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fs: add filp_close_sync()

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Currently close() already does a synchronous release of the last
reference since the task is about to return to userspace and the
deferral through task work buys nothing. Add a filp_close_sync() helper.
We'll use that in the next patches.

No functional changes.

Link: https://patch.msgid.link/20260910-work-coredump-unlock-self-v4-5-a5c1800dc930@kernel.org
Reviewed-by: NeilBrown <neil@brown.name>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2026-09-10 17:48:03 +02:00
parent 5fe5e24a8f
commit 2b256ebe82
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GPG Key ID: 91C61BC06578DCA2
2 changed files with 15 additions and 3 deletions
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1
fs/internal.h
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@ -198,6 +198,7 @@ extern struct file *do_file_open_root(const struct path *,
extern struct open_how build_open_how(int flags, umode_t mode);
extern int build_open_flags(const struct open_how *how, struct open_flags *op);
struct file *file_close_fd_locked(struct files_struct *files, unsigned fd);
int filp_close_sync(struct file *filp, fl_owner_t id);
int do_ftruncate(struct file *file, loff_t length, unsigned int flags);
int chmod_common(const struct path *path, umode_t mode);

17
fs/open.c
View File

@ -1537,6 +1537,19 @@ int filp_close(struct file *filp, fl_owner_t id)
}
EXPORT_SYMBOL(filp_close);
/* Like filp_close() but the last reference is put right here. */
int filp_close_sync(struct file *filp, fl_owner_t id)
{
int retval;
/* Kernel threads must never put their final reference here. */
VFS_WARN_ON_ONCE(current->flags & PF_KTHREAD);
retval = filp_flush(filp, id);
fput_close_sync(filp);
return retval;
}
/*
* Careful here! We test whether the file pointer is NULL before
* releasing the fd. This ensures that one clone task can't release
@ -1551,13 +1564,11 @@ SYSCALL_DEFINE1(close, unsigned int, fd)
if (!file)
return -EBADF;
retval = filp_flush(file, current->files);
/*
* We're returning to user space. Don't bother
* with any delayed fput() cases.
*/
fput_close_sync(file);
retval = filp_close_sync(file, current->files);
if (likely(retval == 0))
return 0;