On Fri, 16 Aug 2024 09:44:30 -0500 ira.weiny@xxxxxxxxx wrote: > From: Navneet Singh <navneet.singh@xxxxxxxxx> > > Dynamic capacity device extents may be left in an accepted state on a > device due to an unexpected host crash. In this case it is expected > that the creation of a new region on top of a DC partition can read > those extents and surface them for continued use. > > Once all endpoint decoders are part of a region and the region is being > realized a read of the devices extent list can reveal these previously > accepted extents. > > CXL r3.1 specifies the mailbox call Get Dynamic Capacity Extent List for > this purpose. The call returns all the extents for all dynamic capacity > partitions. If the fabric manager is adding extents to any DCD > partition, the extent list for the recovered region may change. In this > case the query must retry. Upon retry the query could encounter extents > which were accepted on a previous list query. Adding such extents is > ignored without error because they are entirely within a previous > accepted extent. > > The scan for existing extents races with the dax_cxl driver. This is > synchronized through the region device lock. Extents which are found > after the driver has loaded will surface through the normal notification > path while extents seen prior to the driver are read during driver load. Ah. So the earlier code to just eat duplicates was to handle this race. Add a comment there perhaps so people like me get less confused :) Jonathan > > Signed-off-by: Navneet Singh <navneet.singh@xxxxxxxxx> > Co-developed-by: Ira Weiny <ira.weiny@xxxxxxxxx> > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> LGTM Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
