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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
Andrew Morton3fcfab12006-10-19 23:28:16 -070013struct page;
14
Linus Torvalds1da177e2005-04-16 15:20:36 -070015/*
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) && \
57 (BDI_CAP_READ_MAP != VM_MAYREAD || \
58 BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
59 BDI_CAP_EXEC_MAP != VM_MAYEXEC)
60#error please change backing_dev_info::capabilities flags
61#endif
62
63extern struct backing_dev_info default_backing_dev_info;
64void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
65
66int writeback_acquire(struct backing_dev_info *bdi);
67int writeback_in_progress(struct backing_dev_info *bdi);
68void writeback_release(struct backing_dev_info *bdi);
69
70static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
71{
72 if (bdi->congested_fn)
73 return bdi->congested_fn(bdi->congested_data, bdi_bits);
74 return (bdi->state & bdi_bits);
75}
76
77static inline int bdi_read_congested(struct backing_dev_info *bdi)
78{
79 return bdi_congested(bdi, 1 << BDI_read_congested);
80}
81
82static inline int bdi_write_congested(struct backing_dev_info *bdi)
83{
84 return bdi_congested(bdi, 1 << BDI_write_congested);
85}
86
87static inline int bdi_rw_congested(struct backing_dev_info *bdi)
88{
89 return bdi_congested(bdi, (1 << BDI_read_congested)|
90 (1 << BDI_write_congested));
91}
92
Andrew Morton3fcfab12006-10-19 23:28:16 -070093void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
94void set_bdi_congested(struct backing_dev_info *bdi, int rw);
95long congestion_wait(int rw, long timeout);
96void congestion_end(int rw);
97
Linus Torvalds1da177e2005-04-16 15:20:36 -070098#define bdi_cap_writeback_dirty(bdi) \
99 (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
100
101#define bdi_cap_account_dirty(bdi) \
102 (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
103
104#define mapping_cap_writeback_dirty(mapping) \
105 bdi_cap_writeback_dirty((mapping)->backing_dev_info)
106
107#define mapping_cap_account_dirty(mapping) \
108 bdi_cap_account_dirty((mapping)->backing_dev_info)
109
110
111#endif /* _LINUX_BACKING_DEV_H */