[PATCH] dcache: use kmalloc_flex() in __d_alloc

[PATCH] dcache: use kmalloc_flex() in __d_alloc

[Thorsten Blum]

Use kmalloc_flex() when allocating a new 'struct external_name' in
__d_alloc() to replace offsetof() and the open-coded size arithmetic,
and to keep the size type-safe.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 fs/dcache.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index dbcbd0affb26..4568f9530166 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1753,10 +1753,10 @@ static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 		name = &slash_name;
 		dname = dentry->d_shortname.string;
 	} else if (name->len > DNAME_INLINE_LEN-1) {
-		size_t size = offsetof(struct external_name, name[1]);
-		struct external_name *p = kmalloc(size + name->len,
-						  GFP_KERNEL_ACCOUNT |
-						  __GFP_RECLAIMABLE);
+		struct external_name *p;
+
+		p = kmalloc_flex(*p, name, name->len + 1,
+				 GFP_KERNEL_ACCOUNT | __GFP_RECLAIMABLE);
 		if (!p) {
 			kmem_cache_free(dentry_cache, dentry); 
 			return NULL;

Re: [PATCH] dcache: use kmalloc_flex() in __d_alloc

[Jori Koolstra]

On Fri, Apr 17, 2026 at 11:42:40AM +0200, Thorsten Blum wrote:
> Use kmalloc_flex() when allocating a new 'struct external_name' in
> __d_alloc() to replace offsetof() and the open-coded size arithmetic,
> and to keep the size type-safe.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
>  fs/dcache.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/dcache.c b/fs/dcache.c
> index dbcbd0affb26..4568f9530166 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -1753,10 +1753,10 @@ static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
>  		name = &slash_name;
>  		dname = dentry->d_shortname.string;
>  	} else if (name->len > DNAME_INLINE_LEN-1) {
> -		size_t size = offsetof(struct external_name, name[1]);
> -		struct external_name *p = kmalloc(size + name->len,
> -						  GFP_KERNEL_ACCOUNT |
> -						  __GFP_RECLAIMABLE);
> +		struct external_name *p;
> +
> +		p = kmalloc_flex(*p, name, name->len + 1,
> +				 GFP_KERNEL_ACCOUNT | __GFP_RECLAIMABLE);
>  		if (!p) {
>  			kmem_cache_free(dentry_cache, dentry); 
>  			return NULL;

Looks reasonable to me. Is the idea to completely outphase this old way
of requesting memory for structs with flexible array members?

Feel free to add:

Reviewed-by: Jori Koolstra <jkoolstra@xs4all.nl>