Collaboration diagram for Parity Math Component:

Modules
	Incremental recovery APIs

Data Structures
struct	m0_sns_ir_block

struct	m0_reed_solomon

struct	m0_parity_math

struct	m0_sns_ir

Enumerations
enum	m0_parity_cal_algo { M0_PARITY_CAL_ALGO_XOR, M0_PARITY_CAL_ALGO_REED_SOLOMON, M0_PARITY_CAL_ALGO_NR }

enum	m0_sns_ir_block_status { M0_SI_BLOCK_ALIVE, M0_SI_BLOCK_FAILED }

enum	m0_sns_ir_block_type { M0_SI_BLOCK_LOCAL, M0_SI_BLOCK_REMOTE }

enum	m0_parity_linsys_algo { M0_LA_GAUSSIAN, M0_LA_INVERSE }

Functions
M0_INTERNAL int	m0_parity_math_init (struct m0_parity_math *math, uint32_t data_count, uint32_t parity_count)

M0_INTERNAL void	m0_parity_math_fini (struct m0_parity_math *math)

M0_INTERNAL void	m0_parity_math_calculate (struct m0_parity_math math, struct m0_buf data, struct m0_buf *parity)

M0_INTERNAL int	m0_parity_math_diff (struct m0_parity_math math, struct m0_buf old_ver, struct m0_buf new_ver, struct m0_buf parity, uint32_t index)

M0_INTERNAL void	m0_parity_math_refine (struct m0_parity_math math, struct m0_buf data, struct m0_buf *parity, uint32_t data_ind_changed)

M0_INTERNAL int	m0_parity_math_recover (struct m0_parity_math math, struct m0_buf data, struct m0_buf parity, struct m0_buf fails, enum m0_parity_linsys_algo algo)

M0_INTERNAL void	m0_parity_math_fail_index_recover (struct m0_parity_math math, struct m0_buf data, struct m0_buf *parity, const uint32_t failure_index)

M0_INTERNAL void	m0_parity_math_buffer_xor (struct m0_buf dest, const struct m0_buf src)

Detailed Description

A parity math component is a part of Motr core and serving several purposes:

Provide algorithms for calculation of SNS parity units (checksums) for given data units;
Provide algorithms for quick update of parity units in case of minor data changes;
Provide algorithms for SNS repair (recovery) in case of failure.

Enumeration Type Documentation

◆ m0_parity_cal_algo

enum m0_parity_cal_algo

Parity calculation type indicating various algorithms of parity calculation.

Enumerator
M0_PARITY_CAL_ALGO_XOR
M0_PARITY_CAL_ALGO_REED_SOLOMON
M0_PARITY_CAL_ALGO_NR

Definition at line 49 of file parity_math.h.

◆ m0_parity_linsys_algo

enum m0_parity_linsys_algo

Enumerator
M0_LA_GAUSSIAN
M0_LA_INVERSE

Definition at line 65 of file parity_math.h.

◆ m0_sns_ir_block_status

enum m0_sns_ir_block_status

Enumerator
M0_SI_BLOCK_ALIVE
M0_SI_BLOCK_FAILED

Definition at line 55 of file parity_math.h.

◆ m0_sns_ir_block_type

enum m0_sns_ir_block_type

Enumerator
M0_SI_BLOCK_LOCAL
M0_SI_BLOCK_REMOTE

Definition at line 60 of file parity_math.h.

Function Documentation

◆ m0_parity_math_buffer_xor()

M0_INTERNAL void m0_parity_math_buffer_xor	(	struct m0_buf *	dest,
		const struct m0_buf *	src
	)

XORs the source and destination buffers and stores the output in destination buffer.

Parameters

dest	- destination buffer, treated as uint8_t block with b_nob elements, containing the output of src XOR dest.
src	- source buffer, treated as uint8_t block with b_nob elements.

Definition at line 415 of file parity_math.c.

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◆ m0_parity_math_calculate()

M0_INTERNAL void m0_parity_math_calculate	(	struct m0_parity_math *	math,
		struct m0_buf *	data,
		struct m0_buf *	parity
	)

Calculates parity block data.

Parameters

[in]	data	- data block, treated as uint8_t block with b_nob elements.
[out]	parity	- parity block, treated as uint8_t block with b_nob elements.

Precondition: m0_parity_math_init() succeeded.

Definition at line 362 of file parity_math.c.

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◆ m0_parity_math_diff()

M0_INTERNAL int m0_parity_math_diff	(	struct m0_parity_math *	math,
		struct m0_buf *	old_ver,
		struct m0_buf *	new_ver,
		struct m0_buf *	parity,
		uint32_t	index
	)

Calculates parity in a differential manner.

Precondition: math != NULL && old_ver != NULL && new_ver != NULL && parity != NULL && index < math->pmi_parity_count

Parameters

old_ver	Old version of data block.
new_ver	New version of data block.
parity	Parity block.
index	Index of data unit in parity group for which old and new versions are sent.

Definition at line 371 of file parity_math.c.

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◆ m0_parity_math_fail_index_recover()

M0_INTERNAL void m0_parity_math_fail_index_recover	(	struct m0_parity_math *	math,
		struct m0_buf *	data,
		struct m0_buf *	parity,
		const uint32_t	failure_index
	)

Recovers data or parity units partially or fully depending on the parity calculation algorithm, given the failure index.

Parameters

math	- math context.
data	- data block, treated as uint8_t block with b_nob elements.
parity	- parity block, treated as uint8_t block with b_nob elements.
failure_index	- Index of the failed block.

Precondition: m0_parity_math_init() succeeded.

Definition at line 396 of file parity_math.c.

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◆ m0_parity_math_fini()

M0_INTERNAL void m0_parity_math_fini ( struct m0_parity_math * math )

Deinitialization of parity math algorithms. Frees all memory blocks allocated by m0_parity_math_init().

Definition at line 325 of file parity_math.c.

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◆ m0_parity_math_init()

M0_INTERNAL int m0_parity_math_init	(	struct m0_parity_math *	math,
		uint32_t	data_count,
		uint32_t	parity_count
	)

Initialization of parity math algorithms. Fills '*math' with appropriate values.

Parameters

data_count	- count of SNS data units used in system.
parity_count	- count of SNS parity units used in system.

Definition at line 333 of file parity_math.c.

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◆ m0_parity_math_recover()

M0_INTERNAL int m0_parity_math_recover	(	struct m0_parity_math *	math,
		struct m0_buf *	data,
		struct m0_buf *	parity,
		struct m0_buf *	fails,
		enum m0_parity_linsys_algo	algo
	)

Recovers data units' data words from single or multiple errors. If parity also needs to be recovered, user of the function needs to place a separate call for m0_parity_math_calculate().

Parameters

[in,out]	data	- data block, treated as uint8_t block with b_nob elements.
[in,out]	parity	- parity block, treated as uint8_t block with b_nob elements.
[in]	fails	- block with flags, treated as uint8_t block with b_nob elements, if element is '1' then data or parity block with given index is treated as broken.
[in]	algo	- algorithm for recovery of data in case reed solomon encoding is used.

Precondition: m0_parity_math_init() succeeded.

Definition at line 383 of file parity_math.c.

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◆ m0_parity_math_refine()

M0_INTERNAL void m0_parity_math_refine	(	struct m0_parity_math *	math,
		struct m0_buf *	data,
		struct m0_buf *	parity,
		uint32_t	data_ind_changed
	)

Parity block refinement iff one data word of one data unit had changed.

Parameters

[in]	data	- data block, treated as uint8_t block with b_nob elements.
[out]	parity	- parity block, treated as uint8_t block with b_nob elements.
[in]	data_ind_changed	- index of data unit recently changed.

Precondition: m0_parity_math_init() succeeded.

Definition at line 406 of file parity_math.c.

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Modules

Data Structures

Enumerations

Functions

Detailed Description

Enumeration Type Documentation

◆ m0_parity_cal_algo

◆ m0_parity_linsys_algo

◆ m0_sns_ir_block_status

◆ m0_sns_ir_block_type

Function Documentation

◆ m0_parity_math_buffer_xor()

◆ m0_parity_math_calculate()

◆ m0_parity_math_diff()

◆ m0_parity_math_fail_index_recover()

◆ m0_parity_math_fini()

◆ m0_parity_math_init()

◆ m0_parity_math_recover()

◆ m0_parity_math_refine()