Zygo Blaxell cbc76a7457 hash: don't spin when writes fail ...

When a hash table write fails, we skip over the write throttling because
we didn't report that we successfully wrote an extent.  This can be bad
if the filesystem is full and the allocations for writes are burning a
lot of CPU time searching for free space.

We also don't retry the write later on since we assume the extent is
clean after a write attempt whether it was successful or not, so the
extent might not be written out later when writes are possible again.

Check whether a hash extent is dirty, and always throttle after
attempting the write.

If a write fails, leave the extent dirty so we attempt to write it out
the next time flush cycles through the hash table.  During shutdown
this will reattempt each failing write once, after that the updated hash
table data will be dropped.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

2023-01-23 00:09:26 -05:00

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