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scsi: Rework handling of scsi_device.vpd_pg8[03]

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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 09e2b0b146 ("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>
This commit is contained in:
Bart Van Assche
2017-08-29 08:50:13 -07:00
committed by Martin K. Petersen
parent 1e3f720a67
commit ccf1e0045e
4 changed files with 60 additions and 47 deletions
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16
drivers/scsi/scsi_lib.c
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@@ -3272,8 +3272,8 @@ int scsi_vpd_lun_id(struct scsi_device *sdev, char *id, size_t id_len)
{
u8 cur_id_type = 0xff;
u8 cur_id_size = 0;
unsigned char *d, *cur_id_str;
unsigned char __rcu *vpd_pg83;
const unsigned char *d, *cur_id_str;
const struct scsi_vpd *vpd_pg83;
int id_size = -EINVAL;
rcu_read_lock();
@@ -3304,8 +3304,8 @@ int scsi_vpd_lun_id(struct scsi_device *sdev, char *id, size_t id_len)
}
memset(id, 0, id_len);
d = vpd_pg83 + 4;
while (d < vpd_pg83 + sdev->vpd_pg83_len) {
d = vpd_pg83->data + 4;
while (d < vpd_pg83->data + vpd_pg83->len) {
/* Skip designators not referring to the LUN */
if ((d[1] & 0x30) != 0x00)
goto next_desig;
@@ -3421,8 +3421,8 @@ EXPORT_SYMBOL(scsi_vpd_lun_id);
*/
int scsi_vpd_tpg_id(struct scsi_device *sdev, int *rel_id)
{
unsigned char *d;
unsigned char __rcu *vpd_pg83;
const unsigned char *d;
const struct scsi_vpd *vpd_pg83;
int group_id = -EAGAIN, rel_port = -1;
rcu_read_lock();
@@ -3432,8 +3432,8 @@ int scsi_vpd_tpg_id(struct scsi_device *sdev, int *rel_id)
return -ENXIO;
}
d = sdev->vpd_pg83 + 4;
while (d < sdev->vpd_pg83 + sdev->vpd_pg83_len) {
d = vpd_pg83->data + 4;
while (d < vpd_pg83->data + vpd_pg83->len) {
switch (d[1] & 0xf) {
case 0x4:
/* Relative target port */