[PATCH 4/6] powerpc: book3s: vas: use lock guard for mutex

[Shrikanth Hegde <sshegde@linux.ibm.com>]

use guard(mutex) 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

There is also an example of using scoped_guard. 

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
 arch/powerpc/platforms/book3s/vas-api.c | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c
index 0b6365d85d11..eb1a97271afb 100644
--- a/arch/powerpc/platforms/book3s/vas-api.c
+++ b/arch/powerpc/platforms/book3s/vas-api.c
@@ -425,7 +425,7 @@ static vm_fault_t vas_mmap_fault(struct vm_fault *vmf)
 		return VM_FAULT_SIGBUS;
 	}
 
-	mutex_lock(&txwin->task_ref.mmap_mutex);
+	guard(mutex)(&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
@@ -437,11 +437,9 @@ static vm_fault_t vas_mmap_fault(struct vm_fault *vmf)
 		if (paste_addr) {
 			fault = vmf_insert_pfn(vma, vma->vm_start,
 					(paste_addr >> PAGE_SHIFT));
-			mutex_unlock(&txwin->task_ref.mmap_mutex);
 			return fault;
 		}
 	}
-	mutex_unlock(&txwin->task_ref.mmap_mutex);
 
 	/*
 	 * Received this fault due to closing the actual window.
@@ -494,9 +492,8 @@ 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 +540,16 @@ 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 +569,6 @@ 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