3db2bd548a
This patch adds some improvements to the way the trim module considers
TXGs:
- Free ZIOs are registered with the TXG from the ZIO itself, not the
current SPA syncing TXG (which may be out of date);
- L2ARC are registered with a zero TXG number, as L2ARC has no concept
of TXGs;
- The TXG limit for issuing TRIMs is now computed from the last synced
TXG, not the currently syncing TXG. Indeed, under extremely unlikely
race conditions, there is a risk we could trim blocks which have been
freed in a TXG that has not finished syncing, resulting in potential
data corruption in case of a crash.
Reviewed by: pjd (mentor)
Approved by: pjd (mentor)
Obtained from: 5b46ad40d9
MFC after: 2 weeks
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