Occasionally, FC HBAs might lose track of the status of the attached remote ports. This will cause I/O to be stuck and the FC HBAs to invoke the error handler, which will take _LONG_ to complete (we're speaking hours here). This patch implements a 'suspend path' mechanism in multipath for handling these situations. Key point is to have a writeable 'port_state' sysfs attribute for the remote ports. This is introduced by the patch 'scsi_transport_fc: Make 'port_state' writeable' posted to linux-scsi. There are two ways of suspending a path, either by a path checker returning 'PATH_TIMEOUT', or by the user invoking the new CLI command 'suspend path'. This will then set the 'port_state' attribute to 'blocked', causing the 'fast_io_fail' mechanism to trigger. This will eventually cause all outstanding I/O to be aborted and result in a quick failover. Paths will be resumed either from the FC HBA when a new RSCN state update is recieved from the SAN, or by the user by calling the new CLI command 'resume path'. Signed-off-by: Hannes Reinecke <hare@xxxxxxx> Hannes Reinecke (6): libmultipath: return PATH_DOWN for quiesced paths libmultipath: Implement PATH_TIMEOUT libmultipath: improve debugging messages in sysfs_attr_set_value() libmultipath: Implement sysfs_attr_get_value() libmultipath: Implement sysfs_set_fc_rport_state() multipathd: Implement 'suspend/resume path' libmultipath/checkers.h | 5 ++++ libmultipath/checkers/tur.c | 2 +- libmultipath/discovery.c | 65 ++++++++++++++++++++++++++++++++++++++++++- libmultipath/discovery.h | 1 + libmultipath/print.c | 4 +++ libmultipath/sysfs.c | 64 ++++++++++++++++++++++++++++++++++++++++-- libmultipath/sysfs.h | 2 ++ multipathd/cli.c | 2 ++ multipathd/cli_handlers.c | 50 +++++++++++++++++++++++++++++++++ multipathd/cli_handlers.h | 2 ++ multipathd/main.c | 7 +++++ 11 files changed, 200 insertions(+), 4 deletions(-) -- 1.7.10.4 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
