Atomic Test And Set Of Disk Block Returned False For Equality -

A return of false is a safe failure. It guarantees that the caller did not proceed under the assumption that they had exclusive access. This preserves data integrity. If the operation had erroneously returned true while another process held the lock, a race condition would occur, leading to data corruption on the disk block.

You may have computed the expected value incorrectly—for example, using a stale version number. Recompute the expected value by re-reading the block immediately before TAS, not relying on cached data more than a few milliseconds old.

Scenario: A node caches disk block values but fails to invalidate the cache after a write from another node.
Result: The node issues a test-and-set based on stale data, causing an unexpected failure.
Solution: Disable aggressive caching for shared block devices; use O_DIRECT or O_SYNC where appropriate. A return of false is a safe failure

When applying Atomic Test-and-Set to a "disk block," the scenario typically falls into one of two architectural patterns:

The Test-and-Set instruction is defined by the following atomic (indivisible) sequence: Check vendor release notes for terms like "COMPARE

If a dead node left a reservation, clear it:

# Register a new key
sg_persist -o -G -K 0x12345678 /dev/sdX
Many "false for equality" errors stem from firmware bugs in: " or "reservation."

Check vendor release notes for terms like "COMPARE AND WRITE," "atomic," or "reservation."