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 */ 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 */ 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 */ 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 */ 86 static inline int folio_wait_fscache_killable(struct folio *folio) 87 { 88 return folio_wait_private_2_killable(folio); 89 } 90 91 static inline void set_page_fscache(struct page *page) 92 { 93 folio_start_fscache(page_folio(page)); 94 } 95 96 static inline void end_page_fscache(struct page *page) 97 { 98 folio_end_private_2(page_folio(page)); 99 } 100 101 static inline void wait_on_page_fscache(struct page *page) 102 { 103 folio_wait_private_2(page_folio(page)); 104 } 105 106 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 description. This must be directly after the inode struct. 123 */ 124 struct netfs_i_context { 125 const struct netfs_request_ops *ops; 126 #if IS_ENABLED(CONFIG_FSCACHE) 127 struct fscache_cookie *cache; 128 #endif 129 loff_t remote_i_size; /* Size of the remote file */ 130 }; 131 132 /* 133 * Resources required to do operations on a cache. 134 */ 135 struct netfs_cache_resources { 136 const struct netfs_cache_ops *ops; 137 void *cache_priv; 138 void *cache_priv2; 139 unsigned int debug_id; /* Cookie debug ID */ 140 unsigned int inval_counter; /* object->inval_counter at begin_op */ 141 }; 142 143 /* 144 * Descriptor for a single component subrequest. 145 */ 146 struct netfs_io_subrequest { 147 struct netfs_io_request *rreq; /* Supervising I/O request */ 148 struct list_head rreq_link; /* Link in rreq->subrequests */ 149 loff_t start; /* Where to start the I/O */ 150 size_t len; /* Size of the I/O */ 151 size_t transferred; /* Amount of data transferred */ 152 refcount_t ref; 153 short error; /* 0 or error that occurred */ 154 unsigned short debug_index; /* Index in list (for debugging output) */ 155 enum netfs_io_source source; /* Where to read from/write to */ 156 unsigned long flags; 157 #define NETFS_SREQ_COPY_TO_CACHE 0 /* Set if should copy the data to the cache */ 158 #define NETFS_SREQ_CLEAR_TAIL 1 /* Set if the rest of the read should be cleared */ 159 #define NETFS_SREQ_SHORT_IO 2 /* Set if the I/O was short */ 160 #define NETFS_SREQ_SEEK_DATA_READ 3 /* Set if ->read() should SEEK_DATA first */ 161 #define NETFS_SREQ_NO_PROGRESS 4 /* Set if we didn't manage to read any data */ 162 }; 163 164 enum netfs_io_origin { 165 NETFS_READAHEAD, /* This read was triggered by readahead */ 166 NETFS_READPAGE, /* This read is a synchronous read */ 167 NETFS_READ_FOR_WRITE, /* This read is to prepare a write */ 168 } __mode(byte); 169 170 /* 171 * Descriptor for an I/O helper request. This is used to make multiple I/O 172 * operations to a variety of data stores and then stitch the result together. 173 */ 174 struct netfs_io_request { 175 struct work_struct work; 176 struct inode *inode; /* The file being accessed */ 177 struct address_space *mapping; /* The mapping being accessed */ 178 struct netfs_cache_resources cache_resources; 179 struct list_head subrequests; /* Contributory I/O operations */ 180 void *netfs_priv; /* Private data for the netfs */ 181 unsigned int debug_id; 182 atomic_t nr_outstanding; /* Number of ops in progress */ 183 atomic_t nr_copy_ops; /* Number of copy-to-cache ops in progress */ 184 size_t submitted; /* Amount submitted for I/O so far */ 185 size_t len; /* Length of the request */ 186 short error; /* 0 or error that occurred */ 187 enum netfs_io_origin origin; /* Origin of the request */ 188 loff_t i_size; /* Size of the file */ 189 loff_t start; /* Start position */ 190 pgoff_t no_unlock_folio; /* Don't unlock this folio after read */ 191 refcount_t ref; 192 unsigned long flags; 193 #define NETFS_RREQ_INCOMPLETE_IO 0 /* Some ioreqs terminated short or with error */ 194 #define NETFS_RREQ_COPY_TO_CACHE 1 /* Need to write to the cache */ 195 #define NETFS_RREQ_NO_UNLOCK_FOLIO 2 /* Don't unlock no_unlock_folio on completion */ 196 #define NETFS_RREQ_DONT_UNLOCK_FOLIOS 3 /* Don't unlock the folios on completion */ 197 #define NETFS_RREQ_FAILED 4 /* The request failed */ 198 #define NETFS_RREQ_IN_PROGRESS 5 /* Unlocked when the request completes */ 199 const struct netfs_request_ops *netfs_ops; 200 }; 201 202 /* 203 * Operations the network filesystem can/must provide to the helpers. 204 */ 205 struct netfs_request_ops { 206 int (*init_request)(struct netfs_io_request *rreq, struct file *file); 207 int (*begin_cache_operation)(struct netfs_io_request *rreq); 208 void (*expand_readahead)(struct netfs_io_request *rreq); 209 bool (*clamp_length)(struct netfs_io_subrequest *subreq); 210 void (*issue_read)(struct netfs_io_subrequest *subreq); 211 bool (*is_still_valid)(struct netfs_io_request *rreq); 212 int (*check_write_begin)(struct file *file, loff_t pos, unsigned len, 213 struct folio *folio, void **_fsdata); 214 void (*done)(struct netfs_io_request *rreq); 215 void (*cleanup)(struct address_space *mapping, void *netfs_priv); 216 }; 217 218 /* 219 * How to handle reading from a hole. 220 */ 221 enum netfs_read_from_hole { 222 NETFS_READ_HOLE_IGNORE, 223 NETFS_READ_HOLE_CLEAR, 224 NETFS_READ_HOLE_FAIL, 225 }; 226 227 /* 228 * Table of operations for access to a cache. This is obtained by 229 * rreq->ops->begin_cache_operation(). 230 */ 231 struct netfs_cache_ops { 232 /* End an operation */ 233 void (*end_operation)(struct netfs_cache_resources *cres); 234 235 /* Read data from the cache */ 236 int (*read)(struct netfs_cache_resources *cres, 237 loff_t start_pos, 238 struct iov_iter *iter, 239 enum netfs_read_from_hole read_hole, 240 netfs_io_terminated_t term_func, 241 void *term_func_priv); 242 243 /* Write data to the cache */ 244 int (*write)(struct netfs_cache_resources *cres, 245 loff_t start_pos, 246 struct iov_iter *iter, 247 netfs_io_terminated_t term_func, 248 void *term_func_priv); 249 250 /* Expand readahead request */ 251 void (*expand_readahead)(struct netfs_cache_resources *cres, 252 loff_t *_start, size_t *_len, loff_t i_size); 253 254 /* Prepare a read operation, shortening it to a cached/uncached 255 * boundary as appropriate. 256 */ 257 enum netfs_io_source (*prepare_read)(struct netfs_io_subrequest *subreq, 258 loff_t i_size); 259 260 /* Prepare a write operation, working out what part of the write we can 261 * actually do. 262 */ 263 int (*prepare_write)(struct netfs_cache_resources *cres, 264 loff_t *_start, size_t *_len, loff_t i_size, 265 bool no_space_allocated_yet); 266 267 /* Query the occupancy of the cache in a region, returning where the 268 * next chunk of data starts and how long it is. 269 */ 270 int (*query_occupancy)(struct netfs_cache_resources *cres, 271 loff_t start, size_t len, size_t granularity, 272 loff_t *_data_start, size_t *_data_len); 273 }; 274 275 struct readahead_control; 276 extern void netfs_readahead(struct readahead_control *); 277 extern int netfs_readpage(struct file *, struct page *); 278 extern int netfs_write_begin(struct file *, struct address_space *, 279 loff_t, unsigned int, unsigned int, struct folio **, 280 void **); 281 282 extern void netfs_subreq_terminated(struct netfs_io_subrequest *, ssize_t, bool); 283 extern void netfs_get_subrequest(struct netfs_io_subrequest *subreq, 284 enum netfs_sreq_ref_trace what); 285 extern void netfs_put_subrequest(struct netfs_io_subrequest *subreq, 286 bool was_async, enum netfs_sreq_ref_trace what); 287 extern void netfs_stats_show(struct seq_file *); 288 289 /** 290 * netfs_i_context - Get the netfs inode context from the inode 291 * @inode: The inode to query 292 * 293 * Get the netfs lib inode context from the network filesystem's inode. The 294 * context struct is expected to directly follow on from the VFS inode struct. 295 */ 296 static inline struct netfs_i_context *netfs_i_context(struct inode *inode) 297 { 298 return (struct netfs_i_context *)(inode + 1); 299 } 300 301 /** 302 * netfs_inode - Get the netfs inode from the inode context 303 * @ctx: The context to query 304 * 305 * Get the netfs inode from the netfs library's inode context. The VFS inode 306 * is expected to directly precede the context struct. 307 */ 308 static inline struct inode *netfs_inode(struct netfs_i_context *ctx) 309 { 310 return ((struct inode *)ctx) - 1; 311 } 312 313 /** 314 * netfs_i_context_init - Initialise a netfs lib context 315 * @inode: The inode with which the context is associated 316 * @ops: The netfs's operations list 317 * 318 * Initialise the netfs library context struct. This is expected to follow on 319 * directly from the VFS inode struct. 320 */ 321 static inline void netfs_i_context_init(struct inode *inode, 322 const struct netfs_request_ops *ops) 323 { 324 struct netfs_i_context *ctx = netfs_i_context(inode); 325 326 memset(ctx, 0, sizeof(*ctx)); 327 ctx->ops = ops; 328 ctx->remote_i_size = i_size_read(inode); 329 } 330 331 /** 332 * netfs_resize_file - Note that a file got resized 333 * @inode: The inode being resized 334 * @new_i_size: The new file size 335 * 336 * Inform the netfs lib that a file got resized so that it can adjust its state. 337 */ 338 static inline void netfs_resize_file(struct inode *inode, loff_t new_i_size) 339 { 340 struct netfs_i_context *ctx = netfs_i_context(inode); 341 342 ctx->remote_i_size = new_i_size; 343 } 344 345 /** 346 * netfs_i_cookie - Get the cache cookie from the inode 347 * @inode: The inode to query 348 * 349 * Get the caching cookie (if enabled) from the network filesystem's inode. 350 */ 351 static inline struct fscache_cookie *netfs_i_cookie(struct inode *inode) 352 { 353 #if IS_ENABLED(CONFIG_FSCACHE) 354 struct netfs_i_context *ctx = netfs_i_context(inode); 355 return ctx->cache; 356 #else 357 return NULL; 358 #endif 359 } 360 361 #endif /* _LINUX_NETFS_H */ 362