include/linux/crush/crush.h

Source file repositories/reference/linux-study-clean/include/linux/crush/crush.h

File Facts

System
Linux kernel
Corpus path
include/linux/crush/crush.h
Extension
.h
Size
11076 bytes
Lines
361
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

struct crush_rule_step {
	__u32 op;
	__s32 arg1;
	__s32 arg2;
};

/* step op codes */
enum {
	CRUSH_RULE_NOOP = 0,
	CRUSH_RULE_TAKE = 1,          /* arg1 = value to start with */
	CRUSH_RULE_CHOOSE_FIRSTN = 2, /* arg1 = num items to pick */
				      /* arg2 = type */
	CRUSH_RULE_CHOOSE_INDEP = 3,  /* same */
	CRUSH_RULE_EMIT = 4,          /* no args */
	CRUSH_RULE_CHOOSELEAF_FIRSTN = 6,
	CRUSH_RULE_CHOOSELEAF_INDEP = 7,

	CRUSH_RULE_SET_CHOOSE_TRIES = 8, /* override choose_total_tries */
	CRUSH_RULE_SET_CHOOSELEAF_TRIES = 9, /* override chooseleaf_descend_once */
	CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES = 10,
	CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES = 11,
	CRUSH_RULE_SET_CHOOSELEAF_VARY_R = 12,
	CRUSH_RULE_SET_CHOOSELEAF_STABLE = 13
};

/*
 * for specifying choose num (arg1) relative to the max parameter
 * passed to do_rule
 */
#define CRUSH_CHOOSE_N            0
#define CRUSH_CHOOSE_N_MINUS(x)   (-(x))

/*
 * The rule mask is used to describe what the rule is intended for.
 * Given a ruleset and size of output set, we search through the
 * rule list for a matching rule_mask.
 */
struct crush_rule_mask {
	__u8 ruleset;
	__u8 type;
	__u8 min_size;
	__u8 max_size;
};

struct crush_rule {
	__u32 len;
	struct crush_rule_mask mask;
	struct crush_rule_step steps[];
};

#define crush_rule_size(len) (sizeof(struct crush_rule) + \
			      (len)*sizeof(struct crush_rule_step))



/*
 * A bucket is a named container of other items (either devices or
 * other buckets).  Items within a bucket are chosen using one of a
 * few different algorithms.  The table summarizes how the speed of
 * each option measures up against mapping stability when items are
 * added or removed.
 *
 *  Bucket Alg     Speed       Additions    Removals
 *  ------------------------------------------------
 *  uniform         O(1)       poor         poor
 *  list            O(n)       optimal      poor
 *  tree            O(log n)   good         good
 *  straw           O(n)       better       better
 *  straw2          O(n)       optimal      optimal
 */
enum {
	CRUSH_BUCKET_UNIFORM = 1,
	CRUSH_BUCKET_LIST = 2,
	CRUSH_BUCKET_TREE = 3,
	CRUSH_BUCKET_STRAW = 4,
	CRUSH_BUCKET_STRAW2 = 5,
};
extern const char *crush_bucket_alg_name(int alg);

/*
 * although tree was a legacy algorithm, it has been buggy, so
 * exclude it.
 */
#define CRUSH_LEGACY_ALLOWED_BUCKET_ALGS (	\
		(1 << CRUSH_BUCKET_UNIFORM) |	\
		(1 << CRUSH_BUCKET_LIST) |	\
		(1 << CRUSH_BUCKET_STRAW))

struct crush_bucket {
	__s32 id;        /* this'll be negative */

Annotation

Implementation Notes