aboutsummaryrefslogtreecommitdiffstats
path: root/fs/relayfs/inode.c
blob: 0f7f88d067adad67b0d846fc9ebfb2f7109f3202 (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
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
/*
 * VFS-related code for RelayFS, a high-speed data relay filesystem.
 *
 * Copyright (C) 2003-2005 - Tom Zanussi <zanussi@us.ibm.com>, IBM Corp
 * Copyright (C) 2003-2005 - Karim Yaghmour <karim@opersys.com>
 *
 * Based on ramfs, Copyright (C) 2002 - Linus Torvalds
 *
 * This file is released under the GPL.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/namei.h>
#include <linux/poll.h>
#include <linux/relayfs_fs.h>
#include "relay.h"
#include "buffers.h"

#define RELAYFS_MAGIC			0xF0B4A981

static struct vfsmount *		relayfs_mount;
static int				relayfs_mount_count;
static kmem_cache_t *			relayfs_inode_cachep;

static struct backing_dev_info		relayfs_backing_dev_info = {
	.ra_pages	= 0,	/* No readahead */
	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};

static struct inode *relayfs_get_inode(struct super_block *sb, int mode,
				       struct rchan *chan)
{
	struct rchan_buf *buf = NULL;
	struct inode *inode;

	if (S_ISREG(mode)) {
		BUG_ON(!chan);
		buf = relay_create_buf(chan);
		if (!buf)
			return NULL;
	}

	inode = new_inode(sb);
	if (!inode) {
		relay_destroy_buf(buf);
		return NULL;
	}

	inode->i_mode = mode;
	inode->i_uid = 0;
	inode->i_gid = 0;
	inode->i_blksize = PAGE_CACHE_SIZE;
	inode->i_blocks = 0;
	inode->i_mapping->backing_dev_info = &relayfs_backing_dev_info;
	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
	switch (mode & S_IFMT) {
	case S_IFREG:
		inode->i_fop = &relayfs_file_operations;
		RELAYFS_I(inode)->buf = buf;
		break;
	case S_IFDIR:
		inode->i_op = &simple_dir_inode_operations;
		inode->i_fop = &simple_dir_operations;

		/* directory inodes start off with i_nlink == 2 (for "." entry) */
		inode->i_nlink++;
		break;
	default:
		break;
	}

	return inode;
}

/**
 *	relayfs_create_entry - create a relayfs directory or file
 *	@name: the name of the file to create
 *	@parent: parent directory
 *	@mode: mode
 *	@chan: relay channel associated with the file
 *
 *	Returns the new dentry, NULL on failure
 *
 *	Creates a file or directory with the specifed permissions.
 */
static struct dentry *relayfs_create_entry(const char *name,
					   struct dentry *parent,
					   int mode,
					   struct rchan *chan)
{
	struct dentry *d;
	struct inode *inode;
	int error = 0;

	BUG_ON(!name || !(S_ISREG(mode) || S_ISDIR(mode)));

	error = simple_pin_fs("relayfs", &relayfs_mount, &relayfs_mount_count);
	if (error) {
		printk(KERN_ERR "Couldn't mount relayfs: errcode %d\n", error);
		return NULL;
	}

	if (!parent && relayfs_mount && relayfs_mount->mnt_sb)
		parent = relayfs_mount->mnt_sb->s_root;

	if (!parent) {
		simple_release_fs(&relayfs_mount, &relayfs_mount_count);
		return NULL;
	}

	parent = dget(parent);
	down(&parent->d_inode->i_sem);
	d = lookup_one_len(name, parent, strlen(name));
	if (IS_ERR(d)) {
		d = NULL;
		goto release_mount;
	}

	if (d->d_inode) {
		d = NULL;
		goto release_mount;
	}

	inode = relayfs_get_inode(parent->d_inode->i_sb, mode, chan);
	if (!inode) {
		d = NULL;
		goto release_mount;
	}

	d_instantiate(d, inode);
	dget(d);	/* Extra count - pin the dentry in core */

	if (S_ISDIR(mode))
		parent->d_inode->i_nlink++;

	goto exit;

release_mount:
	simple_release_fs(&relayfs_mount, &relayfs_mount_count);

exit:
	up(&parent->d_inode->i_sem);
	dput(parent);
	return d;
}

/**
 *	relayfs_create_file - create a file in the relay filesystem
 *	@name: the name of the file to create
 *	@parent: parent directory
 *	@mode: mode, if not specied the default perms are used
 *	@chan: channel associated with the file
 *
 *	Returns file dentry if successful, NULL otherwise.
 *
 *	The file will be created user r on behalf of current user.
 */
struct dentry *relayfs_create_file(const char *name, struct dentry *parent,
				   int mode, struct rchan *chan)
{
	if (!mode)
		mode = S_IRUSR;
	mode = (mode & S_IALLUGO) | S_IFREG;

	return relayfs_create_entry(name, parent, mode, chan);
}

/**
 *	relayfs_create_dir - create a directory in the relay filesystem
 *	@name: the name of the directory to create
 *	@parent: parent directory, NULL if parent should be fs root
 *
 *	Returns directory dentry if successful, NULL otherwise.
 *
 *	The directory will be created world rwx on behalf of current user.
 */
struct dentry *relayfs_create_dir(const char *name, struct dentry *parent)
{
	int mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
	return relayfs_create_entry(name, parent, mode, NULL);
}

/**
 *	relayfs_remove - remove a file or directory in the relay filesystem
 *	@dentry: file or directory dentry
 *
 *	Returns 0 if successful, negative otherwise.
 */
int relayfs_remove(struct dentry *dentry)
{
	struct dentry *parent;
	int error = 0;

	if (!dentry)
		return -EINVAL;
	parent = dentry->d_parent;
	if (!parent)
		return -EINVAL;

	parent = dget(parent);
	down(&parent->d_inode->i_sem);
	if (dentry->d_inode) {
		if (S_ISDIR(dentry->d_inode->i_mode))
			error = simple_rmdir(parent->d_inode, dentry);
		else
			error = simple_unlink(parent->d_inode, dentry);
		if (!error)
			d_delete(dentry);
	}
	if (!error)
		dput(dentry);
	up(&parent->d_inode->i_sem);
	dput(parent);

	if (!error)
		simple_release_fs(&relayfs_mount, &relayfs_mount_count);

	return error;
}

/**
 *	relayfs_remove_dir - remove a directory in the relay filesystem
 *	@dentry: directory dentry
 *
 *	Returns 0 if successful, negative otherwise.
 */
int relayfs_remove_dir(struct dentry *dentry)
{
	return relayfs_remove(dentry);
}

/**
 *	relayfs_open - open file op for relayfs files
 *	@inode: the inode
 *	@filp: the file
 *
 *	Increments the channel buffer refcount.
 */
static int relayfs_open(struct inode *inode, struct file *filp)
{
	struct rchan_buf *buf = RELAYFS_I(inode)->buf;
	kref_get(&buf->kref);

	return 0;
}

/**
 *	relayfs_mmap - mmap file op for relayfs files
 *	@filp: the file
 *	@vma: the vma describing what to map
 *
 *	Calls upon relay_mmap_buf to map the file into user space.
 */
static int relayfs_mmap(struct file *filp, struct vm_area_struct *vma)
{
	struct inode *inode = filp->f_dentry->d_inode;
	return relay_mmap_buf(RELAYFS_I(inode)->buf, vma);
}

/**
 *	relayfs_poll - poll file op for relayfs files
 *	@filp: the file
 *	@wait: poll table
 *
 *	Poll implemention.
 */
static unsigned int relayfs_poll(struct file *filp, poll_table *wait)
{
	unsigned int mask = 0;
	struct inode *inode = filp->f_dentry->d_inode;
	struct rchan_buf *buf = RELAYFS_I(inode)->buf;

	if (buf->finalized)
		return POLLERR;

	if (filp->f_mode & FMODE_READ) {
		poll_wait(filp, &buf->read_wait, wait);
		if (!relay_buf_empty(buf))
			mask |= POLLIN | POLLRDNORM;
	}

	return mask;
}

/**
 *	relayfs_release - release file op for relayfs files
 *	@inode: the inode
 *	@filp: the file
 *
 *	Decrements the channel refcount, as the filesystem is
 *	no longer using it.
 */
static int relayfs_release(struct inode *inode, struct file *filp)
{
	struct rchan_buf *buf = RELAYFS_I(inode)->buf;
	kref_put(&buf->kref, relay_remove_buf);

	return 0;
}

/**
 *	relayfs_read_consume - update the consumed count for the buffer
 */
static void relayfs_read_consume(struct rchan_buf *buf,
				 size_t read_pos,
				 size_t bytes_consumed)
{
	size_t subbuf_size = buf->chan->subbuf_size;
	size_t n_subbufs = buf->chan->n_subbufs;
	size_t read_subbuf;

	if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
		relay_subbufs_consumed(buf->chan, buf->cpu, 1);
		buf->bytes_consumed = 0;
	}

	buf->bytes_consumed += bytes_consumed;
	read_subbuf = read_pos / buf->chan->subbuf_size;
	if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
		if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
		    (buf->offset == subbuf_size))
			return;
		relay_subbufs_consumed(buf->chan, buf->cpu, 1);
		buf->bytes_consumed = 0;
	}
}

/**
 *	relayfs_read_avail - boolean, are there unconsumed bytes available?
 */
static int relayfs_read_avail(struct rchan_buf *buf, size_t read_pos)
{
	size_t bytes_produced, bytes_consumed, write_offset;
	size_t subbuf_size = buf->chan->subbuf_size;
	size_t n_subbufs = buf->chan->n_subbufs;
	size_t produced = buf->subbufs_produced % n_subbufs;
	size_t consumed = buf->subbufs_consumed % n_subbufs;

	write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;

	if (consumed > produced) {
		if ((produced > n_subbufs) &&
		    (produced + n_subbufs - consumed <= n_subbufs))
			produced += n_subbufs;
	} else if (consumed == produced) {
		if (buf->offset > subbuf_size) {
			produced += n_subbufs;
			if (buf->subbufs_produced == buf->subbufs_consumed)
				consumed += n_subbufs;
		}
	}

	if (buf->offset > subbuf_size)
		bytes_produced = (produced - 1) * subbuf_size + write_offset;
	else
		bytes_produced = produced * subbuf_size + write_offset;
	bytes_consumed = consumed * subbuf_size + buf->bytes_consumed;

	if (bytes_produced == bytes_consumed)
		return 0;

	relayfs_read_consume(buf, read_pos, 0);

	return 1;
}

/**
 *	relayfs_read_subbuf_avail - return bytes available in sub-buffer
 */
static size_t relayfs_read_subbuf_avail(size_t read_pos,
					struct rchan_buf *buf)
{
	size_t padding, avail = 0;
	size_t read_subbuf, read_offset, write_subbuf, write_offset;
	size_t subbuf_size = buf->chan->subbuf_size;

	write_subbuf = (buf->data - buf->start) / subbuf_size;
	write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
	read_subbuf = read_pos / subbuf_size;
	read_offset = read_pos % subbuf_size;
	padding = buf->padding[read_subbuf];

	if (read_subbuf == write_subbuf) {
		if (read_offset + padding < write_offset)
			avail = write_offset - (read_offset + padding);
	} else
		avail = (subbuf_size - padding) - read_offset;

	return avail;
}

/**
 *	relayfs_read_start_pos - find the first available byte to read
 *
 *	If the read_pos is in the middle of padding, return the
 *	position of the first actually available byte, otherwise
 *	return the original value.
 */
static size_t relayfs_read_start_pos(size_t read_pos,
				     struct rchan_buf *buf)
{
	size_t read_subbuf, padding, padding_start, padding_end;
	size_t subbuf_size = buf->chan->subbuf_size;
	size_t n_subbufs = buf->chan->n_subbufs;

	read_subbuf = read_pos / subbuf_size;
	padding = buf->padding[read_subbuf];
	padding_start = (read_subbuf + 1) * subbuf_size - padding;
	padding_end = (read_subbuf + 1) * subbuf_size;
	if (read_pos >= padding_start && read_pos < padding_end) {
		read_subbuf = (read_subbuf + 1) % n_subbufs;
		read_pos = read_subbuf * subbuf_size;
	}

	return read_pos;
}

/**
 *	relayfs_read_end_pos - return the new read position
 */
static size_t relayfs_read_end_pos(struct rchan_buf *buf,
				   size_t read_pos,
				   size_t count)
{
	size_t read_subbuf, padding, end_pos;
	size_t subbuf_size = buf->chan->subbuf_size;
	size_t n_subbufs = buf->chan->n_subbufs;

	read_subbuf = read_pos / subbuf_size;
	padding = buf->padding[read_subbuf];
	if (read_pos % subbuf_size + count + padding == subbuf_size)
		end_pos = (read_subbuf + 1) * subbuf_size;
	else
		end_pos = read_pos + count;
	if (end_pos >= subbuf_size * n_subbufs)
		end_pos = 0;

	return end_pos;
}

/**
 *	relayfs_read - read file op for relayfs files
 *	@filp: the file
 *	@buffer: the userspace buffer
 *	@count: number of bytes to read
 *	@ppos: position to read from
 *
 *	Reads count bytes or the number of bytes available in the
 *	current sub-buffer being read, whichever is smaller.
 */
static ssize_t relayfs_read(struct file *filp,
			    char __user *buffer,
			    size_t count,
			    loff_t *ppos)
{
	struct inode *inode = filp->f_dentry->d_inode;
	struct rchan_buf *buf = RELAYFS_I(inode)->buf;
	size_t read_start, avail;
	ssize_t ret = 0;
	void *from;

	down(&inode->i_sem);
	if(!relayfs_read_avail(buf, *ppos))
		goto out;

	read_start = relayfs_read_start_pos(*ppos, buf);
	avail = relayfs_read_subbuf_avail(read_start, buf);
	if (!avail)
		goto out;

	from = buf->start + read_start;
	ret = count = min(count, avail);
	if (copy_to_user(buffer, from, count)) {
		ret = -EFAULT;
		goto out;
	}
	relayfs_read_consume(buf, read_start, count);
	*ppos = relayfs_read_end_pos(buf, read_start, count);
out:
	up(&inode->i_sem);
	return ret;
}

/**
 *	relayfs alloc_inode() implementation
 */
static struct inode *relayfs_alloc_inode(struct super_block *sb)
{
	struct relayfs_inode_info *p = kmem_cache_alloc(relayfs_inode_cachep, SLAB_KERNEL);
	if (!p)
		return NULL;
	p->buf = NULL;

	return &p->vfs_inode;
}

/**
 *	relayfs destroy_inode() implementation
 */
static void relayfs_destroy_inode(struct inode *inode)
{
	if (RELAYFS_I(inode)->buf)
		relay_destroy_buf(RELAYFS_I(inode)->buf);

	kmem_cache_free(relayfs_inode_cachep, RELAYFS_I(inode));
}

static void init_once(void *p, kmem_cache_t *cachep, unsigned long flags)
{
	struct relayfs_inode_info *i = p;
	if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) == SLAB_CTOR_CONSTRUCTOR)
		inode_init_once(&i->vfs_inode);
}

struct file_operations relayfs_file_operations = {
	.open		= relayfs_open,
	.poll		= relayfs_poll,
	.mmap		= relayfs_mmap,
	.read		= relayfs_read,
	.llseek		= no_llseek,
	.release	= relayfs_release,
};

static struct super_operations relayfs_ops = {
	.statfs		= simple_statfs,
	.drop_inode	= generic_delete_inode,
	.alloc_inode	= relayfs_alloc_inode,
	.destroy_inode	= relayfs_destroy_inode,
};

static int relayfs_fill_super(struct super_block * sb, void * data, int silent)
{
	struct inode *inode;
	struct dentry *root;
	int mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;

	sb->s_blocksize = PAGE_CACHE_SIZE;
	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
	sb->s_magic = RELAYFS_MAGIC;
	sb->s_op = &relayfs_ops;
	inode = relayfs_get_inode(sb, mode, NULL);

	if (!inode)
		return -ENOMEM;

	root = d_alloc_root(inode);
	if (!root) {
		iput(inode);
		return -ENOMEM;
	}
	sb->s_root = root;

	return 0;
}

static struct super_block * relayfs_get_sb(struct file_system_type *fs_type,
					   int flags, const char *dev_name,
					   void *data)
{
	return get_sb_single(fs_type, flags, data, relayfs_fill_super);
}

static struct file_system_type relayfs_fs_type = {
	.owner		= THIS_MODULE,
	.name		= "relayfs",
	.get_sb		= relayfs_get_sb,
	.kill_sb	= kill_litter_super,
};

static int __init init_relayfs_fs(void)
{
	int err;

	relayfs_inode_cachep = kmem_cache_create("relayfs_inode_cache",
				sizeof(struct relayfs_inode_info), 0,
				0, init_once, NULL);
	if (!relayfs_inode_cachep)
		return -ENOMEM;

	err = register_filesystem(&relayfs_fs_type);
	if (err)
		kmem_cache_destroy(relayfs_inode_cachep);

	return err;
}

static void __exit exit_relayfs_fs(void)
{
	unregister_filesystem(&relayfs_fs_type);
	kmem_cache_destroy(relayfs_inode_cachep);
}

module_init(init_relayfs_fs)
module_exit(exit_relayfs_fs)

EXPORT_SYMBOL_GPL(relayfs_file_operations);
EXPORT_SYMBOL_GPL(relayfs_create_dir);
EXPORT_SYMBOL_GPL(relayfs_remove_dir);

MODULE_AUTHOR("Tom Zanussi <zanussi@us.ibm.com> and Karim Yaghmour <karim@opersys.com>");
MODULE_DESCRIPTION("Relay Filesystem");
MODULE_LICENSE("GPL");