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Correct raid_scan documentation on candidate search and return semantics

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Andrea Mazzoleni 2026-08-20 20:56:48 +02:00
parent ecb26a6aee
commit e5ca862a37
2 changed files with 17 additions and 6 deletions
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9
raid/README
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@ -62,9 +62,12 @@ detect CPU capabilities and initialize mode dispatch.
int raid_scan(int *ir, int nd, int np, size_t size, void **v)
Searches for up to 'np - 1' failed blocks using available redundancy.
Each block pointed to by 'v' must be aligned to a 64-byte boundary.
Fills 'ir' with failed block indexes and returns the number of failures
found (0 if no error), or -1 if failed blocks cannot be uniquely located.
Candidates are tested with an increasing number of failures, and the
first combination matching the redundancy is returned. If multiple
combinations match, the first one encountered is returned without
checking uniqueness. Each block pointed to by 'v' must be aligned to a
64-byte boundary. Fills 'ir' with the matching block indexes and returns
their number (0 if no error), or -1 if no compatible combination is found.
int raid_selftest(void)
Runs startup verification tests for parity generation, recovery, and

14
raid/raid.h
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@ -267,8 +267,16 @@ int raid_check(int nr, int *ir, int nd, int np, size_t size, void **v);
/**
* Scan for failed blocks.
*
* This function identifies the failed data and parity blocks using the
* available redundancy.
* This function searches for a set of failed data and parity blocks
* compatible with the available redundancy.
*
* It first checks for no failures, and then tries candidate combinations
* with an increasing number of failures, from 1 up to @np - 1. The first
* combination satisfying the redundancy information is returned.
*
* If multiple combinations satisfy the redundancy information, only the
* first one encountered is returned. This function does not check that the
* returned combination is unique.
*
* It uses a brute force method, and then the call can be expensive.
* The expected execution time is proportional to the binomial coefficient
@ -299,7 +307,7 @@ int raid_check(int nr, int *ir, int nd, int np, size_t size, void **v);
* Each block has @size bytes and must be aligned to a 64-byte boundary.
* @return Number of block indexes returned in the @ir vector.
* 0 if no error is detected.
* -1 if it's not possible to identify the failed disks.
* -1 if no compatible combination with fewer than @np failures is found.
*/
int raid_scan(int *ir, int nd, int np, size_t size, void **v);