4.4-stable review patch. If anyone has any objections, please let me know.
------------------ [ Upstream commit b45cdbaf9f7f0486847c52f60747fb108724652a ] If an async error interrupt is generated, and the error requires the FC link to be reset, it cannot be performed in the interrupt context. So a work element is scheduled to complete the link reset in a process context. If either an EEH event or an escalation occurs in between when the interrupt is generated and the scheduled work is started, the MMIO space may no longer be available. This will cause an oops in the worker thread. [ 606.806583] NIP kthread_data+0x28/0x40 [ 606.806633] LR wq_worker_sleeping+0x30/0x100 [ 606.806694] Call Trace: [ 606.806721] 0x50 (unreliable) [ 606.806796] wq_worker_sleeping+0x30/0x100 [ 606.806884] __schedule+0x69c/0x8a0 [ 606.806959] schedule+0x44/0xc0 [ 606.807034] do_exit+0x770/0xb90 [ 606.807109] die+0x300/0x460 [ 606.807185] bad_page_fault+0xd8/0x150 [ 606.807259] handle_page_fault+0x2c/0x30 [ 606.807338] wait_port_offline.constprop.12+0x60/0x130 [cxlflash] To prevent the problem space area from being unmapped, when there is pending work, a mapcount (using the kref mechanism) is held. The mapcount is released only when the work is completed. The last reference release is tied to the unmapping service. Signed-off-by: Manoj N. Kumar <[email protected]> Acked-by: Matthew R. Ochs <[email protected]> Reviewed-by: Uma Krishnan <[email protected]> Signed-off-by: Martin K. Petersen <[email protected]> Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/scsi/cxlflash/common.h | 2 ++ drivers/scsi/cxlflash/main.c | 27 ++++++++++++++++++++++++--- 2 files changed, 26 insertions(+), 3 deletions(-) --- a/drivers/scsi/cxlflash/common.h +++ b/drivers/scsi/cxlflash/common.h @@ -165,6 +165,8 @@ struct afu { struct sisl_host_map __iomem *host_map; /* MC host map */ struct sisl_ctrl_map __iomem *ctrl_map; /* MC control map */ + struct kref mapcount; + ctx_hndl_t ctx_hndl; /* master's context handle */ u64 *hrrq_start; u64 *hrrq_end; --- a/drivers/scsi/cxlflash/main.c +++ b/drivers/scsi/cxlflash/main.c @@ -368,6 +368,7 @@ out: no_room: afu->read_room = true; + kref_get(&cfg->afu->mapcount); schedule_work(&cfg->work_q); rc = SCSI_MLQUEUE_HOST_BUSY; goto out; @@ -473,6 +474,16 @@ out: return rc; } +static void afu_unmap(struct kref *ref) +{ + struct afu *afu = container_of(ref, struct afu, mapcount); + + if (likely(afu->afu_map)) { + cxl_psa_unmap((void __iomem *)afu->afu_map); + afu->afu_map = NULL; + } +} + /** * cxlflash_driver_info() - information handler for this host driver * @host: SCSI host associated with device. @@ -503,6 +514,7 @@ static int cxlflash_queuecommand(struct ulong lock_flags; short lflag = 0; int rc = 0; + int kref_got = 0; dev_dbg_ratelimited(dev, "%s: (scp=%p) %d/%d/%d/%llu " "cdb=(%08X-%08X-%08X-%08X)\n", @@ -547,6 +559,9 @@ static int cxlflash_queuecommand(struct goto out; } + kref_get(&cfg->afu->mapcount); + kref_got = 1; + cmd->rcb.ctx_id = afu->ctx_hndl; cmd->rcb.port_sel = port_sel; cmd->rcb.lun_id = lun_to_lunid(scp->device->lun); @@ -587,6 +602,8 @@ static int cxlflash_queuecommand(struct } out: + if (kref_got) + kref_put(&afu->mapcount, afu_unmap); pr_devel("%s: returning rc=%d\n", __func__, rc); return rc; } @@ -661,6 +678,7 @@ static void stop_afu(struct cxlflash_cfg cxl_psa_unmap((void __iomem *)afu->afu_map); afu->afu_map = NULL; } + kref_put(&afu->mapcount, afu_unmap); } } @@ -746,8 +764,8 @@ static void cxlflash_remove(struct pci_d scsi_remove_host(cfg->host); /* fall through */ case INIT_STATE_AFU: - term_afu(cfg); cancel_work_sync(&cfg->work_q); + term_afu(cfg); case INIT_STATE_PCI: pci_release_regions(cfg->dev); pci_disable_device(pdev); @@ -1331,6 +1349,7 @@ static irqreturn_t cxlflash_async_err_ir __func__, port); cfg->lr_state = LINK_RESET_REQUIRED; cfg->lr_port = port; + kref_get(&cfg->afu->mapcount); schedule_work(&cfg->work_q); } @@ -1351,6 +1370,7 @@ static irqreturn_t cxlflash_async_err_ir if (info->action & SCAN_HOST) { atomic_inc(&cfg->scan_host_needed); + kref_get(&cfg->afu->mapcount); schedule_work(&cfg->work_q); } } @@ -1746,6 +1766,7 @@ static int init_afu(struct cxlflash_cfg rc = -ENOMEM; goto err1; } + kref_init(&afu->mapcount); /* No byte reverse on reading afu_version or string will be backwards */ reg = readq(&afu->afu_map->global.regs.afu_version); @@ -1780,8 +1801,7 @@ out: return rc; err2: - cxl_psa_unmap((void __iomem *)afu->afu_map); - afu->afu_map = NULL; + kref_put(&afu->mapcount, afu_unmap); err1: term_mc(cfg, UNDO_START); goto out; @@ -2354,6 +2374,7 @@ static void cxlflash_worker_thread(struc if (atomic_dec_if_positive(&cfg->scan_host_needed) >= 0) scsi_scan_host(cfg->host); + kref_put(&afu->mapcount, afu_unmap); } /**
