summaryrefslogtreecommitdiff
path: root/fs/xfs/xfs_buf_mem.c
blob: 9bb2d24de7094114a6f8c303647fe1b857805fb4 (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
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (c) 2023-2024 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <djwong@kernel.org>
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_buf.h"
#include "xfs_buf_mem.h"
#include "xfs_trace.h"
#include <linux/shmem_fs.h>
#include "xfs_log_format.h"
#include "xfs_trans.h"
#include "xfs_buf_item.h"
#include "xfs_error.h"

/*
 * Buffer Cache for In-Memory Files
 * ================================
 *
 * Online fsck wants to create ephemeral ordered recordsets.  The existing
 * btree infrastructure can do this, but we need the buffer cache to target
 * memory instead of block devices.
 *
 * When CONFIG_TMPFS=y, shmemfs is enough of a filesystem to meet those
 * requirements.  Therefore, the xmbuf mechanism uses an unlinked shmem file to
 * store our staging data.  This file is not installed in the file descriptor
 * table so that user programs cannot access the data, which means that the
 * xmbuf must be freed with xmbuf_destroy.
 *
 * xmbufs assume that the caller will handle all required concurrency
 * management; standard vfs locks (freezer and inode) are not taken.  Reads
 * and writes are satisfied directly from the page cache.
 *
 * The only supported block size is PAGE_SIZE, and we cannot use highmem.
 */

/*
 * shmem files used to back an in-memory buffer cache must not be exposed to
 * userspace.  Upper layers must coordinate access to the one handle returned
 * by the constructor, so establish a separate lock class for xmbufs to avoid
 * confusing lockdep.
 */
static struct lock_class_key xmbuf_i_mutex_key;

/*
 * Allocate a buffer cache target for a memory-backed file and set up the
 * buffer target.
 */
int
xmbuf_alloc(
	struct xfs_mount	*mp,
	const char		*descr,
	struct xfs_buftarg	**btpp)
{
	struct file		*file;
	struct inode		*inode;
	struct xfs_buftarg	*btp;
	int			error;

	btp = kzalloc(struct_size(btp, bt_cache, 1), GFP_KERNEL);
	if (!btp)
		return -ENOMEM;

	file = shmem_kernel_file_setup(descr, 0, 0);
	if (IS_ERR(file)) {
		error = PTR_ERR(file);
		goto out_free_btp;
	}
	inode = file_inode(file);

	/* private file, private locking */
	lockdep_set_class(&inode->i_rwsem, &xmbuf_i_mutex_key);

	/*
	 * We don't want to bother with kmapping data during repair, so don't
	 * allow highmem pages to back this mapping.
	 */
	mapping_set_gfp_mask(inode->i_mapping, GFP_KERNEL);

	/* ensure all writes are below EOF to avoid pagecache zeroing */
	i_size_write(inode, inode->i_sb->s_maxbytes);

	error = xfs_buf_cache_init(btp->bt_cache);
	if (error)
		goto out_file;

	/* Initialize buffer target */
	btp->bt_mount = mp;
	btp->bt_dev = (dev_t)-1U;
	btp->bt_bdev = NULL; /* in-memory buftargs have no bdev */
	btp->bt_file = file;
	btp->bt_meta_sectorsize = XMBUF_BLOCKSIZE;
	btp->bt_meta_sectormask = XMBUF_BLOCKSIZE - 1;

	error = xfs_init_buftarg(btp, XMBUF_BLOCKSIZE, descr);
	if (error)
		goto out_bcache;

	trace_xmbuf_create(btp);

	*btpp = btp;
	return 0;

out_bcache:
	xfs_buf_cache_destroy(btp->bt_cache);
out_file:
	fput(file);
out_free_btp:
	kfree(btp);
	return error;
}

/* Free a buffer cache target for a memory-backed buffer cache. */
void
xmbuf_free(
	struct xfs_buftarg	*btp)
{
	ASSERT(xfs_buftarg_is_mem(btp));
	ASSERT(percpu_counter_sum(&btp->bt_io_count) == 0);

	trace_xmbuf_free(btp);

	xfs_destroy_buftarg(btp);
	xfs_buf_cache_destroy(btp->bt_cache);
	fput(btp->bt_file);
	kfree(btp);
}

/* Directly map a shmem page into the buffer cache. */
int
xmbuf_map_page(
	struct xfs_buf		*bp)
{
	struct inode		*inode = file_inode(bp->b_target->bt_file);
	struct folio		*folio = NULL;
	struct page		*page;
	loff_t                  pos = BBTOB(xfs_buf_daddr(bp));
	int			error;

	ASSERT(xfs_buftarg_is_mem(bp->b_target));

	if (bp->b_map_count != 1)
		return -ENOMEM;
	if (BBTOB(bp->b_length) != XMBUF_BLOCKSIZE)
		return -ENOMEM;
	if (offset_in_page(pos) != 0) {
		ASSERT(offset_in_page(pos));
		return -ENOMEM;
	}

	error = shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio, SGP_CACHE);
	if (error)
		return error;

	if (filemap_check_wb_err(inode->i_mapping, 0)) {
		folio_unlock(folio);
		folio_put(folio);
		return -EIO;
	}

	page = folio_file_page(folio, pos >> PAGE_SHIFT);

	/*
	 * Mark the page dirty so that it won't be reclaimed once we drop the
	 * (potentially last) reference in xmbuf_unmap_page.
	 */
	set_page_dirty(page);
	unlock_page(page);

	bp->b_addr = page_address(page);
	bp->b_pages = bp->b_page_array;
	bp->b_pages[0] = page;
	bp->b_page_count = 1;
	return 0;
}

/* Unmap a shmem page that was mapped into the buffer cache. */
void
xmbuf_unmap_page(
	struct xfs_buf		*bp)
{
	struct page		*page = bp->b_pages[0];

	ASSERT(xfs_buftarg_is_mem(bp->b_target));

	put_page(page);

	bp->b_addr = NULL;
	bp->b_pages[0] = NULL;
	bp->b_pages = NULL;
	bp->b_page_count = 0;
}

/* Is this a valid daddr within the buftarg? */
bool
xmbuf_verify_daddr(
	struct xfs_buftarg	*btp,
	xfs_daddr_t		daddr)
{
	struct inode		*inode = file_inode(btp->bt_file);

	ASSERT(xfs_buftarg_is_mem(btp));

	return daddr < (inode->i_sb->s_maxbytes >> BBSHIFT);
}

/* Discard the page backing this buffer. */
static void
xmbuf_stale(
	struct xfs_buf		*bp)
{
	struct inode		*inode = file_inode(bp->b_target->bt_file);
	loff_t			pos;

	ASSERT(xfs_buftarg_is_mem(bp->b_target));

	pos = BBTOB(xfs_buf_daddr(bp));
	shmem_truncate_range(inode, pos, pos + BBTOB(bp->b_length) - 1);
}

/*
 * Finalize a buffer -- discard the backing page if it's stale, or run the
 * write verifier to detect problems.
 */
int
xmbuf_finalize(
	struct xfs_buf		*bp)
{
	xfs_failaddr_t		fa;
	int			error = 0;

	if (bp->b_flags & XBF_STALE) {
		xmbuf_stale(bp);
		return 0;
	}

	/*
	 * Although this btree is ephemeral, validate the buffer structure so
	 * that we can detect memory corruption errors and software bugs.
	 */
	fa = bp->b_ops->verify_struct(bp);
	if (fa) {
		error = -EFSCORRUPTED;
		xfs_verifier_error(bp, error, fa);
	}

	return error;
}

/*
 * Detach this xmbuf buffer from the transaction by any means necessary.
 * All buffers are direct-mapped, so they do not need bwrite.
 */
void
xmbuf_trans_bdetach(
	struct xfs_trans	*tp,
	struct xfs_buf		*bp)
{
	struct xfs_buf_log_item	*bli = bp->b_log_item;

	ASSERT(bli != NULL);

	bli->bli_flags &= ~(XFS_BLI_DIRTY | XFS_BLI_ORDERED |
			    XFS_BLI_LOGGED | XFS_BLI_STALE);
	clear_bit(XFS_LI_DIRTY, &bli->bli_item.li_flags);

	while (bp->b_log_item != NULL)
		xfs_trans_bdetach(tp, bp);
}