[PATCH RFC 04/10] pidfs: add inode allocation

[Christian Brauner <brauner@kernel.org>]

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 61be98f7ad0b..64428697996f 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;
+};
+
+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");

-- 
2.47.2