/*
* include/linux/backing-dev.h
*
* low-level device information and state which is propagated up through
* to high-level code.
*/
#ifndef _LINUX_BACKING_DEV_H
#define _LINUX_BACKING_DEV_H
#include <linux/percpu_counter.h>
#include <linux/log2.h>
#include <asm/atomic.h>
struct page;
/*
* Bits in backing_dev_info.state
*/
enum bdi_state {
BDI_pdflush, /* A pdflush thread is working this device */
BDI_write_congested, /* The write queue is getting full */
BDI_read_congested, /* The read queue is getting full */
BDI_unused, /* Available bits start here */
};
typedef int (congested_fn)(void *, int);
enum bdi_stat_item {
BDI_RECLAIMABLE,
BDI_WRITEBACK,
NR_BDI_STAT_ITEMS
};
#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
struct backing_dev_info {
unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
unsigned long state; /* Always use atomic bitops on this */
unsigned int capabilities; /* Device capabilities */
congested_fn *congested_fn; /* Function pointer if device is md/dm */
void *congested_data; /* Pointer to aux data for congested func */
void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
void *unplug_io_data;
struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
};
int bdi_init(struct backing_dev_info *bdi);
void bdi_destroy(struct backing_dev_info *bdi);
static inline void __add_bdi_stat(struct backing_dev_info *bdi,
enum bdi_stat_item item, s64 amount)
{
__percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
}
static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
enum bdi_stat_item item)
{
__add_bdi_stat(bdi, item, 1);
}
static inline void inc_bdi_stat(struct backing_dev_info *bdi,
enum bdi_stat_item item)
{
unsigned long flags;
local_irq_save(flags);
__inc_bdi_stat(bdi, item);
local_irq_restore(flags);
}
static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
enum bdi_stat_item item)
{
__add_bdi_stat(bdi, item, -1);
}
static inline void dec_bdi_stat(struct backing_dev_info *bdi,
enum bdi_stat_item item)
{
unsigned long flags;
local_irq_save(flags);
__dec_bdi_stat(bdi, item);
local_irq_restore(flags);
}
static inline s64 bdi_stat(struct backing_dev_info *bdi,
enum bdi_stat_item item)
{
return percpu_counter_read_positive(&bdi->bdi_stat[item]);
}
static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
enum bdi_stat_item item)
{
return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
}
static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
enum bdi_stat_item item)
{
s64 sum;
unsigned long flags;
local_irq_save(flags);
sum = __bdi_stat_sum(bdi, item);
local_irq_restore(flags);
return sum;
}
/*
* maximal error of a stat counter.
*/
static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
{
#ifdef CONFIG_SMP
return nr_cpu_ids * BDI_STAT_BATCH;
#else
return 1;
#endif
}
/*
* Flags in backing_dev_info::capability
* - The first two flags control whether dirty pages will contribute to the
* VM's accounting and whether writepages() should be called for dirty pages
* (something that would not, for example, be appropriate for ramfs)
* - These flags let !MMU mmap() govern direct device mapping vs immediate
* copying more easily for MAP_PRIVATE, especially for ROM filesystems
*/
#define BDI_CAP_NO_ACCT_DIRTY 0x00000001 /* Dirty pages shouldn't contribute to accounting */
#define BDI_CAP_NO_WRITEBACK 0x00000002 /* Don't write pages back */
#define BDI_CAP_MAP_COPY 0x00000004 /* Copy can be mapped (MAP_PRIVATE) */
#define BDI_CAP_MAP_DIRECT 0x00000008 /* Can be mapped directly (MAP_SHARED) */
#define BDI_CAP_READ_MAP 0x00000010 /* Can be mapped for reading */
#define BDI_CAP_WRITE_MAP 0x00000020 /* Can be mapped for writing */
#define BDI_CAP_EXEC_MAP 0x00000040 /* Can be mapped for execution */
#define BDI_CAP_VMFLAGS \
(BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
#if defined(VM_MAYREAD) && \
(BDI_CAP_READ_MAP != VM_MAYREAD || \
BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
BDI_CAP_EXEC_MAP != VM_MAYEXEC)
#error please change backing_dev_info::capabilities flags
#endif
extern struct backing_dev_info default_backing_dev_info;
void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
int writeback_acquire(struct backing_dev_info *bdi);
int writeback_in_progress(struct backing_dev_info *bdi);
void writeback_release(struct backing_dev_info *bdi);
static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
{
if (bdi->congested_fn)
return bdi->congested_fn(bdi->congested_data, bdi_bits);
return (bdi->state & bdi_bits);
}
static inline int bdi_read_congested(struct backing_dev_info *bdi)
{
return bdi_congested(bdi, 1 << BDI_read_congested);
}
static inline int bdi_write_congested(struct backing_dev_info *bdi)
{
return bdi_congested(bdi, 1 << BDI_write_congested);
}
static inline int bdi_rw_congested(struct backing_dev_info *bdi)
{
return bdi_congested(bdi, (1 << BDI_read_congested)|
(1 << BDI_write_congested));
}
void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
void set_bdi_congested(struct backing_dev_info *bdi, int rw);
long congestion_wait(int rw, long timeout);
#define bdi_cap_writeback_dirty(bdi) \
(!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
#define bdi_cap_account_dirty(bdi) \
(!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
#define mapping_cap_writeback_dirty(mapping) \
bdi_cap_writeback_dirty((mapping)->backing_dev_info)
#define mapping_cap_account_dirty(mapping) \
bdi_cap_account_dirty((mapping)->backing_dev_info)
#endif /* _LINUX_BACKING_DEV_H */
