* Recently used, don't discard. */
194#define DCACHE_RCUACCESS 0x0080 /* Entry has ever been RCU-visible */
195
196#define DCACHE_CANT_MOUNT 0x0100
197#define DCACHE_GENOCIDE 0x0200
198#define DCACHE_SHRINK_LIST 0x0400
199
200#define DCACHE_NFSFS_RENAMED 0x1000
201 /* this dentry has been "silly renamed" and has to be deleted on the last
202 * dput() */
203#define DCACHE_COOKIE 0x2000 /* For use by dcookie subsystem */
204#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000
205 /* Parent inode is watched by some fsnotify listener */
206
207#define DCACHE_MOUNTED 0x10000 /* is a mountpoint */
208#define DCACHE_NEED_AUTOMOUNT 0x20000 /* handle automount on this dir */
209#define DCACHE_MANAGE_TRANSIT 0x40000 /* manage transit from this dirent */
210#define DCACHE_NEED_LOOKUP 0x80000 /* dentry requires i_op->lookup */
211#define DCACHE_MANAGED_DENTRY \
212 (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
213
214extern seqlock_t rename_lock;
215
216static inline int dname_external(struct dentry *dentry)
217{
218 return dentry->d_name.name != dentry->d_iname;
219}
220
221/*
222 * These are the low-level FS interfaces to the dcache..
223 */
224extern void d_instantiate(struct dentry *, struct inode *);
225extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
226extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
227extern void __d_drop(struct dentry *dentry);
228extern void d_drop(struct dentry *dentry);
229extern void d_delete(struct dentry *);
230extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
231
232/* allocate/de-allocate */
233extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
234extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
235extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
236extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
237extern struct dentry *d_find_any_alias(struct inode *inode);
238extern struct dentry * d_obtain_alias(struct inode *);
239extern void shrink_dcache_sb(struct super_block *);
240extern void shrink_dcache_parent(struct dentry *);
241extern void shrink_dcache_for_umount(struct super_block *);
242extern int d_invalidate(struct dentry *);
243
244/* only used at mount-time */
245extern struct dentry * d_alloc_root(struct inode *);
246extern struct dentry * d_make_root(struct inode *);
247
248/* <clickety>-<click> the ramfs-type tree */
249extern void d_genocide(struct dentry *);
250
251extern struct dentry *d_find_alias(struct inode *);
252extern void d_prune_aliases(struct inode *);
253
254/* test whether we have any submounts in a subdir tree */
255extern int have_submounts(struct dentry *);
256
257/*
258 * This adds the entry to the hash queues.
259 */
260extern void d_rehash(struct dentry *);
261
262/**
263 * d_add - add dentry to hash queues
264 * @entry: dentry to add
265 * @inode: The inode to attach to this dentry
266 *
267 * This adds the entry to the hash queues and initializes @inode.
268 * The entry was actually filled in earlier during d_alloc().
269 */
270
271static inline void d_add(struct dentry *entry, struct inode *inode)
272{
273 d_instantiate(entry, inode);
274 d_rehash(entry);
275}
276
277/**
278 * d_add_unique - add dentry to hash queues without aliasing
279 * @entry: dentry to add
280 * @inode: The inode to attach to this dentry
281 *
282 * This adds the entry to the hash queues and initializes @inode.
283 * The entry was actually filled in earlier during d_alloc().
284 */
285static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
286{
287 struct dentry *res;
288
289 res = d_instantiate_unique(entry, inode);
290 d_rehash(res != NULL ? res : entry);
291 return res;
292}
293
294extern void dentry_update_name_case(struct dentry *, struct qstr *);
295
296/* used for rename() and baskets */
297extern void d_move(struct dentry *, struct dentry *);
298extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
299
300/* appendix may either be NULL or be used for transname suffixes */
301extern struct dentry *d_lookup(struct dentry *, struct qstr *);
302extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
303extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
304extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
305 const struct qstr *name,
306 unsigned *seq, struct inode **inode);
307
308/**
309 * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
310 * @dentry: dentry to take a ref on
311 * @seq: seqcount to verify against
312 * Returns: 0 on failure, else 1.
313 *
314 * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
315 * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
316 */
317static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
318{
319 int ret = 0;
320
321 assert_spin_locked(&dentry->d_lock);
322 if (!read_seqcount_retry(&dentry->d_seq, seq)) {
323 ret = 1;
324 dentry->d_count++;
325 }
326
327 return ret;
328}
329
330/* validate "insecure" dentry pointer */
331extern int d_validate(struct dentry *, struct dentry *);
332
333/*
334 * helper function for dentry_operations.d_dname() members
335 */
336extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
337
338extern char *__d_path(const struct path *, const struct path *, char *, int);
339extern char *d_absolute_path(const struct path *, char *, int);
340extern char *d_path(const struct path *, char *, int);
341extern char *d_path_with_unreachable(const struct path *, char *, int);
342extern char *dentry_path_raw(struct dentry *, char *, int);
343extern char *dentry_path(struct dentry *, char *, int);
344
345/* Allocation counts.. */
346
347/**
348 * dget, dget_dlock - get a reference to a dentry
349 * @dentry: dentry to get a reference to
350 *
351 * Given a dentry or %NULL pointer increment the reference count
352 * if appropriate and return the dentry. A dentry will not be
353 * destroyed when it has references.
354 */
355static inline struct dentry *dget_dlock(struct dentry *dentry)
356{
357 if (dentry)
358 dentry->d_count++;
359 return dentry;
360}
361
362static inline struct dentry *dget(struct dentry *dentry)
363{
364 if (dentry) {
365 spin_lock(&dentry->d_lock);
366 dget_dlock(dentry);
367 spin_unlock(&dentry->d_lock);
368 }
369 return dentry;
370}
371
372extern struct dentry *dget_parent(struct dentry *dentry);
373
374/**
375 * d_unhashed - is dentry hashed
376 * @dentry: entry to check
377 *
378 * Returns true if the dentry passed is not currently hashed.
379 */
380
381static inline int d_unhashed(struct dentry *dentry)
382{
383 return hlist_bl_unhashed(&dentry->d_hash);
384}
385
386static inline int d_unlinked(struct dentry *dentry)
387{
388 return d_unhashed(dentry) && !IS_ROOT(dentry);
389}
390
391static inline int cant_mount(struct dentry *dentry)
392{
393 return (dentry->d_flags & DCACHE_CANT_MOUNT);
394}
395
396static inline void dont_mount(struct dentry *dentry)
397{
398 spin_lock(&dentry->d_lock);
399 dentry->d_flags |= DCACHE_CANT_MOUNT;
400 spin_unlock(&dentry->d_lock);
401}
402
403extern void dput(struct dentry *);
404
405static inline bool d_managed(struct dentry *dentry)
406{
407 return dentry->d_flags & DCACHE_MANAGED_DENTRY;
408}
409
410static inline bool d_mountpoint(struct dentry *dentry)
411{
412 return dentry->d_flags & DCACHE_MOUNTED;
413}
414
415static inline bool d_need_lookup(struct dentry *dentry)
416{
417 return dentry->d_flags & DCACHE_NEED_LOOKUP;
418}
419
420extern void d_clear_need_lookup(struct dentry *dentry);
421
422extern int sysctl_vfs_cache_pressure;
423
424#endif /* __LINUX_DCACHE_H */