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

From: Shrikanth Hegde
Date: Fri Mar 14 2025 - 01:46:55 EST


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