| 1 | |
| 2 | |
| 3 | * fs/mpage.c
|
| 4 | *
|
| 5 | * Copyright (C) 2002, Linus Torvalds.
|
| 6 | *
|
| 7 | * Contains functions related to preparing and submitting BIOs which contain
|
| 8 | * multiple pagecache pages.
|
| 9 | *
|
| 10 | * 15May2002 Andrew Morton
|
| 11 | * Initial version
|
| 12 | * 27Jun2002 [email protected]
|
| 13 | * use bio_add_page() to build bio's just the right size
|
| 14 |
|
| 15 |
|
| 16 | #include <linux/kernel.h>
|
| 17 | #include <linux/export.h>
|
| 18 | #include <linux/mm.h>
|
| 19 | #include <linux/kdev_t.h>
|
| 20 | #include <linux/gfp.h>
|
| 21 | #include <linux/bio.h>
|
| 22 | #include <linux/fs.h>
|
| 23 | #include <linux/buffer_head.h>
|
| 24 | #include <linux/blkdev.h>
|
| 25 | #include <linux/highmem.h>
|
| 26 | #include <linux/prefetch.h>
|
| 27 | #include <linux/mpage.h>
|
| 28 | #include <linux/mm_inline.h>
|
| 29 | #include <linux/writeback.h>
|
| 30 | #include <linux/backing-dev.h>
|
| 31 | #include "internal.h"
|
| 32 |
|
| 33 | |
| 34 | * I/O completion handler for multipage BIOs.
|
| 35 | *
|
| 36 | * The mpage code never puts partial pages into a BIO (except for end-of-file).
|
| 37 | * If a page does not map to a contiguous run of blocks then it simply falls
|
| 38 | * back to block_read_full_folio().
|
| 39 | *
|
| 40 | * Why is this? If a page's completion depends on a number of different BIOs
|
| 41 | * which can complete in any order (or at the same time) then determining the
|
| 42 | * status of that page is hard. See end_buffer_async_read() for the details.
|
| 43 | * There is no point in duplicating all that complexity.
|
| 44 |
|
| 45 | static void mpage_read_end_io(struct bio *bio)
|
| 46 | {
|
| 47 | struct folio_iter fi;
|
| 48 | int err = blk_status_to_errno(bio->bi_status);
|
| 49 |
|
| 50 | bio_for_each_folio_all(fi, bio)
|
| 51 | folio_end_read(fi.folio, err == 0);
|
| 52 |
|
| 53 | bio_put(bio);
|
| 54 | }
|
| 55 |
|
| 56 | static void mpage_write_end_io(struct bio *bio)
|
| 57 | {
|
| 58 | struct folio_iter fi;
|
| 59 | int err = blk_status_to_errno(bio->bi_status);
|
| 60 |
|
| 61 | bio_for_each_folio_all(fi, bio) {
|
| 62 | if (err)
|
| 63 | mapping_set_error(fi.folio->mapping, err);
|
| 64 | folio_end_writeback(fi.folio);
|
| 65 | }
|
| 66 |
|
| 67 | bio_put(bio);
|
| 68 | }
|
| 69 |
|
| 70 | static struct bio *mpage_bio_submit_read(struct bio *bio)
|
| 71 | {
|
| 72 | bio->bi_end_io = mpage_read_end_io;
|
| 73 | guard_bio_eod(bio);
|
| 74 | submit_bio(bio);
|
| 75 | return NULL;
|
| 76 | }
|
| 77 |
|
| 78 | static struct bio *mpage_bio_submit_write(struct bio *bio)
|
| 79 | {
|
| 80 | bio->bi_end_io = mpage_write_end_io;
|
| 81 | guard_bio_eod(bio);
|
| 82 | submit_bio(bio);
|
| 83 | return NULL;
|
| 84 | }
|
| 85 |
|
| 86 | |
| 87 | * support function for mpage_readahead. The fs supplied get_block might
|
| 88 | * return an up to date buffer. This is used to map that buffer into
|
| 89 | * the page, which allows read_folio to avoid triggering a duplicate call
|
| 90 | * to get_block.
|
| 91 | *
|
| 92 | * The idea is to avoid adding buffers to pages that don't already have
|
| 93 | * them. So when the buffer is up to date and the page size == block size,
|
| 94 | * this marks the page up to date instead of adding new buffers.
|
| 95 |
|
| 96 | static void map_buffer_to_folio(struct folio *folio, struct buffer_head *bh,
|
| 97 | int page_block)
|
| 98 | {
|
| 99 | struct inode *inode = folio->mapping->host;
|
| 100 | struct buffer_head *page_bh, *head;
|
| 101 | int block = 0;
|
| 102 |
|
| 103 | head = folio_buffers(folio);
|
| 104 | if (!head) {
|
| 105 | |
| 106 | * don't make any buffers if there is only one buffer on
|
| 107 | * the folio and the folio just needs to be set up to date
|
| 108 |
|
| 109 | if (inode->i_blkbits == folio_shift(folio) &&
|
| 110 | buffer_uptodate(bh)) {
|
| 111 | folio_mark_uptodate(folio);
|
| 112 | return;
|
| 113 | }
|
| 114 | head = create_empty_buffers(folio, i_blocksize(inode), 0);
|
| 115 | }
|
| 116 |
|
| 117 | page_bh = head;
|
| 118 | do {
|
| 119 | if (block == page_block) {
|
| 120 | page_bh->b_state = bh->b_state;
|
| 121 | page_bh->b_bdev = bh->b_bdev;
|
| 122 | page_bh->b_blocknr = bh->b_blocknr;
|
| 123 | break;
|
| 124 | }
|
| 125 | page_bh = page_bh->b_this_page;
|
| 126 | block++;
|
| 127 | } while (page_bh != head);
|
| 128 | }
|
| 129 |
|
| 130 | struct mpage_readpage_args {
|
| 131 | struct bio *bio;
|
| 132 | struct folio *folio;
|
| 133 | unsigned int nr_pages;
|
| 134 | bool is_readahead;
|
| 135 | sector_t last_block_in_bio;
|
| 136 | struct buffer_head map_bh;
|
| 137 | unsigned long first_logical_block;
|
| 138 | get_block_t *get_block;
|
| 139 | };
|
| 140 |
|
| 141 | |
| 142 | * This is the worker routine which does all the work of mapping the disk
|
| 143 | * blocks and constructs largest possible bios, submits them for IO if the
|
| 144 | * blocks are not contiguous on the disk.
|
| 145 | *
|
| 146 | * We pass a buffer_head back and forth and use its buffer_mapped() flag to
|
| 147 | * represent the validity of its disk mapping and to decide when to do the next
|
| 148 | * get_block() call.
|
| 149 |
|
| 150 | static void do_mpage_readpage(struct mpage_readpage_args *args)
|
| 151 | {
|
| 152 | struct folio *folio = args->folio;
|
| 153 | struct inode *inode = folio->mapping->host;
|
| 154 | const unsigned blkbits = inode->i_blkbits;
|
| 155 | const unsigned blocks_per_folio = folio_size(folio) >> blkbits;
|
| 156 | const unsigned blocksize = 1 << blkbits;
|
| 157 | struct buffer_head *map_bh = &args->map_bh;
|
| 158 | sector_t block_in_file;
|
| 159 | sector_t last_block;
|
| 160 | sector_t last_block_in_file;
|
| 161 | sector_t first_block;
|
| 162 | unsigned page_block;
|
| 163 | unsigned first_hole = blocks_per_folio;
|
| 164 | struct block_device *bdev = NULL;
|
| 165 | int length;
|
| 166 | int fully_mapped = 1;
|
| 167 | blk_opf_t opf = REQ_OP_READ;
|
| 168 | unsigned nblocks;
|
| 169 | unsigned relative_block;
|
| 170 | gfp_t gfp = mapping_gfp_constraint(folio->mapping, GFP_KERNEL);
|
| 171 |
|
| 172 | if (args->is_readahead) {
|
| 173 | opf |= REQ_RAHEAD;
|
| 174 | gfp |= __GFP_NORETRY | __GFP_NOWARN;
|
| 175 | }
|
| 176 |
|
| 177 | if (folio_buffers(folio))
|
| 178 | goto confused;
|
| 179 |
|
| 180 | block_in_file = folio_pos(folio) >> blkbits;
|
| 181 | last_block = block_in_file + ((args->nr_pages * PAGE_SIZE) >> blkbits);
|
| 182 | last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
|
| 183 | if (last_block > last_block_in_file)
|
| 184 | last_block = last_block_in_file;
|
| 185 | page_block = 0;
|
| 186 |
|
| 187 | |
| 188 | * Map blocks using the result from the previous get_blocks call first.
|
| 189 |
|
| 190 | nblocks = map_bh->b_size >> blkbits;
|
| 191 | if (buffer_mapped(map_bh) &&
|
| 192 | block_in_file > args->first_logical_block &&
|
| 193 | block_in_file < (args->first_logical_block + nblocks)) {
|
| 194 | unsigned map_offset = block_in_file - args->first_logical_block;
|
| 195 | unsigned last = nblocks - map_offset;
|
| 196 |
|
| 197 | first_block = map_bh->b_blocknr + map_offset;
|
| 198 | for (relative_block = 0; ; relative_block++) {
|
| 199 | if (relative_block == last) {
|
| 200 | clear_buffer_mapped(map_bh);
|
| 201 | break;
|
| 202 | }
|
| 203 | if (page_block == blocks_per_folio)
|
| 204 | break;
|
| 205 | page_block++;
|
| 206 | block_in_file++;
|
| 207 | }
|
| 208 | bdev = map_bh->b_bdev;
|
| 209 | }
|
| 210 |
|
| 211 | |
| 212 | * Then do more get_blocks calls until we are done with this folio.
|
| 213 |
|
| 214 | map_bh->b_folio = folio;
|
| 215 | while (page_block < blocks_per_folio) {
|
| 216 | map_bh->b_state = 0;
|
| 217 | map_bh->b_size = 0;
|
| 218 |
|
| 219 | if (block_in_file < last_block) {
|
| 220 | map_bh->b_size = (last_block-block_in_file) << blkbits;
|
| 221 | if (args->get_block(inode, block_in_file, map_bh, 0))
|
| 222 | goto confused;
|
| 223 | args->first_logical_block = block_in_file;
|
| 224 | }
|
| 225 |
|
| 226 | if (!buffer_mapped(map_bh)) {
|
| 227 | fully_mapped = 0;
|
| 228 | if (first_hole == blocks_per_folio)
|
| 229 | first_hole = page_block;
|
| 230 | page_block++;
|
| 231 | block_in_file++;
|
| 232 | continue;
|
| 233 | }
|
| 234 |
|
| 235 | |
| 236 | * the get_block call, in which case we don't want to
|
| 237 | * read it again. map_buffer_to_folio copies the data
|
| 238 | * we just collected from get_block into the folio's buffers
|
| 239 | * so read_folio doesn't have to repeat the get_block call
|
| 240 |
|
| 241 | if (buffer_uptodate(map_bh)) {
|
| 242 | map_buffer_to_folio(folio, map_bh, page_block);
|
| 243 | goto confused;
|
| 244 | }
|
| 245 |
|
| 246 | if (first_hole != blocks_per_folio)
|
| 247 | goto confused;
|
| 248 |
|
| 249 |
|
| 250 | if (!page_block)
|
| 251 | first_block = map_bh->b_blocknr;
|
| 252 | else if (first_block + page_block != map_bh->b_blocknr)
|
| 253 | goto confused;
|
| 254 | nblocks = map_bh->b_size >> blkbits;
|
| 255 | for (relative_block = 0; ; relative_block++) {
|
| 256 | if (relative_block == nblocks) {
|
| 257 | clear_buffer_mapped(map_bh);
|
| 258 | break;
|
| 259 | } else if (page_block == blocks_per_folio)
|
| 260 | break;
|
| 261 | page_block++;
|
| 262 | block_in_file++;
|
| 263 | }
|
| 264 | bdev = map_bh->b_bdev;
|
| 265 | }
|
| 266 |
|
| 267 | if (first_hole != blocks_per_folio) {
|
| 268 | folio_zero_segment(folio, first_hole << blkbits, folio_size(folio));
|
| 269 | if (first_hole == 0) {
|
| 270 | folio_mark_uptodate(folio);
|
| 271 | folio_unlock(folio);
|
| 272 | goto out;
|
| 273 | }
|
| 274 | } else if (fully_mapped) {
|
| 275 | folio_set_mappedtodisk(folio);
|
| 276 | }
|
| 277 |
|
| 278 | |
| 279 | * This folio will go to BIO. Do we need to send this BIO off first?
|
| 280 |
|
| 281 | if (args->bio && (args->last_block_in_bio != first_block - 1))
|
| 282 | args->bio = mpage_bio_submit_read(args->bio);
|
| 283 |
|
| 284 | alloc_new:
|
| 285 | if (args->bio == NULL) {
|
| 286 | args->bio = bio_alloc(bdev, bio_max_segs(args->nr_pages), opf,
|
| 287 | gfp);
|
| 288 | if (args->bio == NULL)
|
| 289 | goto confused;
|
| 290 | args->bio->bi_iter.bi_sector = first_block << (blkbits - 9);
|
| 291 | }
|
| 292 |
|
| 293 | length = first_hole << blkbits;
|
| 294 | if (!bio_add_folio(args->bio, folio, length, 0)) {
|
| 295 | args->bio = mpage_bio_submit_read(args->bio);
|
| 296 | goto alloc_new;
|
| 297 | }
|
| 298 |
|
| 299 | relative_block = block_in_file - args->first_logical_block;
|
| 300 | nblocks = map_bh->b_size >> blkbits;
|
| 301 | if ((buffer_boundary(map_bh) && relative_block == nblocks) ||
|
| 302 | (first_hole != blocks_per_folio))
|
| 303 | args->bio = mpage_bio_submit_read(args->bio);
|
| 304 | else
|
| 305 | args->last_block_in_bio = first_block + blocks_per_folio - 1;
|
| 306 | out:
|
| 307 | return;
|
| 308 |
|
| 309 | confused:
|
| 310 | if (args->bio)
|
| 311 | args->bio = mpage_bio_submit_read(args->bio);
|
| 312 | if (!folio_test_uptodate(folio))
|
| 313 | block_read_full_folio(folio, args->get_block);
|
| 314 | else
|
| 315 | folio_unlock(folio);
|
| 316 | goto out;
|
| 317 | }
|
| 318 |
|
| 319 | |
| 320 | * mpage_readahead - start reads against pages
|
| 321 | * @rac: Describes which pages to read.
|
| 322 | * @get_block: The filesystem's block mapper function.
|
| 323 | *
|
| 324 | * This function walks the pages and the blocks within each page, building and
|
| 325 | * emitting large BIOs.
|
| 326 | *
|
| 327 | * If anything unusual happens, such as:
|
| 328 | *
|
| 329 | * - encountering a page which has buffers
|
| 330 | * - encountering a page which has a non-hole after a hole
|
| 331 | * - encountering a page with non-contiguous blocks
|
| 332 | *
|
| 333 | * then this code just gives up and calls the buffer_head-based read function.
|
| 334 | * It does handle a page which has holes at the end - that is a common case:
|
| 335 | * the end-of-file on blocksize < PAGE_SIZE setups.
|
| 336 | *
|
| 337 | * BH_Boundary explanation:
|
| 338 | *
|
| 339 | * There is a problem. The mpage read code assembles several pages, gets all
|
| 340 | * their disk mappings, and then submits them all. That's fine, but obtaining
|
| 341 | * the disk mappings may require I/O. Reads of indirect blocks, for example.
|
| 342 | *
|
| 343 | * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
|
| 344 | * submitted in the following order:
|
| 345 | *
|
| 346 | * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
|
| 347 | *
|
| 348 | * because the indirect block has to be read to get the mappings of blocks
|
| 349 | * 13,14,15,16. Obviously, this impacts performance.
|
| 350 | *
|
| 351 | * So what we do it to allow the filesystem's get_block() function to set
|
| 352 | * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block
|
| 353 | * after this one will require I/O against a block which is probably close to
|
| 354 | * this one. So you should push what I/O you have currently accumulated.
|
| 355 | *
|
| 356 | * This all causes the disk requests to be issued in the correct order.
|
| 357 |
|
| 358 | void mpage_readahead(struct readahead_control *rac, get_block_t get_block)
|
| 359 | {
|
| 360 | struct folio *folio;
|
| 361 | struct mpage_readpage_args args = {
|
| 362 | .get_block = get_block,
|
| 363 | .is_readahead = true,
|
| 364 | };
|
| 365 |
|
| 366 | while ((folio = readahead_folio(rac))) {
|
| 367 | prefetchw(&folio->flags);
|
| 368 | args.folio = folio;
|
| 369 | args.nr_pages = readahead_count(rac);
|
| 370 | do_mpage_readpage(&args);
|
| 371 | |
| 372 | * If read ahead failed synchronously, it may cause by removed
|
| 373 | * device, or some filesystem metadata error.
|
| 374 |
|
| 375 | if (!folio_test_locked(folio) && !folio_test_uptodate(folio))
|
| 376 | break;
|
| 377 | }
|
| 378 | if (args.bio)
|
| 379 | mpage_bio_submit_read(args.bio);
|
| 380 | }
|
| 381 | EXPORT_SYMBOL(mpage_readahead);
|
| 382 |
|
| 383 | |
| 384 | * This isn't called much at all
|
| 385 |
|
| 386 | int mpage_read_folio(struct folio *folio, get_block_t get_block)
|
| 387 | {
|
| 388 | struct mpage_readpage_args args = {
|
| 389 | .folio = folio,
|
| 390 | .nr_pages = folio_nr_pages(folio),
|
| 391 | .get_block = get_block,
|
| 392 | };
|
| 393 |
|
| 394 | do_mpage_readpage(&args);
|
| 395 | if (args.bio)
|
| 396 | mpage_bio_submit_read(args.bio);
|
| 397 | return 0;
|
| 398 | }
|
| 399 | EXPORT_SYMBOL(mpage_read_folio);
|
| 400 |
|
| 401 | |
| 402 | * Writing is not so simple.
|
| 403 | *
|
| 404 | * If the page has buffers then they will be used for obtaining the disk
|
| 405 | * mapping. We only support pages which are fully mapped-and-dirty, with a
|
| 406 | * special case for pages which are unmapped at the end: end-of-file.
|
| 407 | *
|
| 408 | * If the page has no buffers (preferred) then the page is mapped here.
|
| 409 | *
|
| 410 | * If all blocks are found to be contiguous then the page can go into the
|
| 411 | * BIO. Otherwise fall back to the mapping's writepage().
|
| 412 | *
|
| 413 | * FIXME: This code wants an estimate of how many pages are still to be
|
| 414 | * written, so it can intelligently allocate a suitably-sized BIO. For now,
|
| 415 | * just allocate full-size (16-page) BIOs.
|
| 416 |
|
| 417 |
|
| 418 | struct mpage_data {
|
| 419 | struct bio *bio;
|
| 420 | sector_t last_block_in_bio;
|
| 421 | get_block_t *get_block;
|
| 422 | };
|
| 423 |
|
| 424 | |
| 425 | * We have our BIO, so we can now mark the buffers clean. Make
|
| 426 | * sure to only clean buffers which we know we'll be writing.
|
| 427 |
|
| 428 | static void clean_buffers(struct folio *folio, unsigned first_unmapped)
|
| 429 | {
|
| 430 | unsigned buffer_counter = 0;
|
| 431 | struct buffer_head *bh, *head = folio_buffers(folio);
|
| 432 |
|
| 433 | if (!head)
|
| 434 | return;
|
| 435 | bh = head;
|
| 436 |
|
| 437 | do {
|
| 438 | if (buffer_counter++ == first_unmapped)
|
| 439 | break;
|
| 440 | clear_buffer_dirty(bh);
|
| 441 | bh = bh->b_this_page;
|
| 442 | } while (bh != head);
|
| 443 |
|
| 444 | |
| 445 | * we cannot drop the bh if the page is not uptodate or a concurrent
|
| 446 | * read_folio would fail to serialize with the bh and it would read from
|
| 447 | * disk before we reach the platter.
|
| 448 |
|
| 449 | if (buffer_heads_over_limit && folio_test_uptodate(folio))
|
| 450 | try_to_free_buffers(folio);
|
| 451 | }
|
| 452 |
|
| 453 | static int mpage_write_folio(struct writeback_control *wbc, struct folio *folio,
|
| 454 | struct mpage_data *mpd)
|
| 455 | {
|
| 456 | struct bio *bio = mpd->bio;
|
| 457 | struct address_space *mapping = folio->mapping;
|
| 458 | struct inode *inode = mapping->host;
|
| 459 | const unsigned blkbits = inode->i_blkbits;
|
| 460 | const unsigned blocks_per_folio = folio_size(folio) >> blkbits;
|
| 461 | sector_t last_block;
|
| 462 | sector_t block_in_file;
|
| 463 | sector_t first_block;
|
| 464 | unsigned page_block;
|
| 465 | unsigned first_unmapped = blocks_per_folio;
|
| 466 | struct block_device *bdev = NULL;
|
| 467 | int boundary = 0;
|
| 468 | sector_t boundary_block = 0;
|
| 469 | struct block_device *boundary_bdev = NULL;
|
| 470 | size_t length;
|
| 471 | struct buffer_head map_bh;
|
| 472 | loff_t i_size = i_size_read(inode);
|
| 473 | int ret = 0;
|
| 474 | struct buffer_head *head = folio_buffers(folio);
|
| 475 |
|
| 476 | if (head) {
|
| 477 | struct buffer_head *bh = head;
|
| 478 |
|
| 479 |
|
| 480 | page_block = 0;
|
| 481 | do {
|
| 482 | BUG_ON(buffer_locked(bh));
|
| 483 | if (!buffer_mapped(bh)) {
|
| 484 | |
| 485 | * unmapped dirty buffers are created by
|
| 486 | * block_dirty_folio -> mmapped data
|
| 487 |
|
| 488 | if (buffer_dirty(bh))
|
| 489 | goto confused;
|
| 490 | if (first_unmapped == blocks_per_folio)
|
| 491 | first_unmapped = page_block;
|
| 492 | continue;
|
| 493 | }
|
| 494 |
|
| 495 | if (first_unmapped != blocks_per_folio)
|
| 496 | goto confused;
|
| 497 |
|
| 498 | if (!buffer_dirty(bh) || !buffer_uptodate(bh))
|
| 499 | goto confused;
|
| 500 | if (page_block) {
|
| 501 | if (bh->b_blocknr != first_block + page_block)
|
| 502 | goto confused;
|
| 503 | } else {
|
| 504 | first_block = bh->b_blocknr;
|
| 505 | }
|
| 506 | page_block++;
|
| 507 | boundary = buffer_boundary(bh);
|
| 508 | if (boundary) {
|
| 509 | boundary_block = bh->b_blocknr;
|
| 510 | boundary_bdev = bh->b_bdev;
|
| 511 | }
|
| 512 | bdev = bh->b_bdev;
|
| 513 | } while ((bh = bh->b_this_page) != head);
|
| 514 |
|
| 515 | if (first_unmapped)
|
| 516 | goto page_is_mapped;
|
| 517 |
|
| 518 | |
| 519 | * Page has buffers, but they are all unmapped. The page was
|
| 520 | * created by pagein or read over a hole which was handled by
|
| 521 | * block_read_full_folio(). If this address_space is also
|
| 522 | * using mpage_readahead then this can rarely happen.
|
| 523 |
|
| 524 | goto confused;
|
| 525 | }
|
| 526 |
|
| 527 | |
| 528 | * The page has no buffers: map it to disk
|
| 529 |
|
| 530 | BUG_ON(!folio_test_uptodate(folio));
|
| 531 | block_in_file = folio_pos(folio) >> blkbits;
|
| 532 | |
| 533 | * Whole page beyond EOF? Skip allocating blocks to avoid leaking
|
| 534 | * space.
|
| 535 |
|
| 536 | if (block_in_file >= (i_size + (1 << blkbits) - 1) >> blkbits)
|
| 537 | goto page_is_mapped;
|
| 538 | last_block = (i_size - 1) >> blkbits;
|
| 539 | map_bh.b_folio = folio;
|
| 540 | for (page_block = 0; page_block < blocks_per_folio; ) {
|
| 541 |
|
| 542 | map_bh.b_state = 0;
|
| 543 | map_bh.b_size = 1 << blkbits;
|
| 544 | if (mpd->get_block(inode, block_in_file, &map_bh, 1))
|
| 545 | goto confused;
|
| 546 | if (!buffer_mapped(&map_bh))
|
| 547 | goto confused;
|
| 548 | if (buffer_new(&map_bh))
|
| 549 | clean_bdev_bh_alias(&map_bh);
|
| 550 | if (buffer_boundary(&map_bh)) {
|
| 551 | boundary_block = map_bh.b_blocknr;
|
| 552 | boundary_bdev = map_bh.b_bdev;
|
| 553 | }
|
| 554 | if (page_block) {
|
| 555 | if (map_bh.b_blocknr != first_block + page_block)
|
| 556 | goto confused;
|
| 557 | } else {
|
| 558 | first_block = map_bh.b_blocknr;
|
| 559 | }
|
| 560 | page_block++;
|
| 561 | boundary = buffer_boundary(&map_bh);
|
| 562 | bdev = map_bh.b_bdev;
|
| 563 | if (block_in_file == last_block)
|
| 564 | break;
|
| 565 | block_in_file++;
|
| 566 | }
|
| 567 | BUG_ON(page_block == 0);
|
| 568 |
|
| 569 | first_unmapped = page_block;
|
| 570 |
|
| 571 | page_is_mapped:
|
| 572 |
|
| 573 | if (folio_pos(folio) >= i_size)
|
| 574 | goto confused;
|
| 575 | length = folio_size(folio);
|
| 576 | if (folio_pos(folio) + length > i_size) {
|
| 577 | |
| 578 | * The page straddles i_size. It must be zeroed out on each
|
| 579 | * and every writepage invocation because it may be mmapped.
|
| 580 | * "A file is mapped in multiples of the page size. For a file
|
| 581 | * that is not a multiple of the page size, the remaining memory
|
| 582 | * is zeroed when mapped, and writes to that region are not
|
| 583 | * written out to the file."
|
| 584 |
|
| 585 | length = i_size - folio_pos(folio);
|
| 586 | folio_zero_segment(folio, length, folio_size(folio));
|
| 587 | }
|
| 588 |
|
| 589 | |
| 590 | * This page will go to BIO. Do we need to send this BIO off first?
|
| 591 |
|
| 592 | if (bio && mpd->last_block_in_bio != first_block - 1)
|
| 593 | bio = mpage_bio_submit_write(bio);
|
| 594 |
|
| 595 | alloc_new:
|
| 596 | if (bio == NULL) {
|
| 597 | bio = bio_alloc(bdev, BIO_MAX_VECS,
|
| 598 | REQ_OP_WRITE | wbc_to_write_flags(wbc),
|
| 599 | GFP_NOFS);
|
| 600 | bio->bi_iter.bi_sector = first_block << (blkbits - 9);
|
| 601 | wbc_init_bio(wbc, bio);
|
| 602 | bio->bi_write_hint = inode->i_write_hint;
|
| 603 | }
|
| 604 |
|
| 605 | |
| 606 | * Must try to add the page before marking the buffer clean or
|
| 607 | * the confused fail path above (OOM) will be very confused when
|
| 608 | * it finds all bh marked clean (i.e. it will not write anything)
|
| 609 |
|
| 610 | wbc_account_cgroup_owner(wbc, folio, folio_size(folio));
|
| 611 | length = first_unmapped << blkbits;
|
| 612 | if (!bio_add_folio(bio, folio, length, 0)) {
|
| 613 | bio = mpage_bio_submit_write(bio);
|
| 614 | goto alloc_new;
|
| 615 | }
|
| 616 |
|
| 617 | clean_buffers(folio, first_unmapped);
|
| 618 |
|
| 619 | BUG_ON(folio_test_writeback(folio));
|
| 620 | folio_start_writeback(folio);
|
| 621 | folio_unlock(folio);
|
| 622 | if (boundary || (first_unmapped != blocks_per_folio)) {
|
| 623 | bio = mpage_bio_submit_write(bio);
|
| 624 | if (boundary_block) {
|
| 625 | write_boundary_block(boundary_bdev,
|
| 626 | boundary_block, 1 << blkbits);
|
| 627 | }
|
| 628 | } else {
|
| 629 | mpd->last_block_in_bio = first_block + blocks_per_folio - 1;
|
| 630 | }
|
| 631 | goto out;
|
| 632 |
|
| 633 | confused:
|
| 634 | if (bio)
|
| 635 | bio = mpage_bio_submit_write(bio);
|
| 636 |
|
| 637 | |
| 638 | * The caller has a ref on the inode, so *mapping is stable
|
| 639 |
|
| 640 | ret = block_write_full_folio(folio, wbc, mpd->get_block);
|
| 641 | mapping_set_error(mapping, ret);
|
| 642 | out:
|
| 643 | mpd->bio = bio;
|
| 644 | return ret;
|
| 645 | }
|
| 646 |
|
| 647 | |
| 648 | * __mpage_writepages - walk the list of dirty pages of the given address space
|
| 649 | * & writepage() all of them
|
| 650 | * @mapping: address space structure to write
|
| 651 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write
|
| 652 | * @get_block: the filesystem's block mapper function.
|
| 653 | * @write_folio: handler to call for each folio before calling
|
| 654 | * mpage_write_folio()
|
| 655 | *
|
| 656 | * This is a library function, which implements the writepages()
|
| 657 | * address_space_operation. It calls @write_folio handler for each folio. If
|
| 658 | * the handler returns value > 0, it calls mpage_write_folio() to do the
|
| 659 | * folio writeback.
|
| 660 |
|
| 661 | int
|
| 662 | __mpage_writepages(struct address_space *mapping,
|
| 663 | struct writeback_control *wbc, get_block_t get_block,
|
| 664 | int (*write_folio)(struct folio *folio,
|
| 665 | struct writeback_control *wbc))
|
| 666 | {
|
| 667 | struct mpage_data mpd = {
|
| 668 | .get_block = get_block,
|
| 669 | };
|
| 670 | struct folio *folio = NULL;
|
| 671 | struct blk_plug plug;
|
| 672 | int error;
|
| 673 |
|
| 674 | blk_start_plug(&plug);
|
| 675 | while ((folio = writeback_iter(mapping, wbc, folio, &error))) {
|
| 676 | if (write_folio) {
|
| 677 | error = write_folio(folio, wbc);
|
| 678 | |
| 679 | * == 0 means folio is handled, < 0 means error. In
|
| 680 | * both cases hand back control to writeback_iter()
|
| 681 |
|
| 682 | if (error <= 0)
|
| 683 | continue;
|
| 684 |
|
| 685 | }
|
| 686 | error = mpage_write_folio(wbc, folio, &mpd);
|
| 687 | }
|
| 688 | if (mpd.bio)
|
| 689 | mpage_bio_submit_write(mpd.bio);
|
| 690 | blk_finish_plug(&plug);
|
| 691 | return error;
|
| 692 | }
|
| 693 | EXPORT_SYMBOL(__mpage_writepages);
|