| 1 | |
| 2 | * fs/mpage.c
|
| 3 | *
|
| 4 | * Copyright (C) 2002, Linus Torvalds.
|
| 5 | *
|
| 6 | * Contains functions related to preparing and submitting BIOs which contain
|
| 7 | * multiple pagecache pages.
|
| 8 | *
|
| 9 | * 15May2002 [email protected]
|
| 10 | * Initial version
|
| 11 | * 27Jun2002 [email protected]
|
| 12 | * use bio_add_page() to build bio's just the right size
|
| 13 |
|
| 14 |
|
| 15 | #include <linux/kernel.h>
|
| 16 | #include <linux/module.h>
|
| 17 | #include <linux/mm.h>
|
| 18 | #include <linux/kdev_t.h>
|
| 19 | #include <linux/bio.h>
|
| 20 | #include <linux/fs.h>
|
| 21 | #include <linux/buffer_head.h>
|
| 22 | #include <linux/blkdev.h>
|
| 23 | #include <linux/highmem.h>
|
| 24 | #include <linux/prefetch.h>
|
| 25 | #include <linux/mpage.h>
|
| 26 | #include <linux/writeback.h>
|
| 27 | #include <linux/backing-dev.h>
|
| 28 | #include <linux/pagevec.h>
|
| 29 |
|
| 30 | |
| 31 | * I/O completion handler for multipage BIOs.
|
| 32 | *
|
| 33 | * The mpage code never puts partial pages into a BIO (except for end-of-file).
|
| 34 | * If a page does not map to a contiguous run of blocks then it simply falls
|
| 35 | * back to block_read_full_page().
|
| 36 | *
|
| 37 | * Why is this? If a page's completion depends on a number of different BIOs
|
| 38 | * which can complete in any order (or at the same time) then determining the
|
| 39 | * status of that page is hard. See end_buffer_async_read() for the details.
|
| 40 | * There is no point in duplicating all that complexity.
|
| 41 |
|
| 42 | static int mpage_end_io_read(struct bio *bio, unsigned int bytes_done, int err)
|
| 43 | {
|
| 44 | const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
|
| 45 | struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
|
| 46 |
|
| 47 | if (bio->bi_size)
|
| 48 | return 1;
|
| 49 |
|
| 50 | do {
|
| 51 | struct page *page = bvec->bv_page;
|
| 52 |
|
| 53 | if (--bvec >= bio->bi_io_vec)
|
| 54 | prefetchw(&bvec->bv_page->flags);
|
| 55 |
|
| 56 | if (uptodate) {
|
| 57 | SetPageUptodate(page);
|
| 58 | } else {
|
| 59 | ClearPageUptodate(page);
|
| 60 | SetPageError(page);
|
| 61 | }
|
| 62 | unlock_page(page);
|
| 63 | } while (bvec >= bio->bi_io_vec);
|
| 64 | bio_put(bio);
|
| 65 | return 0;
|
| 66 | }
|
| 67 |
|
| 68 | static int mpage_end_io_write(struct bio *bio, unsigned int bytes_done, int err)
|
| 69 | {
|
| 70 | const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
|
| 71 | struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
|
| 72 |
|
| 73 | if (bio->bi_size)
|
| 74 | return 1;
|
| 75 |
|
| 76 | do {
|
| 77 | struct page *page = bvec->bv_page;
|
| 78 |
|
| 79 | if (--bvec >= bio->bi_io_vec)
|
| 80 | prefetchw(&bvec->bv_page->flags);
|
| 81 |
|
| 82 | if (!uptodate){
|
| 83 | SetPageError(page);
|
| 84 | if (page->mapping)
|
| 85 | set_bit(AS_EIO, &page->mapping->flags);
|
| 86 | }
|
| 87 | end_page_writeback(page);
|
| 88 | } while (bvec >= bio->bi_io_vec);
|
| 89 | bio_put(bio);
|
| 90 | return 0;
|
| 91 | }
|
| 92 |
|
| 93 | static struct bio *mpage_bio_submit(int rw, struct bio *bio)
|
| 94 | {
|
| 95 | bio->bi_end_io = mpage_end_io_read;
|
| 96 | if (rw == WRITE)
|
| 97 | bio->bi_end_io = mpage_end_io_write;
|
| 98 | submit_bio(rw, bio);
|
| 99 | return NULL;
|
| 100 | }
|
| 101 |
|
| 102 | static struct bio *
|
| 103 | mpage_alloc(struct block_device *bdev,
|
| 104 | sector_t first_sector, int nr_vecs,
|
| 105 | gfp_t gfp_flags)
|
| 106 | {
|
| 107 | struct bio *bio;
|
| 108 |
|
| 109 | bio = bio_alloc(gfp_flags, nr_vecs);
|
| 110 |
|
| 111 | if (bio == NULL && (current->flags & PF_MEMALLOC)) {
|
| 112 | while (!bio && (nr_vecs /= 2))
|
| 113 | bio = bio_alloc(gfp_flags, nr_vecs);
|
| 114 | }
|
| 115 |
|
| 116 | if (bio) {
|
| 117 | bio->bi_bdev = bdev;
|
| 118 | bio->bi_sector = first_sector;
|
| 119 | }
|
| 120 | return bio;
|
| 121 | }
|
| 122 |
|
| 123 | |
| 124 | * support function for mpage_readpages. The fs supplied get_block might
|
| 125 | * return an up to date buffer. This is used to map that buffer into
|
| 126 | * the page, which allows readpage to avoid triggering a duplicate call
|
| 127 | * to get_block.
|
| 128 | *
|
| 129 | * The idea is to avoid adding buffers to pages that don't already have
|
| 130 | * them. So when the buffer is up to date and the page size == block size,
|
| 131 | * this marks the page up to date instead of adding new buffers.
|
| 132 |
|
| 133 | static void
|
| 134 | map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block)
|
| 135 | {
|
| 136 | struct inode *inode = page->mapping->host;
|
| 137 | struct buffer_head *page_bh, *head;
|
| 138 | int block = 0;
|
| 139 |
|
| 140 | if (!page_has_buffers(page)) {
|
| 141 | |
| 142 | * don't make any buffers if there is only one buffer on
|
| 143 | * the page and the page just needs to be set up to date
|
| 144 |
|
| 145 | if (inode->i_blkbits == PAGE_CACHE_SHIFT &&
|
| 146 | buffer_uptodate(bh)) {
|
| 147 | SetPageUptodate(page);
|
| 148 | return;
|
| 149 | }
|
| 150 | create_empty_buffers(page, 1 << inode->i_blkbits, 0);
|
| 151 | }
|
| 152 | head = page_buffers(page);
|
| 153 | page_bh = head;
|
| 154 | do {
|
| 155 | if (block == page_block) {
|
| 156 | page_bh->b_state = bh->b_state;
|
| 157 | page_bh->b_bdev = bh->b_bdev;
|
| 158 | page_bh->b_blocknr = bh->b_blocknr;
|
| 159 | break;
|
| 160 | }
|
| 161 | page_bh = page_bh->b_this_page;
|
| 162 | block++;
|
| 163 | } while (page_bh != head);
|
| 164 | }
|
| 165 |
|
| 166 | |
| 167 | * This is the worker routine which does all the work of mapping the disk
|
| 168 | * blocks and constructs largest possible bios, submits them for IO if the
|
| 169 | * blocks are not contiguous on the disk.
|
| 170 | *
|
| 171 | * We pass a buffer_head back and forth and use its buffer_mapped() flag to
|
| 172 | * represent the validity of its disk mapping and to decide when to do the next
|
| 173 | * get_block() call.
|
| 174 |
|
| 175 | static struct bio *
|
| 176 | do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
|
| 177 | sector_t *last_block_in_bio, struct buffer_head *map_bh,
|
| 178 | unsigned long *first_logical_block, get_block_t get_block)
|
| 179 | {
|
| 180 | struct inode *inode = page->mapping->host;
|
| 181 | const unsigned blkbits = inode->i_blkbits;
|
| 182 | const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
|
| 183 | const unsigned blocksize = 1 << blkbits;
|
| 184 | sector_t block_in_file;
|
| 185 | sector_t last_block;
|
| 186 | sector_t last_block_in_file;
|
| 187 | sector_t blocks[MAX_BUF_PER_PAGE];
|
| 188 | unsigned page_block;
|
| 189 | unsigned first_hole = blocks_per_page;
|
| 190 | struct block_device *bdev = NULL;
|
| 191 | int length;
|
| 192 | int fully_mapped = 1;
|
| 193 | unsigned nblocks;
|
| 194 | unsigned relative_block;
|
| 195 |
|
| 196 | if (page_has_buffers(page))
|
| 197 | goto confused;
|
| 198 |
|
| 199 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
|
| 200 | last_block = block_in_file + nr_pages * blocks_per_page;
|
| 201 | last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
|
| 202 | if (last_block > last_block_in_file)
|
| 203 | last_block = last_block_in_file;
|
| 204 | page_block = 0;
|
| 205 |
|
| 206 | |
| 207 | * Map blocks using the result from the previous get_blocks call first.
|
| 208 |
|
| 209 | nblocks = map_bh->b_size >> blkbits;
|
| 210 | if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&
|
| 211 | block_in_file < (*first_logical_block + nblocks)) {
|
| 212 | unsigned map_offset = block_in_file - *first_logical_block;
|
| 213 | unsigned last = nblocks - map_offset;
|
| 214 |
|
| 215 | for (relative_block = 0; ; relative_block++) {
|
| 216 | if (relative_block == last) {
|
| 217 | clear_buffer_mapped(map_bh);
|
| 218 | break;
|
| 219 | }
|
| 220 | if (page_block == blocks_per_page)
|
| 221 | break;
|
| 222 | blocks[page_block] = map_bh->b_blocknr + map_offset +
|
| 223 | relative_block;
|
| 224 | page_block++;
|
| 225 | block_in_file++;
|
| 226 | }
|
| 227 | bdev = map_bh->b_bdev;
|
| 228 | }
|
| 229 |
|
| 230 | |
| 231 | * Then do more get_blocks calls until we are done with this page.
|
| 232 |
|
| 233 | map_bh->b_page = page;
|
| 234 | while (page_block < blocks_per_page) {
|
| 235 | map_bh->b_state = 0;
|
| 236 | map_bh->b_size = 0;
|
| 237 |
|
| 238 | if (block_in_file < last_block) {
|
| 239 | map_bh->b_size = (last_block-block_in_file) << blkbits;
|
| 240 | if (get_block(inode, block_in_file, map_bh, 0))
|
| 241 | goto confused;
|
| 242 | *first_logical_block = block_in_file;
|
| 243 | }
|
| 244 |
|
| 245 | if (!buffer_mapped(map_bh)) {
|
| 246 | fully_mapped = 0;
|
| 247 | if (first_hole == blocks_per_page)
|
| 248 | first_hole = page_block;
|
| 249 | page_block++;
|
| 250 | block_in_file++;
|
| 251 | clear_buffer_mapped(map_bh);
|
| 252 | continue;
|
| 253 | }
|
| 254 |
|
| 255 | |
| 256 | * the get_block call, in which case we don't want to
|
| 257 | * read it again. map_buffer_to_page copies the data
|
| 258 | * we just collected from get_block into the page's buffers
|
| 259 | * so readpage doesn't have to repeat the get_block call
|
| 260 |
|
| 261 | if (buffer_uptodate(map_bh)) {
|
| 262 | map_buffer_to_page(page, map_bh, page_block);
|
| 263 | goto confused;
|
| 264 | }
|
| 265 |
|
| 266 | if (first_hole != blocks_per_page)
|
| 267 | goto confused;
|
| 268 |
|
| 269 |
|
| 270 | if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
|
| 271 | goto confused;
|
| 272 | nblocks = map_bh->b_size >> blkbits;
|
| 273 | for (relative_block = 0; ; relative_block++) {
|
| 274 | if (relative_block == nblocks) {
|
| 275 | clear_buffer_mapped(map_bh);
|
| 276 | break;
|
| 277 | } else if (page_block == blocks_per_page)
|
| 278 | break;
|
| 279 | blocks[page_block] = map_bh->b_blocknr+relative_block;
|
| 280 | page_block++;
|
| 281 | block_in_file++;
|
| 282 | }
|
| 283 | bdev = map_bh->b_bdev;
|
| 284 | }
|
| 285 |
|
| 286 | if (first_hole != blocks_per_page) {
|
| 287 | char *kaddr = kmap_atomic(page, KM_USER0);
|
| 288 | memset(kaddr + (first_hole << blkbits), 0,
|
| 289 | PAGE_CACHE_SIZE - (first_hole << blkbits));
|
| 290 | flush_dcache_page(page);
|
| 291 | kunmap_atomic(kaddr, KM_USER0);
|
| 292 | if (first_hole == 0) {
|
| 293 | SetPageUptodate(page);
|
| 294 | unlock_page(page);
|
| 295 | goto out;
|
| 296 | }
|
| 297 | } else if (fully_mapped) {
|
| 298 | SetPageMappedToDisk(page);
|
| 299 | }
|
| 300 |
|
| 301 | |
| 302 | * This page will go to BIO. Do we need to send this BIO off first?
|
| 303 |
|
| 304 | if (bio && (*last_block_in_bio != blocks[0] - 1))
|
| 305 | bio = mpage_bio_submit(READ, bio);
|
| 306 |
|
| 307 | alloc_new:
|
| 308 | if (bio == NULL) {
|
| 309 | bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
|
| 310 | min_t(int, nr_pages, bio_get_nr_vecs(bdev)),
|
| 311 | GFP_KERNEL);
|
| 312 | if (bio == NULL)
|
| 313 | goto confused;
|
| 314 | }
|
| 315 |
|
| 316 | length = first_hole << blkbits;
|
| 317 | if (bio_add_page(bio, page, length, 0) < length) {
|
| 318 | bio = mpage_bio_submit(READ, bio);
|
| 319 | goto alloc_new;
|
| 320 | }
|
| 321 |
|
| 322 | if (buffer_boundary(map_bh) || (first_hole != blocks_per_page))
|
| 323 | bio = mpage_bio_submit(READ, bio);
|
| 324 | else
|
| 325 | *last_block_in_bio = blocks[blocks_per_page - 1];
|
| 326 | out:
|
| 327 | return bio;
|
| 328 |
|
| 329 | confused:
|
| 330 | if (bio)
|
| 331 | bio = mpage_bio_submit(READ, bio);
|
| 332 | if (!PageUptodate(page))
|
| 333 | block_read_full_page(page, get_block);
|
| 334 | else
|
| 335 | unlock_page(page);
|
| 336 | goto out;
|
| 337 | }
|
| 338 |
|
| 339 | |
| 340 | * mpage_readpages - populate an address space with some pages, and
|
| 341 | * start reads against them.
|
| 342 | *
|
| 343 | * @mapping: the address_space
|
| 344 | * @pages: The address of a list_head which contains the target pages. These
|
| 345 | * pages have their ->index populated and are otherwise uninitialised.
|
| 346 | *
|
| 347 | * The page at @pages->prev has the lowest file offset, and reads should be
|
| 348 | * issued in @pages->prev to @pages->next order.
|
| 349 | *
|
| 350 | * @nr_pages: The number of pages at *@pages
|
| 351 | * @get_block: The filesystem's block mapper function.
|
| 352 | *
|
| 353 | * This function walks the pages and the blocks within each page, building and
|
| 354 | * emitting large BIOs.
|
| 355 | *
|
| 356 | * If anything unusual happens, such as:
|
| 357 | *
|
| 358 | * - encountering a page which has buffers
|
| 359 | * - encountering a page which has a non-hole after a hole
|
| 360 | * - encountering a page with non-contiguous blocks
|
| 361 | *
|
| 362 | * then this code just gives up and calls the buffer_head-based read function.
|
| 363 | * It does handle a page which has holes at the end - that is a common case:
|
| 364 | * the end-of-file on blocksize < PAGE_CACHE_SIZE setups.
|
| 365 | *
|
| 366 | * BH_Boundary explanation:
|
| 367 | *
|
| 368 | * There is a problem. The mpage read code assembles several pages, gets all
|
| 369 | * their disk mappings, and then submits them all. That's fine, but obtaining
|
| 370 | * the disk mappings may require I/O. Reads of indirect blocks, for example.
|
| 371 | *
|
| 372 | * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
|
| 373 | * submitted in the following order:
|
| 374 | * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
|
| 375 | * because the indirect block has to be read to get the mappings of blocks
|
| 376 | * 13,14,15,16. Obviously, this impacts performance.
|
| 377 | *
|
| 378 | * So what we do it to allow the filesystem's get_block() function to set
|
| 379 | * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block
|
| 380 | * after this one will require I/O against a block which is probably close to
|
| 381 | * this one. So you should push what I/O you have currently accumulated.
|
| 382 | *
|
| 383 | * This all causes the disk requests to be issued in the correct order.
|
| 384 |
|
| 385 | int
|
| 386 | mpage_readpages(struct address_space *mapping, struct list_head *pages,
|
| 387 | unsigned nr_pages, get_block_t get_block)
|
| 388 | {
|
| 389 | struct bio *bio = NULL;
|
| 390 | unsigned page_idx;
|
| 391 | sector_t last_block_in_bio = 0;
|
| 392 | struct pagevec lru_pvec;
|
| 393 | struct buffer_head map_bh;
|
| 394 | unsigned long first_logical_block = 0;
|
| 395 |
|
| 396 | clear_buffer_mapped(&map_bh);
|
| 397 | pagevec_init(&lru_pvec, 0);
|
| 398 | for (page_idx = 0; page_idx < nr_pages; page_idx++) {
|
| 399 | struct page *page = list_entry(pages->prev, struct page, lru);
|
| 400 |
|
| 401 | prefetchw(&page->flags);
|
| 402 | list_del(&page->lru);
|
| 403 | if (!add_to_page_cache(page, mapping,
|
| 404 | page->index, GFP_KERNEL)) {
|
| 405 | bio = do_mpage_readpage(bio, page,
|
| 406 | nr_pages - page_idx,
|
| 407 | &last_block_in_bio, &map_bh,
|
| 408 | &first_logical_block,
|
| 409 | get_block);
|
| 410 | if (!pagevec_add(&lru_pvec, page))
|
| 411 | __pagevec_lru_add(&lru_pvec);
|
| 412 | } else {
|
| 413 | page_cache_release(page);
|
| 414 | }
|
| 415 | }
|
| 416 | pagevec_lru_add(&lru_pvec);
|
| 417 | BUG_ON(!list_empty(pages));
|
| 418 | if (bio)
|
| 419 | mpage_bio_submit(READ, bio);
|
| 420 | return 0;
|
| 421 | }
|
| 422 | EXPORT_SYMBOL(mpage_readpages);
|
| 423 |
|
| 424 | |
| 425 | * This isn't called much at all
|
| 426 |
|
| 427 | int mpage_readpage(struct page *page, get_block_t get_block)
|
| 428 | {
|
| 429 | struct bio *bio = NULL;
|
| 430 | sector_t last_block_in_bio = 0;
|
| 431 | struct buffer_head map_bh;
|
| 432 | unsigned long first_logical_block = 0;
|
| 433 |
|
| 434 | clear_buffer_mapped(&map_bh);
|
| 435 | bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
|
| 436 | &map_bh, &first_logical_block, get_block);
|
| 437 | if (bio)
|
| 438 | mpage_bio_submit(READ, bio);
|
| 439 | return 0;
|
| 440 | }
|
| 441 | EXPORT_SYMBOL(mpage_readpage);
|
| 442 |
|
| 443 | |
| 444 | * Writing is not so simple.
|
| 445 | *
|
| 446 | * If the page has buffers then they will be used for obtaining the disk
|
| 447 | * mapping. We only support pages which are fully mapped-and-dirty, with a
|
| 448 | * special case for pages which are unmapped at the end: end-of-file.
|
| 449 | *
|
| 450 | * If the page has no buffers (preferred) then the page is mapped here.
|
| 451 | *
|
| 452 | * If all blocks are found to be contiguous then the page can go into the
|
| 453 | * BIO. Otherwise fall back to the mapping's writepage().
|
| 454 | *
|
| 455 | * FIXME: This code wants an estimate of how many pages are still to be
|
| 456 | * written, so it can intelligently allocate a suitably-sized BIO. For now,
|
| 457 | * just allocate full-size (16-page) BIOs.
|
| 458 |
|
| 459 | static struct bio *
|
| 460 | __mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block,
|
| 461 | sector_t *last_block_in_bio, int *ret, struct writeback_control *wbc,
|
| 462 | writepage_t writepage_fn)
|
| 463 | {
|
| 464 | struct address_space *mapping = page->mapping;
|
| 465 | struct inode *inode = page->mapping->host;
|
| 466 | const unsigned blkbits = inode->i_blkbits;
|
| 467 | unsigned long end_index;
|
| 468 | const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
|
| 469 | sector_t last_block;
|
| 470 | sector_t block_in_file;
|
| 471 | sector_t blocks[MAX_BUF_PER_PAGE];
|
| 472 | unsigned page_block;
|
| 473 | unsigned first_unmapped = blocks_per_page;
|
| 474 | struct block_device *bdev = NULL;
|
| 475 | int boundary = 0;
|
| 476 | sector_t boundary_block = 0;
|
| 477 | struct block_device *boundary_bdev = NULL;
|
| 478 | int length;
|
| 479 | struct buffer_head map_bh;
|
| 480 | loff_t i_size = i_size_read(inode);
|
| 481 |
|
| 482 | if (page_has_buffers(page)) {
|
| 483 | struct buffer_head *head = page_buffers(page);
|
| 484 | struct buffer_head *bh = head;
|
| 485 |
|
| 486 |
|
| 487 | page_block = 0;
|
| 488 | do {
|
| 489 | BUG_ON(buffer_locked(bh));
|
| 490 | if (!buffer_mapped(bh)) {
|
| 491 | |
| 492 | * unmapped dirty buffers are created by
|
| 493 | * __set_page_dirty_buffers -> mmapped data
|
| 494 |
|
| 495 | if (buffer_dirty(bh))
|
| 496 | goto confused;
|
| 497 | if (first_unmapped == blocks_per_page)
|
| 498 | first_unmapped = page_block;
|
| 499 | continue;
|
| 500 | }
|
| 501 |
|
| 502 | if (first_unmapped != blocks_per_page)
|
| 503 | goto confused;
|
| 504 |
|
| 505 | if (!buffer_dirty(bh) || !buffer_uptodate(bh))
|
| 506 | goto confused;
|
| 507 | if (page_block) {
|
| 508 | if (bh->b_blocknr != blocks[page_block-1] + 1)
|
| 509 | goto confused;
|
| 510 | }
|
| 511 | blocks[page_block++] = bh->b_blocknr;
|
| 512 | boundary = buffer_boundary(bh);
|
| 513 | if (boundary) {
|
| 514 | boundary_block = bh->b_blocknr;
|
| 515 | boundary_bdev = bh->b_bdev;
|
| 516 | }
|
| 517 | bdev = bh->b_bdev;
|
| 518 | } while ((bh = bh->b_this_page) != head);
|
| 519 |
|
| 520 | if (first_unmapped)
|
| 521 | goto page_is_mapped;
|
| 522 |
|
| 523 | |
| 524 | * Page has buffers, but they are all unmapped. The page was
|
| 525 | * created by pagein or read over a hole which was handled by
|
| 526 | * block_read_full_page(). If this address_space is also
|
| 527 | * using mpage_readpages then this can rarely happen.
|
| 528 |
|
| 529 | goto confused;
|
| 530 | }
|
| 531 |
|
| 532 | |
| 533 | * The page has no buffers: map it to disk
|
| 534 |
|
| 535 | BUG_ON(!PageUptodate(page));
|
| 536 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
|
| 537 | last_block = (i_size - 1) >> blkbits;
|
| 538 | map_bh.b_page = page;
|
| 539 | for (page_block = 0; page_block < blocks_per_page; ) {
|
| 540 |
|
| 541 | map_bh.b_state = 0;
|
| 542 | map_bh.b_size = 1 << blkbits;
|
| 543 | if (get_block(inode, block_in_file, &map_bh, 1))
|
| 544 | goto confused;
|
| 545 | if (buffer_new(&map_bh))
|
| 546 | unmap_underlying_metadata(map_bh.b_bdev,
|
| 547 | map_bh.b_blocknr);
|
| 548 | if (buffer_boundary(&map_bh)) {
|
| 549 | boundary_block = map_bh.b_blocknr;
|
| 550 | boundary_bdev = map_bh.b_bdev;
|
| 551 | }
|
| 552 | if (page_block) {
|
| 553 | if (map_bh.b_blocknr != blocks[page_block-1] + 1)
|
| 554 | goto confused;
|
| 555 | }
|
| 556 | blocks[page_block++] = map_bh.b_blocknr;
|
| 557 | boundary = buffer_boundary(&map_bh);
|
| 558 | bdev = map_bh.b_bdev;
|
| 559 | if (block_in_file == last_block)
|
| 560 | break;
|
| 561 | block_in_file++;
|
| 562 | }
|
| 563 | BUG_ON(page_block == 0);
|
| 564 |
|
| 565 | first_unmapped = page_block;
|
| 566 |
|
| 567 | page_is_mapped:
|
| 568 | end_index = i_size >> PAGE_CACHE_SHIFT;
|
| 569 | if (page->index >= end_index) {
|
| 570 | |
| 571 | * The page straddles i_size. It must be zeroed out on each
|
| 572 | * and every writepage invokation because it may be mmapped.
|
| 573 | * "A file is mapped in multiples of the page size. For a file
|
| 574 | * that is not a multiple of the page size, the remaining memory
|
| 575 | * is zeroed when mapped, and writes to that region are not
|
| 576 | * written out to the file."
|
| 577 |
|
| 578 | unsigned offset = i_size & (PAGE_CACHE_SIZE - 1);
|
| 579 | char *kaddr;
|
| 580 |
|
| 581 | if (page->index > end_index || !offset)
|
| 582 | goto confused;
|
| 583 | kaddr = kmap_atomic(page, KM_USER0);
|
| 584 | memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
|
| 585 | flush_dcache_page(page);
|
| 586 | kunmap_atomic(kaddr, KM_USER0);
|
| 587 | }
|
| 588 |
|
| 589 | |
| 590 | * This page will go to BIO. Do we need to send this BIO off first?
|
| 591 |
|
| 592 | if (bio && *last_block_in_bio != blocks[0] - 1)
|
| 593 | bio = mpage_bio_submit(WRITE, bio);
|
| 594 |
|
| 595 | alloc_new:
|
| 596 | if (bio == NULL) {
|
| 597 | bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
|
| 598 | bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH);
|
| 599 | if (bio == NULL)
|
| 600 | goto confused;
|
| 601 | }
|
| 602 |
|
| 603 | |
| 604 | * Must try to add the page before marking the buffer clean or
|
| 605 | * the confused fail path above (OOM) will be very confused when
|
| 606 | * it finds all bh marked clean (i.e. it will not write anything)
|
| 607 |
|
| 608 | length = first_unmapped << blkbits;
|
| 609 | if (bio_add_page(bio, page, length, 0) < length) {
|
| 610 | bio = mpage_bio_submit(WRITE, bio);
|
| 611 | goto alloc_new;
|
| 612 | }
|
| 613 |
|
| 614 | |
| 615 | * OK, we have our BIO, so we can now mark the buffers clean. Make
|
| 616 | * sure to only clean buffers which we know we'll be writing.
|
| 617 |
|
| 618 | if (page_has_buffers(page)) {
|
| 619 | struct buffer_head *head = page_buffers(page);
|
| 620 | struct buffer_head *bh = head;
|
| 621 | unsigned buffer_counter = 0;
|
| 622 |
|
| 623 | do {
|
| 624 | if (buffer_counter++ == first_unmapped)
|
| 625 | break;
|
| 626 | clear_buffer_dirty(bh);
|
| 627 | bh = bh->b_this_page;
|
| 628 | } while (bh != head);
|
| 629 |
|
| 630 | |
| 631 | * we cannot drop the bh if the page is not uptodate
|
| 632 | * or a concurrent readpage would fail to serialize with the bh
|
| 633 | * and it would read from disk before we reach the platter.
|
| 634 |
|
| 635 | if (buffer_heads_over_limit && PageUptodate(page))
|
| 636 | try_to_free_buffers(page);
|
| 637 | }
|
| 638 |
|
| 639 | BUG_ON(PageWriteback(page));
|
| 640 | set_page_writeback(page);
|
| 641 | unlock_page(page);
|
| 642 | if (boundary || (first_unmapped != blocks_per_page)) {
|
| 643 | bio = mpage_bio_submit(WRITE, bio);
|
| 644 | if (boundary_block) {
|
| 645 | write_boundary_block(boundary_bdev,
|
| 646 | boundary_block, 1 << blkbits);
|
| 647 | }
|
| 648 | } else {
|
| 649 | *last_block_in_bio = blocks[blocks_per_page - 1];
|
| 650 | }
|
| 651 | goto out;
|
| 652 |
|
| 653 | confused:
|
| 654 | if (bio)
|
| 655 | bio = mpage_bio_submit(WRITE, bio);
|
| 656 |
|
| 657 | if (writepage_fn) {
|
| 658 | *ret = (*writepage_fn)(page, wbc);
|
| 659 | } else {
|
| 660 | *ret = -EAGAIN;
|
| 661 | goto out;
|
| 662 | }
|
| 663 | |
| 664 | * The caller has a ref on the inode, so *mapping is stable
|
| 665 |
|
| 666 | if (*ret) {
|
| 667 | if (*ret == -ENOSPC)
|
| 668 | set_bit(AS_ENOSPC, &mapping->flags);
|
| 669 | else
|
| 670 | set_bit(AS_EIO, &mapping->flags);
|
| 671 | }
|
| 672 | out:
|
| 673 | return bio;
|
| 674 | }
|
| 675 |
|
| 676 | |
| 677 | * mpage_writepages - walk the list of dirty pages of the given
|
| 678 | * address space and writepage() all of them.
|
| 679 | *
|
| 680 | * @mapping: address space structure to write
|
| 681 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write
|
| 682 | * @get_block: the filesystem's block mapper function.
|
| 683 | * If this is NULL then use a_ops->writepage. Otherwise, go
|
| 684 | * direct-to-BIO.
|
| 685 | *
|
| 686 | * This is a library function, which implements the writepages()
|
| 687 | * address_space_operation.
|
| 688 | *
|
| 689 | * If a page is already under I/O, generic_writepages() skips it, even
|
| 690 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
|
| 691 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
|
| 692 | * and msync() need to guarantee that all the data which was dirty at the time
|
| 693 | * the call was made get new I/O started against them. If wbc->sync_mode is
|
| 694 | * WB_SYNC_ALL then we were called for data integrity and we must wait for
|
| 695 | * existing IO to complete.
|
| 696 | *
|
| 697 | * If you fix this you should check generic_writepages() also!
|
| 698 |
|
| 699 | int
|
| 700 | mpage_writepages(struct address_space *mapping,
|
| 701 | struct writeback_control *wbc, get_block_t get_block)
|
| 702 | {
|
| 703 | struct backing_dev_info *bdi = mapping->backing_dev_info;
|
| 704 | struct bio *bio = NULL;
|
| 705 | sector_t last_block_in_bio = 0;
|
| 706 | int ret = 0;
|
| 707 | int done = 0;
|
| 708 | int (*writepage)(struct page *page, struct writeback_control *wbc);
|
| 709 | struct pagevec pvec;
|
| 710 | int nr_pages;
|
| 711 | pgoff_t index;
|
| 712 | pgoff_t end;
|
| 713 | int scanned = 0;
|
| 714 | int range_whole = 0;
|
| 715 |
|
| 716 | if (wbc->nonblocking && bdi_write_congested(bdi)) {
|
| 717 | wbc->encountered_congestion = 1;
|
| 718 | return 0;
|
| 719 | }
|
| 720 |
|
| 721 | writepage = NULL;
|
| 722 | if (get_block == NULL)
|
| 723 | writepage = mapping->a_ops->writepage;
|
| 724 |
|
| 725 | pagevec_init(&pvec, 0);
|
| 726 | if (wbc->range_cyclic) {
|
| 727 | index = mapping->writeback_index;
|
| 728 | end = -1;
|
| 729 | } else {
|
| 730 | index = wbc->range_start >> PAGE_CACHE_SHIFT;
|
| 731 | end = wbc->range_end >> PAGE_CACHE_SHIFT;
|
| 732 | if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
|
| 733 | range_whole = 1;
|
| 734 | scanned = 1;
|
| 735 | }
|
| 736 | retry:
|
| 737 | while (!done && (index <= end) &&
|
| 738 | (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
|
| 739 | PAGECACHE_TAG_DIRTY,
|
| 740 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
|
| 741 | unsigned i;
|
| 742 |
|
| 743 | scanned = 1;
|
| 744 | for (i = 0; i < nr_pages; i++) {
|
| 745 | struct page *page = pvec.pages[i];
|
| 746 |
|
| 747 | |
| 748 | * At this point we hold neither mapping->tree_lock nor
|
| 749 | * lock on the page itself: the page may be truncated or
|
| 750 | * invalidated (changing page->mapping to NULL), or even
|
| 751 | * swizzled back from swapper_space to tmpfs file
|
| 752 | * mapping
|
| 753 |
|
| 754 |
|
| 755 | lock_page(page);
|
| 756 |
|
| 757 | if (unlikely(page->mapping != mapping)) {
|
| 758 | unlock_page(page);
|
| 759 | continue;
|
| 760 | }
|
| 761 |
|
| 762 | if (!wbc->range_cyclic && page->index > end) {
|
| 763 | done = 1;
|
| 764 | unlock_page(page);
|
| 765 | continue;
|
| 766 | }
|
| 767 |
|
| 768 | if (wbc->sync_mode != WB_SYNC_NONE)
|
| 769 | wait_on_page_writeback(page);
|
| 770 |
|
| 771 | if (PageWriteback(page) ||
|
| 772 | !clear_page_dirty_for_io(page)) {
|
| 773 | unlock_page(page);
|
| 774 | continue;
|
| 775 | }
|
| 776 |
|
| 777 | if (writepage) {
|
| 778 | ret = (*writepage)(page, wbc);
|
| 779 | if (ret) {
|
| 780 | if (ret == -ENOSPC)
|
| 781 | set_bit(AS_ENOSPC,
|
| 782 | &mapping->flags);
|
| 783 | else
|
| 784 | set_bit(AS_EIO,
|
| 785 | &mapping->flags);
|
| 786 | }
|
| 787 | } else {
|
| 788 | bio = __mpage_writepage(bio, page, get_block,
|
| 789 | &last_block_in_bio, &ret, wbc,
|
| 790 | page->mapping->a_ops->writepage);
|
| 791 | }
|
| 792 | if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE))
|
| 793 | unlock_page(page);
|
| 794 | if (ret || (--(wbc->nr_to_write) <= 0))
|
| 795 | done = 1;
|
| 796 | if (wbc->nonblocking && bdi_write_congested(bdi)) {
|
| 797 | wbc->encountered_congestion = 1;
|
| 798 | done = 1;
|
| 799 | }
|
| 800 | }
|
| 801 | pagevec_release(&pvec);
|
| 802 | cond_resched();
|
| 803 | }
|
| 804 | if (!scanned && !done) {
|
| 805 | |
| 806 | * We hit the last page and there is more work to be done: wrap
|
| 807 | * back to the start of the file
|
| 808 |
|
| 809 | scanned = 1;
|
| 810 | index = 0;
|
| 811 | goto retry;
|
| 812 | }
|
| 813 | if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
|
| 814 | mapping->writeback_index = index;
|
| 815 | if (bio)
|
| 816 | mpage_bio_submit(WRITE, bio);
|
| 817 | return ret;
|
| 818 | }
|
| 819 | EXPORT_SYMBOL(mpage_writepages);
|
| 820 |
|
| 821 | int mpage_writepage(struct page *page, get_block_t get_block,
|
| 822 | struct writeback_control *wbc)
|
| 823 | {
|
| 824 | int ret = 0;
|
| 825 | struct bio *bio;
|
| 826 | sector_t last_block_in_bio = 0;
|
| 827 |
|
| 828 | bio = __mpage_writepage(NULL, page, get_block,
|
| 829 | &last_block_in_bio, &ret, wbc, NULL);
|
| 830 | if (bio)
|
| 831 | mpage_bio_submit(WRITE, bio);
|
| 832 |
|
| 833 | return ret;
|
| 834 | }
|
| 835 | EXPORT_SYMBOL(mpage_writepage);
|