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
13struct page;
14
15/*
16 * Bits in backing_dev_info.state
17 */
18enum bdi_state {
19	BDI_pdflush,		/* A pdflush thread is working this device */
20	BDI_write_congested,	/* The write queue is getting full */
21	BDI_read_congested,	/* The read queue is getting full */
22	BDI_unused,		/* Available bits start here */
23};
24
25typedef int (congested_fn)(void *, int);
26
27struct backing_dev_info {
28	unsigned long ra_pages;	/* max readahead in PAGE_CACHE_SIZE units */
29	unsigned long state;	/* Always use atomic bitops on this */
30	unsigned int capabilities; /* Device capabilities */
31	congested_fn *congested_fn; /* Function pointer if device is md/dm */
32	void *congested_data;	/* Pointer to aux data for congested func */
33	void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
34	void *unplug_io_data;
35};
36
37
38/*
39 * Flags in backing_dev_info::capability
40 * - The first two flags control whether dirty pages will contribute to the
41 *   VM's accounting and whether writepages() should be called for dirty pages
42 *   (something that would not, for example, be appropriate for ramfs)
43 * - These flags let !MMU mmap() govern direct device mapping vs immediate
44 *   copying more easily for MAP_PRIVATE, especially for ROM filesystems
45 */
46#define BDI_CAP_NO_ACCT_DIRTY	0x00000001	/* Dirty pages shouldn't contribute to accounting */
47#define BDI_CAP_NO_WRITEBACK	0x00000002	/* Don't write pages back */
48#define BDI_CAP_MAP_COPY	0x00000004	/* Copy can be mapped (MAP_PRIVATE) */
49#define BDI_CAP_MAP_DIRECT	0x00000008	/* Can be mapped directly (MAP_SHARED) */
50#define BDI_CAP_READ_MAP	0x00000010	/* Can be mapped for reading */
51#define BDI_CAP_WRITE_MAP	0x00000020	/* Can be mapped for writing */
52#define BDI_CAP_EXEC_MAP	0x00000040	/* Can be mapped for execution */
53#define BDI_CAP_VMFLAGS \
54	(BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
55
56#if defined(VM_MAYREAD) && (BDI_CAP_READ_MAP != VM_MAYREAD || BDI_CAP_WRITE_MAP != \
57	VM_MAYWRITE || 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
91void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
92void set_bdi_congested(struct backing_dev_info *bdi, int rw);
93long congestion_wait(int rw, long timeout);
94long congestion_wait_interruptible(int rw, long timeout);
95void congestion_end(int rw);
96
97#define bdi_cap_writeback_dirty(bdi) \
98	(!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
99
100#define bdi_cap_account_dirty(bdi) \
101	(!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
102
103#define mapping_cap_writeback_dirty(mapping) \
104	bdi_cap_writeback_dirty((mapping)->backing_dev_info)
105
106#define mapping_cap_account_dirty(mapping) \
107	bdi_cap_account_dirty((mapping)->backing_dev_info)
108
109
110#endif		/* _LINUX_BACKING_DEV_H */
111