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We periodically check the available rt blocks when filling up zones
and start GC if needed, but we may run completely out in between
filling zones, so start GC(unless already running) if we can't reserve
writable space.
This should only happen as a corner case in setups with very few
backing zones.
Fixes: 080d01c41d44 ("xfs: implement zoned garbage collection")
Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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RT groups on a zoned file system need to be completely empty before their
space can be reused. This means that partially empty groups need to be
emptied entirely to free up space if no entirely free groups are
available.
Add a garbage collection thread that moves all data out of the least used
zone when not enough free zones are available, and which resets all zones
that have been emptied. To find empty zone a simple set of 10 buckets
based on the amount of space used in the zone is used. To empty zones,
the rmap is walked to find the owners and the data is read and then
written to the new place.
To automatically defragment files the rmap records are sorted by inode
and logical offset. This means defragmentation of parallel writes into
a single zone happens automatically when performing garbage collection.
Because holding the iolock over the entire GC cycle would inject very
noticeable latency for other accesses to the inodes, the iolock is not
taken while performing I/O. Instead the I/O completion handler checks
that the mapping hasn't changed over the one recorded at the start of
the GC cycle and doesn't update the mapping if it change.
Co-developed-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
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For zoned file systems garbage collection (GC) has to take the iolock
and mmaplock after moving data to a new place to synchronize with
readers. This means waiting for garbage collection with the iolock can
deadlock.
To avoid this, the worst case required blocks have to be reserved before
taking the iolock, which is done using a new RTAVAILABLE counter that
tracks blocks that are free to write into and don't require garbage
collection. The new helpers try to take these available blocks, and
if there aren't enough available it wakes and waits for GC. This is
done using a list of on-stack reservations to ensure fairness.
Co-developed-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
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