1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /* Network filesystem support services.
3  *
4  * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
5  * Written by David Howells (dhowells@redhat.com)
6  *
7  * See:
8  *
9  *	Documentation/filesystems/netfs_library.rst
10  *
11  * for a description of the network filesystem interface declared here.
12  */
13 
14 #ifndef _LINUX_NETFS_H
15 #define _LINUX_NETFS_H
16 
17 #include <linux/workqueue.h>
18 #include <linux/fs.h>
19 #include <linux/pagemap.h>
20 #include <linux/uio.h>
21 
22 enum netfs_sreq_ref_trace;
23 
24 /*
25  * Overload PG_private_2 to give us PG_fscache - this is used to indicate that
26  * a page is currently backed by a local disk cache
27  */
28 #define folio_test_fscache(folio)	folio_test_private_2(folio)
29 #define PageFsCache(page)		PagePrivate2((page))
30 #define SetPageFsCache(page)		SetPagePrivate2((page))
31 #define ClearPageFsCache(page)		ClearPagePrivate2((page))
32 #define TestSetPageFsCache(page)	TestSetPagePrivate2((page))
33 #define TestClearPageFsCache(page)	TestClearPagePrivate2((page))
34 
35 /**
36  * folio_start_fscache - Start an fscache write on a folio.
37  * @folio: The folio.
38  *
39  * Call this function before writing a folio to a local cache.  Starting a
40  * second write before the first one finishes is not allowed.
41  */
folio_start_fscache(struct folio * folio)42 static inline void folio_start_fscache(struct folio *folio)
43 {
44 	VM_BUG_ON_FOLIO(folio_test_private_2(folio), folio);
45 	folio_get(folio);
46 	folio_set_private_2(folio);
47 }
48 
49 /**
50  * folio_end_fscache - End an fscache write on a folio.
51  * @folio: The folio.
52  *
53  * Call this function after the folio has been written to the local cache.
54  * This will wake any sleepers waiting on this folio.
55  */
folio_end_fscache(struct folio * folio)56 static inline void folio_end_fscache(struct folio *folio)
57 {
58 	folio_end_private_2(folio);
59 }
60 
61 /**
62  * folio_wait_fscache - Wait for an fscache write on this folio to end.
63  * @folio: The folio.
64  *
65  * If this folio is currently being written to a local cache, wait for
66  * the write to finish.  Another write may start after this one finishes,
67  * unless the caller holds the folio lock.
68  */
folio_wait_fscache(struct folio * folio)69 static inline void folio_wait_fscache(struct folio *folio)
70 {
71 	folio_wait_private_2(folio);
72 }
73 
74 /**
75  * folio_wait_fscache_killable - Wait for an fscache write on this folio to end.
76  * @folio: The folio.
77  *
78  * If this folio is currently being written to a local cache, wait
79  * for the write to finish or for a fatal signal to be received.
80  * Another write may start after this one finishes, unless the caller
81  * holds the folio lock.
82  *
83  * Return:
84  * - 0 if successful.
85  * - -EINTR if a fatal signal was encountered.
86  */
folio_wait_fscache_killable(struct folio * folio)87 static inline int folio_wait_fscache_killable(struct folio *folio)
88 {
89 	return folio_wait_private_2_killable(folio);
90 }
91 
set_page_fscache(struct page * page)92 static inline void set_page_fscache(struct page *page)
93 {
94 	folio_start_fscache(page_folio(page));
95 }
96 
end_page_fscache(struct page * page)97 static inline void end_page_fscache(struct page *page)
98 {
99 	folio_end_private_2(page_folio(page));
100 }
101 
wait_on_page_fscache(struct page * page)102 static inline void wait_on_page_fscache(struct page *page)
103 {
104 	folio_wait_private_2(page_folio(page));
105 }
106 
wait_on_page_fscache_killable(struct page * page)107 static inline int wait_on_page_fscache_killable(struct page *page)
108 {
109 	return folio_wait_private_2_killable(page_folio(page));
110 }
111 
112 enum netfs_io_source {
113 	NETFS_FILL_WITH_ZEROES,
114 	NETFS_DOWNLOAD_FROM_SERVER,
115 	NETFS_READ_FROM_CACHE,
116 	NETFS_INVALID_READ,
117 } __mode(byte);
118 
119 typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error,
120 				      bool was_async);
121 
122 /*
123  * Per-inode context.  This wraps the VFS inode.
124  */
125 struct netfs_inode {
126 	struct inode		inode;		/* The VFS inode */
127 	const struct netfs_request_ops *ops;
128 #if IS_ENABLED(CONFIG_FSCACHE)
129 	struct fscache_cookie	*cache;
130 #endif
131 	loff_t			remote_i_size;	/* Size of the remote file */
132 };
133 
134 /*
135  * Resources required to do operations on a cache.
136  */
137 struct netfs_cache_resources {
138 	const struct netfs_cache_ops	*ops;
139 	void				*cache_priv;
140 	void				*cache_priv2;
141 	unsigned int			debug_id;	/* Cookie debug ID */
142 	unsigned int			inval_counter;	/* object->inval_counter at begin_op */
143 };
144 
145 /*
146  * Descriptor for a single component subrequest.
147  */
148 struct netfs_io_subrequest {
149 	struct netfs_io_request *rreq;		/* Supervising I/O request */
150 	struct list_head	rreq_link;	/* Link in rreq->subrequests */
151 	loff_t			start;		/* Where to start the I/O */
152 	size_t			len;		/* Size of the I/O */
153 	size_t			transferred;	/* Amount of data transferred */
154 	refcount_t		ref;
155 	short			error;		/* 0 or error that occurred */
156 	unsigned short		debug_index;	/* Index in list (for debugging output) */
157 	enum netfs_io_source	source;		/* Where to read from/write to */
158 	unsigned long		flags;
159 #define NETFS_SREQ_COPY_TO_CACHE	0	/* Set if should copy the data to the cache */
160 #define NETFS_SREQ_CLEAR_TAIL		1	/* Set if the rest of the read should be cleared */
161 #define NETFS_SREQ_SHORT_IO		2	/* Set if the I/O was short */
162 #define NETFS_SREQ_SEEK_DATA_READ	3	/* Set if ->read() should SEEK_DATA first */
163 #define NETFS_SREQ_NO_PROGRESS		4	/* Set if we didn't manage to read any data */
164 #define NETFS_SREQ_ONDEMAND		5	/* Set if it's from on-demand read mode */
165 };
166 
167 enum netfs_io_origin {
168 	NETFS_READAHEAD,		/* This read was triggered by readahead */
169 	NETFS_READPAGE,			/* This read is a synchronous read */
170 	NETFS_READ_FOR_WRITE,		/* This read is to prepare a write */
171 } __mode(byte);
172 
173 /*
174  * Descriptor for an I/O helper request.  This is used to make multiple I/O
175  * operations to a variety of data stores and then stitch the result together.
176  */
177 struct netfs_io_request {
178 	struct work_struct	work;
179 	struct inode		*inode;		/* The file being accessed */
180 	struct address_space	*mapping;	/* The mapping being accessed */
181 	struct netfs_cache_resources cache_resources;
182 	struct list_head	subrequests;	/* Contributory I/O operations */
183 	void			*netfs_priv;	/* Private data for the netfs */
184 	unsigned int		debug_id;
185 	atomic_t		nr_outstanding;	/* Number of ops in progress */
186 	atomic_t		nr_copy_ops;	/* Number of copy-to-cache ops in progress */
187 	size_t			submitted;	/* Amount submitted for I/O so far */
188 	size_t			len;		/* Length of the request */
189 	short			error;		/* 0 or error that occurred */
190 	enum netfs_io_origin	origin;		/* Origin of the request */
191 	loff_t			i_size;		/* Size of the file */
192 	loff_t			start;		/* Start position */
193 	pgoff_t			no_unlock_folio; /* Don't unlock this folio after read */
194 	refcount_t		ref;
195 	unsigned long		flags;
196 #define NETFS_RREQ_INCOMPLETE_IO	0	/* Some ioreqs terminated short or with error */
197 #define NETFS_RREQ_COPY_TO_CACHE	1	/* Need to write to the cache */
198 #define NETFS_RREQ_NO_UNLOCK_FOLIO	2	/* Don't unlock no_unlock_folio on completion */
199 #define NETFS_RREQ_DONT_UNLOCK_FOLIOS	3	/* Don't unlock the folios on completion */
200 #define NETFS_RREQ_FAILED		4	/* The request failed */
201 #define NETFS_RREQ_IN_PROGRESS		5	/* Unlocked when the request completes */
202 	const struct netfs_request_ops *netfs_ops;
203 };
204 
205 /*
206  * Operations the network filesystem can/must provide to the helpers.
207  */
208 struct netfs_request_ops {
209 	int (*init_request)(struct netfs_io_request *rreq, struct file *file);
210 	void (*free_request)(struct netfs_io_request *rreq);
211 	int (*begin_cache_operation)(struct netfs_io_request *rreq);
212 
213 	void (*expand_readahead)(struct netfs_io_request *rreq);
214 	bool (*clamp_length)(struct netfs_io_subrequest *subreq);
215 	void (*issue_read)(struct netfs_io_subrequest *subreq);
216 	bool (*is_still_valid)(struct netfs_io_request *rreq);
217 	int (*check_write_begin)(struct file *file, loff_t pos, unsigned len,
218 				 struct folio **foliop, void **_fsdata);
219 	void (*done)(struct netfs_io_request *rreq);
220 };
221 
222 /*
223  * How to handle reading from a hole.
224  */
225 enum netfs_read_from_hole {
226 	NETFS_READ_HOLE_IGNORE,
227 	NETFS_READ_HOLE_CLEAR,
228 	NETFS_READ_HOLE_FAIL,
229 };
230 
231 /*
232  * Table of operations for access to a cache.  This is obtained by
233  * rreq->ops->begin_cache_operation().
234  */
235 struct netfs_cache_ops {
236 	/* End an operation */
237 	void (*end_operation)(struct netfs_cache_resources *cres);
238 
239 	/* Read data from the cache */
240 	int (*read)(struct netfs_cache_resources *cres,
241 		    loff_t start_pos,
242 		    struct iov_iter *iter,
243 		    enum netfs_read_from_hole read_hole,
244 		    netfs_io_terminated_t term_func,
245 		    void *term_func_priv);
246 
247 	/* Write data to the cache */
248 	int (*write)(struct netfs_cache_resources *cres,
249 		     loff_t start_pos,
250 		     struct iov_iter *iter,
251 		     netfs_io_terminated_t term_func,
252 		     void *term_func_priv);
253 
254 	/* Expand readahead request */
255 	void (*expand_readahead)(struct netfs_cache_resources *cres,
256 				 loff_t *_start, size_t *_len, loff_t i_size);
257 
258 	/* Prepare a read operation, shortening it to a cached/uncached
259 	 * boundary as appropriate.
260 	 */
261 	enum netfs_io_source (*prepare_read)(struct netfs_io_subrequest *subreq,
262 					     loff_t i_size);
263 
264 	/* Prepare a write operation, working out what part of the write we can
265 	 * actually do.
266 	 */
267 	int (*prepare_write)(struct netfs_cache_resources *cres,
268 			     loff_t *_start, size_t *_len, loff_t i_size,
269 			     bool no_space_allocated_yet);
270 
271 	/* Prepare an on-demand read operation, shortening it to a cached/uncached
272 	 * boundary as appropriate.
273 	 */
274 	enum netfs_io_source (*prepare_ondemand_read)(struct netfs_cache_resources *cres,
275 						      loff_t start, size_t *_len,
276 						      loff_t i_size,
277 						      unsigned long *_flags, ino_t ino);
278 
279 	/* Query the occupancy of the cache in a region, returning where the
280 	 * next chunk of data starts and how long it is.
281 	 */
282 	int (*query_occupancy)(struct netfs_cache_resources *cres,
283 			       loff_t start, size_t len, size_t granularity,
284 			       loff_t *_data_start, size_t *_data_len);
285 };
286 
287 struct readahead_control;
288 void netfs_readahead(struct readahead_control *);
289 int netfs_read_folio(struct file *, struct folio *);
290 int netfs_write_begin(struct netfs_inode *, struct file *,
291 		struct address_space *, loff_t pos, unsigned int len,
292 		struct folio **, void **fsdata);
293 
294 void netfs_subreq_terminated(struct netfs_io_subrequest *, ssize_t, bool);
295 void netfs_get_subrequest(struct netfs_io_subrequest *subreq,
296 			  enum netfs_sreq_ref_trace what);
297 void netfs_put_subrequest(struct netfs_io_subrequest *subreq,
298 			  bool was_async, enum netfs_sreq_ref_trace what);
299 void netfs_stats_show(struct seq_file *);
300 ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len,
301 				struct iov_iter *new,
302 				iov_iter_extraction_t extraction_flags);
303 struct sg_table;
304 ssize_t netfs_extract_iter_to_sg(struct iov_iter *iter, size_t len,
305 				 struct sg_table *sgtable, unsigned int sg_max,
306 				 iov_iter_extraction_t extraction_flags);
307 
308 /**
309  * netfs_inode - Get the netfs inode context from the inode
310  * @inode: The inode to query
311  *
312  * Get the netfs lib inode context from the network filesystem's inode.  The
313  * context struct is expected to directly follow on from the VFS inode struct.
314  */
netfs_inode(struct inode * inode)315 static inline struct netfs_inode *netfs_inode(struct inode *inode)
316 {
317 	return container_of(inode, struct netfs_inode, inode);
318 }
319 
320 /**
321  * netfs_inode_init - Initialise a netfslib inode context
322  * @ctx: The netfs inode to initialise
323  * @ops: The netfs's operations list
324  *
325  * Initialise the netfs library context struct.  This is expected to follow on
326  * directly from the VFS inode struct.
327  */
netfs_inode_init(struct netfs_inode * ctx,const struct netfs_request_ops * ops)328 static inline void netfs_inode_init(struct netfs_inode *ctx,
329 				    const struct netfs_request_ops *ops)
330 {
331 	ctx->ops = ops;
332 	ctx->remote_i_size = i_size_read(&ctx->inode);
333 #if IS_ENABLED(CONFIG_FSCACHE)
334 	ctx->cache = NULL;
335 #endif
336 }
337 
338 /**
339  * netfs_resize_file - Note that a file got resized
340  * @ctx: The netfs inode being resized
341  * @new_i_size: The new file size
342  *
343  * Inform the netfs lib that a file got resized so that it can adjust its state.
344  */
netfs_resize_file(struct netfs_inode * ctx,loff_t new_i_size)345 static inline void netfs_resize_file(struct netfs_inode *ctx, loff_t new_i_size)
346 {
347 	ctx->remote_i_size = new_i_size;
348 }
349 
350 /**
351  * netfs_i_cookie - Get the cache cookie from the inode
352  * @ctx: The netfs inode to query
353  *
354  * Get the caching cookie (if enabled) from the network filesystem's inode.
355  */
netfs_i_cookie(struct netfs_inode * ctx)356 static inline struct fscache_cookie *netfs_i_cookie(struct netfs_inode *ctx)
357 {
358 #if IS_ENABLED(CONFIG_FSCACHE)
359 	return ctx->cache;
360 #else
361 	return NULL;
362 #endif
363 }
364 
365 #endif /* _LINUX_NETFS_H */
366