[Ocfs2-devel] [PATCH v2] ocfs2: fix warning 'ocfs2_orphan_del' uses dynamic stack allocation

[Andrew Morton]

On Mon, 26 Jan 2015 11:20:47 +0800 Joseph Qi <joseph.qi at huawei.com> wrote:

> In ocfs2_orphan_del it uses dynamic stack allocation for orphan entry
> name. Fix it by using dynamic heap allocation.
> 
> ...
>
> --- a/fs/ocfs2/namei.c
> +++ b/fs/ocfs2/namei.c
> @@ -2298,18 +2298,22 @@ int ocfs2_orphan_del(struct ocfs2_super *osb,
>  {
>  	int namelen = dio ? OCFS2_DIO_ORPHAN_PREFIX_LEN + OCFS2_ORPHAN_NAMELEN :
>  			OCFS2_ORPHAN_NAMELEN;
> -	char name[namelen + 1];
> +	char *name;
>  	struct ocfs2_dinode *orphan_fe;
>  	int status = 0;
>  	struct ocfs2_dir_lookup_result lookup = { NULL, };
> 
> +	name = kmalloc(namelen + 1, GFP_NOFS);
> +	if (!name)
> +		goto leave;
> +
>  	if (dio) {
>  		status = snprintf(name, OCFS2_DIO_ORPHAN_PREFIX_LEN + 1, "%s",
>  				OCFS2_DIO_ORPHAN_PREFIX);
>  		if (status != OCFS2_DIO_ORPHAN_PREFIX_LEN) {
>  			status = -EINVAL;
>  			mlog_errno(status);
> -			return status;
> +			goto leave;
>  		}
> 
>  		status = ocfs2_blkno_stringify(OCFS2_I(inode)->ip_blkno,
> @@ -2357,6 +2361,7 @@ int ocfs2_orphan_del(struct ocfs2_super *osb,
>  	ocfs2_journal_dirty(handle, orphan_dir_bh);
> 
>  leave:
> +	kfree(name);
>  	ocfs2_free_dir_lookup_result(&lookup);
> 
>  	if (status)

I think I prefer my fix:

--- a/fs/ocfs2/namei.c~ocfs2-add-functions-to-add-and-remove-inode-in-orphan-dir-fix
+++ a/fs/ocfs2/namei.c
@@ -2296,8 +2296,7 @@ int ocfs2_orphan_del(struct ocfs2_super
 		     struct buffer_head *orphan_dir_bh,
 		     bool dio)
 {
-	int namelen = dio ? OCFS2_DIO_ORPHAN_PREFIX_LEN + OCFS2_ORPHAN_NAMELEN :
-			OCFS2_ORPHAN_NAMELEN;
+	const int namelen = OCFS2_DIO_ORPHAN_PREFIX_LEN + OCFS2_ORPHAN_NAMELEN;
 	char name[namelen + 1];
 	struct ocfs2_dinode *orphan_fe;
 	int status = 0;

It means we use 20 bytes of stack all the time, instead of
sometimes-20, sometimes-16.