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| author | Julian Wiedmann <jwi@linux.ibm.com> | 2020-09-10 21:49:16 +0200 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2020-09-16 00:01:58 +0200 |
| commit | d251193d17321d44f96b78d9bb4c8b8ea6786e72 (patch) | |
| tree | 29a65f1cc3abd73acae28d3e2944215efc3eeb60 | |
| parent | scsi: zfcp: Use list_first_entry_or_null() in zfcp_erp_thread() (diff) | |
| download | linux-d251193d17321d44f96b78d9bb4c8b8ea6786e72.tar.xz linux-d251193d17321d44f96b78d9bb4c8b8ea6786e72.zip | |
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>
| -rw-r--r-- | drivers/s390/scsi/zfcp_fsf.c | 10 |
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); |