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
22enum 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 */
42static 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 */
56static 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 */
69static 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 */
87static inline int folio_wait_fscache_killable(struct folio *folio)
88{
89 return folio_wait_private_2_killable(folio);
90}
91
92static inline void set_page_fscache(struct page *page)
93{
94 folio_start_fscache(page_folio(page));
95}
96
97static inline void end_page_fscache(struct page *page)
98{
99 folio_end_private_2(page_folio(page));
100}
101
102static inline void wait_on_page_fscache(struct page *page)
103{
104 folio_wait_private_2(page_folio(page));
105}
106
107static inline int wait_on_page_fscache_killable(struct page *page)
108{
109 return folio_wait_private_2_killable(page_folio(page));
110}
111
112enum 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
119typedef 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 */
125struct 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 */
137struct 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 */
148struct 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
167enum 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 */
177struct 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 */
208struct 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 */
225enum 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 */
235struct 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
287struct readahead_control;
288void netfs_readahead(struct readahead_control *);
289int netfs_read_folio(struct file *, struct folio *);
290int netfs_write_begin(struct netfs_inode *, struct file *,
291 struct address_space *, loff_t pos, unsigned int len,
292 struct folio **, void **fsdata);
293
294void netfs_subreq_terminated(struct netfs_io_subrequest *, ssize_t, bool);
295void netfs_get_subrequest(struct netfs_io_subrequest *subreq,
296 enum netfs_sreq_ref_trace what);
297void netfs_put_subrequest(struct netfs_io_subrequest *subreq,
298 bool was_async, enum netfs_sreq_ref_trace what);
299void netfs_stats_show(struct seq_file *);
300ssize_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
304/**
305 * netfs_inode - Get the netfs inode context from the inode
306 * @inode: The inode to query
307 *
308 * Get the netfs lib inode context from the network filesystem's inode. The
309 * context struct is expected to directly follow on from the VFS inode struct.
310 */
311static inline struct netfs_inode *netfs_inode(struct inode *inode)
312{
313 return container_of(inode, struct netfs_inode, inode);
314}
315
316/**
317 * netfs_inode_init - Initialise a netfslib inode context
318 * @ctx: The netfs inode to initialise
319 * @ops: The netfs's operations list
320 *
321 * Initialise the netfs library context struct. This is expected to follow on
322 * directly from the VFS inode struct.
323 */
324static inline void netfs_inode_init(struct netfs_inode *ctx,
325 const struct netfs_request_ops *ops)
326{
327 ctx->ops = ops;
328 ctx->remote_i_size = i_size_read(inode: &ctx->inode);
329#if IS_ENABLED(CONFIG_FSCACHE)
330 ctx->cache = NULL;
331#endif
332}
333
334/**
335 * netfs_resize_file - Note that a file got resized
336 * @ctx: The netfs inode being resized
337 * @new_i_size: The new file size
338 *
339 * Inform the netfs lib that a file got resized so that it can adjust its state.
340 */
341static inline void netfs_resize_file(struct netfs_inode *ctx, loff_t new_i_size)
342{
343 ctx->remote_i_size = new_i_size;
344}
345
346/**
347 * netfs_i_cookie - Get the cache cookie from the inode
348 * @ctx: The netfs inode to query
349 *
350 * Get the caching cookie (if enabled) from the network filesystem's inode.
351 */
352static inline struct fscache_cookie *netfs_i_cookie(struct netfs_inode *ctx)
353{
354#if IS_ENABLED(CONFIG_FSCACHE)
355 return ctx->cache;
356#else
357 return NULL;
358#endif
359}
360
361#endif /* _LINUX_NETFS_H */
362

source code of linux/include/linux/netfs.h