Hi all, based on the ideas from Doug Gilbert here's now my take on using xarrays for devices and targets. It revolves around two ideas: - The scsi target 'channel' and 'id' numbers are never ever used to the full 32 bit range; channels are well below 10, and no driver is using more than 16 bits for the id. So we can reduce the type of 'channel' and 'id' to 16 bits, and use the 32 bit value 'channel << 16 | id' as the index into the target xarray. - Most SCSI LUNs are below 256 (to ensure compability with older systems). So there we can use the LUN number as the index into the xarray; for larger LUN numbers we'll allocate a separate index. With these changes we can implement an efficient lookup mechanism, devolving into direct lookup for most cases. And iteration should be as efficient as the current, list-based, approach. This patchset now survives basic testing, hence I've removed the 'RFC' tag from the initial patchset. Changes to v1: - Fixup __scsi_iterate_devices() - Include reviews from Johannes - Minor fixes - Include comments from Doug Changes to v2: - Reshuffle hunks as per suggestion from Johannes Hannes Reinecke (4): scsi: convert target lookup to xarray target_core_pscsi: use __scsi_device_lookup() scsi: move target device list to xarray scsi: remove direct device lookup per host drivers/scsi/hosts.c | 3 +- drivers/scsi/scsi.c | 131 ++++++++++++++++++++++++++++--------- drivers/scsi/scsi_lib.c | 9 ++- drivers/scsi/scsi_scan.c | 66 ++++++++----------- drivers/scsi/scsi_sysfs.c | 42 ++++++++---- drivers/target/target_core_pscsi.c | 8 +-- include/scsi/scsi_device.h | 21 +++--- include/scsi/scsi_host.h | 5 +- 8 files changed, 179 insertions(+), 106 deletions(-) -- 2.16.4
