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