INFRA Signal 425
Linux 7.2-rc7 Restoring Btrfs Fixup Worker Infrastructure To Address Silent Data Loss
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Linux 7.2-rc7 restores the Btrfs COW fixup worker infrastructure that was removed earlier to prevent silent data loss.
Without the fixup worker, Btrfs could miss dirty pages that lack an ordered extent, leading to silent data loss. Restoring the mechanism reinstates detection of those conditions. This reduces the risk of unnoticed corruption in Btrfs deployments.
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The Btrfs COW fixup mechanism was dropped during the Linux 7.2 merge window.
Its removal was based on the assumption that the kernel's memory management layer had resolved the underlying issue.
Linux 7.2-rc7 restores the fixup worker infrastructure to address the resulting silent data loss.
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The change reintroduces the Btrfs fixup worker infrastructure in the Linux 7.2-rc7 kernel release. This infrastructure had been previously removed during the 7.2 merge window. The restoration is a direct response to the silent data loss issue that appeared after its removal.
During the merge window, developers removed the COW fixup mechanism because they believed the kernel's memory management layer had already solved the conditions that required it. That belief proved incorrect, as the underlying condition persisted without the fixup worker.
The fixup worker's role is to detect dirty pages that are not associated with an ordered extent, a situation that can lead to silent data corruption if left unchecked. By restoring this detection capability, the kernel can again identify and handle those dirty pages appropriately.
Systems that remain on kernel versions prior to 7.2-rc7 continue to lack this detection mechanism and therefore remain exposed to the risk of silent data loss. Adopting the fix requires moving to a kernel that includes the restored fixup worker infrastructure.
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