summaryrefslogtreecommitdiffstats
path: root/fs/iomap.c
blob: 48141b8eff5f4f799f804674c83173863c156b2c (plain)
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
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
/*
 * Copyright (C) 2010 Red Hat, Inc.
 * Copyright (c) 2016 Christoph Hellwig.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/iomap.h>
#include <linux/uaccess.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/backing-dev.h>
#include <linux/buffer_head.h>
#include <linux/dax.h>
#include "internal.h"

typedef loff_t (*iomap_actor_t)(struct inode *inode, loff_t pos, loff_t len,
		void *data, struct iomap *iomap);

/*
 * Execute a iomap write on a segment of the mapping that spans a
 * contiguous range of pages that have identical block mapping state.
 *
 * This avoids the need to map pages individually, do individual allocations
 * for each page and most importantly avoid the need for filesystem specific
 * locking per page. Instead, all the operations are amortised over the entire
 * range of pages. It is assumed that the filesystems will lock whatever
 * resources they require in the iomap_begin call, and release them in the
 * iomap_end call.
 */
static loff_t
iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
		struct iomap_ops *ops, void *data, iomap_actor_t actor)
{
	struct iomap iomap = { 0 };
	loff_t written = 0, ret;

	/*
	 * Need to map a range from start position for length bytes. This can
	 * span multiple pages - it is only guaranteed to return a range of a
	 * single type of pages (e.g. all into a hole, all mapped or all
	 * unwritten). Failure at this point has nothing to undo.
	 *
	 * If allocation is required for this range, reserve the space now so
	 * that the allocation is guaranteed to succeed later on. Once we copy
	 * the data into the page cache pages, then we cannot fail otherwise we
	 * expose transient stale data. If the reserve fails, we can safely
	 * back out at this point as there is nothing to undo.
	 */
	ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
	if (ret)
		return ret;
	if (WARN_ON(iomap.offset > pos))
		return -EIO;

	/*
	 * Cut down the length to the one actually provided by the filesystem,
	 * as it might not be able to give us the whole size that we requested.
	 */
	if (iomap.offset + iomap.length < pos + length)
		length = iomap.offset + iomap.length - pos;

	/*
	 * Now that we have guaranteed that the space allocation will succeed.
	 * we can do the copy-in page by page without having to worry about
	 * failures exposing transient data.
	 */
	written = actor(inode, pos, length, data, &iomap);

	/*
	 * Now the data has been copied, commit the range we've copied.  This
	 * should not fail unless the filesystem has had a fatal error.
	 */
	ret = ops->iomap_end(inode, pos, length, written > 0 ? written : 0,
			flags, &iomap);

	return written ? written : ret;
}

static void
iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
{
	loff_t i_size = i_size_read(inode);

	/*
	 * Only truncate newly allocated pages beyoned EOF, even if the
	 * write started inside the existing inode size.
	 */
	if (pos + len > i_size)
		truncate_pagecache_range(inode, max(pos, i_size), pos + len);
}

static int
iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
		struct page **pagep, struct iomap *iomap)
{
	pgoff_t index = pos >> PAGE_SHIFT;
	struct page *page;
	int status = 0;

	BUG_ON(pos + len > iomap->offset + iomap->length);

	page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
	if (!page)
		return -ENOMEM;

	status = __block_write_begin_int(page, pos, len, NULL, iomap);
	if (unlikely(status)) {
		unlock_page(page);
		put_page(page);
		page = NULL;

		iomap_write_failed(inode, pos, len);
	}

	*pagep = page;
	return status;
}

static int
iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
		unsigned copied, struct page *page)
{
	int ret;

	ret = generic_write_end(NULL, inode->i_mapping, pos, len,
			copied, page, NULL);
	if (ret < len)
		iomap_write_failed(inode, pos, len);
	return ret;
}

static loff_t
iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
		struct iomap *iomap)
{
	struct iov_iter *i = data;
	long status = 0;
	ssize_t written = 0;
	unsigned int flags = AOP_FLAG_NOFS;

	/*
	 * Copies from kernel address space cannot fail (NFSD is a big user).
	 */
	if (!iter_is_iovec(i))
		flags |= AOP_FLAG_UNINTERRUPTIBLE;

	do {
		struct page *page;
		unsigned long offset;	/* Offset into pagecache page */
		unsigned long bytes;	/* Bytes to write to page */
		size_t copied;		/* Bytes copied from user */

		offset = (pos & (PAGE_SIZE - 1));
		bytes = min_t(unsigned long, PAGE_SIZE - offset,
						iov_iter_count(i));
again:
		if (bytes > length)
			bytes = length;

		/*
		 * Bring in the user page that we will copy from _first_.
		 * Otherwise there's a nasty deadlock on copying from the
		 * same page as we're writing to, without it being marked
		 * up-to-date.
		 *
		 * Not only is this an optimisation, but it is also required
		 * to check that the address is actually valid, when atomic
		 * usercopies are used, below.
		 */
		if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
			status = -EFAULT;
			break;
		}

		status = iomap_write_begin(inode, pos, bytes, flags, &page,
				iomap);
		if (unlikely(status))
			break;

		if (mapping_writably_mapped(inode->i_mapping))
			flush_dcache_page(page);

		pagefault_disable();
		copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
		pagefault_enable();

		flush_dcache_page(page);
		mark_page_accessed(page);

		status = iomap_write_end(inode, pos, bytes, copied, page);
		if (unlikely(status < 0))
			break;
		copied = status;

		cond_resched();

		iov_iter_advance(i, copied);
		if (unlikely(copied == 0)) {
			/*
			 * If we were unable to copy any data at all, we must
			 * fall back to a single segment length write.
			 *
			 * If we didn't fallback here, we could livelock
			 * because not all segments in the iov can be copied at
			 * once without a pagefault.
			 */
			bytes = min_t(unsigned long, PAGE_SIZE - offset,
						iov_iter_single_seg_count(i));
			goto again;
		}
		pos += copied;
		written += copied;
		length -= copied;

		balance_dirty_pages_ratelimited(inode->i_mapping);
	} while (iov_iter_count(i) && length);

	return written ? written : status;
}

ssize_t
iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
		struct iomap_ops *ops)
{
	struct inode *inode = iocb->ki_filp->f_mapping->host;
	loff_t pos = iocb->ki_pos, ret = 0, written = 0;

	while (iov_iter_count(iter)) {
		ret = iomap_apply(inode, pos, iov_iter_count(iter),
				IOMAP_WRITE, ops, iter, iomap_write_actor);
		if (ret <= 0)
			break;
		pos += ret;
		written += ret;
	}

	return written ? written : ret;
}
EXPORT_SYMBOL_GPL(iomap_file_buffered_write);

static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
		unsigned bytes, struct iomap *iomap)
{
	struct page *page;
	int status;

	status = iomap_write_begin(inode, pos, bytes,
			AOP_FLAG_UNINTERRUPTIBLE | AOP_FLAG_NOFS, &page, iomap);
	if (status)
		return status;

	zero_user(page, offset, bytes);
	mark_page_accessed(page);

	return iomap_write_end(inode, pos, bytes, bytes, page);
}

static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
		struct iomap *iomap)
{
	sector_t sector = iomap->blkno +
		(((pos & ~(PAGE_SIZE - 1)) - iomap->offset) >> 9);

	return __dax_zero_page_range(iomap->bdev, sector, offset, bytes);
}

static loff_t
iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
		void *data, struct iomap *iomap)
{
	bool *did_zero = data;
	loff_t written = 0;
	int status;

	/* already zeroed?  we're done. */
	if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
	    	return count;

	do {
		unsigned offset, bytes;

		offset = pos & (PAGE_SIZE - 1); /* Within page */
		bytes = min_t(unsigned, PAGE_SIZE - offset, count);

		if (IS_DAX(inode))
			status = iomap_dax_zero(pos, offset, bytes, iomap);
		else
			status = iomap_zero(inode, pos, offset, bytes, iomap);
		if (status < 0)
			return status;

		pos += bytes;
		count -= bytes;
		written += bytes;
		if (did_zero)
			*did_zero = true;
	} while (count > 0);

	return written;
}

int
iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
		struct iomap_ops *ops)
{
	loff_t ret;

	while (len > 0) {
		ret = iomap_apply(inode, pos, len, IOMAP_ZERO,
				ops, did_zero, iomap_zero_range_actor);
		if (ret <= 0)
			return ret;

		pos += ret;
		len -= ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(iomap_zero_range);

int
iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
		struct iomap_ops *ops)
{
	unsigned blocksize = (1 << inode->i_blkbits);
	unsigned off = pos & (blocksize - 1);

	/* Block boundary? Nothing to do */
	if (!off)
		return 0;
	return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops);
}
EXPORT_SYMBOL_GPL(iomap_truncate_page);

static loff_t
iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
		void *data, struct iomap *iomap)
{
	struct page *page = data;
	int ret;

	ret = __block_write_begin_int(page, pos & ~PAGE_MASK, length,
			NULL, iomap);
	if (ret)
		return ret;

	block_commit_write(page, 0, length);
	return length;
}

int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
		struct iomap_ops *ops)
{
	struct page *page = vmf->page;
	struct inode *inode = file_inode(vma->vm_file);
	unsigned long length;
	loff_t offset, size;
	ssize_t ret;

	lock_page(page);
	size = i_size_read(inode);
	if ((page->mapping != inode->i_mapping) ||
	    (page_offset(page) > size)) {
		/* We overload EFAULT to mean page got truncated */
		ret = -EFAULT;
		goto out_unlock;
	}

	/* page is wholly or partially inside EOF */
	if (((page->index + 1) << PAGE_SHIFT) > size)
		length = size & ~PAGE_MASK;
	else
		length = PAGE_SIZE;

	offset = page_offset(page);
	while (length > 0) {
		ret = iomap_apply(inode, offset, length, IOMAP_WRITE,
				ops, page, iomap_page_mkwrite_actor);
		if (unlikely(ret <= 0))
			goto out_unlock;
		offset += ret;
		length -= ret;
	}

	set_page_dirty(page);
	wait_for_stable_page(page);
	return 0;
out_unlock:
	unlock_page(page);
	return ret;
}
EXPORT_SYMBOL_GPL(iomap_page_mkwrite);

struct fiemap_ctx {
	struct fiemap_extent_info *fi;
	struct iomap prev;
};

static int iomap_to_fiemap(struct fiemap_extent_info *fi,
		struct iomap *iomap, u32 flags)
{
	switch (iomap->type) {
	case IOMAP_HOLE:
		/* skip holes */
		return 0;
	case IOMAP_DELALLOC:
		flags |= FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_UNKNOWN;
		break;
	case IOMAP_UNWRITTEN:
		flags |= FIEMAP_EXTENT_UNWRITTEN;
		break;
	case IOMAP_MAPPED:
		break;
	}

	return fiemap_fill_next_extent(fi, iomap->offset,
			iomap->blkno != IOMAP_NULL_BLOCK ? iomap->blkno << 9: 0,
			iomap->length, flags | FIEMAP_EXTENT_MERGED);

}

static loff_t
iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
		struct iomap *iomap)
{
	struct fiemap_ctx *ctx = data;
	loff_t ret = length;

	if (iomap->type == IOMAP_HOLE)
		return length;

	ret = iomap_to_fiemap(ctx->fi, &ctx->prev, 0);
	ctx->prev = *iomap;
	switch (ret) {
	case 0:		/* success */
		return length;
	case 1:		/* extent array full */
		return 0;
	default:
		return ret;
	}
}

int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
		loff_t start, loff_t len, struct iomap_ops *ops)
{
	struct fiemap_ctx ctx;
	loff_t ret;

	memset(&ctx, 0, sizeof(ctx));
	ctx.fi = fi;
	ctx.prev.type = IOMAP_HOLE;

	ret = fiemap_check_flags(fi, FIEMAP_FLAG_SYNC);
	if (ret)
		return ret;

	ret = filemap_write_and_wait(inode->i_mapping);
	if (ret)
		return ret;

	while (len > 0) {
		ret = iomap_apply(inode, start, len, 0, ops, &ctx,
				iomap_fiemap_actor);
		if (ret < 0)
			return ret;
		if (ret == 0)
			break;

		start += ret;
		len -= ret;
	}

	if (ctx.prev.type != IOMAP_HOLE) {
		ret = iomap_to_fiemap(fi, &ctx.prev, FIEMAP_EXTENT_LAST);
		if (ret < 0)
			return ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(iomap_fiemap);
OpenPOWER on IntegriCloud