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authorJulian Wiedmann <jwi@linux.ibm.com>2020-09-10 21:49:16 +0200
committerMartin K. Petersen <martin.petersen@oracle.com>2020-09-15 18:01:58 -0400
commitd251193d17321d44f96b78d9bb4c8b8ea6786e72 (patch)
tree29a65f1cc3abd73acae28d3e2944215efc3eeb60 /drivers/s390/scsi
parentaddf1372961523cc8cb7ab4ee26d5e1373bf64a0 (diff)
scsi: zfcp: Clarify access to erp_action in zfcp_fsf_req_complete()
While reviewing commit 936e6b85da04 ("scsi: zfcp: Fix panic on ERP timeout for previously dismissed ERP action"), I stumbled over zfcp_fsf_req_complete() and wondered whether it has similar issues wrt concurrent modification of req->erp_action by zfcp_erp_strategy_check_fsfreq(). But a closer look shows that both its two callers [zfcp_fsf_reqid_check(), zfcp_fsf_req_dismiss_all()] remove the request from the adapter's req_list under the req_list's lock. Hence we can trust that if zfcp_erp_strategy_check_fsfreq() concurrently looks up the corresponding req_id, it won't find this request and is thus unable to modify it while it's being processed by zfcp_fsf_req_complete(). Add a code comment that hopefully makes this easier for future readers, and condense the two accesses to ->erp_action that made me trip over this code path in the first place. Link: https://lore.kernel.org/r/c500eac301fcbba5af942bbd200f2d6b14e46994.1599765652.git.bblock@linux.ibm.com Reviewed-by: Steffen Maier <maier@linux.ibm.com> Reviewed-by: Benjamin Block <bblock@linux.ibm.com> Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com> Signed-off-by: Benjamin Block <bblock@linux.ibm.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/s390/scsi')
-rw-r--r--drivers/s390/scsi/zfcp_fsf.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c
index 140186fe1d1e..6cb963a06777 100644
--- a/drivers/s390/scsi/zfcp_fsf.c
+++ b/drivers/s390/scsi/zfcp_fsf.c
@@ -426,9 +426,14 @@ static void zfcp_fsf_protstatus_eval(struct zfcp_fsf_req *req)
* or it has been dismissed due to a queue shutdown, this function
* is called to process the completion status and trigger further
* events related to the FSF request.
+ * Caller must ensure that the request has been removed from
+ * adapter->req_list, to protect against concurrent modification
+ * by zfcp_erp_strategy_check_fsfreq().
*/
static void zfcp_fsf_req_complete(struct zfcp_fsf_req *req)
{
+ struct zfcp_erp_action *erp_action;
+
if (unlikely(zfcp_fsf_req_is_status_read_buffer(req))) {
zfcp_fsf_status_read_handler(req);
return;
@@ -439,8 +444,9 @@ static void zfcp_fsf_req_complete(struct zfcp_fsf_req *req)
zfcp_fsf_fsfstatus_eval(req);
req->handler(req);
- if (req->erp_action)
- zfcp_erp_notify(req->erp_action, 0);
+ erp_action = req->erp_action;
+ if (erp_action)
+ zfcp_erp_notify(erp_action, 0);
if (likely(req->status & ZFCP_STATUS_FSFREQ_CLEANUP))
zfcp_fsf_req_free(req);