1/*
2 * include/linux/backing-dev.h
3 *
4 * low-level device information and state which is propagated up through
5 * to high-level code.
6 */
7
8#ifndef _LINUX_BACKING_DEV_H
9#define _LINUX_BACKING_DEV_H
10
11#include <asm/atomic.h>
12
13/*
14 * Bits in backing_dev_info.state
15 */
16enum bdi_state {
17	BDI_pdflush,		/* A pdflush thread is working this device */
18	BDI_write_congested,	/* The write queue is getting full */
19	BDI_read_congested,	/* The read queue is getting full */
20	BDI_unused,		/* Available bits start here */
21};
22
23typedef int (congested_fn)(void *, int);
24
25struct backing_dev_info {
26	unsigned long ra_pages;	/* max readahead in PAGE_CACHE_SIZE units */
27	unsigned long state;	/* Always use atomic bitops on this */
28	unsigned int capabilities; /* Device capabilities */
29	congested_fn *congested_fn; /* Function pointer if device is md/dm */
30	void *congested_data;	/* Pointer to aux data for congested func */
31	void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
32	void *unplug_io_data;
33};
34
35
36/*
37 * Flags in backing_dev_info::capability
38 * - The first two flags control whether dirty pages will contribute to the
39 *   VM's accounting and whether writepages() should be called for dirty pages
40 *   (something that would not, for example, be appropriate for ramfs)
41 * - These flags let !MMU mmap() govern direct device mapping vs immediate
42 *   copying more easily for MAP_PRIVATE, especially for ROM filesystems
43 */
44#define BDI_CAP_NO_ACCT_DIRTY	0x00000001	/* Dirty pages shouldn't contribute to accounting */
45#define BDI_CAP_NO_WRITEBACK	0x00000002	/* Don't write pages back */
46#define BDI_CAP_MAP_COPY	0x00000004	/* Copy can be mapped (MAP_PRIVATE) */
47#define BDI_CAP_MAP_DIRECT	0x00000008	/* Can be mapped directly (MAP_SHARED) */
48#define BDI_CAP_READ_MAP	0x00000010	/* Can be mapped for reading */
49#define BDI_CAP_WRITE_MAP	0x00000020	/* Can be mapped for writing */
50#define BDI_CAP_EXEC_MAP	0x00000040	/* Can be mapped for execution */
51#define BDI_CAP_VMFLAGS \
52	(BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
53
54#if defined(VM_MAYREAD) && \
55	(BDI_CAP_READ_MAP != VM_MAYREAD || \
56	 BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
57	 BDI_CAP_EXEC_MAP != VM_MAYEXEC)
58#error please change backing_dev_info::capabilities flags
59#endif
60
61extern struct backing_dev_info default_backing_dev_info;
62void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
63
64int writeback_acquire(struct backing_dev_info *bdi);
65int writeback_in_progress(struct backing_dev_info *bdi);
66void writeback_release(struct backing_dev_info *bdi);
67
68static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
69{
70	if (bdi->congested_fn)
71		return bdi->congested_fn(bdi->congested_data, bdi_bits);
72	return (bdi->state & bdi_bits);
73}
74
75static inline int bdi_read_congested(struct backing_dev_info *bdi)
76{
77	return bdi_congested(bdi, 1 << BDI_read_congested);
78}
79
80static inline int bdi_write_congested(struct backing_dev_info *bdi)
81{
82	return bdi_congested(bdi, 1 << BDI_write_congested);
83}
84
85static inline int bdi_rw_congested(struct backing_dev_info *bdi)
86{
87	return bdi_congested(bdi, (1 << BDI_read_congested)|
88				  (1 << BDI_write_congested));
89}
90
91#define bdi_cap_writeback_dirty(bdi) \
92	(!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
93
94#define bdi_cap_account_dirty(bdi) \
95	(!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
96
97#define mapping_cap_writeback_dirty(mapping) \
98	bdi_cap_writeback_dirty((mapping)->backing_dev_info)
99
100#define mapping_cap_account_dirty(mapping) \
101	bdi_cap_account_dirty((mapping)->backing_dev_info)
102
103
104#endif		/* _LINUX_BACKING_DEV_H */
105