[PATCH 0/2] xfs: fix stale disk exposure after crash

Darrick J. Wong
2020-01-16T06:15:59Z

Hi all,

These two patches try to shrink the window during which a crash during
writeback can expose stale disk contents. The first patch causes
delalloc reservations to be converted to unwritten extents for any
writeback that's going on within EOF.

The second patch selectively relaxes the unwritten writeout requirement
when the entire file is being flushed (ala fsync) and ensures that
writeback of a range after the ondisk EOF is expanded downwards to the
old EOF to ensure that increasing a file's size doesn't leave us
vulnerable to exposure of stale disk contents from a previous
speculative allocation.

This solves the regressions in generic/536 and generic/042.

If you're going to start using this mess, you probably ought to just
pull from my git trees, which are linked below.

This has been lightly tested with fstests. Enjoy!
Comments and questions are, as always, welcome.

--D