From:   Vernon Yang <vernon2gm@gmail.com>
To:     torvalds@linux-foundation.org, tytso@mit.edu, Jason@zx2c4.com,
        davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
        pabeni@redhat.com, jejb@linux.ibm.com, martin.petersen@oracle.com,
        yury.norov@gmail.com, andriy.shevchenko@linux.intel.com,
        linux@rasmusvillemoes.dk, james.smart@broadcom.com,
        dick.kennedy@broadcom.com
Cc:     linux-kernel@vger.kernel.org, wireguard@lists.zx2c4.com,
        netdev@vger.kernel.org, linux-scsi@vger.kernel.org,
        Vernon Yang <vernon2gm@gmail.com>
Subject: [PATCH v2 3/4] scsi: lpfc: fix lpfc_cpu_affinity_check() if no further cpus set
Date:   Tue,  7 Mar 2023 05:03:11 +0800
Message-Id: <20230306210312.2614988-4-vernon2gm@gmail.com>
In-Reply-To: <20230306210312.2614988-1-vernon2gm@gmail.com>
References: <20230306210312.2614988-1-vernon2gm@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

When cpumask_next() the return value is greater than or equal to
nr_cpu_ids, it indicates invalid.

Before commit 596ff4a09b89 ("cpumask: re-introduce constant-sized cpumask
optimizations"), when cpumask_next() returned an invalid cpu, the driver
used the judgment equal to nr_cpu_ids to indicate the invalid cpu, so it
happened to work normally, but this is the wrong approach.

After commit 596ff4a09b89 ("cpumask: re-introduce constant-sized cpumask
optimizations"), these incorrect practices actively buggy, so fix it to
correctly.

Signed-off-by: Vernon Yang <vernon2gm@gmail.com>
---
 drivers/scsi/lpfc/lpfc_init.c | 43 ++++++++++++++++-------------------
 1 file changed, 20 insertions(+), 23 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_init.c b/drivers/scsi/lpfc/lpfc_init.c
index 61958a24a43d..acfffdbe9ba1 100644
--- a/drivers/scsi/lpfc/lpfc_init.c
+++ b/drivers/scsi/lpfc/lpfc_init.c
@@ -12473,6 +12473,16 @@ lpfc_hba_eq_hdl_array_init(struct lpfc_hba *phba)
 	}
 }
 
+static inline int lpfc_next_present_cpu(int n, int first_cpu)
+{
+	n = cpumask_next(n, cpu_present_mask);
+
+	if (n >= nr_cpu_ids)
+		n = first_cpu;
+
+	return n;
+}
+
 /**
  * lpfc_cpu_affinity_check - Check vector CPU affinity mappings
  * @phba: pointer to lpfc hba data structure.
@@ -12561,10 +12571,8 @@ lpfc_cpu_affinity_check(struct lpfc_hba *phba, int vectors)
 				    (new_cpup->eq != LPFC_VECTOR_MAP_EMPTY) &&
 				    (new_cpup->phys_id == cpup->phys_id))
 					goto found_same;
-				new_cpu = cpumask_next(
-					new_cpu, cpu_present_mask);
-				if (new_cpu == nr_cpumask_bits)
-					new_cpu = first_cpu;
+
+				new_cpu = lpfc_next_present_cpu(new_cpu, first_cpu);
 			}
 			/* At this point, we leave the CPU as unassigned */
 			continue;
@@ -12576,9 +12584,7 @@ lpfc_cpu_affinity_check(struct lpfc_hba *phba, int vectors)
 			 * chance of having multiple unassigned CPU entries
 			 * selecting the same IRQ.
 			 */
-			start_cpu = cpumask_next(new_cpu, cpu_present_mask);
-			if (start_cpu == nr_cpumask_bits)
-				start_cpu = first_cpu;
+			start_cpu = lpfc_next_present_cpu(new_cpu, first_cpu);
 
 			lpfc_printf_log(phba, KERN_INFO, LOG_INIT,
 					"3337 Set Affinity: CPU %d "
@@ -12611,10 +12617,8 @@ lpfc_cpu_affinity_check(struct lpfc_hba *phba, int vectors)
 				if (!(new_cpup->flag & LPFC_CPU_MAP_UNASSIGN) &&
 				    (new_cpup->eq != LPFC_VECTOR_MAP_EMPTY))
 					goto found_any;
-				new_cpu = cpumask_next(
-					new_cpu, cpu_present_mask);
-				if (new_cpu == nr_cpumask_bits)
-					new_cpu = first_cpu;
+
+				new_cpu = lpfc_next_present_cpu(new_cpu, first_cpu);
 			}
 			/* We should never leave an entry unassigned */
 			lpfc_printf_log(phba, KERN_ERR, LOG_INIT,
@@ -12630,9 +12634,7 @@ lpfc_cpu_affinity_check(struct lpfc_hba *phba, int vectors)
 			 * chance of having multiple unassigned CPU entries
 			 * selecting the same IRQ.
 			 */
-			start_cpu = cpumask_next(new_cpu, cpu_present_mask);
-			if (start_cpu == nr_cpumask_bits)
-				start_cpu = first_cpu;
+			start_cpu = lpfc_next_present_cpu(new_cpu, first_cpu);
 
 			lpfc_printf_log(phba, KERN_INFO, LOG_INIT,
 					"3338 Set Affinity: CPU %d "
@@ -12703,9 +12705,8 @@ lpfc_cpu_affinity_check(struct lpfc_hba *phba, int vectors)
 			    new_cpup->core_id == cpup->core_id) {
 				goto found_hdwq;
 			}
-			new_cpu = cpumask_next(new_cpu, cpu_present_mask);
-			if (new_cpu == nr_cpumask_bits)
-				new_cpu = first_cpu;
+
+			new_cpu = lpfc_next_present_cpu(new_cpu, first_cpu);
 		}
 
 		/* If we can't match both phys_id and core_id,
@@ -12718,9 +12719,7 @@ lpfc_cpu_affinity_check(struct lpfc_hba *phba, int vectors)
 			    new_cpup->phys_id == cpup->phys_id)
 				goto found_hdwq;
 
-			new_cpu = cpumask_next(new_cpu, cpu_present_mask);
-			if (new_cpu == nr_cpumask_bits)
-				new_cpu = first_cpu;
+			new_cpu = lpfc_next_present_cpu(new_cpu, first_cpu);
 		}
 
 		/* Otherwise just round robin on cfg_hdw_queue */
@@ -12729,9 +12728,7 @@ lpfc_cpu_affinity_check(struct lpfc_hba *phba, int vectors)
 		goto logit;
  found_hdwq:
 		/* We found an available entry, copy the IRQ info */
-		start_cpu = cpumask_next(new_cpu, cpu_present_mask);
-		if (start_cpu == nr_cpumask_bits)
-			start_cpu = first_cpu;
+		start_cpu = lpfc_next_present_cpu(new_cpu, first_cpu);
 		cpup->hdwq = new_cpup->hdwq;
  logit:
 		lpfc_printf_log(phba, KERN_INFO, LOG_INIT,
-- 
2.34.1