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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 | // 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 intent is the ext4_mpage_readpages() function here is intended * to replace mpage_readpages() 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" static inline bool ext4_bio_encrypted(struct bio *bio) { #ifdef CONFIG_EXT4_FS_ENCRYPTION return unlikely(bio->bi_private != NULL); #else return false; #endif } /* * 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) { struct bio_vec *bv; int i; if (ext4_bio_encrypted(bio)) { if (bio->bi_status) { fscrypt_release_ctx(bio->bi_private); } else { fscrypt_enqueue_decrypt_bio(bio->bi_private, bio); return; } } bio_for_each_segment_all(bv, bio, i) { struct page *page = bv->bv_page; if (!bio->bi_status) { SetPageUptodate(page); } else { ClearPageUptodate(page); SetPageError(page); } unlock_page(page); } bio_put(bio); } int ext4_mpage_readpages(struct address_space *mapping, struct list_head *pages, struct page *page, unsigned nr_pages, bool is_readahead) { struct bio *bio = NULL; sector_t last_block_in_bio = 0; struct inode *inode = mapping->host; const unsigned blkbits = inode->i_blkbits; const unsigned blocks_per_page = PAGE_SIZE >> blkbits; const unsigned blocksize = 1 << blkbits; 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; 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; prefetchw(&page->flags); if (pages) { page = lru_to_page(pages); list_del(&page->lru); if (add_to_page_cache_lru(page, mapping, page->index, readahead_gfp_mask(mapping))) goto next_page; } if (page_has_buffers(page)) goto confused; block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits); last_block = block_in_file + nr_pages * blocks_per_page; last_block_in_file = (i_size_read(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) { 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)) { submit_and_realloc: submit_bio(bio); bio = NULL; } if (bio == NULL) { struct fscrypt_ctx *ctx = NULL; if (ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode)) { ctx = fscrypt_get_ctx(inode, GFP_NOFS); if (IS_ERR(ctx)) goto set_error_page; } bio = bio_alloc(GFP_KERNEL, min_t(int, nr_pages, BIO_MAX_PAGES)); if (!bio) { if (ctx) fscrypt_release_ctx(ctx); goto set_error_page; } bio_set_dev(bio, bdev); bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9); bio->bi_end_io = mpage_end_io; bio->bi_private = ctx; bio_set_op_attrs(bio, REQ_OP_READ, is_readahead ? 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 (pages) put_page(page); } BUG_ON(pages && !list_empty(pages)); if (bio) submit_bio(bio); return 0; } |