David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
| 2 | /* Network filesystem high-level buffered read support. |
| 3 | * |
| 4 | * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. |
| 5 | * Written by David Howells (dhowells@redhat.com) |
| 6 | */ |
| 7 | |
| 8 | #include <linux/export.h> |
| 9 | #include <linux/task_io_accounting_ops.h> |
| 10 | #include "internal.h" |
| 11 | |
| 12 | /* |
| 13 | * Unlock the folios in a read operation. We need to set PG_fscache on any |
| 14 | * folios we're going to write back before we unlock them. |
| 15 | */ |
| 16 | void netfs_rreq_unlock_folios(struct netfs_io_request *rreq) |
| 17 | { |
| 18 | struct netfs_io_subrequest *subreq; |
| 19 | struct folio *folio; |
| 20 | unsigned int iopos, account = 0; |
| 21 | pgoff_t start_page = rreq->start / PAGE_SIZE; |
| 22 | pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1; |
| 23 | bool subreq_failed = false; |
| 24 | |
| 25 | XA_STATE(xas, &rreq->mapping->i_pages, start_page); |
| 26 | |
| 27 | if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) { |
| 28 | __clear_bit(NETFS_RREQ_COPY_TO_CACHE, &rreq->flags); |
| 29 | list_for_each_entry(subreq, &rreq->subrequests, rreq_link) { |
| 30 | __clear_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags); |
| 31 | } |
| 32 | } |
| 33 | |
| 34 | /* Walk through the pagecache and the I/O request lists simultaneously. |
| 35 | * We may have a mixture of cached and uncached sections and we only |
| 36 | * really want to write out the uncached sections. This is slightly |
| 37 | * complicated by the possibility that we might have huge pages with a |
| 38 | * mixture inside. |
| 39 | */ |
| 40 | subreq = list_first_entry(&rreq->subrequests, |
| 41 | struct netfs_io_subrequest, rreq_link); |
| 42 | iopos = 0; |
| 43 | subreq_failed = (subreq->error < 0); |
| 44 | |
| 45 | trace_netfs_rreq(rreq, netfs_rreq_trace_unlock); |
| 46 | |
| 47 | rcu_read_lock(); |
| 48 | xas_for_each(&xas, folio, last_page) { |
| 49 | unsigned int pgpos = (folio_index(folio) - start_page) * PAGE_SIZE; |
| 50 | unsigned int pgend = pgpos + folio_size(folio); |
| 51 | bool pg_failed = false; |
| 52 | |
| 53 | for (;;) { |
| 54 | if (!subreq) { |
| 55 | pg_failed = true; |
| 56 | break; |
| 57 | } |
| 58 | if (test_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags)) |
| 59 | folio_start_fscache(folio); |
| 60 | pg_failed |= subreq_failed; |
| 61 | if (pgend < iopos + subreq->len) |
| 62 | break; |
| 63 | |
| 64 | account += subreq->transferred; |
| 65 | iopos += subreq->len; |
| 66 | if (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) { |
| 67 | subreq = list_next_entry(subreq, rreq_link); |
| 68 | subreq_failed = (subreq->error < 0); |
| 69 | } else { |
| 70 | subreq = NULL; |
| 71 | subreq_failed = false; |
| 72 | } |
| 73 | if (pgend == iopos) |
| 74 | break; |
| 75 | } |
| 76 | |
| 77 | if (!pg_failed) { |
| 78 | flush_dcache_folio(folio); |
| 79 | folio_mark_uptodate(folio); |
| 80 | } |
| 81 | |
| 82 | if (!test_bit(NETFS_RREQ_DONT_UNLOCK_FOLIOS, &rreq->flags)) { |
| 83 | if (folio_index(folio) == rreq->no_unlock_folio && |
| 84 | test_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags)) |
| 85 | _debug("no unlock"); |
| 86 | else |
| 87 | folio_unlock(folio); |
| 88 | } |
| 89 | } |
| 90 | rcu_read_unlock(); |
| 91 | |
| 92 | task_io_account_read(account); |
| 93 | if (rreq->netfs_ops->done) |
| 94 | rreq->netfs_ops->done(rreq); |
| 95 | } |
| 96 | |
| 97 | static void netfs_cache_expand_readahead(struct netfs_io_request *rreq, |
| 98 | loff_t *_start, size_t *_len, loff_t i_size) |
| 99 | { |
| 100 | struct netfs_cache_resources *cres = &rreq->cache_resources; |
| 101 | |
| 102 | if (cres->ops && cres->ops->expand_readahead) |
| 103 | cres->ops->expand_readahead(cres, _start, _len, i_size); |
| 104 | } |
| 105 | |
| 106 | static void netfs_rreq_expand(struct netfs_io_request *rreq, |
| 107 | struct readahead_control *ractl) |
| 108 | { |
| 109 | /* Give the cache a chance to change the request parameters. The |
| 110 | * resultant request must contain the original region. |
| 111 | */ |
| 112 | netfs_cache_expand_readahead(rreq, &rreq->start, &rreq->len, rreq->i_size); |
| 113 | |
| 114 | /* Give the netfs a chance to change the request parameters. The |
| 115 | * resultant request must contain the original region. |
| 116 | */ |
| 117 | if (rreq->netfs_ops->expand_readahead) |
| 118 | rreq->netfs_ops->expand_readahead(rreq); |
| 119 | |
| 120 | /* Expand the request if the cache wants it to start earlier. Note |
| 121 | * that the expansion may get further extended if the VM wishes to |
| 122 | * insert THPs and the preferred start and/or end wind up in the middle |
| 123 | * of THPs. |
| 124 | * |
| 125 | * If this is the case, however, the THP size should be an integer |
| 126 | * multiple of the cache granule size, so we get a whole number of |
| 127 | * granules to deal with. |
| 128 | */ |
| 129 | if (rreq->start != readahead_pos(ractl) || |
| 130 | rreq->len != readahead_length(ractl)) { |
| 131 | readahead_expand(ractl, rreq->start, rreq->len); |
| 132 | rreq->start = readahead_pos(ractl); |
| 133 | rreq->len = readahead_length(ractl); |
| 134 | |
| 135 | trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl), |
| 136 | netfs_read_trace_expanded); |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | /** |
| 141 | * netfs_readahead - Helper to manage a read request |
| 142 | * @ractl: The description of the readahead request |
| 143 | * |
| 144 | * Fulfil a readahead request by drawing data from the cache if possible, or |
| 145 | * the netfs if not. Space beyond the EOF is zero-filled. Multiple I/O |
| 146 | * requests from different sources will get munged together. If necessary, the |
| 147 | * readahead window can be expanded in either direction to a more convenient |
| 148 | * alighment for RPC efficiency or to make storage in the cache feasible. |
| 149 | * |
| 150 | * The calling netfs must initialise a netfs context contiguous to the vfs |
| 151 | * inode before calling this. |
| 152 | * |
| 153 | * This is usable whether or not caching is enabled. |
| 154 | */ |
| 155 | void netfs_readahead(struct readahead_control *ractl) |
| 156 | { |
| 157 | struct netfs_io_request *rreq; |
David Howells | 874c8ca1 | 2022-06-09 21:46:04 +0100 | [diff] [blame] | 158 | struct netfs_inode *ctx = netfs_inode(ractl->mapping->host); |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 159 | int ret; |
| 160 | |
| 161 | _enter("%lx,%x", readahead_index(ractl), readahead_count(ractl)); |
| 162 | |
| 163 | if (readahead_count(ractl) == 0) |
| 164 | return; |
| 165 | |
| 166 | rreq = netfs_alloc_request(ractl->mapping, ractl->file, |
| 167 | readahead_pos(ractl), |
| 168 | readahead_length(ractl), |
| 169 | NETFS_READAHEAD); |
| 170 | if (IS_ERR(rreq)) |
| 171 | return; |
| 172 | |
| 173 | if (ctx->ops->begin_cache_operation) { |
| 174 | ret = ctx->ops->begin_cache_operation(rreq); |
| 175 | if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) |
| 176 | goto cleanup_free; |
| 177 | } |
| 178 | |
| 179 | netfs_stat(&netfs_n_rh_readahead); |
| 180 | trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl), |
| 181 | netfs_read_trace_readahead); |
| 182 | |
| 183 | netfs_rreq_expand(rreq, ractl); |
| 184 | |
| 185 | /* Drop the refs on the folios here rather than in the cache or |
| 186 | * filesystem. The locks will be dropped in netfs_rreq_unlock(). |
| 187 | */ |
| 188 | while (readahead_folio(ractl)) |
| 189 | ; |
| 190 | |
| 191 | netfs_begin_read(rreq, false); |
| 192 | return; |
| 193 | |
| 194 | cleanup_free: |
| 195 | netfs_put_request(rreq, false, netfs_rreq_trace_put_failed); |
| 196 | return; |
| 197 | } |
| 198 | EXPORT_SYMBOL(netfs_readahead); |
| 199 | |
| 200 | /** |
Matthew Wilcox (Oracle) | 6c62371 | 2022-04-29 08:49:28 -0400 | [diff] [blame] | 201 | * netfs_read_folio - Helper to manage a read_folio request |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 202 | * @file: The file to read from |
Matthew Wilcox (Oracle) | 6c62371 | 2022-04-29 08:49:28 -0400 | [diff] [blame] | 203 | * @folio: The folio to read |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 204 | * |
Matthew Wilcox (Oracle) | 6c62371 | 2022-04-29 08:49:28 -0400 | [diff] [blame] | 205 | * Fulfil a read_folio request by drawing data from the cache if |
| 206 | * possible, or the netfs if not. Space beyond the EOF is zero-filled. |
| 207 | * Multiple I/O requests from different sources will get munged together. |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 208 | * |
| 209 | * The calling netfs must initialise a netfs context contiguous to the vfs |
| 210 | * inode before calling this. |
| 211 | * |
| 212 | * This is usable whether or not caching is enabled. |
| 213 | */ |
Matthew Wilcox (Oracle) | 6c62371 | 2022-04-29 08:49:28 -0400 | [diff] [blame] | 214 | int netfs_read_folio(struct file *file, struct folio *folio) |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 215 | { |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 216 | struct address_space *mapping = folio_file_mapping(folio); |
| 217 | struct netfs_io_request *rreq; |
David Howells | 874c8ca1 | 2022-06-09 21:46:04 +0100 | [diff] [blame] | 218 | struct netfs_inode *ctx = netfs_inode(mapping->host); |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 219 | int ret; |
| 220 | |
| 221 | _enter("%lx", folio_index(folio)); |
| 222 | |
| 223 | rreq = netfs_alloc_request(mapping, file, |
| 224 | folio_file_pos(folio), folio_size(folio), |
| 225 | NETFS_READPAGE); |
| 226 | if (IS_ERR(rreq)) { |
| 227 | ret = PTR_ERR(rreq); |
| 228 | goto alloc_error; |
| 229 | } |
| 230 | |
| 231 | if (ctx->ops->begin_cache_operation) { |
| 232 | ret = ctx->ops->begin_cache_operation(rreq); |
| 233 | if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) |
| 234 | goto discard; |
| 235 | } |
| 236 | |
| 237 | netfs_stat(&netfs_n_rh_readpage); |
| 238 | trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage); |
| 239 | return netfs_begin_read(rreq, true); |
| 240 | |
| 241 | discard: |
| 242 | netfs_put_request(rreq, false, netfs_rreq_trace_put_discard); |
| 243 | alloc_error: |
| 244 | folio_unlock(folio); |
| 245 | return ret; |
| 246 | } |
Matthew Wilcox (Oracle) | 6c62371 | 2022-04-29 08:49:28 -0400 | [diff] [blame] | 247 | EXPORT_SYMBOL(netfs_read_folio); |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 248 | |
| 249 | /* |
| 250 | * Prepare a folio for writing without reading first |
| 251 | * @folio: The folio being prepared |
| 252 | * @pos: starting position for the write |
| 253 | * @len: length of write |
| 254 | * @always_fill: T if the folio should always be completely filled/cleared |
| 255 | * |
| 256 | * In some cases, write_begin doesn't need to read at all: |
| 257 | * - full folio write |
| 258 | * - write that lies in a folio that is completely beyond EOF |
| 259 | * - write that covers the folio from start to EOF or beyond it |
| 260 | * |
| 261 | * If any of these criteria are met, then zero out the unwritten parts |
| 262 | * of the folio and return true. Otherwise, return false. |
| 263 | */ |
| 264 | static bool netfs_skip_folio_read(struct folio *folio, loff_t pos, size_t len, |
| 265 | bool always_fill) |
| 266 | { |
| 267 | struct inode *inode = folio_inode(folio); |
| 268 | loff_t i_size = i_size_read(inode); |
| 269 | size_t offset = offset_in_folio(folio, pos); |
| 270 | size_t plen = folio_size(folio); |
| 271 | |
| 272 | if (unlikely(always_fill)) { |
| 273 | if (pos - offset + len <= i_size) |
| 274 | return false; /* Page entirely before EOF */ |
| 275 | zero_user_segment(&folio->page, 0, plen); |
| 276 | folio_mark_uptodate(folio); |
| 277 | return true; |
| 278 | } |
| 279 | |
| 280 | /* Full folio write */ |
| 281 | if (offset == 0 && len >= plen) |
| 282 | return true; |
| 283 | |
| 284 | /* Page entirely beyond the end of the file */ |
| 285 | if (pos - offset >= i_size) |
| 286 | goto zero_out; |
| 287 | |
| 288 | /* Write that covers from the start of the folio to EOF or beyond */ |
| 289 | if (offset == 0 && (pos + len) >= i_size) |
| 290 | goto zero_out; |
| 291 | |
| 292 | return false; |
| 293 | zero_out: |
| 294 | zero_user_segments(&folio->page, 0, offset, offset + len, plen); |
| 295 | return true; |
| 296 | } |
| 297 | |
| 298 | /** |
| 299 | * netfs_write_begin - Helper to prepare for writing |
Linus Torvalds | e81fb41 | 2022-06-09 15:04:01 -0700 | [diff] [blame] | 300 | * @ctx: The netfs context |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 301 | * @file: The file to read from |
| 302 | * @mapping: The mapping to read from |
| 303 | * @pos: File position at which the write will begin |
| 304 | * @len: The length of the write (may extend beyond the end of the folio chosen) |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 305 | * @_folio: Where to put the resultant folio |
| 306 | * @_fsdata: Place for the netfs to store a cookie |
| 307 | * |
| 308 | * Pre-read data for a write-begin request by drawing data from the cache if |
| 309 | * possible, or the netfs if not. Space beyond the EOF is zero-filled. |
| 310 | * Multiple I/O requests from different sources will get munged together. If |
| 311 | * necessary, the readahead window can be expanded in either direction to a |
| 312 | * more convenient alighment for RPC efficiency or to make storage in the cache |
| 313 | * feasible. |
| 314 | * |
| 315 | * The calling netfs must provide a table of operations, only one of which, |
| 316 | * issue_op, is mandatory. |
| 317 | * |
| 318 | * The check_write_begin() operation can be provided to check for and flush |
| 319 | * conflicting writes once the folio is grabbed and locked. It is passed a |
| 320 | * pointer to the fsdata cookie that gets returned to the VM to be passed to |
| 321 | * write_end. It is permitted to sleep. It should return 0 if the request |
Xiubo Li | fac47b4 | 2022-07-11 12:11:21 +0800 | [diff] [blame] | 322 | * should go ahead or it may return an error. It may also unlock and put the |
| 323 | * folio, provided it sets ``*foliop`` to NULL, in which case a return of 0 |
| 324 | * will cause the folio to be re-got and the process to be retried. |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 325 | * |
| 326 | * The calling netfs must initialise a netfs context contiguous to the vfs |
| 327 | * inode before calling this. |
| 328 | * |
| 329 | * This is usable whether or not caching is enabled. |
| 330 | */ |
Linus Torvalds | e81fb41 | 2022-06-09 15:04:01 -0700 | [diff] [blame] | 331 | int netfs_write_begin(struct netfs_inode *ctx, |
| 332 | struct file *file, struct address_space *mapping, |
Matthew Wilcox (Oracle) | de2a9311 | 2022-02-22 10:47:09 -0500 | [diff] [blame] | 333 | loff_t pos, unsigned int len, struct folio **_folio, |
| 334 | void **_fsdata) |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 335 | { |
| 336 | struct netfs_io_request *rreq; |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 337 | struct folio *folio; |
Matthew Wilcox (Oracle) | 236d93c | 2022-02-22 10:40:11 -0500 | [diff] [blame] | 338 | unsigned int fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE; |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 339 | pgoff_t index = pos >> PAGE_SHIFT; |
| 340 | int ret; |
| 341 | |
| 342 | DEFINE_READAHEAD(ractl, file, NULL, mapping, index); |
| 343 | |
| 344 | retry: |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 345 | folio = __filemap_get_folio(mapping, index, fgp_flags, |
| 346 | mapping_gfp_mask(mapping)); |
| 347 | if (!folio) |
| 348 | return -ENOMEM; |
| 349 | |
| 350 | if (ctx->ops->check_write_begin) { |
| 351 | /* Allow the netfs (eg. ceph) to flush conflicts. */ |
Xiubo Li | fac47b4 | 2022-07-11 12:11:21 +0800 | [diff] [blame] | 352 | ret = ctx->ops->check_write_begin(file, pos, len, &folio, _fsdata); |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 353 | if (ret < 0) { |
| 354 | trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin); |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 355 | goto error; |
| 356 | } |
Xiubo Li | fac47b4 | 2022-07-11 12:11:21 +0800 | [diff] [blame] | 357 | if (!folio) |
| 358 | goto retry; |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 359 | } |
| 360 | |
| 361 | if (folio_test_uptodate(folio)) |
| 362 | goto have_folio; |
| 363 | |
| 364 | /* If the page is beyond the EOF, we want to clear it - unless it's |
| 365 | * within the cache granule containing the EOF, in which case we need |
| 366 | * to preload the granule. |
| 367 | */ |
| 368 | if (!netfs_is_cache_enabled(ctx) && |
| 369 | netfs_skip_folio_read(folio, pos, len, false)) { |
| 370 | netfs_stat(&netfs_n_rh_write_zskip); |
| 371 | goto have_folio_no_wait; |
| 372 | } |
| 373 | |
| 374 | rreq = netfs_alloc_request(mapping, file, |
| 375 | folio_file_pos(folio), folio_size(folio), |
| 376 | NETFS_READ_FOR_WRITE); |
| 377 | if (IS_ERR(rreq)) { |
| 378 | ret = PTR_ERR(rreq); |
| 379 | goto error; |
| 380 | } |
| 381 | rreq->no_unlock_folio = folio_index(folio); |
| 382 | __set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags); |
| 383 | |
| 384 | if (ctx->ops->begin_cache_operation) { |
| 385 | ret = ctx->ops->begin_cache_operation(rreq); |
| 386 | if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) |
| 387 | goto error_put; |
| 388 | } |
| 389 | |
| 390 | netfs_stat(&netfs_n_rh_write_begin); |
| 391 | trace_netfs_read(rreq, pos, len, netfs_read_trace_write_begin); |
| 392 | |
| 393 | /* Expand the request to meet caching requirements and download |
| 394 | * preferences. |
| 395 | */ |
| 396 | ractl._nr_pages = folio_nr_pages(folio); |
| 397 | netfs_rreq_expand(rreq, &ractl); |
| 398 | |
| 399 | /* We hold the folio locks, so we can drop the references */ |
| 400 | folio_get(folio); |
| 401 | while (readahead_folio(&ractl)) |
| 402 | ; |
| 403 | |
| 404 | ret = netfs_begin_read(rreq, true); |
| 405 | if (ret < 0) |
| 406 | goto error; |
| 407 | |
| 408 | have_folio: |
| 409 | ret = folio_wait_fscache_killable(folio); |
| 410 | if (ret < 0) |
| 411 | goto error; |
| 412 | have_folio_no_wait: |
| 413 | *_folio = folio; |
| 414 | _leave(" = 0"); |
| 415 | return 0; |
| 416 | |
| 417 | error_put: |
| 418 | netfs_put_request(rreq, false, netfs_rreq_trace_put_failed); |
| 419 | error: |
Xiubo Li | fac47b4 | 2022-07-11 12:11:21 +0800 | [diff] [blame] | 420 | if (folio) { |
| 421 | folio_unlock(folio); |
| 422 | folio_put(folio); |
| 423 | } |
David Howells | 1621126 | 2022-03-01 14:35:58 +0000 | [diff] [blame] | 424 | _leave(" = %d", ret); |
| 425 | return ret; |
| 426 | } |
| 427 | EXPORT_SYMBOL(netfs_write_begin); |