Re: [PATCH v2 04/15] pidfs: add inode allocation

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2025-03-04 at 10:41 +0100, Christian Brauner wrote:
> Signed-off-by: Christian Brauner <brauner@kernel.org>
> ---
>  fs/pidfs.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
> 
> diff --git a/fs/pidfs.c b/fs/pidfs.c
> index ecc0dd886714..eaecb0a947f0 100644
> --- a/fs/pidfs.c
> +++ b/fs/pidfs.c
> @@ -24,6 +24,27 @@
>  #include "internal.h"
>  #include "mount.h"
>  
> +static struct kmem_cache *pidfs_cachep __ro_after_init;
> +
> +/*
> + * Stashes information that userspace needs to access even after the
> + * process has been reaped.
> + */
> +struct pidfs_exit_info {
> +	__u64 cgroupid;
> +	__u64 exit_code;

This is changed to __s32 in the next patch. Might as well do that here.

> +};
> +
> +struct pidfs_inode {
> +	struct pidfs_exit_info exit_info;
> +	struct inode vfs_inode;
> +};
> +
> +static inline struct pidfs_inode *pidfs_i(struct inode *inode)
> +{
> +	return container_of(inode, struct pidfs_inode, vfs_inode);
> +}
> +
>  static struct rb_root pidfs_ino_tree = RB_ROOT;
>  
>  #if BITS_PER_LONG == 32
> @@ -492,9 +513,29 @@ static void pidfs_evict_inode(struct inode *inode)
>  	put_pid(pid);
>  }
>  
> +static struct inode *pidfs_alloc_inode(struct super_block *sb)
> +{
> +	struct pidfs_inode *pi;
> +
> +	pi = alloc_inode_sb(sb, pidfs_cachep, GFP_KERNEL);
> +	if (!pi)
> +		return NULL;
> +
> +	memset(&pi->exit_info, 0, sizeof(pi->exit_info));
> +
> +	return &pi->vfs_inode;
> +}
> +
> +static void pidfs_free_inode(struct inode *inode)
> +{
> +	kmem_cache_free(pidfs_cachep, pidfs_i(inode));
> +}
> +
>  static const struct super_operations pidfs_sops = {
> +	.alloc_inode	= pidfs_alloc_inode,
>  	.drop_inode	= generic_delete_inode,
>  	.evict_inode	= pidfs_evict_inode,
> +	.free_inode	= pidfs_free_inode,
>  	.statfs		= simple_statfs,
>  };
>  
> @@ -704,8 +745,19 @@ struct file *pidfs_alloc_file(struct pid *pid, unsigned int flags)
>  	return pidfd_file;
>  }
>  
> +static void pidfs_inode_init_once(void *data)
> +{
> +	struct pidfs_inode *pi = data;
> +
> +	inode_init_once(&pi->vfs_inode);
> +}
> +
>  void __init pidfs_init(void)
>  {
> +	pidfs_cachep = kmem_cache_create("pidfs_cache", sizeof(struct pidfs_inode), 0,
> +					 (SLAB_HWCACHE_ALIGN | SLAB_RECLAIM_ACCOUNT |
> +					  SLAB_ACCOUNT | SLAB_PANIC),
> +					 pidfs_inode_init_once);
>  	pidfs_mnt = kern_mount(&pidfs_type);
>  	if (IS_ERR(pidfs_mnt))
>  		panic("Failed to mount pidfs pseudo filesystem");
> 

Reviewed-by: Jeff Layton <jlayton@kernel.org>