From ad6e3ea683ef4086cdf3d2ec40cb3f6e62edb945 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Tue, 28 Oct 2025 09:45:51 +0100 Subject: [PATCH] pidfs: prepare to drop exit_info pointer There will likely be more info that we need to store in struct pidfs_attr. We need to make sure that some of the information such as exit info or coredump info that consists of multiple bits is either available completely or not at all, but never partially. Currently we use a pointer that we assign to. That doesn't scale. We can't waste a pointer for each mulit-part information struct we want to expose. Use a bitmask instead. Link: https://patch.msgid.link/20251028-work-coredump-signal-v1-6-ca449b7b7aa0@kernel.org Reviewed-by: Alexander Mikhalitsyn Reviewed-by: Oleg Nesterov Signed-off-by: Christian Brauner --- fs/pidfs.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/pidfs.c b/fs/pidfs.c index 204ebd32791a..0fad0c969b7a 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -49,7 +49,12 @@ struct pidfs_exit_info { __u32 coredump_mask; }; +enum pidfs_attr_mask_bits { + PIDFS_ATTR_BIT_EXIT = 0, +}; + struct pidfs_attr { + unsigned long attr_mask; struct simple_xattrs *xattrs; struct pidfs_exit_info __pei; struct pidfs_exit_info *exit_info; @@ -333,8 +338,8 @@ static long pidfd_info(struct file *file, unsigned int cmd, unsigned long arg) attr = READ_ONCE(pid->attr); if (mask & PIDFD_INFO_EXIT) { - exit_info = READ_ONCE(attr->exit_info); - if (exit_info) { + if (test_bit(PIDFS_ATTR_BIT_EXIT, &attr->attr_mask)) { + smp_rmb(); kinfo.mask |= PIDFD_INFO_EXIT; #ifdef CONFIG_CGROUPS kinfo.cgroupid = exit_info->cgroupid; @@ -663,7 +668,8 @@ void pidfs_exit(struct task_struct *tsk) exit_info->exit_code = tsk->exit_code; /* Ensure that PIDFD_GET_INFO sees either all or nothing. */ - smp_store_release(&attr->exit_info, &attr->__pei); + smp_wmb(); + set_bit(PIDFS_ATTR_BIT_EXIT, &attr->attr_mask); } #ifdef CONFIG_COREDUMP