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.
Instead of manually coding finding the files struct for a task and then calling files_lookup_fd_rcu, use the helper task_lookup_fd_rcu that combines those to steps. Making the code simpler and removing the need to get a reference on a files_struct. [1] https://lkml.kernel.org/r/[email protected] Suggested-by: Oleg Nesterov <[email protected]> Acked-by: Christian Brauner <[email protected]> v1: https://lkml.kernel.org/r/[email protected] Signed-off-by: "Eric W. Biederman" <[email protected]> --- fs/proc/fd.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/fs/proc/fd.c b/fs/proc/fd.c index 3dec44d7c5c5..c1a984f3c4df 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 = files_lookup_fd_rcu(files, fd); + file = task_lookup_fd_rcu(task, fd); if (file) *mode = file->f_mode; rcu_read_unlock(); - put_files_struct(files); return !!file; } -- 2.25.0
