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1 | /* | |
2 | * linux/fs/ext4/readpage.c | |
3 | * | |
4 | * Copyright (C) 2002, Linus Torvalds. | |
5 | * Copyright (C) 2015, Google, Inc. | |
6 | * | |
7 | * This was originally taken from fs/mpage.c | |
8 | * | |
9 | * The intent is the ext4_mpage_readpages() function here is intended | |
10 | * to replace mpage_readpages() in the general case, not just for | |
11 | * encrypted files. It has some limitations (see below), where it | |
12 | * will fall back to read_block_full_page(), but these limitations | |
13 | * should only be hit when page_size != block_size. | |
14 | * | |
15 | * This will allow us to attach a callback function to support ext4 | |
16 | * encryption. | |
17 | * | |
18 | * If anything unusual happens, such as: | |
19 | * | |
20 | * - encountering a page which has buffers | |
21 | * - encountering a page which has a non-hole after a hole | |
22 | * - encountering a page with non-contiguous blocks | |
23 | * | |
24 | * then this code just gives up and calls the buffer_head-based read function. | |
25 | * It does handle a page which has holes at the end - that is a common case: | |
26 | * the end-of-file on blocksize < PAGE_CACHE_SIZE setups. | |
27 | * | |
28 | */ | |
29 | ||
30 | #include <linux/kernel.h> | |
31 | #include <linux/export.h> | |
32 | #include <linux/mm.h> | |
33 | #include <linux/kdev_t.h> | |
34 | #include <linux/gfp.h> | |
35 | #include <linux/bio.h> | |
36 | #include <linux/fs.h> | |
37 | #include <linux/buffer_head.h> | |
38 | #include <linux/blkdev.h> | |
39 | #include <linux/highmem.h> | |
40 | #include <linux/prefetch.h> | |
41 | #include <linux/mpage.h> | |
42 | #include <linux/writeback.h> | |
43 | #include <linux/backing-dev.h> | |
44 | #include <linux/pagevec.h> | |
45 | #include <linux/cleancache.h> | |
46 | ||
47 | #include "ext4.h" | |
48 | ||
49 | /* | |
50 | * Call ext4_decrypt on every single page, reusing the encryption | |
51 | * context. | |
52 | */ | |
53 | static void completion_pages(struct work_struct *work) | |
54 | { | |
55 | #ifdef CONFIG_EXT4_FS_ENCRYPTION | |
56 | struct ext4_crypto_ctx *ctx = | |
57 | container_of(work, struct ext4_crypto_ctx, r.work); | |
58 | struct bio *bio = ctx->r.bio; | |
59 | struct bio_vec *bv; | |
60 | int i; | |
61 | ||
62 | bio_for_each_segment_all(bv, bio, i) { | |
63 | struct page *page = bv->bv_page; | |
64 | ||
65 | int ret = ext4_decrypt(page); | |
66 | if (ret) { | |
67 | WARN_ON_ONCE(1); | |
68 | SetPageError(page); | |
69 | } else | |
70 | SetPageUptodate(page); | |
71 | unlock_page(page); | |
72 | } | |
73 | ext4_release_crypto_ctx(ctx); | |
74 | bio_put(bio); | |
75 | #else | |
76 | BUG(); | |
77 | #endif | |
78 | } | |
79 | ||
80 | static inline bool ext4_bio_encrypted(struct bio *bio) | |
81 | { | |
82 | #ifdef CONFIG_EXT4_FS_ENCRYPTION | |
83 | return unlikely(bio->bi_private != NULL); | |
84 | #else | |
85 | return false; | |
86 | #endif | |
87 | } | |
88 | ||
89 | /* | |
90 | * I/O completion handler for multipage BIOs. | |
91 | * | |
92 | * The mpage code never puts partial pages into a BIO (except for end-of-file). | |
93 | * If a page does not map to a contiguous run of blocks then it simply falls | |
94 | * back to block_read_full_page(). | |
95 | * | |
96 | * Why is this? If a page's completion depends on a number of different BIOs | |
97 | * which can complete in any order (or at the same time) then determining the | |
98 | * status of that page is hard. See end_buffer_async_read() for the details. | |
99 | * There is no point in duplicating all that complexity. | |
100 | */ | |
101 | static void mpage_end_io(struct bio *bio) | |
102 | { | |
103 | struct bio_vec *bv; | |
104 | int i; | |
105 | ||
106 | if (ext4_bio_encrypted(bio)) { | |
107 | struct ext4_crypto_ctx *ctx = bio->bi_private; | |
108 | ||
109 | if (bio->bi_error) { | |
110 | ext4_release_crypto_ctx(ctx); | |
111 | } else { | |
112 | INIT_WORK(&ctx->r.work, completion_pages); | |
113 | ctx->r.bio = bio; | |
114 | queue_work(ext4_read_workqueue, &ctx->r.work); | |
115 | return; | |
116 | } | |
117 | } | |
118 | bio_for_each_segment_all(bv, bio, i) { | |
119 | struct page *page = bv->bv_page; | |
120 | ||
121 | if (!bio->bi_error) { | |
122 | SetPageUptodate(page); | |
123 | } else { | |
124 | ClearPageUptodate(page); | |
125 | SetPageError(page); | |
126 | } | |
127 | unlock_page(page); | |
128 | } | |
129 | ||
130 | bio_put(bio); | |
131 | } | |
132 | ||
133 | int ext4_mpage_readpages(struct address_space *mapping, | |
134 | struct list_head *pages, struct page *page, | |
135 | unsigned nr_pages) | |
136 | { | |
137 | struct bio *bio = NULL; | |
138 | unsigned page_idx; | |
139 | sector_t last_block_in_bio = 0; | |
140 | ||
141 | struct inode *inode = mapping->host; | |
142 | const unsigned blkbits = inode->i_blkbits; | |
143 | const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; | |
144 | const unsigned blocksize = 1 << blkbits; | |
145 | sector_t block_in_file; | |
146 | sector_t last_block; | |
147 | sector_t last_block_in_file; | |
148 | sector_t blocks[MAX_BUF_PER_PAGE]; | |
149 | unsigned page_block; | |
150 | struct block_device *bdev = inode->i_sb->s_bdev; | |
151 | int length; | |
152 | unsigned relative_block = 0; | |
153 | struct ext4_map_blocks map; | |
154 | ||
155 | map.m_pblk = 0; | |
156 | map.m_lblk = 0; | |
157 | map.m_len = 0; | |
158 | map.m_flags = 0; | |
159 | ||
160 | for (page_idx = 0; nr_pages; page_idx++, nr_pages--) { | |
161 | int fully_mapped = 1; | |
162 | unsigned first_hole = blocks_per_page; | |
163 | ||
164 | prefetchw(&page->flags); | |
165 | if (pages) { | |
166 | page = list_entry(pages->prev, struct page, lru); | |
167 | list_del(&page->lru); | |
168 | if (add_to_page_cache_lru(page, mapping, page->index, | |
169 | mapping_gfp_constraint(mapping, GFP_KERNEL))) | |
170 | goto next_page; | |
171 | } | |
172 | ||
173 | if (page_has_buffers(page)) | |
174 | goto confused; | |
175 | ||
176 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); | |
177 | last_block = block_in_file + nr_pages * blocks_per_page; | |
178 | last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits; | |
179 | if (last_block > last_block_in_file) | |
180 | last_block = last_block_in_file; | |
181 | page_block = 0; | |
182 | ||
183 | /* | |
184 | * Map blocks using the previous result first. | |
185 | */ | |
186 | if ((map.m_flags & EXT4_MAP_MAPPED) && | |
187 | block_in_file > map.m_lblk && | |
188 | block_in_file < (map.m_lblk + map.m_len)) { | |
189 | unsigned map_offset = block_in_file - map.m_lblk; | |
190 | unsigned last = map.m_len - map_offset; | |
191 | ||
192 | for (relative_block = 0; ; relative_block++) { | |
193 | if (relative_block == last) { | |
194 | /* needed? */ | |
195 | map.m_flags &= ~EXT4_MAP_MAPPED; | |
196 | break; | |
197 | } | |
198 | if (page_block == blocks_per_page) | |
199 | break; | |
200 | blocks[page_block] = map.m_pblk + map_offset + | |
201 | relative_block; | |
202 | page_block++; | |
203 | block_in_file++; | |
204 | } | |
205 | } | |
206 | ||
207 | /* | |
208 | * Then do more ext4_map_blocks() calls until we are | |
209 | * done with this page. | |
210 | */ | |
211 | while (page_block < blocks_per_page) { | |
212 | if (block_in_file < last_block) { | |
213 | map.m_lblk = block_in_file; | |
214 | map.m_len = last_block - block_in_file; | |
215 | ||
216 | if (ext4_map_blocks(NULL, inode, &map, 0) < 0) { | |
217 | set_error_page: | |
218 | SetPageError(page); | |
219 | zero_user_segment(page, 0, | |
220 | PAGE_CACHE_SIZE); | |
221 | unlock_page(page); | |
222 | goto next_page; | |
223 | } | |
224 | } | |
225 | if ((map.m_flags & EXT4_MAP_MAPPED) == 0) { | |
226 | fully_mapped = 0; | |
227 | if (first_hole == blocks_per_page) | |
228 | first_hole = page_block; | |
229 | page_block++; | |
230 | block_in_file++; | |
231 | continue; | |
232 | } | |
233 | if (first_hole != blocks_per_page) | |
234 | goto confused; /* hole -> non-hole */ | |
235 | ||
236 | /* Contiguous blocks? */ | |
237 | if (page_block && blocks[page_block-1] != map.m_pblk-1) | |
238 | goto confused; | |
239 | for (relative_block = 0; ; relative_block++) { | |
240 | if (relative_block == map.m_len) { | |
241 | /* needed? */ | |
242 | map.m_flags &= ~EXT4_MAP_MAPPED; | |
243 | break; | |
244 | } else if (page_block == blocks_per_page) | |
245 | break; | |
246 | blocks[page_block] = map.m_pblk+relative_block; | |
247 | page_block++; | |
248 | block_in_file++; | |
249 | } | |
250 | } | |
251 | if (first_hole != blocks_per_page) { | |
252 | zero_user_segment(page, first_hole << blkbits, | |
253 | PAGE_CACHE_SIZE); | |
254 | if (first_hole == 0) { | |
255 | SetPageUptodate(page); | |
256 | unlock_page(page); | |
257 | goto next_page; | |
258 | } | |
259 | } else if (fully_mapped) { | |
260 | SetPageMappedToDisk(page); | |
261 | } | |
262 | if (fully_mapped && blocks_per_page == 1 && | |
263 | !PageUptodate(page) && cleancache_get_page(page) == 0) { | |
264 | SetPageUptodate(page); | |
265 | goto confused; | |
266 | } | |
267 | ||
268 | /* | |
269 | * This page will go to BIO. Do we need to send this | |
270 | * BIO off first? | |
271 | */ | |
272 | if (bio && (last_block_in_bio != blocks[0] - 1)) { | |
273 | submit_and_realloc: | |
274 | submit_bio(READ, bio); | |
275 | bio = NULL; | |
276 | } | |
277 | if (bio == NULL) { | |
278 | struct ext4_crypto_ctx *ctx = NULL; | |
279 | ||
280 | if (ext4_encrypted_inode(inode) && | |
281 | S_ISREG(inode->i_mode)) { | |
282 | ctx = ext4_get_crypto_ctx(inode); | |
283 | if (IS_ERR(ctx)) | |
284 | goto set_error_page; | |
285 | } | |
286 | bio = bio_alloc(GFP_KERNEL, | |
287 | min_t(int, nr_pages, BIO_MAX_PAGES)); | |
288 | if (!bio) { | |
289 | if (ctx) | |
290 | ext4_release_crypto_ctx(ctx); | |
291 | goto set_error_page; | |
292 | } | |
293 | bio->bi_bdev = bdev; | |
294 | bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9); | |
295 | bio->bi_end_io = mpage_end_io; | |
296 | bio->bi_private = ctx; | |
297 | } | |
298 | ||
299 | length = first_hole << blkbits; | |
300 | if (bio_add_page(bio, page, length, 0) < length) | |
301 | goto submit_and_realloc; | |
302 | ||
303 | if (((map.m_flags & EXT4_MAP_BOUNDARY) && | |
304 | (relative_block == map.m_len)) || | |
305 | (first_hole != blocks_per_page)) { | |
306 | submit_bio(READ, bio); | |
307 | bio = NULL; | |
308 | } else | |
309 | last_block_in_bio = blocks[blocks_per_page - 1]; | |
310 | goto next_page; | |
311 | confused: | |
312 | if (bio) { | |
313 | submit_bio(READ, bio); | |
314 | bio = NULL; | |
315 | } | |
316 | if (!PageUptodate(page)) | |
317 | block_read_full_page(page, ext4_get_block); | |
318 | else | |
319 | unlock_page(page); | |
320 | next_page: | |
321 | if (pages) | |
322 | page_cache_release(page); | |
323 | } | |
324 | BUG_ON(pages && !list_empty(pages)); | |
325 | if (bio) | |
326 | submit_bio(READ, bio); | |
327 | return 0; | |
328 | } |