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