On Mon, Mar 2, 2020 at 11:23 AM Minchan Kim <minchan@xxxxxxxxxx> wrote: > > On Fri, Feb 28, 2020 at 02:41:07PM -0800, Suren Baghdasaryan wrote: > > On Tue, Feb 18, 2020 at 5:44 PM Minchan Kim <minchan@xxxxxxxxxx> wrote: > > > > > > There is a demand[1] to support pid as well pidfd for process_madvise > > > to reduce unnecessary syscall to get pidfd if the user has control of > > > the target process(ie, they could guarantee the process is not gone > > > or pid is not reused. Or, it might be okay to give a hint to wrong > > > process). > > > > nit: When would "give a hint to wrong process" be ok? I would just > > remove this part. > > I wanted to say non destructive hints. It's already true for other > some hints because they are just best effort so it's not critical > to be failed. If you mind it, I will remove the phrase. Up to you, or maybe call it a "non-fatal" error? Saying that it's ok to hint a wrong process sounds wrong to me. > > Thanks. > > > > > > > > > This patch aims for supporting both options like waitid(2). So, the > > > syscall is currently, > > > > > > int process_madvise(int which, pid_t pid, void *addr, > > > size_t length, int advise, unsigned long flag); > > > > > > @which is actually idtype_t for userspace libray and currently, > > > it supports P_PID and P_PIDFD. > > > > > > [1] https://lore.kernel.org/linux-mm/9d849087-3359-c4ab-fbec-859e8186c509@xxxxxxxxxxxxx/ > > > > > > Cc: Christian Brauner <christian@xxxxxxxxxx> > > > Suggested-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> > > > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> > > > --- > > > include/linux/syscalls.h | 3 ++- > > > mm/madvise.c | 34 ++++++++++++++++++++++------------ > > > 2 files changed, 24 insertions(+), 13 deletions(-) > > > > > > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > > > index e4cd2c2f8bb4..f5ada20e2943 100644 > > > --- a/include/linux/syscalls.h > > > +++ b/include/linux/syscalls.h > > > @@ -876,7 +876,8 @@ asmlinkage long sys_munlockall(void); > > > asmlinkage long sys_mincore(unsigned long start, size_t len, > > > unsigned char __user * vec); > > > asmlinkage long sys_madvise(unsigned long start, size_t len, int behavior); > > > -asmlinkage long sys_process_madvise(int pidfd, unsigned long start, > > > + > > > +asmlinkage long sys_process_madvise(int which, pid_t pid, unsigned long start, > > > size_t len, int behavior, unsigned long flags); > > > asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size, > > > unsigned long prot, unsigned long pgoff, > > > diff --git a/mm/madvise.c b/mm/madvise.c > > > index def1507c2030..f6d9b9e66243 100644 > > > --- a/mm/madvise.c > > > +++ b/mm/madvise.c > > > @@ -1182,11 +1182,10 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) > > > return do_madvise(current, current->mm, start, len_in, behavior); > > > } > > > > > > -SYSCALL_DEFINE5(process_madvise, int, pidfd, unsigned long, start, > > > +SYSCALL_DEFINE6(process_madvise, int, which, pid_t, upid, unsigned long, start, > > > size_t, len_in, int, behavior, unsigned long, flags) > > > { > > > int ret; > > > - struct fd f; > > > struct pid *pid; > > > struct task_struct *task; > > > struct mm_struct *mm; > > > @@ -1197,20 +1196,31 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, unsigned long, start, > > > if (!process_madvise_behavior_valid(behavior)) > > > return -EINVAL; > > > > > > - f = fdget(pidfd); > > > - if (!f.file) > > > - return -EBADF; > > > + switch (which) { > > > + case P_PID: > > > + if (upid <= 0) > > > + return -EINVAL; > > > + > > > + pid = find_get_pid(upid); > > > + if (!pid) > > > + return -ESRCH; > > > + break; > > > + case P_PIDFD: > > > + if (upid < 0) > > > + return -EINVAL; > > > > > > - pid = pidfd_pid(f.file); > > > - if (IS_ERR(pid)) { > > > - ret = PTR_ERR(pid); > > > - goto fdput; > > > + pid = pidfd_get_pid(upid); > > > + if (IS_ERR(pid)) > > > + return PTR_ERR(pid); > > > + break; > > > + default: > > > + return -EINVAL; > > > } > > > > > > task = get_pid_task(pid, PIDTYPE_PID); > > > if (!task) { > > > ret = -ESRCH; > > > - goto fdput; > > > + goto put_pid; > > > } > > > > > > mm = mm_access(task, PTRACE_MODE_ATTACH_FSCREDS); > > > @@ -1223,7 +1233,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, unsigned long, start, > > > mmput(mm); > > > release_task: > > > put_task_struct(task); > > > -fdput: > > > - fdput(f); > > > +put_pid: > > > + put_pid(pid); > > > return ret; > > > } > > > -- > > > 2.25.0.265.gbab2e86ba0-goog > > > > > > > Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
