ref: 02044e5668850757a17a2ba0a1f41754f96fde7e
dir: /extents.h/
/*
An ordered linked list sorted by block number (->low, ->high).
->big or ->small sorted by size and then block number.
This is similar in functionality to pool(2).
Extents are used to manage contiguous space (such as memory space and disk space).
The space is is split into units of the same size (quantum).
The scaling of the addresses (start) by the unit is the responsibility
of the client.
All space is split into a sequence of units. Each such sequence of units
is called an Extent. The data structure Extents is used to contain this
information. Space is added to the Extents using ufree() and allocated
using ualloc(). When freed, adjacent extents are coalesced to create a
large extent, if they are continuous.
Debugging
Verbosity induces the dumping of the pool via p->print at each lock operation.
By default, only one line is logged for each qalloc and qfree.
*/
#pragma lib "libextents.a"
enum
{
Nlru = 32,
/* flags */
Everbose = 1,
Edebug = 2,
};
typedef signed char s8;
typedef signed short s16;
typedef signed int s32;
typedef signed long long s64;
typedef unsigned char u8;
typedef unsigned short u16;
typedef unsigned int u32;
typedef unsigned long long u64;
typedef struct Extent Extent;
typedef struct Extents Extents;
/*
When allocating blocks from extents:
1. Of all the extents with the len we need, pick the extent with the lowest blkno.
2. If no extent of the len we need is available, then break up the smallest extent.
When freeing blocks, it tries to merge with the neighbours to become bigger extents.
*/
struct Extents {
char name[32];
void (*flush)(void);/* flush when nothing is available */
u8 linger; /* wait until something becomes available */
u8 loglevel; /* Everbose or Edebug */
u32 logfd;
int (*log)(int fd, char *fmt, ...);
void (*panic)(char *fmt, ...);
void *(*malloc)(u32 sz); /* as 9p servers use a different malloc */
/* private and derived */
Extent *lowest; /* find the first block number in a jiffy */
QLock lck;
u64 n; /* number of extents */
Rendez isempty; /* fully used, nothing available */
u8 nlru; /* number of items in the lru linked list */
Extent *lru; /* least recently used extent in the circular lru linked list */
};
struct Extent {
struct Extent *low, *high; /* sorted by start */
struct Extent *small, *big; /* sorted by the number of blocks in this extent */
u64 start; /* where this extent starts from */
u64 len; /* how many units in this extent */
/* circular least recently used linked list limited to Nlru items */
struct Extent *prev, *next;
};
void initextents(Extents *es, char *name, u8 linger, u8 loglevel, u32 logfd, void (*flush)(void), int (*log)(int fd, char *fmt, ...), void (*panic)(char *fmt, ...), void *(*malloc)(u32 sz));
void freeextents(Extents *es);
/* allocate n quanta */
s8 ualloc(Extents *es, u64 n, u64 *start);
void ufree(Extents *es, u64 start, u64 len);/* free len units starting from start */
u64 nfrees(Extents *es);
Extents *holes(Extents *es, Extents *inv);
void showblocknos(int fd, Extents *es);
void showextents(int fd, char *msg, Extents *es);
void showextentslists(int fd, char *msg, Extents *es);
void showextentspointers(int fd, char *msg, Extents *es);
s32 sizeofextents(Extents *es);
s32 sizeoftxtextents(Extents *es);
s32 saveextents(Extents *es, s8 *buf, u32 nbuf);
s32 savetxtextents(Extents *es, s8 *buf, u32 nbuf);
s32 loadextents(Extents *es, s8 *buf, u32 nbuf);