Hi F2FS experts,
The following confuses me:

A typical fsync() goes like this:
1) Issue data block IOs
2) Wait for completion
3) Issue chained node block IOs
4) Wait for completion
5) Issue flush command

In order to preserve data consistency under sudden power failure, it requires 
that the storage device persists data blocks prior to node blocks.
Otherwise, under sudden power failure, it's possible that the persisted node 
block points to NULL data blocks.

However, according to this study 
(https://www.usenix.org/conference/fast18/presentation/won), the persistent 
order of requests doesn't necessarily equals to the request finish order (due 
to device volatile caches). This means that its possible that the node blocks 
get persisted prior to data blocks.

Does F2FS have other mechanisms to prevent such inconsistency? Or does it 
require the device to persist data without reordering?


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