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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 | // SPDX-License-Identifier: GPL-2.0 /* * linux/fs/ext4/readpage.c * * Copyright (C) 2002, Linus Torvalds. * Copyright (C) 2015, Google, Inc. * * This was originally taken from fs/mpage.c * * The ext4_mpage_readpages() function here is intended to * replace mpage_readahead() in the general case, not just for * encrypted files. It has some limitations (see below), where it * will fall back to read_block_full_page(), but these limitations * should only be hit when page_size != block_size. * * This will allow us to attach a callback function to support ext4 * encryption. * * If anything unusual happens, such as: * * - encountering a page which has buffers * - encountering a page which has a non-hole after a hole * - encountering a page with non-contiguous blocks * * then this code just gives up and calls the buffer_head-based read function. * It does handle a page which has holes at the end - that is a common case: * the end-of-file on blocksize < PAGE_SIZE setups. * */ #include <linux/kernel.h> #include <linux/export.h> #include <linux/mm.h> #include <linux/kdev_t.h> #include <linux/gfp.h> #include <linux/bio.h> #include <linux/fs.h> #include <linux/buffer_head.h> #include <linux/blkdev.h> #include <linux/highmem.h> #include <linux/prefetch.h> #include <linux/mpage.h> #include <linux/writeback.h> #include <linux/backing-dev.h> #include <linux/pagevec.h> #include <linux/cleancache.h> #include "ext4.h" #define NUM_PREALLOC_POST_READ_CTXS 128 static struct kmem_cache *bio_post_read_ctx_cache; static mempool_t *bio_post_read_ctx_pool; /* postprocessing steps for read bios */ enum bio_post_read_step { STEP_INITIAL = 0, STEP_DECRYPT, STEP_VERITY, STEP_MAX, }; struct bio_post_read_ctx { struct bio *bio; struct work_struct work; unsigned int cur_step; unsigned int enabled_steps; }; static void __read_end_io(struct bio *bio) { struct page *page; struct bio_vec *bv; struct bvec_iter_all iter_all; bio_for_each_segment_all(bv, bio, iter_all) { page = bv->bv_page; /* PG_error was set if any post_read step failed */ if (bio->bi_status || PageError(page)) { ClearPageUptodate(page); /* will re-read again later */ ClearPageError(page); } else { SetPageUptodate(page); } unlock_page(page); } if (bio->bi_private) mempool_free(bio->bi_private, bio_post_read_ctx_pool); bio_put(bio); } static void bio_post_read_processing(struct bio_post_read_ctx *ctx); static void decrypt_work(struct work_struct *work) { struct bio_post_read_ctx *ctx = container_of(work, struct bio_post_read_ctx, work); fscrypt_decrypt_bio(ctx->bio); bio_post_read_processing(ctx); } static void verity_work(struct work_struct *work) { struct bio_post_read_ctx *ctx = container_of(work, struct bio_post_read_ctx, work); struct bio *bio = ctx->bio; /* * fsverity_verify_bio() may call readpages() again, and although verity * will be disabled for that, decryption may still be needed, causing * another bio_post_read_ctx to be allocated. So to guarantee that * mempool_alloc() never deadlocks we must free the current ctx first. * This is safe because verity is the last post-read step. */ BUILD_BUG_ON(STEP_VERITY + 1 != STEP_MAX); mempool_free(ctx, bio_post_read_ctx_pool); bio->bi_private = NULL; fsverity_verify_bio(bio); __read_end_io(bio); } static void bio_post_read_processing(struct bio_post_read_ctx *ctx) { /* * We use different work queues for decryption and for verity because * verity may require reading metadata pages that need decryption, and * we shouldn't recurse to the same workqueue. */ switch (++ctx->cur_step) { case STEP_DECRYPT: if (ctx->enabled_steps & (1 << STEP_DECRYPT)) { INIT_WORK(&ctx->work, decrypt_work); fscrypt_enqueue_decrypt_work(&ctx->work); return; } ctx->cur_step++; fallthrough; case STEP_VERITY: if (ctx->enabled_steps & (1 << STEP_VERITY)) { INIT_WORK(&ctx->work, verity_work); fsverity_enqueue_verify_work(&ctx->work); return; } ctx->cur_step++; fallthrough; default: __read_end_io(ctx->bio); } } static bool bio_post_read_required(struct bio *bio) { return bio->bi_private && !bio->bi_status; } /* * I/O completion handler for multipage BIOs. * * The mpage code never puts partial pages into a BIO (except for end-of-file). * If a page does not map to a contiguous run of blocks then it simply falls * back to block_read_full_page(). * * Why is this? If a page's completion depends on a number of different BIOs * which can complete in any order (or at the same time) then determining the * status of that page is hard. See end_buffer_async_read() for the details. * There is no point in duplicating all that complexity. */ static void mpage_end_io(struct bio *bio) { if (bio_post_read_required(bio)) { struct bio_post_read_ctx *ctx = bio->bi_private; ctx->cur_step = STEP_INITIAL; bio_post_read_processing(ctx); return; } __read_end_io(bio); } static inline bool ext4_need_verity(const struct inode *inode, pgoff_t idx) { return fsverity_active(inode) && idx < DIV_ROUND_UP(inode->i_size, PAGE_SIZE); } static void ext4_set_bio_post_read_ctx(struct bio *bio, const struct inode *inode, pgoff_t first_idx) { unsigned int post_read_steps = 0; if (fscrypt_inode_uses_fs_layer_crypto(inode)) post_read_steps |= 1 << STEP_DECRYPT; if (ext4_need_verity(inode, first_idx)) post_read_steps |= 1 << STEP_VERITY; if (post_read_steps) { /* Due to the mempool, this never fails. */ struct bio_post_read_ctx *ctx = mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS); ctx->bio = bio; ctx->enabled_steps = post_read_steps; bio->bi_private = ctx; } } static inline loff_t ext4_readpage_limit(struct inode *inode) { if (IS_ENABLED(CONFIG_FS_VERITY) && (IS_VERITY(inode) || ext4_verity_in_progress(inode))) return inode->i_sb->s_maxbytes; return i_size_read(inode); } int ext4_mpage_readpages(struct inode *inode, struct readahead_control *rac, struct page *page) { struct bio *bio = NULL; sector_t last_block_in_bio = 0; const unsigned blkbits = inode->i_blkbits; const unsigned blocks_per_page = PAGE_SIZE >> blkbits; const unsigned blocksize = 1 << blkbits; sector_t next_block; sector_t block_in_file; sector_t last_block; sector_t last_block_in_file; sector_t blocks[MAX_BUF_PER_PAGE]; unsigned page_block; struct block_device *bdev = inode->i_sb->s_bdev; int length; unsigned relative_block = 0; struct ext4_map_blocks map; unsigned int nr_pages = rac ? readahead_count(rac) : 1; map.m_pblk = 0; map.m_lblk = 0; map.m_len = 0; map.m_flags = 0; for (; nr_pages; nr_pages--) { int fully_mapped = 1; unsigned first_hole = blocks_per_page; if (rac) { page = readahead_page(rac); prefetchw(&page->flags); } if (page_has_buffers(page)) goto confused; block_in_file = next_block = (sector_t)page->index << (PAGE_SHIFT - blkbits); last_block = block_in_file + nr_pages * blocks_per_page; last_block_in_file = (ext4_readpage_limit(inode) + blocksize - 1) >> blkbits; if (last_block > last_block_in_file) last_block = last_block_in_file; page_block = 0; /* * Map blocks using the previous result first. */ if ((map.m_flags & EXT4_MAP_MAPPED) && block_in_file > map.m_lblk && block_in_file < (map.m_lblk + map.m_len)) { unsigned map_offset = block_in_file - map.m_lblk; unsigned last = map.m_len - map_offset; for (relative_block = 0; ; relative_block++) { if (relative_block == last) { /* needed? */ map.m_flags &= ~EXT4_MAP_MAPPED; break; } if (page_block == blocks_per_page) break; blocks[page_block] = map.m_pblk + map_offset + relative_block; page_block++; block_in_file++; } } /* * Then do more ext4_map_blocks() calls until we are * done with this page. */ while (page_block < blocks_per_page) { if (block_in_file < last_block) { map.m_lblk = block_in_file; map.m_len = last_block - block_in_file; if (ext4_map_blocks(NULL, inode, &map, 0) < 0) { set_error_page: SetPageError(page); zero_user_segment(page, 0, PAGE_SIZE); unlock_page(page); goto next_page; } } if ((map.m_flags & EXT4_MAP_MAPPED) == 0) { fully_mapped = 0; if (first_hole == blocks_per_page) first_hole = page_block; page_block++; block_in_file++; continue; } if (first_hole != blocks_per_page) goto confused; /* hole -> non-hole */ /* Contiguous blocks? */ if (page_block && blocks[page_block-1] != map.m_pblk-1) goto confused; for (relative_block = 0; ; relative_block++) { if (relative_block == map.m_len) { /* needed? */ map.m_flags &= ~EXT4_MAP_MAPPED; break; } else if (page_block == blocks_per_page) break; blocks[page_block] = map.m_pblk+relative_block; page_block++; block_in_file++; } } if (first_hole != blocks_per_page) { zero_user_segment(page, first_hole << blkbits, PAGE_SIZE); if (first_hole == 0) { if (ext4_need_verity(inode, page->index) && !fsverity_verify_page(page)) goto set_error_page; SetPageUptodate(page); unlock_page(page); goto next_page; } } else if (fully_mapped) { SetPageMappedToDisk(page); } if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) && cleancache_get_page(page) == 0) { SetPageUptodate(page); goto confused; } /* * This page will go to BIO. Do we need to send this * BIO off first? */ if (bio && (last_block_in_bio != blocks[0] - 1 || !fscrypt_mergeable_bio(bio, inode, next_block))) { submit_and_realloc: submit_bio(bio); bio = NULL; } if (bio == NULL) { /* * bio_alloc will _always_ be able to allocate a bio if * __GFP_DIRECT_RECLAIM is set, see bio_alloc_bioset(). */ bio = bio_alloc(GFP_KERNEL, bio_max_segs(nr_pages)); fscrypt_set_bio_crypt_ctx(bio, inode, next_block, GFP_KERNEL); ext4_set_bio_post_read_ctx(bio, inode, page->index); bio_set_dev(bio, bdev); bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9); bio->bi_end_io = mpage_end_io; bio_set_op_attrs(bio, REQ_OP_READ, rac ? REQ_RAHEAD : 0); } length = first_hole << blkbits; if (bio_add_page(bio, page, length, 0) < length) goto submit_and_realloc; if (((map.m_flags & EXT4_MAP_BOUNDARY) && (relative_block == map.m_len)) || (first_hole != blocks_per_page)) { submit_bio(bio); bio = NULL; } else last_block_in_bio = blocks[blocks_per_page - 1]; goto next_page; confused: if (bio) { submit_bio(bio); bio = NULL; } if (!PageUptodate(page)) block_read_full_page(page, ext4_get_block); else unlock_page(page); next_page: if (rac) put_page(page); } if (bio) submit_bio(bio); return 0; } int __init ext4_init_post_read_processing(void) { bio_post_read_ctx_cache = kmem_cache_create("ext4_bio_post_read_ctx", sizeof(struct bio_post_read_ctx), 0, 0, NULL); if (!bio_post_read_ctx_cache) goto fail; bio_post_read_ctx_pool = mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS, bio_post_read_ctx_cache); if (!bio_post_read_ctx_pool) goto fail_free_cache; return 0; fail_free_cache: kmem_cache_destroy(bio_post_read_ctx_cache); fail: return -ENOMEM; } void ext4_exit_post_read_processing(void) { mempool_destroy(bio_post_read_ctx_pool); kmem_cache_destroy(bio_post_read_ctx_cache); } |