Introduce a private inode slab cache for pidfs. In follow-up patches pidfs will gain the ability to provide exit information to userspace after the task has been reaped. This means storing exit information even after the task has already been released and struct pid's task linkage is gone. Store that information alongside the inode. Link: https://lore.kernel.org/r/20250304-work-pidfs-kill_on_last_close-v2-4-44fdacfaa7b7@xxxxxxxxxx Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx> --- fs/pidfs.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) diff --git a/fs/pidfs.c b/fs/pidfs.c index ecc0dd886714..282511a36fd9 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; + __s32 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
