[PATCH 2/6] powerpc: rtas: use lock guard for mutex

[Shrikanth Hegde]

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@xxxxxxxxxxxxx/T/#u

Signed-off-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
---
 arch/powerpc/kernel/rtas_flash.c | 64 ++++++++++----------------------
 1 file changed, 20 insertions(+), 44 deletions(-)

diff --git a/arch/powerpc/kernel/rtas_flash.c b/arch/powerpc/kernel/rtas_flash.c
index 5407024881e5..583dc16e9d3c 100644
--- a/arch/powerpc/kernel/rtas_flash.c
+++ b/arch/powerpc/kernel/rtas_flash.c
@@ -312,13 +312,13 @@ static ssize_t rtas_flash_write(struct file *file, const char __user *buffer,
 {
 	struct rtas_update_flash_t *const uf = &rtas_update_flash_data;
 	char *p;
-	int next_free, rc;
+	int next_free;
 	struct flash_block_list *fl;
 
-	mutex_lock(&rtas_update_flash_mutex);
+	guard(mutex)(&rtas_update_flash_mutex);
 
 	if (uf->status == FLASH_AUTH || count == 0)
-		goto out;	/* discard data */
+		return count;	/* discard data */
 
 	/* In the case that the image is not ready for flashing, the memory
 	 * allocated for the block list will be freed upon the release of the 
@@ -327,7 +327,7 @@ static ssize_t rtas_flash_write(struct file *file, const char __user *buffer,
 	if (uf->flist == NULL) {
 		uf->flist = kmem_cache_zalloc(flash_block_cache, GFP_KERNEL);
 		if (!uf->flist)
-			goto nomem;
+			return -ENOMEM;
 	}
 
 	fl = uf->flist;
@@ -338,7 +338,7 @@ static ssize_t rtas_flash_write(struct file *file, const char __user *buffer,
 		/* Need to allocate another block_list */
 		fl->next = kmem_cache_zalloc(flash_block_cache, GFP_KERNEL);
 		if (!fl->next)
-			goto nomem;
+			return -ENOMEM;
 		fl = fl->next;
 		next_free = 0;
 	}
@@ -347,25 +347,17 @@ static ssize_t rtas_flash_write(struct file *file, const char __user *buffer,
 		count = RTAS_BLK_SIZE;
 	p = kmem_cache_zalloc(flash_block_cache, GFP_KERNEL);
 	if (!p)
-		goto nomem;
+		return -ENOMEM;
 	
 	if(copy_from_user(p, buffer, count)) {
 		kmem_cache_free(flash_block_cache, p);
-		rc = -EFAULT;
-		goto error;
+		return -EFAULT;
 	}
 	fl->blocks[next_free].data = p;
 	fl->blocks[next_free].length = count;
 	fl->num_blocks++;
-out:
-	mutex_unlock(&rtas_update_flash_mutex);
-	return count;
 
-nomem:
-	rc = -ENOMEM;
-error:
-	mutex_unlock(&rtas_update_flash_mutex);
-	return rc;
+	return count;
 }
 
 /*
@@ -405,19 +397,18 @@ static ssize_t manage_flash_write(struct file *file, const char __user *buf,
 	static const char reject_str[] = "0";
 	static const char commit_str[] = "1";
 	char stkbuf[10];
-	int op, rc;
+	int op;
 
-	mutex_lock(&rtas_manage_flash_mutex);
+	guard(mutex)(&rtas_manage_flash_mutex);
 
 	if ((args_buf->status == MANAGE_AUTH) || (count == 0))
-		goto out;
+		return count;
 		
 	op = -1;
 	if (buf) {
 		if (count > 9) count = 9;
-		rc = -EFAULT;
 		if (copy_from_user (stkbuf, buf, count))
-			goto error;
+			return -EFAULT;
 		if (strncmp(stkbuf, reject_str, strlen(reject_str)) == 0) 
 			op = RTAS_REJECT_TMP_IMG;
 		else if (strncmp(stkbuf, commit_str, strlen(commit_str)) == 0) 
@@ -425,18 +416,11 @@ static ssize_t manage_flash_write(struct file *file, const char __user *buf,
 	}
 	
 	if (op == -1) {   /* buf is empty, or contains invalid string */
-		rc = -EINVAL;
-		goto error;
+		return -EINVAL;
 	}
 
 	manage_flash(args_buf, op);
-out:
-	mutex_unlock(&rtas_manage_flash_mutex);
 	return count;
-
-error:
-	mutex_unlock(&rtas_manage_flash_mutex);
-	return rc;
 }
 
 /*
@@ -499,16 +483,14 @@ static ssize_t validate_flash_write(struct file *file, const char __user *buf,
 {
 	struct rtas_validate_flash_t *const args_buf =
 		&rtas_validate_flash_data;
-	int rc;
 
-	mutex_lock(&rtas_validate_flash_mutex);
+	guard(mutex)(&rtas_validate_flash_mutex);
 
 	/* We are only interested in the first 4K of the
 	 * candidate image */
 	if ((*off >= VALIDATE_BUF_SIZE) || 
 		(args_buf->status == VALIDATE_AUTH)) {
 		*off += count;
-		mutex_unlock(&rtas_validate_flash_mutex);
 		return count;
 	}
 
@@ -519,20 +501,14 @@ static ssize_t validate_flash_write(struct file *file, const char __user *buf,
 		args_buf->status = VALIDATE_INCOMPLETE;
 	}
 
-	if (!access_ok(buf, count)) {
-		rc = -EFAULT;
-		goto done;
-	}
-	if (copy_from_user(args_buf->buf + *off, buf, count)) {
-		rc = -EFAULT;
-		goto done;
-	}
+	if (!access_ok(buf, count))
+		return -EFAULT;
+
+	if (copy_from_user(args_buf->buf + *off, buf, count))
+		return -EFAULT;
 
 	*off += count;
-	rc = count;
-done:
-	mutex_unlock(&rtas_validate_flash_mutex);
-	return rc;
+	return count;
 }
 
 static int validate_flash_release(struct inode *inode, struct file *file)
-- 
2.39.3