xref: /openbmc/linux/include/linux/nfs_fs.h (revision 0bf49ffb)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  *  linux/include/linux/nfs_fs.h
4  *
5  *  Copyright (C) 1992  Rick Sladkey
6  *
7  *  OS-specific nfs filesystem definitions and declarations
8  */
9 #ifndef _LINUX_NFS_FS_H
10 #define _LINUX_NFS_FS_H
11 
12 #include <uapi/linux/nfs_fs.h>
13 
14 
15 /*
16  * Enable dprintk() debugging support for nfs client.
17  */
18 #ifdef CONFIG_NFS_DEBUG
19 # define NFS_DEBUG
20 #endif
21 
22 #include <linux/in.h>
23 #include <linux/mm.h>
24 #include <linux/pagemap.h>
25 #include <linux/rbtree.h>
26 #include <linux/refcount.h>
27 #include <linux/rwsem.h>
28 #include <linux/wait.h>
29 
30 #include <linux/sunrpc/debug.h>
31 #include <linux/sunrpc/auth.h>
32 #include <linux/sunrpc/clnt.h>
33 
34 #include <linux/nfs.h>
35 #include <linux/nfs2.h>
36 #include <linux/nfs3.h>
37 #include <linux/nfs4.h>
38 #include <linux/nfs_xdr.h>
39 #include <linux/nfs_fs_sb.h>
40 
41 #include <linux/mempool.h>
42 
43 /*
44  * These are the default flags for swap requests
45  */
46 #define NFS_RPC_SWAPFLAGS		(RPC_TASK_SWAPPER|RPC_TASK_ROOTCREDS)
47 
48 /*
49  * Size of the NFS directory verifier
50  */
51 #define NFS_DIR_VERIFIER_SIZE		2
52 
53 /*
54  * NFSv3/v4 Access mode cache entry
55  */
56 struct nfs_access_entry {
57 	struct rb_node		rb_node;
58 	struct list_head	lru;
59 	const struct cred *	cred;
60 	__u32			mask;
61 	struct rcu_head		rcu_head;
62 };
63 
64 struct nfs_lock_context {
65 	refcount_t count;
66 	struct list_head list;
67 	struct nfs_open_context *open_context;
68 	fl_owner_t lockowner;
69 	atomic_t io_count;
70 	struct rcu_head	rcu_head;
71 };
72 
73 struct nfs4_state;
74 struct nfs_open_context {
75 	struct nfs_lock_context lock_context;
76 	fl_owner_t flock_owner;
77 	struct dentry *dentry;
78 	const struct cred *cred;
79 	struct rpc_cred *ll_cred;	/* low-level cred - use to check for expiry */
80 	struct nfs4_state *state;
81 	fmode_t mode;
82 
83 	unsigned long flags;
84 #define NFS_CONTEXT_RESEND_WRITES	(1)
85 #define NFS_CONTEXT_BAD			(2)
86 #define NFS_CONTEXT_UNLOCK	(3)
87 	int error;
88 
89 	struct list_head list;
90 	struct nfs4_threshold	*mdsthreshold;
91 	struct rcu_head	rcu_head;
92 };
93 
94 struct nfs_open_dir_context {
95 	struct list_head list;
96 	unsigned long attr_gencount;
97 	__be32	verf[NFS_DIR_VERIFIER_SIZE];
98 	__u64 dir_cookie;
99 	__u64 dup_cookie;
100 	signed char duped;
101 };
102 
103 /*
104  * NFSv4 delegation
105  */
106 struct nfs_delegation;
107 
108 struct posix_acl;
109 
110 struct nfs4_xattr_cache;
111 
112 /*
113  * nfs fs inode data in memory
114  */
115 struct nfs_inode {
116 	/*
117 	 * The 64bit 'inode number'
118 	 */
119 	__u64 fileid;
120 
121 	/*
122 	 * NFS file handle
123 	 */
124 	struct nfs_fh		fh;
125 
126 	/*
127 	 * Various flags
128 	 */
129 	unsigned long		flags;			/* atomic bit ops */
130 	unsigned long		cache_validity;		/* bit mask */
131 
132 	/*
133 	 * read_cache_jiffies is when we started read-caching this inode.
134 	 * attrtimeo is for how long the cached information is assumed
135 	 * to be valid. A successful attribute revalidation doubles
136 	 * attrtimeo (up to acregmax/acdirmax), a failure resets it to
137 	 * acregmin/acdirmin.
138 	 *
139 	 * We need to revalidate the cached attrs for this inode if
140 	 *
141 	 *	jiffies - read_cache_jiffies >= attrtimeo
142 	 *
143 	 * Please note the comparison is greater than or equal
144 	 * so that zero timeout values can be specified.
145 	 */
146 	unsigned long		read_cache_jiffies;
147 	unsigned long		attrtimeo;
148 	unsigned long		attrtimeo_timestamp;
149 
150 	unsigned long		attr_gencount;
151 	/* "Generation counter" for the attribute cache. This is
152 	 * bumped whenever we update the metadata on the
153 	 * server.
154 	 */
155 	unsigned long		cache_change_attribute;
156 
157 	struct rb_root		access_cache;
158 	struct list_head	access_cache_entry_lru;
159 	struct list_head	access_cache_inode_lru;
160 
161 	/*
162 	 * This is the cookie verifier used for NFSv3 readdir
163 	 * operations
164 	 */
165 	__be32			cookieverf[NFS_DIR_VERIFIER_SIZE];
166 
167 	atomic_long_t		nrequests;
168 	struct nfs_mds_commit_info commit_info;
169 
170 	/* Open contexts for shared mmap writes */
171 	struct list_head	open_files;
172 
173 	/* Readers: in-flight sillydelete RPC calls */
174 	/* Writers: rmdir */
175 	struct rw_semaphore	rmdir_sem;
176 	struct mutex		commit_mutex;
177 
178 	/* track last access to cached pages */
179 	unsigned long		page_index;
180 
181 #if IS_ENABLED(CONFIG_NFS_V4)
182 	struct nfs4_cached_acl	*nfs4_acl;
183         /* NFSv4 state */
184 	struct list_head	open_states;
185 	struct nfs_delegation __rcu *delegation;
186 	struct rw_semaphore	rwsem;
187 
188 	/* pNFS layout information */
189 	struct pnfs_layout_hdr *layout;
190 #endif /* CONFIG_NFS_V4*/
191 	/* how many bytes have been written/read and how many bytes queued up */
192 	__u64 write_io;
193 	__u64 read_io;
194 #ifdef CONFIG_NFS_FSCACHE
195 	struct fscache_cookie	*fscache;
196 #endif
197 	struct inode		vfs_inode;
198 
199 #ifdef CONFIG_NFS_V4_2
200 	struct nfs4_xattr_cache *xattr_cache;
201 #endif
202 };
203 
204 struct nfs4_copy_state {
205 	struct list_head	copies;
206 	struct list_head	src_copies;
207 	nfs4_stateid		stateid;
208 	struct completion	completion;
209 	uint64_t		count;
210 	struct nfs_writeverf	verf;
211 	int			error;
212 	int			flags;
213 	struct nfs4_state	*parent_src_state;
214 	struct nfs4_state	*parent_dst_state;
215 };
216 
217 /*
218  * Access bit flags
219  */
220 #define NFS_ACCESS_READ        0x0001
221 #define NFS_ACCESS_LOOKUP      0x0002
222 #define NFS_ACCESS_MODIFY      0x0004
223 #define NFS_ACCESS_EXTEND      0x0008
224 #define NFS_ACCESS_DELETE      0x0010
225 #define NFS_ACCESS_EXECUTE     0x0020
226 #define NFS_ACCESS_XAREAD      0x0040
227 #define NFS_ACCESS_XAWRITE     0x0080
228 #define NFS_ACCESS_XALIST      0x0100
229 
230 /*
231  * Cache validity bit flags
232  */
233 #define NFS_INO_INVALID_DATA	BIT(1)		/* cached data is invalid */
234 #define NFS_INO_INVALID_ATIME	BIT(2)		/* cached atime is invalid */
235 #define NFS_INO_INVALID_ACCESS	BIT(3)		/* cached access cred invalid */
236 #define NFS_INO_INVALID_ACL	BIT(4)		/* cached acls are invalid */
237 #define NFS_INO_REVAL_PAGECACHE	BIT(5)		/* must revalidate pagecache */
238 #define NFS_INO_REVAL_FORCED	BIT(6)		/* force revalidation ignoring a delegation */
239 #define NFS_INO_INVALID_LABEL	BIT(7)		/* cached label is invalid */
240 #define NFS_INO_INVALID_CHANGE	BIT(8)		/* cached change is invalid */
241 #define NFS_INO_INVALID_CTIME	BIT(9)		/* cached ctime is invalid */
242 #define NFS_INO_INVALID_MTIME	BIT(10)		/* cached mtime is invalid */
243 #define NFS_INO_INVALID_SIZE	BIT(11)		/* cached size is invalid */
244 #define NFS_INO_INVALID_OTHER	BIT(12)		/* other attrs are invalid */
245 #define NFS_INO_DATA_INVAL_DEFER	\
246 				BIT(13)		/* Deferred cache invalidation */
247 #define NFS_INO_INVALID_BLOCKS	BIT(14)         /* cached blocks are invalid */
248 #define NFS_INO_INVALID_XATTR	BIT(15)		/* xattrs are invalid */
249 
250 #define NFS_INO_INVALID_ATTR	(NFS_INO_INVALID_CHANGE \
251 		| NFS_INO_INVALID_CTIME \
252 		| NFS_INO_INVALID_MTIME \
253 		| NFS_INO_INVALID_SIZE \
254 		| NFS_INO_INVALID_OTHER)	/* inode metadata is invalid */
255 
256 /*
257  * Bit offsets in flags field
258  */
259 #define NFS_INO_ADVISE_RDPLUS	(0)		/* advise readdirplus */
260 #define NFS_INO_STALE		(1)		/* possible stale inode */
261 #define NFS_INO_ACL_LRU_SET	(2)		/* Inode is on the LRU list */
262 #define NFS_INO_INVALIDATING	(3)		/* inode is being invalidated */
263 #define NFS_INO_FSCACHE		(5)		/* inode can be cached by FS-Cache */
264 #define NFS_INO_FSCACHE_LOCK	(6)		/* FS-Cache cookie management lock */
265 #define NFS_INO_LAYOUTCOMMIT	(9)		/* layoutcommit required */
266 #define NFS_INO_LAYOUTCOMMITTING (10)		/* layoutcommit inflight */
267 #define NFS_INO_LAYOUTSTATS	(11)		/* layoutstats inflight */
268 #define NFS_INO_ODIRECT		(12)		/* I/O setting is O_DIRECT */
269 
270 static inline struct nfs_inode *NFS_I(const struct inode *inode)
271 {
272 	return container_of(inode, struct nfs_inode, vfs_inode);
273 }
274 
275 static inline struct nfs_server *NFS_SB(const struct super_block *s)
276 {
277 	return (struct nfs_server *)(s->s_fs_info);
278 }
279 
280 static inline struct nfs_fh *NFS_FH(const struct inode *inode)
281 {
282 	return &NFS_I(inode)->fh;
283 }
284 
285 static inline struct nfs_server *NFS_SERVER(const struct inode *inode)
286 {
287 	return NFS_SB(inode->i_sb);
288 }
289 
290 static inline struct rpc_clnt *NFS_CLIENT(const struct inode *inode)
291 {
292 	return NFS_SERVER(inode)->client;
293 }
294 
295 static inline const struct nfs_rpc_ops *NFS_PROTO(const struct inode *inode)
296 {
297 	return NFS_SERVER(inode)->nfs_client->rpc_ops;
298 }
299 
300 static inline unsigned NFS_MINATTRTIMEO(const struct inode *inode)
301 {
302 	struct nfs_server *nfss = NFS_SERVER(inode);
303 	return S_ISDIR(inode->i_mode) ? nfss->acdirmin : nfss->acregmin;
304 }
305 
306 static inline unsigned NFS_MAXATTRTIMEO(const struct inode *inode)
307 {
308 	struct nfs_server *nfss = NFS_SERVER(inode);
309 	return S_ISDIR(inode->i_mode) ? nfss->acdirmax : nfss->acregmax;
310 }
311 
312 static inline int NFS_STALE(const struct inode *inode)
313 {
314 	return test_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
315 }
316 
317 static inline struct fscache_cookie *nfs_i_fscache(struct inode *inode)
318 {
319 #ifdef CONFIG_NFS_FSCACHE
320 	return NFS_I(inode)->fscache;
321 #else
322 	return NULL;
323 #endif
324 }
325 
326 static inline __u64 NFS_FILEID(const struct inode *inode)
327 {
328 	return NFS_I(inode)->fileid;
329 }
330 
331 static inline void set_nfs_fileid(struct inode *inode, __u64 fileid)
332 {
333 	NFS_I(inode)->fileid = fileid;
334 }
335 
336 static inline void nfs_mark_for_revalidate(struct inode *inode)
337 {
338 	struct nfs_inode *nfsi = NFS_I(inode);
339 
340 	spin_lock(&inode->i_lock);
341 	nfsi->cache_validity |= NFS_INO_REVAL_PAGECACHE
342 		| NFS_INO_INVALID_ACCESS
343 		| NFS_INO_INVALID_ACL
344 		| NFS_INO_INVALID_CHANGE
345 		| NFS_INO_INVALID_CTIME;
346 	if (S_ISDIR(inode->i_mode))
347 		nfsi->cache_validity |= NFS_INO_INVALID_DATA;
348 	spin_unlock(&inode->i_lock);
349 }
350 
351 static inline int nfs_server_capable(struct inode *inode, int cap)
352 {
353 	return NFS_SERVER(inode)->caps & cap;
354 }
355 
356 /**
357  * nfs_save_change_attribute - Returns the inode attribute change cookie
358  * @dir - pointer to parent directory inode
359  * The "cache change attribute" is updated when we need to revalidate
360  * our dentry cache after a directory was seen to change on the server.
361  */
362 static inline unsigned long nfs_save_change_attribute(struct inode *dir)
363 {
364 	return NFS_I(dir)->cache_change_attribute;
365 }
366 
367 /*
368  * linux/fs/nfs/inode.c
369  */
370 extern int nfs_sync_mapping(struct address_space *mapping);
371 extern void nfs_zap_mapping(struct inode *inode, struct address_space *mapping);
372 extern void nfs_zap_caches(struct inode *);
373 extern void nfs_set_inode_stale(struct inode *inode);
374 extern void nfs_invalidate_atime(struct inode *);
375 extern struct inode *nfs_fhget(struct super_block *, struct nfs_fh *,
376 				struct nfs_fattr *, struct nfs4_label *);
377 struct inode *nfs_ilookup(struct super_block *sb, struct nfs_fattr *, struct nfs_fh *);
378 extern int nfs_refresh_inode(struct inode *, struct nfs_fattr *);
379 extern int nfs_post_op_update_inode(struct inode *inode, struct nfs_fattr *fattr);
380 extern int nfs_post_op_update_inode_force_wcc(struct inode *inode, struct nfs_fattr *fattr);
381 extern int nfs_post_op_update_inode_force_wcc_locked(struct inode *inode, struct nfs_fattr *fattr);
382 extern int nfs_getattr(struct user_namespace *, const struct path *,
383 		       struct kstat *, u32, unsigned int);
384 extern void nfs_access_add_cache(struct inode *, struct nfs_access_entry *);
385 extern void nfs_access_set_mask(struct nfs_access_entry *, u32);
386 extern int nfs_permission(struct user_namespace *, struct inode *, int);
387 extern int nfs_open(struct inode *, struct file *);
388 extern int nfs_attribute_cache_expired(struct inode *inode);
389 extern int nfs_revalidate_inode(struct nfs_server *server, struct inode *inode);
390 extern int __nfs_revalidate_inode(struct nfs_server *, struct inode *);
391 extern int nfs_clear_invalid_mapping(struct address_space *mapping);
392 extern bool nfs_mapping_need_revalidate_inode(struct inode *inode);
393 extern int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping);
394 extern int nfs_revalidate_mapping_rcu(struct inode *inode);
395 extern int nfs_setattr(struct user_namespace *, struct dentry *, struct iattr *);
396 extern void nfs_setattr_update_inode(struct inode *inode, struct iattr *attr, struct nfs_fattr *);
397 extern void nfs_setsecurity(struct inode *inode, struct nfs_fattr *fattr,
398 				struct nfs4_label *label);
399 extern struct nfs_open_context *get_nfs_open_context(struct nfs_open_context *ctx);
400 extern void put_nfs_open_context(struct nfs_open_context *ctx);
401 extern struct nfs_open_context *nfs_find_open_context(struct inode *inode, const struct cred *cred, fmode_t mode);
402 extern struct nfs_open_context *alloc_nfs_open_context(struct dentry *dentry, fmode_t f_mode, struct file *filp);
403 extern void nfs_inode_attach_open_context(struct nfs_open_context *ctx);
404 extern void nfs_file_set_open_context(struct file *filp, struct nfs_open_context *ctx);
405 extern void nfs_file_clear_open_context(struct file *flip);
406 extern struct nfs_lock_context *nfs_get_lock_context(struct nfs_open_context *ctx);
407 extern void nfs_put_lock_context(struct nfs_lock_context *l_ctx);
408 extern u64 nfs_compat_user_ino64(u64 fileid);
409 extern void nfs_fattr_init(struct nfs_fattr *fattr);
410 extern void nfs_fattr_set_barrier(struct nfs_fattr *fattr);
411 extern unsigned long nfs_inc_attr_generation_counter(void);
412 
413 extern struct nfs_fattr *nfs_alloc_fattr(void);
414 
415 static inline void nfs_free_fattr(const struct nfs_fattr *fattr)
416 {
417 	kfree(fattr);
418 }
419 
420 extern struct nfs_fh *nfs_alloc_fhandle(void);
421 
422 static inline void nfs_free_fhandle(const struct nfs_fh *fh)
423 {
424 	kfree(fh);
425 }
426 
427 #ifdef NFS_DEBUG
428 extern u32 _nfs_display_fhandle_hash(const struct nfs_fh *fh);
429 static inline u32 nfs_display_fhandle_hash(const struct nfs_fh *fh)
430 {
431 	return _nfs_display_fhandle_hash(fh);
432 }
433 extern void _nfs_display_fhandle(const struct nfs_fh *fh, const char *caption);
434 #define nfs_display_fhandle(fh, caption)			\
435 	do {							\
436 		if (unlikely(nfs_debug & NFSDBG_FACILITY))	\
437 			_nfs_display_fhandle(fh, caption);	\
438 	} while (0)
439 #else
440 static inline u32 nfs_display_fhandle_hash(const struct nfs_fh *fh)
441 {
442 	return 0;
443 }
444 static inline void nfs_display_fhandle(const struct nfs_fh *fh,
445 				       const char *caption)
446 {
447 }
448 #endif
449 
450 /*
451  * linux/fs/nfs/nfsroot.c
452  */
453 extern int  nfs_root_data(char **root_device, char **root_data); /*__init*/
454 /* linux/net/ipv4/ipconfig.c: trims ip addr off front of name, too. */
455 extern __be32 root_nfs_parse_addr(char *name); /*__init*/
456 
457 /*
458  * linux/fs/nfs/file.c
459  */
460 extern const struct file_operations nfs_file_operations;
461 #if IS_ENABLED(CONFIG_NFS_V4)
462 extern const struct file_operations nfs4_file_operations;
463 #endif /* CONFIG_NFS_V4 */
464 extern const struct address_space_operations nfs_file_aops;
465 extern const struct address_space_operations nfs_dir_aops;
466 
467 static inline struct nfs_open_context *nfs_file_open_context(struct file *filp)
468 {
469 	return filp->private_data;
470 }
471 
472 static inline const struct cred *nfs_file_cred(struct file *file)
473 {
474 	if (file != NULL) {
475 		struct nfs_open_context *ctx =
476 			nfs_file_open_context(file);
477 		if (ctx)
478 			return ctx->cred;
479 	}
480 	return NULL;
481 }
482 
483 /*
484  * linux/fs/nfs/direct.c
485  */
486 extern ssize_t nfs_direct_IO(struct kiocb *, struct iov_iter *);
487 extern ssize_t nfs_file_direct_read(struct kiocb *iocb,
488 			struct iov_iter *iter);
489 extern ssize_t nfs_file_direct_write(struct kiocb *iocb,
490 			struct iov_iter *iter);
491 
492 /*
493  * linux/fs/nfs/dir.c
494  */
495 extern const struct file_operations nfs_dir_operations;
496 extern const struct dentry_operations nfs_dentry_operations;
497 
498 extern void nfs_force_lookup_revalidate(struct inode *dir);
499 extern void nfs_set_verifier(struct dentry * dentry, unsigned long verf);
500 #if IS_ENABLED(CONFIG_NFS_V4)
501 extern void nfs_clear_verifier_delegated(struct inode *inode);
502 #endif /* IS_ENABLED(CONFIG_NFS_V4) */
503 extern struct dentry *nfs_add_or_obtain(struct dentry *dentry,
504 			struct nfs_fh *fh, struct nfs_fattr *fattr,
505 			struct nfs4_label *label);
506 extern int nfs_instantiate(struct dentry *dentry, struct nfs_fh *fh,
507 			struct nfs_fattr *fattr, struct nfs4_label *label);
508 extern int nfs_may_open(struct inode *inode, const struct cred *cred, int openflags);
509 extern void nfs_access_zap_cache(struct inode *inode);
510 extern int nfs_access_get_cached(struct inode *inode, const struct cred *cred, struct nfs_access_entry *res,
511 				 bool may_block);
512 
513 /*
514  * linux/fs/nfs/symlink.c
515  */
516 extern const struct inode_operations nfs_symlink_inode_operations;
517 
518 /*
519  * linux/fs/nfs/sysctl.c
520  */
521 #ifdef CONFIG_SYSCTL
522 extern int nfs_register_sysctl(void);
523 extern void nfs_unregister_sysctl(void);
524 #else
525 #define nfs_register_sysctl() 0
526 #define nfs_unregister_sysctl() do { } while(0)
527 #endif
528 
529 /*
530  * linux/fs/nfs/namespace.c
531  */
532 extern const struct inode_operations nfs_mountpoint_inode_operations;
533 extern const struct inode_operations nfs_referral_inode_operations;
534 extern int nfs_mountpoint_expiry_timeout;
535 extern void nfs_release_automount_timer(void);
536 
537 /*
538  * linux/fs/nfs/unlink.c
539  */
540 extern void nfs_complete_unlink(struct dentry *dentry, struct inode *);
541 
542 /*
543  * linux/fs/nfs/write.c
544  */
545 extern int  nfs_congestion_kb;
546 extern int  nfs_writepage(struct page *page, struct writeback_control *wbc);
547 extern int  nfs_writepages(struct address_space *, struct writeback_control *);
548 extern int  nfs_flush_incompatible(struct file *file, struct page *page);
549 extern int  nfs_updatepage(struct file *, struct page *, unsigned int, unsigned int);
550 
551 /*
552  * Try to write back everything synchronously (but check the
553  * return value!)
554  */
555 extern int nfs_sync_inode(struct inode *inode);
556 extern int nfs_wb_all(struct inode *inode);
557 extern int nfs_wb_page(struct inode *inode, struct page *page);
558 extern int nfs_wb_page_cancel(struct inode *inode, struct page* page);
559 extern int  nfs_commit_inode(struct inode *, int);
560 extern struct nfs_commit_data *nfs_commitdata_alloc(bool never_fail);
561 extern void nfs_commit_free(struct nfs_commit_data *data);
562 
563 static inline int
564 nfs_have_writebacks(struct inode *inode)
565 {
566 	return atomic_long_read(&NFS_I(inode)->nrequests) != 0;
567 }
568 
569 /*
570  * linux/fs/nfs/read.c
571  */
572 extern int  nfs_readpage(struct file *, struct page *);
573 extern int  nfs_readpages(struct file *, struct address_space *,
574 		struct list_head *, unsigned);
575 
576 /*
577  * inline functions
578  */
579 
580 static inline loff_t nfs_size_to_loff_t(__u64 size)
581 {
582 	return min_t(u64, size, OFFSET_MAX);
583 }
584 
585 static inline ino_t
586 nfs_fileid_to_ino_t(u64 fileid)
587 {
588 	ino_t ino = (ino_t) fileid;
589 	if (sizeof(ino_t) < sizeof(u64))
590 		ino ^= fileid >> (sizeof(u64)-sizeof(ino_t)) * 8;
591 	return ino;
592 }
593 
594 #define NFS_JUKEBOX_RETRY_TIME (5 * HZ)
595 
596 
597 # undef ifdebug
598 # ifdef NFS_DEBUG
599 #  define ifdebug(fac)		if (unlikely(nfs_debug & NFSDBG_##fac))
600 #  define NFS_IFDEBUG(x)	x
601 # else
602 #  define ifdebug(fac)		if (0)
603 #  define NFS_IFDEBUG(x)
604 # endif
605 #endif
606