From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2F25AC04AAF for ; Tue, 21 May 2019 11:51:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DF94021773 for ; Tue, 21 May 2019 11:51:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=brauner.io header.i=@brauner.io header.b="I2SlfVLI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728078AbfEULvs (ORCPT ); Tue, 21 May 2019 07:51:48 -0400 Received: from mail-pf1-f196.google.com ([209.85.210.196]:34580 "EHLO mail-pf1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727060AbfEULvr (ORCPT ); Tue, 21 May 2019 07:51:47 -0400 Received: by mail-pf1-f196.google.com with SMTP id n19so8970319pfa.1 for ; Tue, 21 May 2019 04:51:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=brauner.io; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=UtDqUNgJnZynvBlOnHH9iSsJaf+tEnVzROAfsvS8DBE=; b=I2SlfVLIPpeoN83/RVrIDZ2txEnNA5/ACU8WMfVJGvRRYeZHhJySKHjwhWV/Bn5LJm +AmEBzMgvcsaSN80G2haPXgR93//O72qJf3u00s1Lc49RDald+0XCvtiLunT8uN4SzfK 3nzT6LPSjwfmpTlI4jYN/Zrt/8fBget25T1htvMTEqJMoQGulRy7aRQKGfemlBvsamMV o3cxKBFERwOrGDOEYVv8JGqp+46X/kmpcRFsNuN2BuuTY2vQRfosbUAKnxe86l+4fDI0 fn9C+x+qSs1SOPXkwCmesLYZU4PPDRMHNq2meRvHYQGuFwUhCvt0/uF2R5N2PXaI/H8Z UHRg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=UtDqUNgJnZynvBlOnHH9iSsJaf+tEnVzROAfsvS8DBE=; b=WwHL5PHvO/gnqsubTPgt9UL3B6Q3hlIJryGRhg50AEKFPsNav1gJnwJqk1N4O5VD3U vMd+dpTFq8CedhQfPJohRd4z74Pqm09/LLjWJnIvMITRLVP7BSDrZbAWSn47QUynwRnq 6QqLXC3ykbDVPQ1sc72fGomLnt6oQt/5xMJfserGALwHPjSA29gWIaasrpON/iL6P2jd tL9Rx7l7ypt1LsnWSy0/UfqUZEbdMLGG0WqaqvOfX7hujoSuYeAdopX+lyn/QdD+FCm4 RbIJGDETDQaYrw9b1+RlBLB6mXCFwUKCYJD4d10BADQUlLoASHvZlDfKVCh72UCCXs28 OKzQ== X-Gm-Message-State: APjAAAWoxVjXXhs1eLd862AJ+VscaH4OxFHm374vQWFL/UIRfv2C83Km cRKLO1r3vApMuyn/lr9ykAa7/g== X-Google-Smtp-Source: APXvYqzVAPpLqpOw3CzPXblES0fZoluJzsflh2rJavwNsVzz1QjsTvWNUJgpYR5jM9xP6oesamRJVA== X-Received: by 2002:a65:5588:: with SMTP id j8mr81657084pgs.306.1558439506334; Tue, 21 May 2019 04:51:46 -0700 (PDT) Received: from brauner.io ([208.54.39.182]) by smtp.gmail.com with ESMTPSA id t25sm34940175pfq.91.2019.05.21.04.51.39 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 21 May 2019 04:51:45 -0700 (PDT) Date: Tue, 21 May 2019 13:51:36 +0200 From: Christian Brauner To: Minchan Kim Cc: Andrew Morton , LKML , linux-mm , Michal Hocko , Johannes Weiner , Tim Murray , Joel Fernandes , Suren Baghdasaryan , Daniel Colascione , Shakeel Butt , Sonny Rao , Brian Geffon , jannh@google.com, oleg@redhat.com Subject: Re: [RFC 5/7] mm: introduce external memory hinting API Message-ID: <20190521115134.rzknm4q2r5cpr6az@brauner.io> References: <20190520035254.57579-1-minchan@kernel.org> <20190520035254.57579-6-minchan@kernel.org> <20190521090058.mdx4qecmdbum45t2@brauner.io> <20190521113510.GI219653@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190521113510.GI219653@google.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 21, 2019 at 08:35:10PM +0900, Minchan Kim wrote: > On Tue, May 21, 2019 at 11:01:01AM +0200, Christian Brauner wrote: > > Cc: Jann and Oleg too > > > > On Mon, May 20, 2019 at 12:52:52PM +0900, Minchan Kim wrote: > > > There is some usecase that centralized userspace daemon want to give > > > a memory hint like MADV_[COOL|COLD] to other process. Android's > > > ActivityManagerService is one of them. > > > > > > It's similar in spirit to madvise(MADV_WONTNEED), but the information > > > required to make the reclaim decision is not known to the app. Instead, > > > it is known to the centralized userspace daemon(ActivityManagerService), > > > and that daemon must be able to initiate reclaim on its own without > > > any app involvement. > > > > > > To solve the issue, this patch introduces new syscall process_madvise(2) > > > which works based on pidfd so it could give a hint to the exeternal > > > process. > > > > > > int process_madvise(int pidfd, void *addr, size_t length, int advise); > > > > > > All advises madvise provides can be supported in process_madvise, too. > > > Since it could affect other process's address range, only privileged > > > process(CAP_SYS_PTRACE) or something else(e.g., being the same UID) > > > gives it the right to ptrrace the process could use it successfully. > > > > > > Please suggest better idea if you have other idea about the permission. > > > > > > * from v1r1 > > > * use ptrace capability - surenb, dancol > > > > > > Signed-off-by: Minchan Kim > > > --- > > > arch/x86/entry/syscalls/syscall_32.tbl | 1 + > > > arch/x86/entry/syscalls/syscall_64.tbl | 1 + > > > include/linux/proc_fs.h | 1 + > > > include/linux/syscalls.h | 2 ++ > > > include/uapi/asm-generic/unistd.h | 2 ++ > > > kernel/signal.c | 2 +- > > > kernel/sys_ni.c | 1 + > > > mm/madvise.c | 45 ++++++++++++++++++++++++++ > > > 8 files changed, 54 insertions(+), 1 deletion(-) > > > > > > diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl > > > index 4cd5f982b1e5..5b9dd55d6b57 100644 > > > --- a/arch/x86/entry/syscalls/syscall_32.tbl > > > +++ b/arch/x86/entry/syscalls/syscall_32.tbl > > > @@ -438,3 +438,4 @@ > > > 425 i386 io_uring_setup sys_io_uring_setup __ia32_sys_io_uring_setup > > > 426 i386 io_uring_enter sys_io_uring_enter __ia32_sys_io_uring_enter > > > 427 i386 io_uring_register sys_io_uring_register __ia32_sys_io_uring_register > > > +428 i386 process_madvise sys_process_madvise __ia32_sys_process_madvise > > > diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl > > > index 64ca0d06259a..0e5ee78161c9 100644 > > > --- a/arch/x86/entry/syscalls/syscall_64.tbl > > > +++ b/arch/x86/entry/syscalls/syscall_64.tbl > > > @@ -355,6 +355,7 @@ > > > 425 common io_uring_setup __x64_sys_io_uring_setup > > > 426 common io_uring_enter __x64_sys_io_uring_enter > > > 427 common io_uring_register __x64_sys_io_uring_register > > > +428 common process_madvise __x64_sys_process_madvise > > > > > > # > > > # x32-specific system call numbers start at 512 to avoid cache impact > > > diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h > > > index 52a283ba0465..f8545d7c5218 100644 > > > --- a/include/linux/proc_fs.h > > > +++ b/include/linux/proc_fs.h > > > @@ -122,6 +122,7 @@ static inline struct pid *tgid_pidfd_to_pid(const struct file *file) > > > > > > #endif /* CONFIG_PROC_FS */ > > > > > > +extern struct pid *pidfd_to_pid(const struct file *file); > > > struct net; > > > > > > static inline struct proc_dir_entry *proc_net_mkdir( > > > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > > > index e2870fe1be5b..21c6c9a62006 100644 > > > --- a/include/linux/syscalls.h > > > +++ b/include/linux/syscalls.h > > > @@ -872,6 +872,8 @@ 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 pid_fd, unsigned long start, > > > + size_t len, int behavior); > > > asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size, > > > unsigned long prot, unsigned long pgoff, > > > unsigned long flags); > > > diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h > > > index dee7292e1df6..7ee82ce04620 100644 > > > --- a/include/uapi/asm-generic/unistd.h > > > +++ b/include/uapi/asm-generic/unistd.h > > > @@ -832,6 +832,8 @@ __SYSCALL(__NR_io_uring_setup, sys_io_uring_setup) > > > __SYSCALL(__NR_io_uring_enter, sys_io_uring_enter) > > > #define __NR_io_uring_register 427 > > > __SYSCALL(__NR_io_uring_register, sys_io_uring_register) > > > +#define __NR_process_madvise 428 > > > +__SYSCALL(__NR_process_madvise, sys_process_madvise) > > > > > > #undef __NR_syscalls > > > #define __NR_syscalls 428 > > > diff --git a/kernel/signal.c b/kernel/signal.c > > > index 1c86b78a7597..04e75daab1f8 100644 > > > --- a/kernel/signal.c > > > +++ b/kernel/signal.c > > > @@ -3620,7 +3620,7 @@ static int copy_siginfo_from_user_any(kernel_siginfo_t *kinfo, siginfo_t *info) > > > return copy_siginfo_from_user(kinfo, info); > > > } > > > > > > -static struct pid *pidfd_to_pid(const struct file *file) > > > +struct pid *pidfd_to_pid(const struct file *file) > > > { > > > if (file->f_op == &pidfd_fops) > > > return file->private_data; > > > diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c > > > index 4d9ae5ea6caf..5277421795ab 100644 > > > --- a/kernel/sys_ni.c > > > +++ b/kernel/sys_ni.c > > > @@ -278,6 +278,7 @@ COND_SYSCALL(mlockall); > > > COND_SYSCALL(munlockall); > > > COND_SYSCALL(mincore); > > > COND_SYSCALL(madvise); > > > +COND_SYSCALL(process_madvise); > > > COND_SYSCALL(remap_file_pages); > > > COND_SYSCALL(mbind); > > > COND_SYSCALL_COMPAT(mbind); > > > diff --git a/mm/madvise.c b/mm/madvise.c > > > index 119e82e1f065..af02aa17e5c1 100644 > > > --- a/mm/madvise.c > > > +++ b/mm/madvise.c > > > @@ -9,6 +9,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > #include > > > #include > > > #include > > > @@ -16,6 +17,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > #include > > > #include > > > #include > > > @@ -1140,3 +1142,46 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) > > > { > > > return madvise_core(current, start, len_in, behavior); > > > } > > > + > > > +SYSCALL_DEFINE4(process_madvise, int, pidfd, unsigned long, start, > > > + size_t, len_in, int, behavior) > > > +{ > > > + int ret; > > > + struct fd f; > > > + struct pid *pid; > > > + struct task_struct *tsk; > > > + struct mm_struct *mm; > > > + > > > + f = fdget(pidfd); > > > + if (!f.file) > > > + return -EBADF; > > > + > > > + pid = pidfd_to_pid(f.file); > > > > pidfd_to_pid() should not be directly exported since this allows > > /proc/ fds to be used too. That's something we won't be going > > forward with. All new syscalls should only allow to operate on pidfds > > created through CLONE_PIDFD or pidfd_open() (cf. [1]). > > Thanks for the information. > > > > > So e.g. please export a simple helper like > > > > struct pid *pidfd_to_pid(const struct file *file) > > { > > if (file->f_op == &pidfd_fops) > > return file->private_data; > > > > return NULL; > > } > > > > turning the old pidfd_to_pid() into something like: > > > > static struct pid *__fd_to_pid(const struct file *file) > > { > > struct pid *pid; > > > > pid = pidfd_to_pid(file); > > if (pid) > > return pid; > > > > return tgid_pidfd_to_pid(file); > > } > > So, I want to clarify what you suggest here. > > 1. modify pidfd_to_pid as what you described above(ie, return NULL > instead of returning tgid_pidfd_to_pid(file); > 2. never export pidfd_to_pid > 3. create wrapper __fd_to_pid which calls pidfd_to_pid internally > 4. export __fd_to_pid and use it Sorry, seems I was not clear enough. :) What I meant was something along the lines of (not compile tested): diff --git a/include/linux/pid.h b/include/linux/pid.h index 3c8ef5a199ca..3ccc07010603 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -68,6 +68,10 @@ extern struct pid init_struct_pid; extern const struct file_operations pidfd_fops; +struct file; + +extern struct pid *pidfd_pid(const struct file *file); + static inline struct pid *get_pid(struct pid *pid) { if (pid) diff --git a/kernel/fork.c b/kernel/fork.c index b4cba953040a..0fcfffaf5fdc 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1711,6 +1711,14 @@ const struct file_operations pidfd_fops = { #endif }; +struct pid *pidfd_pid(const struct file *file) +{ + if (file->f_op == &pidfd_fops) + return file->private_data; + + return ERR_PTR(-EBADF); +} + /** * pidfd_create() - Create a new pid file descriptor. * diff --git a/kernel/signal.c b/kernel/signal.c index a1eb44dc9ff5..7fca9d7e1633 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -3611,8 +3611,11 @@ static int copy_siginfo_from_user_any(kernel_siginfo_t *kinfo, siginfo_t *info) static struct pid *pidfd_to_pid(const struct file *file) { - if (file->f_op == &pidfd_fops) - return file->private_data; + struct pid *pid; + + pid = pidfd_pid(file); + if (pid) + return pid; return tgid_pidfd_to_pid(file); }