Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : /*
3 : * linux/fs/ext4/readpage.c
4 : *
5 : * Copyright (C) 2002, Linus Torvalds.
6 : * Copyright (C) 2015, Google, Inc.
7 : *
8 : * This was originally taken from fs/mpage.c
9 : *
10 : * The ext4_mpage_readpages() function here is intended to
11 : * replace mpage_readahead() in the general case, not just for
12 : * encrypted files. It has some limitations (see below), where it
13 : * will fall back to read_block_full_page(), but these limitations
14 : * should only be hit when page_size != block_size.
15 : *
16 : * This will allow us to attach a callback function to support ext4
17 : * encryption.
18 : *
19 : * If anything unusual happens, such as:
20 : *
21 : * - encountering a page which has buffers
22 : * - encountering a page which has a non-hole after a hole
23 : * - encountering a page with non-contiguous blocks
24 : *
25 : * then this code just gives up and calls the buffer_head-based read function.
26 : * It does handle a page which has holes at the end - that is a common case:
27 : * the end-of-file on blocksize < PAGE_SIZE setups.
28 : *
29 : */
30 :
31 : #include <linux/kernel.h>
32 : #include <linux/export.h>
33 : #include <linux/mm.h>
34 : #include <linux/kdev_t.h>
35 : #include <linux/gfp.h>
36 : #include <linux/bio.h>
37 : #include <linux/fs.h>
38 : #include <linux/buffer_head.h>
39 : #include <linux/blkdev.h>
40 : #include <linux/highmem.h>
41 : #include <linux/prefetch.h>
42 : #include <linux/mpage.h>
43 : #include <linux/writeback.h>
44 : #include <linux/backing-dev.h>
45 : #include <linux/pagevec.h>
46 : #include <linux/cleancache.h>
47 :
48 : #include "ext4.h"
49 :
50 : #define NUM_PREALLOC_POST_READ_CTXS 128
51 :
52 : static struct kmem_cache *bio_post_read_ctx_cache;
53 : static mempool_t *bio_post_read_ctx_pool;
54 :
55 : /* postprocessing steps for read bios */
56 : enum bio_post_read_step {
57 : STEP_INITIAL = 0,
58 : STEP_DECRYPT,
59 : STEP_VERITY,
60 : STEP_MAX,
61 : };
62 :
63 : struct bio_post_read_ctx {
64 : struct bio *bio;
65 : struct work_struct work;
66 : unsigned int cur_step;
67 : unsigned int enabled_steps;
68 : };
69 :
70 1677 : static void __read_end_io(struct bio *bio)
71 : {
72 1677 : struct page *page;
73 1677 : struct bio_vec *bv;
74 1677 : struct bvec_iter_all iter_all;
75 :
76 22696 : bio_for_each_segment_all(bv, bio, iter_all) {
77 21018 : page = bv->bv_page;
78 :
79 : /* PG_error was set if any post_read step failed */
80 42037 : if (bio->bi_status || PageError(page)) {
81 0 : ClearPageUptodate(page);
82 : /* will re-read again later */
83 0 : ClearPageError(page);
84 : } else {
85 21019 : SetPageUptodate(page);
86 : }
87 21019 : unlock_page(page);
88 : }
89 1677 : if (bio->bi_private)
90 0 : mempool_free(bio->bi_private, bio_post_read_ctx_pool);
91 1677 : bio_put(bio);
92 1677 : }
93 :
94 : static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
95 :
96 0 : static void decrypt_work(struct work_struct *work)
97 : {
98 0 : struct bio_post_read_ctx *ctx =
99 0 : container_of(work, struct bio_post_read_ctx, work);
100 :
101 0 : fscrypt_decrypt_bio(ctx->bio);
102 :
103 0 : bio_post_read_processing(ctx);
104 0 : }
105 :
106 0 : static void verity_work(struct work_struct *work)
107 : {
108 0 : struct bio_post_read_ctx *ctx =
109 0 : container_of(work, struct bio_post_read_ctx, work);
110 0 : struct bio *bio = ctx->bio;
111 :
112 : /*
113 : * fsverity_verify_bio() may call readpages() again, and although verity
114 : * will be disabled for that, decryption may still be needed, causing
115 : * another bio_post_read_ctx to be allocated. So to guarantee that
116 : * mempool_alloc() never deadlocks we must free the current ctx first.
117 : * This is safe because verity is the last post-read step.
118 : */
119 0 : BUILD_BUG_ON(STEP_VERITY + 1 != STEP_MAX);
120 0 : mempool_free(ctx, bio_post_read_ctx_pool);
121 0 : bio->bi_private = NULL;
122 :
123 0 : fsverity_verify_bio(bio);
124 :
125 0 : __read_end_io(bio);
126 0 : }
127 :
128 0 : static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
129 : {
130 : /*
131 : * We use different work queues for decryption and for verity because
132 : * verity may require reading metadata pages that need decryption, and
133 : * we shouldn't recurse to the same workqueue.
134 : */
135 0 : switch (++ctx->cur_step) {
136 0 : case STEP_DECRYPT:
137 0 : if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
138 0 : INIT_WORK(&ctx->work, decrypt_work);
139 0 : fscrypt_enqueue_decrypt_work(&ctx->work);
140 0 : return;
141 : }
142 0 : ctx->cur_step++;
143 0 : fallthrough;
144 0 : case STEP_VERITY:
145 0 : if (ctx->enabled_steps & (1 << STEP_VERITY)) {
146 0 : INIT_WORK(&ctx->work, verity_work);
147 0 : fsverity_enqueue_verify_work(&ctx->work);
148 0 : return;
149 : }
150 0 : ctx->cur_step++;
151 0 : fallthrough;
152 0 : default:
153 0 : __read_end_io(ctx->bio);
154 : }
155 : }
156 :
157 1677 : static bool bio_post_read_required(struct bio *bio)
158 : {
159 0 : return bio->bi_private && !bio->bi_status;
160 : }
161 :
162 : /*
163 : * I/O completion handler for multipage BIOs.
164 : *
165 : * The mpage code never puts partial pages into a BIO (except for end-of-file).
166 : * If a page does not map to a contiguous run of blocks then it simply falls
167 : * back to block_read_full_page().
168 : *
169 : * Why is this? If a page's completion depends on a number of different BIOs
170 : * which can complete in any order (or at the same time) then determining the
171 : * status of that page is hard. See end_buffer_async_read() for the details.
172 : * There is no point in duplicating all that complexity.
173 : */
174 1677 : static void mpage_end_io(struct bio *bio)
175 : {
176 3354 : if (bio_post_read_required(bio)) {
177 0 : struct bio_post_read_ctx *ctx = bio->bi_private;
178 :
179 0 : ctx->cur_step = STEP_INITIAL;
180 0 : bio_post_read_processing(ctx);
181 0 : return;
182 : }
183 1677 : __read_end_io(bio);
184 : }
185 :
186 1724 : static inline bool ext4_need_verity(const struct inode *inode, pgoff_t idx)
187 : {
188 1724 : return fsverity_active(inode) &&
189 : idx < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
190 : }
191 :
192 1677 : static void ext4_set_bio_post_read_ctx(struct bio *bio,
193 : const struct inode *inode,
194 : pgoff_t first_idx)
195 : {
196 1677 : unsigned int post_read_steps = 0;
197 :
198 1677 : if (fscrypt_inode_uses_fs_layer_crypto(inode))
199 : post_read_steps |= 1 << STEP_DECRYPT;
200 :
201 1677 : if (ext4_need_verity(inode, first_idx))
202 : post_read_steps |= 1 << STEP_VERITY;
203 :
204 1677 : if (post_read_steps) {
205 : /* Due to the mempool, this never fails. */
206 : struct bio_post_read_ctx *ctx =
207 : mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
208 :
209 : ctx->bio = bio;
210 : ctx->enabled_steps = post_read_steps;
211 : bio->bi_private = ctx;
212 : }
213 : }
214 :
215 21066 : static inline loff_t ext4_readpage_limit(struct inode *inode)
216 : {
217 21066 : if (IS_ENABLED(CONFIG_FS_VERITY) &&
218 : (IS_VERITY(inode) || ext4_verity_in_progress(inode)))
219 : return inode->i_sb->s_maxbytes;
220 :
221 21066 : return i_size_read(inode);
222 : }
223 :
224 1556 : int ext4_mpage_readpages(struct inode *inode,
225 : struct readahead_control *rac, struct page *page)
226 : {
227 1556 : struct bio *bio = NULL;
228 1556 : sector_t last_block_in_bio = 0;
229 :
230 1556 : const unsigned blkbits = inode->i_blkbits;
231 1556 : const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
232 1556 : const unsigned blocksize = 1 << blkbits;
233 1556 : sector_t next_block;
234 1556 : sector_t block_in_file;
235 1556 : sector_t last_block;
236 1556 : sector_t last_block_in_file;
237 1556 : sector_t blocks[MAX_BUF_PER_PAGE];
238 1556 : unsigned page_block;
239 1556 : struct block_device *bdev = inode->i_sb->s_bdev;
240 1556 : int length;
241 1556 : unsigned relative_block = 0;
242 1556 : struct ext4_map_blocks map;
243 1556 : unsigned int nr_pages = rac ? readahead_count(rac) : 1;
244 :
245 1556 : map.m_pblk = 0;
246 1556 : map.m_lblk = 0;
247 1556 : map.m_len = 0;
248 1556 : map.m_flags = 0;
249 :
250 22622 : for (; nr_pages; nr_pages--) {
251 21066 : int fully_mapped = 1;
252 21066 : unsigned first_hole = blocks_per_page;
253 :
254 21066 : if (rac) {
255 21038 : page = readahead_page(rac);
256 21038 : prefetchw(&page->flags);
257 : }
258 :
259 21066 : if (page_has_buffers(page))
260 0 : goto confused;
261 :
262 21066 : block_in_file = next_block =
263 21066 : (sector_t)page->index << (PAGE_SHIFT - blkbits);
264 21066 : last_block = block_in_file + nr_pages * blocks_per_page;
265 21066 : last_block_in_file = (ext4_readpage_limit(inode) +
266 21066 : blocksize - 1) >> blkbits;
267 21066 : if (last_block > last_block_in_file)
268 : last_block = last_block_in_file;
269 21066 : page_block = 0;
270 :
271 : /*
272 : * Map blocks using the previous result first.
273 : */
274 21066 : if ((map.m_flags & EXT4_MAP_MAPPED) &&
275 19342 : block_in_file > map.m_lblk &&
276 19342 : block_in_file < (map.m_lblk + map.m_len)) {
277 19342 : unsigned map_offset = block_in_file - map.m_lblk;
278 19342 : unsigned last = map.m_len - map_offset;
279 :
280 19342 : for (relative_block = 0; ; relative_block++) {
281 38684 : if (relative_block == last) {
282 : /* needed? */
283 1278 : map.m_flags &= ~EXT4_MAP_MAPPED;
284 1278 : break;
285 : }
286 37406 : if (page_block == blocks_per_page)
287 : break;
288 19342 : blocks[page_block] = map.m_pblk + map_offset +
289 : relative_block;
290 19342 : page_block++;
291 19342 : block_in_file++;
292 : }
293 : }
294 :
295 : /*
296 : * Then do more ext4_map_blocks() calls until we are
297 : * done with this page.
298 : */
299 22790 : while (page_block < blocks_per_page) {
300 1724 : if (block_in_file < last_block) {
301 1696 : map.m_lblk = block_in_file;
302 1696 : map.m_len = last_block - block_in_file;
303 :
304 1696 : if (ext4_map_blocks(NULL, inode, &map, 0) < 0) {
305 0 : set_error_page:
306 0 : SetPageError(page);
307 0 : zero_user_segment(page, 0,
308 : PAGE_SIZE);
309 0 : unlock_page(page);
310 0 : goto next_page;
311 : }
312 : }
313 1724 : if ((map.m_flags & EXT4_MAP_MAPPED) == 0) {
314 47 : fully_mapped = 0;
315 47 : if (first_hole == blocks_per_page)
316 47 : first_hole = page_block;
317 47 : page_block++;
318 47 : block_in_file++;
319 47 : continue;
320 : }
321 1677 : if (first_hole != blocks_per_page)
322 0 : goto confused; /* hole -> non-hole */
323 :
324 : /* Contiguous blocks? */
325 1677 : if (page_block && blocks[page_block-1] != map.m_pblk-1)
326 0 : goto confused;
327 1677 : for (relative_block = 0; ; relative_block++) {
328 3354 : if (relative_block == map.m_len) {
329 : /* needed? */
330 399 : map.m_flags &= ~EXT4_MAP_MAPPED;
331 399 : break;
332 2955 : } else if (page_block == blocks_per_page)
333 : break;
334 1677 : blocks[page_block] = map.m_pblk+relative_block;
335 1677 : page_block++;
336 1677 : block_in_file++;
337 : }
338 : }
339 21066 : if (first_hole != blocks_per_page) {
340 47 : zero_user_segment(page, first_hole << blkbits,
341 : PAGE_SIZE);
342 47 : if (first_hole == 0) {
343 47 : if (ext4_need_verity(inode, page->index) &&
344 : !fsverity_verify_page(page))
345 : goto set_error_page;
346 47 : SetPageUptodate(page);
347 47 : unlock_page(page);
348 47 : goto next_page;
349 : }
350 21019 : } else if (fully_mapped) {
351 21019 : SetPageMappedToDisk(page);
352 : }
353 42038 : if (fully_mapped && blocks_per_page == 1 &&
354 42038 : !PageUptodate(page) && cleancache_get_page(page) == 0) {
355 0 : SetPageUptodate(page);
356 0 : goto confused;
357 : }
358 :
359 : /*
360 : * This page will go to BIO. Do we need to send this
361 : * BIO off first?
362 : */
363 21019 : if (bio && (last_block_in_bio != blocks[0] - 1 ||
364 21019 : !fscrypt_mergeable_bio(bio, inode, next_block))) {
365 149 : submit_and_realloc:
366 149 : submit_bio(bio);
367 149 : bio = NULL;
368 : }
369 21019 : if (bio == NULL) {
370 : /*
371 : * bio_alloc will _always_ be able to allocate a bio if
372 : * __GFP_DIRECT_RECLAIM is set, see bio_alloc_bioset().
373 : */
374 1677 : bio = bio_alloc(GFP_KERNEL, bio_max_segs(nr_pages));
375 1677 : fscrypt_set_bio_crypt_ctx(bio, inode, next_block,
376 : GFP_KERNEL);
377 1677 : ext4_set_bio_post_read_ctx(bio, inode, page->index);
378 1677 : bio_set_dev(bio, bdev);
379 1677 : bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
380 1677 : bio->bi_end_io = mpage_end_io;
381 1677 : bio_set_op_attrs(bio, REQ_OP_READ,
382 : rac ? REQ_RAHEAD : 0);
383 : }
384 :
385 21019 : length = first_hole << blkbits;
386 21019 : if (bio_add_page(bio, page, length, 0) < length)
387 0 : goto submit_and_realloc;
388 :
389 21019 : if (((map.m_flags & EXT4_MAP_BOUNDARY) &&
390 21019 : (relative_block == map.m_len)) ||
391 : (first_hole != blocks_per_page)) {
392 0 : submit_bio(bio);
393 0 : bio = NULL;
394 : } else
395 21019 : last_block_in_bio = blocks[blocks_per_page - 1];
396 21019 : goto next_page;
397 0 : confused:
398 0 : if (bio) {
399 0 : submit_bio(bio);
400 0 : bio = NULL;
401 : }
402 0 : if (!PageUptodate(page))
403 0 : block_read_full_page(page, ext4_get_block);
404 : else
405 0 : unlock_page(page);
406 21066 : next_page:
407 21066 : if (rac)
408 21038 : put_page(page);
409 : }
410 1556 : if (bio)
411 1528 : submit_bio(bio);
412 1556 : return 0;
413 : }
414 :
415 1 : int __init ext4_init_post_read_processing(void)
416 : {
417 2 : bio_post_read_ctx_cache =
418 1 : kmem_cache_create("ext4_bio_post_read_ctx",
419 : sizeof(struct bio_post_read_ctx), 0, 0, NULL);
420 1 : if (!bio_post_read_ctx_cache)
421 0 : goto fail;
422 2 : bio_post_read_ctx_pool =
423 1 : mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS,
424 : bio_post_read_ctx_cache);
425 1 : if (!bio_post_read_ctx_pool)
426 0 : goto fail_free_cache;
427 : return 0;
428 :
429 0 : fail_free_cache:
430 0 : kmem_cache_destroy(bio_post_read_ctx_cache);
431 : fail:
432 : return -ENOMEM;
433 : }
434 :
435 0 : void ext4_exit_post_read_processing(void)
436 : {
437 0 : mempool_destroy(bio_post_read_ctx_pool);
438 0 : kmem_cache_destroy(bio_post_read_ctx_cache);
439 0 : }
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