scsi: Rework handling of scsi_device.vpd_pg8[03]
authorBart Van Assche <bart.vanassche@wdc.com>
Tue, 29 Aug 2017 15:50:13 +0000 (08:50 -0700)
committerMartin K. Petersen <martin.petersen@oracle.com>
Wed, 30 Aug 2017 01:51:42 +0000 (21:51 -0400)
commitccf1e0045eea8f98d60fc9327bcb14c958d2e4c7
treebc32bc41b24ce324d06deec7528c3310db49ddcd
parent1e3f720a67c29e145321ed9b4ef7a83e6416d201
scsi: Rework handling of scsi_device.vpd_pg8[03]

Introduce struct scsi_vpd for the VPD page length, data and the RCU head
that will be used to free the VPD data. Use kfree_rcu() instead of
kfree() to free VPD data. Move the VPD buffer pointer check inside the
RCU read lock in the sysfs code. Only annotate pointers that are shared
across threads with __rcu. Use rcu_dereference() when dereferencing an
RCU pointer. This patch suppresses about twenty sparse complaints about
the vpd_pg8[03] pointers. This patch also fixes a race condition, namely
that updating of the VPD pointers and length variables in struct
scsi_device was not atomic with reference to the code reading these
variables. See also "Does the update code tolerate concurrent accesses?"
in Documentation/RCU/checklist.txt.

Fixes: commit 09e2b0b14690 ("scsi: rescan VPD attributes")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Acked-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Shane Seymour <shane.seymour@hpe.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Shane Seymour <shane.seymour@hpe.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
drivers/scsi/scsi.c
drivers/scsi/scsi_lib.c
drivers/scsi/scsi_sysfs.c
include/scsi/scsi_device.h