summaryrefslogtreecommitdiffstats
path: root/include/linux/netfs.h
blob: 9062adfa2fb9dc940abe42bbd9f3c15825d157b8 (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
/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Network filesystem support services.
 *
 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * See:
 *
 *	Documentation/filesystems/netfs_library.rst
 *
 * for a description of the network filesystem interface declared here.
 */

#ifndef _LINUX_NETFS_H
#define _LINUX_NETFS_H

#include <linux/workqueue.h>
#include <linux/fs.h>
#include <linux/pagemap.h>

/*
 * Overload PG_private_2 to give us PG_fscache - this is used to indicate that
 * a page is currently backed by a local disk cache
 */
#define PageFsCache(page)		PagePrivate2((page))
#define SetPageFsCache(page)		SetPagePrivate2((page))
#define ClearPageFsCache(page)		ClearPagePrivate2((page))
#define TestSetPageFsCache(page)	TestSetPagePrivate2((page))
#define TestClearPageFsCache(page)	TestClearPagePrivate2((page))

/**
 * set_page_fscache - Set PG_fscache on a page and take a ref
 * @page: The page.
 *
 * Set the PG_fscache (PG_private_2) flag on a page and take the reference
 * needed for the VM to handle its lifetime correctly.  This sets the flag and
 * takes the reference unconditionally, so care must be taken not to set the
 * flag again if it's already set.
 */
static inline void set_page_fscache(struct page *page)
{
	set_page_private_2(page);
}

/**
 * end_page_fscache - Clear PG_fscache and release any waiters
 * @page: The page
 *
 * Clear the PG_fscache (PG_private_2) bit on a page and wake up any sleepers
 * waiting for this.  The page ref held for PG_private_2 being set is released.
 *
 * This is, for example, used when a netfs page is being written to a local
 * disk cache, thereby allowing writes to the cache for the same page to be
 * serialised.
 */
static inline void end_page_fscache(struct page *page)
{
	end_page_private_2(page);
}

/**
 * wait_on_page_fscache - Wait for PG_fscache to be cleared on a page
 * @page: The page to wait on
 *
 * Wait for PG_fscache (aka PG_private_2) to be cleared on a page.
 */
static inline void wait_on_page_fscache(struct page *page)
{
	wait_on_page_private_2(page);
}

/**
 * wait_on_page_fscache_killable - Wait for PG_fscache to be cleared on a page
 * @page: The page to wait on
 *
 * Wait for PG_fscache (aka PG_private_2) to be cleared on a page or until a
 * fatal signal is received by the calling task.
 *
 * Return:
 * - 0 if successful.
 * - -EINTR if a fatal signal was encountered.
 */
static inline int wait_on_page_fscache_killable(struct page *page)
{
	return wait_on_page_private_2_killable(page);
}

enum netfs_read_source {
	NETFS_FILL_WITH_ZEROES,
	NETFS_DOWNLOAD_FROM_SERVER,
	NETFS_READ_FROM_CACHE,
	NETFS_INVALID_READ,
} __mode(byte);

typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error,
				      bool was_async);

/*
 * Resources required to do operations on a cache.
 */
struct netfs_cache_resources {
	const struct netfs_cache_ops	*ops;
	void				*cache_priv;
	void				*cache_priv2;
};

/*
 * Descriptor for a single component subrequest.
 */
struct netfs_read_subrequest {
	struct netfs_read_request *rreq;	/* Supervising read request */
	struct list_head	rreq_link;	/* Link in rreq->subrequests */
	loff_t			start;		/* Where to start the I/O */
	size_t			len;		/* Size of the I/O */
	size_t			transferred;	/* Amount of data transferred */
	refcount_t		usage;
	short			error;		/* 0 or error that occurred */
	unsigned short		debug_index;	/* Index in list (for debugging output) */
	enum netfs_read_source	source;		/* Where to read from */
	unsigned long		flags;
#define NETFS_SREQ_WRITE_TO_CACHE	0	/* Set if should write to cache */
#define NETFS_SREQ_CLEAR_TAIL		1	/* Set if the rest of the read should be cleared */
#define NETFS_SREQ_SHORT_READ		2	/* Set if there was a short read from the cache */
#define NETFS_SREQ_SEEK_DATA_READ	3	/* Set if ->read() should SEEK_DATA first */
#define NETFS_SREQ_NO_PROGRESS		4	/* Set if we didn't manage to read any data */
};

/*
 * Descriptor for a read helper request.  This is used to make multiple I/O
 * requests on a variety of sources and then stitch the result together.
 */
struct netfs_read_request {
	struct work_struct	work;
	struct inode		*inode;		/* The file being accessed */
	struct address_space	*mapping;	/* The mapping being accessed */
	struct netfs_cache_resources cache_resources;
	struct list_head	subrequests;	/* Requests to fetch I/O from disk or net */
	void			*netfs_priv;	/* Private data for the netfs */
	unsigned int		debug_id;
	unsigned int		cookie_debug_id;
	atomic_t		nr_rd_ops;	/* Number of read ops in progress */
	atomic_t		nr_wr_ops;	/* Number of write ops in progress */
	size_t			submitted;	/* Amount submitted for I/O so far */
	size_t			len;		/* Length of the request */
	short			error;		/* 0 or error that occurred */
	loff_t			i_size;		/* Size of the file */
	loff_t			start;		/* Start position */
	pgoff_t			no_unlock_page;	/* Don't unlock this page after read */
	refcount_t		usage;
	unsigned long		flags;
#define NETFS_RREQ_INCOMPLETE_IO	0	/* Some ioreqs terminated short or with error */
#define NETFS_RREQ_WRITE_TO_CACHE	1	/* Need to write to the cache */
#define NETFS_RREQ_NO_UNLOCK_PAGE	2	/* Don't unlock no_unlock_page on completion */
#define NETFS_RREQ_DONT_UNLOCK_PAGES	3	/* Don't unlock the pages on completion */
#define NETFS_RREQ_FAILED		4	/* The request failed */
#define NETFS_RREQ_IN_PROGRESS		5	/* Unlocked when the request completes */
	const struct netfs_read_request_ops *netfs_ops;
};

/*
 * Operations the network filesystem can/must provide to the helpers.
 */
struct netfs_read_request_ops {
	bool (*is_cache_enabled)(struct inode *inode);
	void (*init_rreq)(struct netfs_read_request *rreq, struct file *file);
	int (*begin_cache_operation)(struct netfs_read_request *rreq);
	void (*expand_readahead)(struct netfs_read_request *rreq);
	bool (*clamp_length)(struct netfs_read_subrequest *subreq);
	void (*issue_op)(struct netfs_read_subrequest *subreq);
	bool (*is_still_valid)(struct netfs_read_request *rreq);
	int (*check_write_begin)(struct file *file, loff_t pos, unsigned len,
				 struct page *page, void **_fsdata);
	void (*done)(struct netfs_read_request *rreq);
	void (*cleanup)(struct address_space *mapping, void *netfs_priv);
};

/*
 * Table of operations for access to a cache.  This is obtained by
 * rreq->ops->begin_cache_operation().
 */
struct netfs_cache_ops {
	/* End an operation */
	void (*end_operation)(struct netfs_cache_resources *cres);

	/* Read data from the cache */
	int (*read)(struct netfs_cache_resources *cres,
		    loff_t start_pos,
		    struct iov_iter *iter,
		    bool seek_data,
		    netfs_io_terminated_t term_func,
		    void *term_func_priv);

	/* Write data to the cache */
	int (*write)(struct netfs_cache_resources *cres,
		     loff_t start_pos,
		     struct iov_iter *iter,
		     netfs_io_terminated_t term_func,
		     void *term_func_priv);

	/* Expand readahead request */
	void (*expand_readahead)(struct netfs_cache_resources *cres,
				 loff_t *_start, size_t *_len, loff_t i_size);

	/* Prepare a read operation, shortening it to a cached/uncached
	 * boundary as appropriate.
	 */
	enum netfs_read_source (*prepare_read)(struct netfs_read_subrequest *subreq,
					       loff_t i_size);

	/* Prepare a write operation, working out what part of the write we can
	 * actually do.
	 */
	int (*prepare_write)(struct netfs_cache_resources *cres,
			     loff_t *_start, size_t *_len, loff_t i_size);
};

struct readahead_control;
extern void netfs_readahead(struct readahead_control *,
			    const struct netfs_read_request_ops *,
			    void *);
extern int netfs_readpage(struct file *,
			  struct page *,
			  const struct netfs_read_request_ops *,
			  void *);
extern int netfs_write_begin(struct file *, struct address_space *,
			     loff_t, unsigned int, unsigned int, struct page **,
			     void **,
			     const struct netfs_read_request_ops *,
			     void *);

extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool);
extern void netfs_stats_show(struct seq_file *);

#endif /* _LINUX_NETFS_H */