| Message ID | 20200817220425.9389-7-ebiederm@xmission.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [01/17] exec: Move unshare_files to fix posix file locking during exec | expand |
On Mon, Aug 17, 2020 at 05:04:15PM -0500, Eric W. Biederman wrote: > When discussing[1] exec and posix file locks it was realized that none > of the callers of get_files_struct fundamentally needed to call > get_files_struct, and that by switching them to helper functions > instead it will both simplify their code and remove unnecessary > increments of files_struct.count. Those unnecessary increments can > result in exec unnecessarily unsharing files_struct which breaking > posix locks, and it can result in fget_light having to fallback to > fget reducing system performance. > > Using fcheck_task instead of get_files_struct clarifies tid_fd_mode by > removing a step. > > [1] https://lkml.kernel.org/r/20180915160423.GA31461@redhat.com > Suggested-by: Oleg Nesterov <oleg@redhat.com> > Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> > --- Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
diff --git a/fs/proc/fd.c b/fs/proc/fd.c index 81882a13212d..4048a87c51ee 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -83,18 +83,13 @@ static const struct file_operations proc_fdinfo_file_operations = { static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode) { - struct files_struct *files = get_files_struct(task); struct file *file; - if (!files) - return false; - rcu_read_lock(); - file = fcheck_files(files, fd); + file = fcheck_task(task, fd); if (file) *mode = file->f_mode; rcu_read_unlock(); - put_files_struct(files); return !!file; }
When discussing[1] exec and posix file locks it was realized that none of the callers of get_files_struct fundamentally needed to call get_files_struct, and that by switching them to helper functions instead it will both simplify their code and remove unnecessary increments of files_struct.count. Those unnecessary increments can result in exec unnecessarily unsharing files_struct which breaking posix locks, and it can result in fget_light having to fallback to fget reducing system performance. Using fcheck_task instead of get_files_struct clarifies tid_fd_mode by removing a step. [1] https://lkml.kernel.org/r/20180915160423.GA31461@redhat.com Suggested-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> --- fs/proc/fd.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-)