| 1 | // SPDX-License-Identifier: GPL-2.0 |
| 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 axboe@suse.de |
| 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 <linux/pagevec.h> |
| 32 | #include <linux/cleancache.h> |
| 33 | #include "internal.h" |
| 34 | |
| 35 | /* |
| 36 | * I/O completion handler for multipage BIOs. |
| 37 | * |
| 38 | * The mpage code never puts partial pages into a BIO (except for end-of-file). |
| 39 | * If a page does not map to a contiguous run of blocks then it simply falls |
| 40 | * back to block_read_full_page(). |
| 41 | * |
| 42 | * Why is this? If a page's completion depends on a number of different BIOs |
| 43 | * which can complete in any order (or at the same time) then determining the |
| 44 | * status of that page is hard. See end_buffer_async_read() for the details. |
| 45 | * There is no point in duplicating all that complexity. |
| 46 | */ |
| 47 | static void mpage_end_io(struct bio *bio) |
| 48 | { |
| 49 | struct bio_vec *bv; |
| 50 | int i; |
| 51 | |
| 52 | bio_for_each_segment_all(bv, bio, i) { |
| 53 | struct page *page = bv->bv_page; |
| 54 | page_endio(page, bio_op(bio), |
| 55 | blk_status_to_errno(bio->bi_status)); |
| 56 | } |
| 57 | |
| 58 | bio_put(bio); |
| 59 | } |
| 60 | |
| 61 | static struct bio *mpage_bio_submit(int op, int op_flags, struct bio *bio) |
| 62 | { |
| 63 | bio->bi_end_io = mpage_end_io; |
| 64 | bio_set_op_attrs(bio, op, op_flags); |
| 65 | guard_bio_eod(op, bio); |
| 66 | submit_bio(bio); |
| 67 | return NULL; |
| 68 | } |
| 69 | |
| 70 | static struct bio * |
| 71 | mpage_alloc(struct block_device *bdev, |
| 72 | sector_t first_sector, int nr_vecs, |
| 73 | gfp_t gfp_flags) |
| 74 | { |
| 75 | struct bio *bio; |
| 76 | |
| 77 | /* Restrict the given (page cache) mask for slab allocations */ |
| 78 | gfp_flags &= GFP_KERNEL; |
| 79 | bio = bio_alloc(gfp_flags, nr_vecs); |
| 80 | |
| 81 | if (bio == NULL && (current->flags & PF_MEMALLOC)) { |
| 82 | while (!bio && (nr_vecs /= 2)) |
| 83 | bio = bio_alloc(gfp_flags, nr_vecs); |
| 84 | } |
| 85 | |
| 86 | if (bio) { |
| 87 | bio_set_dev(bio, bdev); |
| 88 | bio->bi_iter.bi_sector = first_sector; |
| 89 | } |
| 90 | return bio; |
| 91 | } |
| 92 | |
| 93 | /* |
| 94 | * support function for mpage_readpages. The fs supplied get_block might |
| 95 | * return an up to date buffer. This is used to map that buffer into |
| 96 | * the page, which allows readpage to avoid triggering a duplicate call |
| 97 | * to get_block. |
| 98 | * |
| 99 | * The idea is to avoid adding buffers to pages that don't already have |
| 100 | * them. So when the buffer is up to date and the page size == block size, |
| 101 | * this marks the page up to date instead of adding new buffers. |
| 102 | */ |
| 103 | static void |
| 104 | map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) |
| 105 | { |
| 106 | struct inode *inode = page->mapping->host; |
| 107 | struct buffer_head *page_bh, *head; |
| 108 | int block = 0; |
| 109 | |
| 110 | if (!page_has_buffers(page)) { |
| 111 | /* |
| 112 | * don't make any buffers if there is only one buffer on |
| 113 | * the page and the page just needs to be set up to date |
| 114 | */ |
| 115 | if (inode->i_blkbits == PAGE_SHIFT && |
| 116 | buffer_uptodate(bh)) { |
| 117 | SetPageUptodate(page); |
| 118 | return; |
| 119 | } |
| 120 | create_empty_buffers(page, i_blocksize(inode), 0); |
| 121 | } |
| 122 | head = page_buffers(page); |
| 123 | page_bh = head; |
| 124 | do { |
| 125 | if (block == page_block) { |
| 126 | page_bh->b_state = bh->b_state; |
| 127 | page_bh->b_bdev = bh->b_bdev; |
| 128 | page_bh->b_blocknr = bh->b_blocknr; |
| 129 | break; |
| 130 | } |
| 131 | page_bh = page_bh->b_this_page; |
| 132 | block++; |
| 133 | } while (page_bh != head); |
| 134 | } |
| 135 | |
| 136 | struct mpage_readpage_args { |
| 137 | struct bio *bio; |
| 138 | struct page *page; |
| 139 | unsigned int nr_pages; |
| 140 | bool is_readahead; |
| 141 | sector_t last_block_in_bio; |
| 142 | struct buffer_head map_bh; |
| 143 | unsigned long first_logical_block; |
| 144 | get_block_t *get_block; |
| 145 | }; |
| 146 | |
| 147 | /* |
| 148 | * This is the worker routine which does all the work of mapping the disk |
| 149 | * blocks and constructs largest possible bios, submits them for IO if the |
| 150 | * blocks are not contiguous on the disk. |
| 151 | * |
| 152 | * We pass a buffer_head back and forth and use its buffer_mapped() flag to |
| 153 | * represent the validity of its disk mapping and to decide when to do the next |
| 154 | * get_block() call. |
| 155 | */ |
| 156 | static struct bio *do_mpage_readpage(struct mpage_readpage_args *args) |
| 157 | { |
| 158 | struct page *page = args->page; |
| 159 | struct inode *inode = page->mapping->host; |
| 160 | const unsigned blkbits = inode->i_blkbits; |
| 161 | const unsigned blocks_per_page = PAGE_SIZE >> blkbits; |
| 162 | const unsigned blocksize = 1 << blkbits; |
| 163 | struct buffer_head *map_bh = &args->map_bh; |
| 164 | sector_t block_in_file; |
| 165 | sector_t last_block; |
| 166 | sector_t last_block_in_file; |
| 167 | sector_t blocks[MAX_BUF_PER_PAGE]; |
| 168 | unsigned page_block; |
| 169 | unsigned first_hole = blocks_per_page; |
| 170 | struct block_device *bdev = NULL; |
| 171 | int length; |
| 172 | int fully_mapped = 1; |
| 173 | int op_flags; |
| 174 | unsigned nblocks; |
| 175 | unsigned relative_block; |
| 176 | gfp_t gfp; |
| 177 | |
| 178 | if (args->is_readahead) { |
| 179 | op_flags = REQ_RAHEAD; |
| 180 | gfp = readahead_gfp_mask(page->mapping); |
| 181 | } else { |
| 182 | op_flags = 0; |
| 183 | gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL); |
| 184 | } |
| 185 | |
| 186 | if (page_has_buffers(page)) |
| 187 | goto confused; |
| 188 | |
| 189 | block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits); |
| 190 | last_block = block_in_file + args->nr_pages * blocks_per_page; |
| 191 | last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits; |
| 192 | if (last_block > last_block_in_file) |
| 193 | last_block = last_block_in_file; |
| 194 | page_block = 0; |
| 195 | |
| 196 | /* |
| 197 | * Map blocks using the result from the previous get_blocks call first. |
| 198 | */ |
| 199 | nblocks = map_bh->b_size >> blkbits; |
| 200 | if (buffer_mapped(map_bh) && |
| 201 | block_in_file > args->first_logical_block && |
| 202 | block_in_file < (args->first_logical_block + nblocks)) { |
| 203 | unsigned map_offset = block_in_file - args->first_logical_block; |
| 204 | unsigned last = nblocks - map_offset; |
| 205 | |
| 206 | for (relative_block = 0; ; relative_block++) { |
| 207 | if (relative_block == last) { |
| 208 | clear_buffer_mapped(map_bh); |
| 209 | break; |
| 210 | } |
| 211 | if (page_block == blocks_per_page) |
| 212 | break; |
| 213 | blocks[page_block] = map_bh->b_blocknr + map_offset + |
| 214 | relative_block; |
| 215 | page_block++; |
| 216 | block_in_file++; |
| 217 | } |
| 218 | bdev = map_bh->b_bdev; |
| 219 | } |
| 220 | |
| 221 | /* |
| 222 | * Then do more get_blocks calls until we are done with this page. |
| 223 | */ |
| 224 | map_bh->b_page = page; |
| 225 | while (page_block < blocks_per_page) { |
| 226 | map_bh->b_state = 0; |
| 227 | map_bh->b_size = 0; |
| 228 | |
| 229 | if (block_in_file < last_block) { |
| 230 | map_bh->b_size = (last_block-block_in_file) << blkbits; |
| 231 | if (args->get_block(inode, block_in_file, map_bh, 0)) |
| 232 | goto confused; |
| 233 | args->first_logical_block = block_in_file; |
| 234 | } |
| 235 | |
| 236 | if (!buffer_mapped(map_bh)) { |
| 237 | fully_mapped = 0; |
| 238 | if (first_hole == blocks_per_page) |
| 239 | first_hole = page_block; |
| 240 | page_block++; |
| 241 | block_in_file++; |
| 242 | continue; |
| 243 | } |
| 244 | |
| 245 | /* some filesystems will copy data into the page during |
| 246 | * the get_block call, in which case we don't want to |
| 247 | * read it again. map_buffer_to_page copies the data |
| 248 | * we just collected from get_block into the page's buffers |
| 249 | * so readpage doesn't have to repeat the get_block call |
| 250 | */ |
| 251 | if (buffer_uptodate(map_bh)) { |
| 252 | map_buffer_to_page(page, map_bh, page_block); |
| 253 | goto confused; |
| 254 | } |
| 255 | |
| 256 | if (first_hole != blocks_per_page) |
| 257 | goto confused; /* hole -> non-hole */ |
| 258 | |
| 259 | /* Contiguous blocks? */ |
| 260 | if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1) |
| 261 | goto confused; |
| 262 | nblocks = map_bh->b_size >> blkbits; |
| 263 | for (relative_block = 0; ; relative_block++) { |
| 264 | if (relative_block == nblocks) { |
| 265 | clear_buffer_mapped(map_bh); |
| 266 | break; |
| 267 | } else if (page_block == blocks_per_page) |
| 268 | break; |
| 269 | blocks[page_block] = map_bh->b_blocknr+relative_block; |
| 270 | page_block++; |
| 271 | block_in_file++; |
| 272 | } |
| 273 | bdev = map_bh->b_bdev; |
| 274 | } |
| 275 | |
| 276 | if (first_hole != blocks_per_page) { |
| 277 | zero_user_segment(page, first_hole << blkbits, PAGE_SIZE); |
| 278 | if (first_hole == 0) { |
| 279 | SetPageUptodate(page); |
| 280 | unlock_page(page); |
| 281 | goto out; |
| 282 | } |
| 283 | } else if (fully_mapped) { |
| 284 | SetPageMappedToDisk(page); |
| 285 | } |
| 286 | |
| 287 | if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) && |
| 288 | cleancache_get_page(page) == 0) { |
| 289 | SetPageUptodate(page); |
| 290 | goto confused; |
| 291 | } |
| 292 | |
| 293 | /* |
| 294 | * This page will go to BIO. Do we need to send this BIO off first? |
| 295 | */ |
| 296 | if (args->bio && (args->last_block_in_bio != blocks[0] - 1)) |
| 297 | args->bio = mpage_bio_submit(REQ_OP_READ, op_flags, args->bio); |
| 298 | |
| 299 | alloc_new: |
| 300 | if (args->bio == NULL) { |
| 301 | if (first_hole == blocks_per_page) { |
| 302 | if (!bdev_read_page(bdev, blocks[0] << (blkbits - 9), |
| 303 | page)) |
| 304 | goto out; |
| 305 | } |
| 306 | args->bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), |
| 307 | min_t(int, args->nr_pages, |
| 308 | BIO_MAX_PAGES), |
| 309 | gfp); |
| 310 | if (args->bio == NULL) |
| 311 | goto confused; |
| 312 | } |
| 313 | |
| 314 | length = first_hole << blkbits; |
| 315 | if (bio_add_page(args->bio, page, length, 0) < length) { |
| 316 | args->bio = mpage_bio_submit(REQ_OP_READ, op_flags, args->bio); |
| 317 | goto alloc_new; |
| 318 | } |
| 319 | |
| 320 | relative_block = block_in_file - args->first_logical_block; |
| 321 | nblocks = map_bh->b_size >> blkbits; |
| 322 | if ((buffer_boundary(map_bh) && relative_block == nblocks) || |
| 323 | (first_hole != blocks_per_page)) |
| 324 | args->bio = mpage_bio_submit(REQ_OP_READ, op_flags, args->bio); |
| 325 | else |
| 326 | args->last_block_in_bio = blocks[blocks_per_page - 1]; |
| 327 | out: |
| 328 | return args->bio; |
| 329 | |
| 330 | confused: |
| 331 | if (args->bio) |
| 332 | args->bio = mpage_bio_submit(REQ_OP_READ, op_flags, args->bio); |
| 333 | if (!PageUptodate(page)) |
| 334 | block_read_full_page(page, args->get_block); |
| 335 | else |
| 336 | unlock_page(page); |
| 337 | goto out; |
| 338 | } |
| 339 | |
| 340 | /** |
| 341 | * mpage_readpages - populate an address space with some pages & start reads against them |
| 342 | * @mapping: the address_space |
| 343 | * @pages: The address of a list_head which contains the target pages. These |
| 344 | * pages have their ->index populated and are otherwise uninitialised. |
| 345 | * The page at @pages->prev has the lowest file offset, and reads should be |
| 346 | * issued in @pages->prev to @pages->next order. |
| 347 | * @nr_pages: The number of pages at *@pages |
| 348 | * @get_block: The filesystem's block mapper function. |
| 349 | * |
| 350 | * This function walks the pages and the blocks within each page, building and |
| 351 | * emitting large BIOs. |
| 352 | * |
| 353 | * If anything unusual happens, such as: |
| 354 | * |
| 355 | * - encountering a page which has buffers |
| 356 | * - encountering a page which has a non-hole after a hole |
| 357 | * - encountering a page with non-contiguous blocks |
| 358 | * |
| 359 | * then this code just gives up and calls the buffer_head-based read function. |
| 360 | * It does handle a page which has holes at the end - that is a common case: |
| 361 | * the end-of-file on blocksize < PAGE_SIZE setups. |
| 362 | * |
| 363 | * BH_Boundary explanation: |
| 364 | * |
| 365 | * There is a problem. The mpage read code assembles several pages, gets all |
| 366 | * their disk mappings, and then submits them all. That's fine, but obtaining |
| 367 | * the disk mappings may require I/O. Reads of indirect blocks, for example. |
| 368 | * |
| 369 | * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be |
| 370 | * submitted in the following order: |
| 371 | * |
| 372 | * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 |
| 373 | * |
| 374 | * because the indirect block has to be read to get the mappings of blocks |
| 375 | * 13,14,15,16. Obviously, this impacts performance. |
| 376 | * |
| 377 | * So what we do it to allow the filesystem's get_block() function to set |
| 378 | * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block |
| 379 | * after this one will require I/O against a block which is probably close to |
| 380 | * this one. So you should push what I/O you have currently accumulated. |
| 381 | * |
| 382 | * This all causes the disk requests to be issued in the correct order. |
| 383 | */ |
| 384 | int |
| 385 | mpage_readpages(struct address_space *mapping, struct list_head *pages, |
| 386 | unsigned nr_pages, get_block_t get_block) |
| 387 | { |
| 388 | struct mpage_readpage_args args = { |
| 389 | .get_block = get_block, |
| 390 | .is_readahead = true, |
| 391 | }; |
| 392 | unsigned page_idx; |
| 393 | |
| 394 | for (page_idx = 0; page_idx < nr_pages; page_idx++) { |
| 395 | struct page *page = lru_to_page(pages); |
| 396 | |
| 397 | prefetchw(&page->flags); |
| 398 | list_del(&page->lru); |
| 399 | if (!add_to_page_cache_lru(page, mapping, |
| 400 | page->index, |
| 401 | readahead_gfp_mask(mapping))) { |
| 402 | args.page = page; |
| 403 | args.nr_pages = nr_pages - page_idx; |
| 404 | args.bio = do_mpage_readpage(&args); |
| 405 | } |
| 406 | put_page(page); |
| 407 | } |
| 408 | BUG_ON(!list_empty(pages)); |
| 409 | if (args.bio) |
| 410 | mpage_bio_submit(REQ_OP_READ, REQ_RAHEAD, args.bio); |
| 411 | return 0; |
| 412 | } |
| 413 | EXPORT_SYMBOL(mpage_readpages); |
| 414 | |
| 415 | /* |
| 416 | * This isn't called much at all |
| 417 | */ |
| 418 | int mpage_readpage(struct page *page, get_block_t get_block) |
| 419 | { |
| 420 | struct mpage_readpage_args args = { |
| 421 | .page = page, |
| 422 | .nr_pages = 1, |
| 423 | .get_block = get_block, |
| 424 | }; |
| 425 | |
| 426 | args.bio = do_mpage_readpage(&args); |
| 427 | if (args.bio) |
| 428 | mpage_bio_submit(REQ_OP_READ, 0, args.bio); |
| 429 | return 0; |
| 430 | } |
| 431 | EXPORT_SYMBOL(mpage_readpage); |
| 432 | |
| 433 | /* |
| 434 | * Writing is not so simple. |
| 435 | * |
| 436 | * If the page has buffers then they will be used for obtaining the disk |
| 437 | * mapping. We only support pages which are fully mapped-and-dirty, with a |
| 438 | * special case for pages which are unmapped at the end: end-of-file. |
| 439 | * |
| 440 | * If the page has no buffers (preferred) then the page is mapped here. |
| 441 | * |
| 442 | * If all blocks are found to be contiguous then the page can go into the |
| 443 | * BIO. Otherwise fall back to the mapping's writepage(). |
| 444 | * |
| 445 | * FIXME: This code wants an estimate of how many pages are still to be |
| 446 | * written, so it can intelligently allocate a suitably-sized BIO. For now, |
| 447 | * just allocate full-size (16-page) BIOs. |
| 448 | */ |
| 449 | |
| 450 | struct mpage_data { |
| 451 | struct bio *bio; |
| 452 | sector_t last_block_in_bio; |
| 453 | get_block_t *get_block; |
| 454 | unsigned use_writepage; |
| 455 | }; |
| 456 | |
| 457 | /* |
| 458 | * We have our BIO, so we can now mark the buffers clean. Make |
| 459 | * sure to only clean buffers which we know we'll be writing. |
| 460 | */ |
| 461 | static void clean_buffers(struct page *page, unsigned first_unmapped) |
| 462 | { |
| 463 | unsigned buffer_counter = 0; |
| 464 | struct buffer_head *bh, *head; |
| 465 | if (!page_has_buffers(page)) |
| 466 | return; |
| 467 | head = page_buffers(page); |
| 468 | bh = head; |
| 469 | |
| 470 | do { |
| 471 | if (buffer_counter++ == first_unmapped) |
| 472 | break; |
| 473 | clear_buffer_dirty(bh); |
| 474 | bh = bh->b_this_page; |
| 475 | } while (bh != head); |
| 476 | |
| 477 | /* |
| 478 | * we cannot drop the bh if the page is not uptodate or a concurrent |
| 479 | * readpage would fail to serialize with the bh and it would read from |
| 480 | * disk before we reach the platter. |
| 481 | */ |
| 482 | if (buffer_heads_over_limit && PageUptodate(page)) |
| 483 | try_to_free_buffers(page); |
| 484 | } |
| 485 | |
| 486 | /* |
| 487 | * For situations where we want to clean all buffers attached to a page. |
| 488 | * We don't need to calculate how many buffers are attached to the page, |
| 489 | * we just need to specify a number larger than the maximum number of buffers. |
| 490 | */ |
| 491 | void clean_page_buffers(struct page *page) |
| 492 | { |
| 493 | clean_buffers(page, ~0U); |
| 494 | } |
| 495 | |
| 496 | static int __mpage_writepage(struct page *page, struct writeback_control *wbc, |
| 497 | void *data) |
| 498 | { |
| 499 | struct mpage_data *mpd = data; |
| 500 | struct bio *bio = mpd->bio; |
| 501 | struct address_space *mapping = page->mapping; |
| 502 | struct inode *inode = page->mapping->host; |
| 503 | const unsigned blkbits = inode->i_blkbits; |
| 504 | unsigned long end_index; |
| 505 | const unsigned blocks_per_page = PAGE_SIZE >> blkbits; |
| 506 | sector_t last_block; |
| 507 | sector_t block_in_file; |
| 508 | sector_t blocks[MAX_BUF_PER_PAGE]; |
| 509 | unsigned page_block; |
| 510 | unsigned first_unmapped = blocks_per_page; |
| 511 | struct block_device *bdev = NULL; |
| 512 | int boundary = 0; |
| 513 | sector_t boundary_block = 0; |
| 514 | struct block_device *boundary_bdev = NULL; |
| 515 | int length; |
| 516 | struct buffer_head map_bh; |
| 517 | loff_t i_size = i_size_read(inode); |
| 518 | int ret = 0; |
| 519 | int op_flags = wbc_to_write_flags(wbc); |
| 520 | |
| 521 | if (page_has_buffers(page)) { |
| 522 | struct buffer_head *head = page_buffers(page); |
| 523 | struct buffer_head *bh = head; |
| 524 | |
| 525 | /* If they're all mapped and dirty, do it */ |
| 526 | page_block = 0; |
| 527 | do { |
| 528 | BUG_ON(buffer_locked(bh)); |
| 529 | if (!buffer_mapped(bh)) { |
| 530 | /* |
| 531 | * unmapped dirty buffers are created by |
| 532 | * __set_page_dirty_buffers -> mmapped data |
| 533 | */ |
| 534 | if (buffer_dirty(bh)) |
| 535 | goto confused; |
| 536 | if (first_unmapped == blocks_per_page) |
| 537 | first_unmapped = page_block; |
| 538 | continue; |
| 539 | } |
| 540 | |
| 541 | if (first_unmapped != blocks_per_page) |
| 542 | goto confused; /* hole -> non-hole */ |
| 543 | |
| 544 | if (!buffer_dirty(bh) || !buffer_uptodate(bh)) |
| 545 | goto confused; |
| 546 | if (page_block) { |
| 547 | if (bh->b_blocknr != blocks[page_block-1] + 1) |
| 548 | goto confused; |
| 549 | } |
| 550 | blocks[page_block++] = bh->b_blocknr; |
| 551 | boundary = buffer_boundary(bh); |
| 552 | if (boundary) { |
| 553 | boundary_block = bh->b_blocknr; |
| 554 | boundary_bdev = bh->b_bdev; |
| 555 | } |
| 556 | bdev = bh->b_bdev; |
| 557 | } while ((bh = bh->b_this_page) != head); |
| 558 | |
| 559 | if (first_unmapped) |
| 560 | goto page_is_mapped; |
| 561 | |
| 562 | /* |
| 563 | * Page has buffers, but they are all unmapped. The page was |
| 564 | * created by pagein or read over a hole which was handled by |
| 565 | * block_read_full_page(). If this address_space is also |
| 566 | * using mpage_readpages then this can rarely happen. |
| 567 | */ |
| 568 | goto confused; |
| 569 | } |
| 570 | |
| 571 | /* |
| 572 | * The page has no buffers: map it to disk |
| 573 | */ |
| 574 | BUG_ON(!PageUptodate(page)); |
| 575 | block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits); |
| 576 | last_block = (i_size - 1) >> blkbits; |
| 577 | map_bh.b_page = page; |
| 578 | for (page_block = 0; page_block < blocks_per_page; ) { |
| 579 | |
| 580 | map_bh.b_state = 0; |
| 581 | map_bh.b_size = 1 << blkbits; |
| 582 | if (mpd->get_block(inode, block_in_file, &map_bh, 1)) |
| 583 | goto confused; |
| 584 | if (buffer_new(&map_bh)) |
| 585 | clean_bdev_bh_alias(&map_bh); |
| 586 | if (buffer_boundary(&map_bh)) { |
| 587 | boundary_block = map_bh.b_blocknr; |
| 588 | boundary_bdev = map_bh.b_bdev; |
| 589 | } |
| 590 | if (page_block) { |
| 591 | if (map_bh.b_blocknr != blocks[page_block-1] + 1) |
| 592 | goto confused; |
| 593 | } |
| 594 | blocks[page_block++] = map_bh.b_blocknr; |
| 595 | boundary = buffer_boundary(&map_bh); |
| 596 | bdev = map_bh.b_bdev; |
| 597 | if (block_in_file == last_block) |
| 598 | break; |
| 599 | block_in_file++; |
| 600 | } |
| 601 | BUG_ON(page_block == 0); |
| 602 | |
| 603 | first_unmapped = page_block; |
| 604 | |
| 605 | page_is_mapped: |
| 606 | end_index = i_size >> PAGE_SHIFT; |
| 607 | if (page->index >= end_index) { |
| 608 | /* |
| 609 | * The page straddles i_size. It must be zeroed out on each |
| 610 | * and every writepage invocation because it may be mmapped. |
| 611 | * "A file is mapped in multiples of the page size. For a file |
| 612 | * that is not a multiple of the page size, the remaining memory |
| 613 | * is zeroed when mapped, and writes to that region are not |
| 614 | * written out to the file." |
| 615 | */ |
| 616 | unsigned offset = i_size & (PAGE_SIZE - 1); |
| 617 | |
| 618 | if (page->index > end_index || !offset) |
| 619 | goto confused; |
| 620 | zero_user_segment(page, offset, PAGE_SIZE); |
| 621 | } |
| 622 | |
| 623 | /* |
| 624 | * This page will go to BIO. Do we need to send this BIO off first? |
| 625 | */ |
| 626 | if (bio && mpd->last_block_in_bio != blocks[0] - 1) |
| 627 | bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio); |
| 628 | |
| 629 | alloc_new: |
| 630 | if (bio == NULL) { |
| 631 | if (first_unmapped == blocks_per_page) { |
| 632 | if (!bdev_write_page(bdev, blocks[0] << (blkbits - 9), |
| 633 | page, wbc)) |
| 634 | goto out; |
| 635 | } |
| 636 | bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), |
| 637 | BIO_MAX_PAGES, GFP_NOFS|__GFP_HIGH); |
| 638 | if (bio == NULL) |
| 639 | goto confused; |
| 640 | |
| 641 | wbc_init_bio(wbc, bio); |
| 642 | bio->bi_write_hint = inode->i_write_hint; |
| 643 | } |
| 644 | |
| 645 | /* |
| 646 | * Must try to add the page before marking the buffer clean or |
| 647 | * the confused fail path above (OOM) will be very confused when |
| 648 | * it finds all bh marked clean (i.e. it will not write anything) |
| 649 | */ |
| 650 | wbc_account_io(wbc, page, PAGE_SIZE); |
| 651 | length = first_unmapped << blkbits; |
| 652 | if (bio_add_page(bio, page, length, 0) < length) { |
| 653 | bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio); |
| 654 | goto alloc_new; |
| 655 | } |
| 656 | |
| 657 | clean_buffers(page, first_unmapped); |
| 658 | |
| 659 | BUG_ON(PageWriteback(page)); |
| 660 | set_page_writeback(page); |
| 661 | unlock_page(page); |
| 662 | if (boundary || (first_unmapped != blocks_per_page)) { |
| 663 | bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio); |
| 664 | if (boundary_block) { |
| 665 | write_boundary_block(boundary_bdev, |
| 666 | boundary_block, 1 << blkbits); |
| 667 | } |
| 668 | } else { |
| 669 | mpd->last_block_in_bio = blocks[blocks_per_page - 1]; |
| 670 | } |
| 671 | goto out; |
| 672 | |
| 673 | confused: |
| 674 | if (bio) |
| 675 | bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio); |
| 676 | |
| 677 | if (mpd->use_writepage) { |
| 678 | ret = mapping->a_ops->writepage(page, wbc); |
| 679 | } else { |
| 680 | ret = -EAGAIN; |
| 681 | goto out; |
| 682 | } |
| 683 | /* |
| 684 | * The caller has a ref on the inode, so *mapping is stable |
| 685 | */ |
| 686 | mapping_set_error(mapping, ret); |
| 687 | out: |
| 688 | mpd->bio = bio; |
| 689 | return ret; |
| 690 | } |
| 691 | |
| 692 | /** |
| 693 | * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them |
| 694 | * @mapping: address space structure to write |
| 695 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write |
| 696 | * @get_block: the filesystem's block mapper function. |
| 697 | * If this is NULL then use a_ops->writepage. Otherwise, go |
| 698 | * direct-to-BIO. |
| 699 | * |
| 700 | * This is a library function, which implements the writepages() |
| 701 | * address_space_operation. |
| 702 | * |
| 703 | * If a page is already under I/O, generic_writepages() skips it, even |
| 704 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
| 705 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() |
| 706 | * and msync() need to guarantee that all the data which was dirty at the time |
| 707 | * the call was made get new I/O started against them. If wbc->sync_mode is |
| 708 | * WB_SYNC_ALL then we were called for data integrity and we must wait for |
| 709 | * existing IO to complete. |
| 710 | */ |
| 711 | int |
| 712 | mpage_writepages(struct address_space *mapping, |
| 713 | struct writeback_control *wbc, get_block_t get_block) |
| 714 | { |
| 715 | struct blk_plug plug; |
| 716 | int ret; |
| 717 | |
| 718 | blk_start_plug(&plug); |
| 719 | |
| 720 | if (!get_block) |
| 721 | ret = generic_writepages(mapping, wbc); |
| 722 | else { |
| 723 | struct mpage_data mpd = { |
| 724 | .bio = NULL, |
| 725 | .last_block_in_bio = 0, |
| 726 | .get_block = get_block, |
| 727 | .use_writepage = 1, |
| 728 | }; |
| 729 | |
| 730 | ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd); |
| 731 | if (mpd.bio) { |
| 732 | int op_flags = (wbc->sync_mode == WB_SYNC_ALL ? |
| 733 | REQ_SYNC : 0); |
| 734 | mpage_bio_submit(REQ_OP_WRITE, op_flags, mpd.bio); |
| 735 | } |
| 736 | } |
| 737 | blk_finish_plug(&plug); |
| 738 | return ret; |
| 739 | } |
| 740 | EXPORT_SYMBOL(mpage_writepages); |
| 741 | |
| 742 | int mpage_writepage(struct page *page, get_block_t get_block, |
| 743 | struct writeback_control *wbc) |
| 744 | { |
| 745 | struct mpage_data mpd = { |
| 746 | .bio = NULL, |
| 747 | .last_block_in_bio = 0, |
| 748 | .get_block = get_block, |
| 749 | .use_writepage = 0, |
| 750 | }; |
| 751 | int ret = __mpage_writepage(page, wbc, &mpd); |
| 752 | if (mpd.bio) { |
| 753 | int op_flags = (wbc->sync_mode == WB_SYNC_ALL ? |
| 754 | REQ_SYNC : 0); |
| 755 | mpage_bio_submit(REQ_OP_WRITE, op_flags, mpd.bio); |
| 756 | } |
| 757 | return ret; |
| 758 | } |
| 759 | EXPORT_SYMBOL(mpage_writepage); |