linux-kernel - [PATCH v2 4/6] powerpc: book3s: vas: use lock guard for mutex

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Message-ID: <20250314114502.2083434-5-sshegde@linux.ibm.com>
Date: Fri, 14 Mar 2025 17:15:00 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: maddy@...ux.ibm.com, linuxppc-dev@...ts.ozlabs.org
Cc: sshegde@...ux.ibm.com, npiggin@...il.com, christophe.leroy@...roup.eu,
        mpe@...erman.id.au, peterz@...radead.org, fbarrat@...ux.ibm.com,
        ajd@...ux.ibm.com, mahesh@...ux.ibm.com, oohall@...il.com,
        hbathini@...ux.ibm.com, dhowells@...hat.com, haren@...ux.ibm.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 4/6] powerpc: book3s: vas: use lock guard for mutex

use lock guards for scope based resource management of mutex.
This would make the code simpler and easier to maintain.

More details on lock guards can be found at
https://lore.kernel.org/all/20230612093537.614161713@infradead.org/T/#u

This shows the use of both guard and scoped_guard

Signed-off-by: Shrikanth Hegde <sshegde@...ux.ibm.com>
---
 arch/powerpc/platforms/book3s/vas-api.c | 32 ++++++++++---------------
 1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c
index 0b6365d85d11..d7462c16d828 100644
--- a/arch/powerpc/platforms/book3s/vas-api.c
+++ b/arch/powerpc/platforms/book3s/vas-api.c
@@ -425,23 +425,22 @@ static vm_fault_t vas_mmap_fault(struct vm_fault *vmf)
 		return VM_FAULT_SIGBUS;
 	}
 
-	mutex_lock(&txwin->task_ref.mmap_mutex);
 	/*
 	 * The window may be inactive due to lost credit (Ex: core
 	 * removal with DLPAR). If the window is active again when
 	 * the credit is available, map the new paste address at the
 	 * window virtual address.
 	 */
-	if (txwin->status == VAS_WIN_ACTIVE) {
-		paste_addr = cp_inst->coproc->vops->paste_addr(txwin);
-		if (paste_addr) {
-			fault = vmf_insert_pfn(vma, vma->vm_start,
-					(paste_addr >> PAGE_SHIFT));
-			mutex_unlock(&txwin->task_ref.mmap_mutex);
-			return fault;
+	scoped_guard(mutex, &txwin->task_ref.mmap_mutex) {
+		if (txwin->status == VAS_WIN_ACTIVE) {
+			paste_addr = cp_inst->coproc->vops->paste_addr(txwin);
+			if (paste_addr) {
+				fault = vmf_insert_pfn(vma, vma->vm_start,
+						(paste_addr >> PAGE_SHIFT));
+				return fault;
+			}
 		}
 	}
-	mutex_unlock(&txwin->task_ref.mmap_mutex);
 
 	/*
 	 * Received this fault due to closing the actual window.
@@ -494,9 +493,8 @@ static void vas_mmap_close(struct vm_area_struct *vma)
 		return;
 	}
 
-	mutex_lock(&txwin->task_ref.mmap_mutex);
-	txwin->task_ref.vma = NULL;
-	mutex_unlock(&txwin->task_ref.mmap_mutex);
+	scoped_guard(mutex, &txwin->task_ref.mmap_mutex)
+		txwin->task_ref.vma = NULL;
 }
 
 static const struct vm_operations_struct vas_vm_ops = {
@@ -543,18 +541,16 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
 	 * close/open event and allows mmap() only when the window is
 	 * active.
 	 */
-	mutex_lock(&txwin->task_ref.mmap_mutex);
+	guard(mutex)(&txwin->task_ref.mmap_mutex);
 	if (txwin->status != VAS_WIN_ACTIVE) {
 		pr_err("Window is not active\n");
-		rc = -EACCES;
-		goto out;
+		return -EACCES;
 	}
 
 	paste_addr = cp_inst->coproc->vops->paste_addr(txwin);
 	if (!paste_addr) {
 		pr_err("Window paste address failed\n");
-		rc = -EINVAL;
-		goto out;
+		return -EINVAL;
 	}
 
 	pfn = paste_addr >> PAGE_SHIFT;
@@ -574,8 +570,6 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
 	txwin->task_ref.vma = vma;
 	vma->vm_ops = &vas_vm_ops;
 
-out:
-	mutex_unlock(&txwin->task_ref.mmap_mutex);
 	return rc;
 }
 
-- 
2.39.3