1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * This file contians vfs address (mmap) ops for 9P2000. 4 * 5 * Copyright (C) 2005 by Eric Van Hensbergen <ericvh@gmail.com> 6 * Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov> 7 */ 8 9 #include <linux/module.h> 10 #include <linux/errno.h> 11 #include <linux/fs.h> 12 #include <linux/file.h> 13 #include <linux/stat.h> 14 #include <linux/string.h> 15 #include <linux/inet.h> 16 #include <linux/pagemap.h> 17 #include <linux/idr.h> 18 #include <linux/sched.h> 19 #include <linux/uio.h> 20 #include <linux/netfs.h> 21 #include <net/9p/9p.h> 22 #include <net/9p/client.h> 23 24 #include "v9fs.h" 25 #include "v9fs_vfs.h" 26 #include "cache.h" 27 #include "fid.h" 28 29 /** 30 * v9fs_req_issue_op - Issue a read from 9P 31 * @subreq: The read to make 32 */ 33 static void v9fs_req_issue_op(struct netfs_read_subrequest *subreq) 34 { 35 struct netfs_read_request *rreq = subreq->rreq; 36 struct p9_fid *fid = rreq->netfs_priv; 37 struct iov_iter to; 38 loff_t pos = subreq->start + subreq->transferred; 39 size_t len = subreq->len - subreq->transferred; 40 int total, err; 41 42 iov_iter_xarray(&to, READ, &rreq->mapping->i_pages, pos, len); 43 44 total = p9_client_read(fid, pos, &to, &err); 45 netfs_subreq_terminated(subreq, err ?: total, false); 46 } 47 48 /** 49 * v9fs_init_rreq - Initialise a read request 50 * @rreq: The read request 51 * @file: The file being read from 52 */ 53 static void v9fs_init_rreq(struct netfs_read_request *rreq, struct file *file) 54 { 55 struct p9_fid *fid = file->private_data; 56 57 refcount_inc(&fid->count); 58 rreq->netfs_priv = fid; 59 } 60 61 /** 62 * v9fs_req_cleanup - Cleanup request initialized by v9fs_init_rreq 63 * @mapping: unused mapping of request to cleanup 64 * @priv: private data to cleanup, a fid, guaranted non-null. 65 */ 66 static void v9fs_req_cleanup(struct address_space *mapping, void *priv) 67 { 68 struct p9_fid *fid = priv; 69 70 p9_client_clunk(fid); 71 } 72 73 /** 74 * v9fs_is_cache_enabled - Determine if caching is enabled for an inode 75 * @inode: The inode to check 76 */ 77 static bool v9fs_is_cache_enabled(struct inode *inode) 78 { 79 struct fscache_cookie *cookie = v9fs_inode_cookie(V9FS_I(inode)); 80 81 return fscache_cookie_enabled(cookie) && !hlist_empty(&cookie->backing_objects); 82 } 83 84 /** 85 * v9fs_begin_cache_operation - Begin a cache operation for a read 86 * @rreq: The read request 87 */ 88 static int v9fs_begin_cache_operation(struct netfs_read_request *rreq) 89 { 90 struct fscache_cookie *cookie = v9fs_inode_cookie(V9FS_I(rreq->inode)); 91 92 return fscache_begin_read_operation(rreq, cookie); 93 } 94 95 static const struct netfs_read_request_ops v9fs_req_ops = { 96 .init_rreq = v9fs_init_rreq, 97 .is_cache_enabled = v9fs_is_cache_enabled, 98 .begin_cache_operation = v9fs_begin_cache_operation, 99 .issue_op = v9fs_req_issue_op, 100 .cleanup = v9fs_req_cleanup, 101 }; 102 103 /** 104 * v9fs_vfs_readpage - read an entire page in from 9P 105 * @file: file being read 106 * @page: structure to page 107 * 108 */ 109 static int v9fs_vfs_readpage(struct file *file, struct page *page) 110 { 111 struct folio *folio = page_folio(page); 112 113 return netfs_readpage(file, folio, &v9fs_req_ops, NULL); 114 } 115 116 /** 117 * v9fs_vfs_readahead - read a set of pages from 9P 118 * @ractl: The readahead parameters 119 */ 120 static void v9fs_vfs_readahead(struct readahead_control *ractl) 121 { 122 netfs_readahead(ractl, &v9fs_req_ops, NULL); 123 } 124 125 /** 126 * v9fs_release_page - release the private state associated with a page 127 * @page: The page to be released 128 * @gfp: The caller's allocation restrictions 129 * 130 * Returns 1 if the page can be released, false otherwise. 131 */ 132 133 static int v9fs_release_page(struct page *page, gfp_t gfp) 134 { 135 struct folio *folio = page_folio(page); 136 137 if (folio_test_private(folio)) 138 return 0; 139 #ifdef CONFIG_9P_FSCACHE 140 if (folio_test_fscache(folio)) { 141 if (!(gfp & __GFP_DIRECT_RECLAIM) || !(gfp & __GFP_FS)) 142 return 0; 143 folio_wait_fscache(folio); 144 } 145 #endif 146 return 1; 147 } 148 149 /** 150 * v9fs_invalidate_page - Invalidate a page completely or partially 151 * @page: The page to be invalidated 152 * @offset: offset of the invalidated region 153 * @length: length of the invalidated region 154 */ 155 156 static void v9fs_invalidate_page(struct page *page, unsigned int offset, 157 unsigned int length) 158 { 159 struct folio *folio = page_folio(page); 160 161 folio_wait_fscache(folio); 162 } 163 164 static int v9fs_vfs_write_folio_locked(struct folio *folio) 165 { 166 struct inode *inode = folio_inode(folio); 167 struct v9fs_inode *v9inode = V9FS_I(inode); 168 loff_t start = folio_pos(folio); 169 loff_t i_size = i_size_read(inode); 170 struct iov_iter from; 171 size_t len = folio_size(folio); 172 int err; 173 174 if (start >= i_size) 175 return 0; /* Simultaneous truncation occurred */ 176 177 len = min_t(loff_t, i_size - start, len); 178 179 iov_iter_xarray(&from, WRITE, &folio_mapping(folio)->i_pages, start, len); 180 181 /* We should have writeback_fid always set */ 182 BUG_ON(!v9inode->writeback_fid); 183 184 folio_start_writeback(folio); 185 186 p9_client_write(v9inode->writeback_fid, start, &from, &err); 187 188 folio_end_writeback(folio); 189 return err; 190 } 191 192 static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc) 193 { 194 struct folio *folio = page_folio(page); 195 int retval; 196 197 p9_debug(P9_DEBUG_VFS, "folio %p\n", folio); 198 199 retval = v9fs_vfs_write_folio_locked(folio); 200 if (retval < 0) { 201 if (retval == -EAGAIN) { 202 folio_redirty_for_writepage(wbc, folio); 203 retval = 0; 204 } else { 205 mapping_set_error(folio_mapping(folio), retval); 206 } 207 } else 208 retval = 0; 209 210 folio_unlock(folio); 211 return retval; 212 } 213 214 /** 215 * v9fs_launder_page - Writeback a dirty page 216 * @page: The page to be cleaned up 217 * 218 * Returns 0 on success. 219 */ 220 221 static int v9fs_launder_page(struct page *page) 222 { 223 struct folio *folio = page_folio(page); 224 int retval; 225 226 if (folio_clear_dirty_for_io(folio)) { 227 retval = v9fs_vfs_write_folio_locked(folio); 228 if (retval) 229 return retval; 230 } 231 folio_wait_fscache(folio); 232 return 0; 233 } 234 235 /** 236 * v9fs_direct_IO - 9P address space operation for direct I/O 237 * @iocb: target I/O control block 238 * @iter: The data/buffer to use 239 * 240 * The presence of v9fs_direct_IO() in the address space ops vector 241 * allowes open() O_DIRECT flags which would have failed otherwise. 242 * 243 * In the non-cached mode, we shunt off direct read and write requests before 244 * the VFS gets them, so this method should never be called. 245 * 246 * Direct IO is not 'yet' supported in the cached mode. Hence when 247 * this routine is called through generic_file_aio_read(), the read/write fails 248 * with an error. 249 * 250 */ 251 static ssize_t 252 v9fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) 253 { 254 struct file *file = iocb->ki_filp; 255 loff_t pos = iocb->ki_pos; 256 ssize_t n; 257 int err = 0; 258 259 if (iov_iter_rw(iter) == WRITE) { 260 n = p9_client_write(file->private_data, pos, iter, &err); 261 if (n) { 262 struct inode *inode = file_inode(file); 263 loff_t i_size = i_size_read(inode); 264 265 if (pos + n > i_size) 266 inode_add_bytes(inode, pos + n - i_size); 267 } 268 } else { 269 n = p9_client_read(file->private_data, pos, iter, &err); 270 } 271 return n ? n : err; 272 } 273 274 static int v9fs_write_begin(struct file *filp, struct address_space *mapping, 275 loff_t pos, unsigned int len, unsigned int flags, 276 struct page **subpagep, void **fsdata) 277 { 278 int retval; 279 struct folio *folio; 280 struct v9fs_inode *v9inode = V9FS_I(mapping->host); 281 282 p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping); 283 284 BUG_ON(!v9inode->writeback_fid); 285 286 /* Prefetch area to be written into the cache if we're caching this 287 * file. We need to do this before we get a lock on the page in case 288 * there's more than one writer competing for the same cache block. 289 */ 290 retval = netfs_write_begin(filp, mapping, pos, len, flags, &folio, fsdata, 291 &v9fs_req_ops, NULL); 292 if (retval < 0) 293 return retval; 294 295 *subpagep = &folio->page; 296 return retval; 297 } 298 299 static int v9fs_write_end(struct file *filp, struct address_space *mapping, 300 loff_t pos, unsigned int len, unsigned int copied, 301 struct page *subpage, void *fsdata) 302 { 303 loff_t last_pos = pos + copied; 304 struct folio *folio = page_folio(subpage); 305 struct inode *inode = mapping->host; 306 307 p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping); 308 309 if (!folio_test_uptodate(folio)) { 310 if (unlikely(copied < len)) { 311 copied = 0; 312 goto out; 313 } 314 315 folio_mark_uptodate(folio); 316 } 317 318 /* 319 * No need to use i_size_read() here, the i_size 320 * cannot change under us because we hold the i_mutex. 321 */ 322 if (last_pos > inode->i_size) { 323 inode_add_bytes(inode, last_pos - inode->i_size); 324 i_size_write(inode, last_pos); 325 } 326 folio_mark_dirty(folio); 327 out: 328 folio_unlock(folio); 329 folio_put(folio); 330 331 return copied; 332 } 333 334 335 const struct address_space_operations v9fs_addr_operations = { 336 .readpage = v9fs_vfs_readpage, 337 .readahead = v9fs_vfs_readahead, 338 .set_page_dirty = __set_page_dirty_nobuffers, 339 .writepage = v9fs_vfs_writepage, 340 .write_begin = v9fs_write_begin, 341 .write_end = v9fs_write_end, 342 .releasepage = v9fs_release_page, 343 .invalidatepage = v9fs_invalidate_page, 344 .launder_page = v9fs_launder_page, 345 .direct_IO = v9fs_direct_IO, 346 }; 347