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[209.132.180.67]) by mx.google.com with ESMTP id i19si5365362oik.272.2020.01.13.00.49.27; Mon, 13 Jan 2020 00:49:39 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=virtuozzo.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728841AbgAMIrf (ORCPT + 99 others); Mon, 13 Jan 2020 03:47:35 -0500 Received: from relay.sw.ru ([185.231.240.75]:37296 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727331AbgAMIre (ORCPT ); Mon, 13 Jan 2020 03:47:34 -0500 Received: from dhcp-172-16-24-104.sw.ru ([172.16.24.104]) by relay.sw.ru with esmtp (Exim 4.92.3) (envelope-from ) id 1iqvNQ-0000B7-6e; Mon, 13 Jan 2020 11:47:12 +0300 Subject: Re: [PATCH 2/4] mm: introduce external memory hinting API To: Minchan Kim , Andrew Morton Cc: LKML , linux-mm , linux-api@vger.kernel.org, oleksandr@redhat.com, Suren Baghdasaryan , Tim Murray , Daniel Colascione , Sandeep Patil , Sonny Rao , Brian Geffon , Michal Hocko , Johannes Weiner , Shakeel Butt , John Dias References: <20200110213433.94739-1-minchan@kernel.org> <20200110213433.94739-3-minchan@kernel.org> From: Kirill Tkhai Message-ID: <56ea0927-ad2e-3fbd-3366-3813330f6cec@virtuozzo.com> Date: Mon, 13 Jan 2020 11:47:11 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <20200110213433.94739-3-minchan@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11.01.2020 00:34, Minchan Kim wrote: > There are usecases that System Management Software(SMS) want to give > a memory hint to other processes because it's not known to the > application. In the case of Android, ActivityManagerService daemon > manges app's life cycle 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). > It uses pidfd of an external processs to give the hint. > > int process_madvise(int pidfd, void *addr, size_t length, int advise, > unsigned long flag); > > 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 ptrace the process could use it successfully. > The flag argument is reserved for future use if we need to extend the > API. > > Supporting all hints madvise has/will supported/support to process_madvise > is rather risky. Because we are not sure all hints make sense from external > process and implementation for the hint may rely on the caller being > in the current context so it could be error-prone. Thus, I just limited > hints as MADV_[COLD|PAGEOUT] in this patch. > > If someone want to add other hints, we could hear hear the usecase and > review it for each hint. It's more safe for maintainace rather than > introducing a buggy syscall but hard to fix it later. > > Signed-off-by: Minchan Kim > --- > arch/alpha/kernel/syscalls/syscall.tbl | 1 + > arch/arm/tools/syscall.tbl | 1 + > arch/arm64/include/asm/unistd.h | 2 +- > arch/arm64/include/asm/unistd32.h | 2 + > arch/ia64/kernel/syscalls/syscall.tbl | 1 + > arch/m68k/kernel/syscalls/syscall.tbl | 1 + > arch/microblaze/kernel/syscalls/syscall.tbl | 1 + > arch/mips/kernel/syscalls/syscall_n32.tbl | 1 + > arch/mips/kernel/syscalls/syscall_n64.tbl | 1 + > arch/parisc/kernel/syscalls/syscall.tbl | 1 + > arch/powerpc/kernel/syscalls/syscall.tbl | 1 + > arch/s390/kernel/syscalls/syscall.tbl | 1 + > arch/sh/kernel/syscalls/syscall.tbl | 1 + > arch/sparc/kernel/syscalls/syscall.tbl | 1 + > arch/x86/entry/syscalls/syscall_32.tbl | 1 + > arch/x86/entry/syscalls/syscall_64.tbl | 1 + > arch/xtensa/kernel/syscalls/syscall.tbl | 1 + > include/linux/syscalls.h | 2 + > include/uapi/asm-generic/unistd.h | 5 +- > kernel/sys_ni.c | 1 + > mm/madvise.c | 64 +++++++++++++++++++++ > 21 files changed, 89 insertions(+), 2 deletions(-) > > diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl > index e56950f23b49..776c61803315 100644 > --- a/arch/alpha/kernel/syscalls/syscall.tbl > +++ b/arch/alpha/kernel/syscalls/syscall.tbl > @@ -477,3 +477,4 @@ > # 545 reserved for clone3 > 546 common watch_devices sys_watch_devices > 547 common openat2 sys_openat2 > +548 common process_madvise sys_process_madvise > diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl > index 7fb2f4d59210..a43381542276 100644 > --- a/arch/arm/tools/syscall.tbl > +++ b/arch/arm/tools/syscall.tbl > @@ -451,3 +451,4 @@ > 435 common clone3 sys_clone3 > 436 common watch_devices sys_watch_devices > 437 common openat2 sys_openat2 > +438 common process_madvise sys_process_madvise > diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h > index 8aa00ccb0b96..b722e47377a5 100644 > --- a/arch/arm64/include/asm/unistd.h > +++ b/arch/arm64/include/asm/unistd.h > @@ -38,7 +38,7 @@ > #define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5) > #define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800) > > -#define __NR_compat_syscalls 438 > +#define __NR_compat_syscalls 439 > #endif > > #define __ARCH_WANT_SYS_CLONE > diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h > index 31f0ce25719e..5c82557d408f 100644 > --- a/arch/arm64/include/asm/unistd32.h > +++ b/arch/arm64/include/asm/unistd32.h > @@ -883,6 +883,8 @@ __SYSCALL(__NR_clone3, sys_clone3) > __SYSCALL(__NR_watch_devices, sys_watch_devices) > #define __NR_openat2 437 > __SYSCALL(__NR_openat2, sys_openat2) > +#define __NR_openat2 438 > +__SYSCALL(__NR_process_madvise, process_madvise) > > /* > * Please add new compat syscalls above this comment and update > diff --git a/arch/ia64/kernel/syscalls/syscall.tbl b/arch/ia64/kernel/syscalls/syscall.tbl > index b9aa59931905..c156abc9a298 100644 > --- a/arch/ia64/kernel/syscalls/syscall.tbl > +++ b/arch/ia64/kernel/syscalls/syscall.tbl > @@ -358,3 +358,4 @@ > # 435 reserved for clone3 > 436 common watch_devices sys_watch_devices > 437 common openat2 sys_openat2 > +438 common process_madvise sys_process_madvise > diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl > index 868c1ef89d35..5b6034b6650f 100644 > --- a/arch/m68k/kernel/syscalls/syscall.tbl > +++ b/arch/m68k/kernel/syscalls/syscall.tbl > @@ -437,3 +437,4 @@ > # 435 reserved for clone3 > 436 common watch_devices sys_watch_devices > 437 common openat2 sys_openat2 > +438 common process_madvise sys_process_madvise > diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl > index 544b4cef18b3..4bef584af09c 100644 > --- a/arch/microblaze/kernel/syscalls/syscall.tbl > +++ b/arch/microblaze/kernel/syscalls/syscall.tbl > @@ -443,3 +443,4 @@ > 435 common clone3 sys_clone3 > 436 common watch_devices sys_watch_devices > 437 common openat2 sys_openat2 > +438 common process_madvise sys_process_madvise > diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl > index 05e8aee5dae7..94fbd0fcccce 100644 > --- a/arch/mips/kernel/syscalls/syscall_n32.tbl > +++ b/arch/mips/kernel/syscalls/syscall_n32.tbl > @@ -376,3 +376,4 @@ > 435 n32 clone3 __sys_clone3 > 436 n32 watch_devices sys_watch_devices > 437 n32 openat2 sys_openat2 > +437 n32 process_madivse sys_process_madvise 438. And several places below has the same mistake. > diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl > index 24d6c01328fb..4e6982c429d5 100644 > --- a/arch/mips/kernel/syscalls/syscall_n64.tbl > +++ b/arch/mips/kernel/syscalls/syscall_n64.tbl > @@ -352,3 +352,4 @@ > 435 n64 clone3 __sys_clone3 > 436 n64 watch_devices sys_watch_devices > 437 n64 openat2 sys_openat2 > +437 n64 process_madvise sys_process_madvise > diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl > index 4b5f77a4e1a2..3aa990caf9dc 100644 > --- a/arch/parisc/kernel/syscalls/syscall.tbl > +++ b/arch/parisc/kernel/syscalls/syscall.tbl > @@ -435,3 +435,4 @@ > 435 common clone3 sys_clone3_wrapper > 436 common watch_devices sys_watch_devices > 437 common openat2 sys_openat2 > +437 common process_madvise sys_process_madvise > diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl > index 9716dc85a517..30e727a23f33 100644 > --- a/arch/powerpc/kernel/syscalls/syscall.tbl > +++ b/arch/powerpc/kernel/syscalls/syscall.tbl > @@ -519,3 +519,4 @@ > 435 nospu clone3 ppc_clone3 > 436 common watch_devices sys_watch_devices > 437 common openat2 sys_openat2 > +437 common process_madvise sys_process_madvise > diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl > index 7da330f8b03e..75722e5ff496 100644 > --- a/arch/s390/kernel/syscalls/syscall.tbl > +++ b/arch/s390/kernel/syscalls/syscall.tbl > @@ -440,3 +440,4 @@ > 435 common clone3 sys_clone3 sys_clone3 > 436 common watch_devices sys_watch_devices sys_watch_devices > 437 common openat2 sys_openat2 sys_openat2 > +437 common process_madvise sys_process_madvise sys_process_madvise > diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl > index bb7e68e25337..7d7bc7befad3 100644 > --- a/arch/sh/kernel/syscalls/syscall.tbl > +++ b/arch/sh/kernel/syscalls/syscall.tbl > @@ -440,3 +440,4 @@ > # 435 reserved for clone3 > 436 common watch_devices sys_watch_devices > 437 common openat2 sys_openat2 > +437 common process_madvise sys_process_madvise > diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl > index 646a1fad7218..581d331ff62f 100644 > --- a/arch/sparc/kernel/syscalls/syscall.tbl > +++ b/arch/sparc/kernel/syscalls/syscall.tbl > @@ -483,3 +483,4 @@ > # 435 reserved for clone3 > 436 common watch_devices sys_watch_devices > 437 common openat2 sys_openat2 > +437 common process_madvise sys_process_madvise > diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl > index 57c53acee290..76a2c266fe7e 100644 > --- a/arch/x86/entry/syscalls/syscall_32.tbl > +++ b/arch/x86/entry/syscalls/syscall_32.tbl > @@ -442,3 +442,4 @@ > 435 i386 clone3 sys_clone3 __ia32_sys_clone3 > 436 i386 watch_devices sys_watch_devices __ia32_sys_watch_devices > 437 i386 openat2 sys_openat2 __ia32_sys_openat2 > +438 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 1dd8d21f6500..b697cd8620cb 100644 > --- a/arch/x86/entry/syscalls/syscall_64.tbl > +++ b/arch/x86/entry/syscalls/syscall_64.tbl > @@ -359,6 +359,7 @@ > 435 common clone3 __x64_sys_clone3/ptregs > 436 common watch_devices __x64_sys_watch_devices > 437 common openat2 __x64_sys_openat2 > +438 common process_madvise __x64_sys_process_madvise > > # > # x32-specific system call numbers start at 512 to avoid cache impact > diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl > index 0f48ab7bd75b..2e9813ecfd7d 100644 > --- a/arch/xtensa/kernel/syscalls/syscall.tbl > +++ b/arch/xtensa/kernel/syscalls/syscall.tbl > @@ -408,3 +408,4 @@ > 435 common clone3 sys_clone3 > 436 common watch_devices sys_watch_devices > 437 common openat2 sys_openat2 > +438 common process_madvise sys_process_madvise > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > index 433c8c85636e..1b58a11ff49f 100644 > --- a/include/linux/syscalls.h > +++ b/include/linux/syscalls.h > @@ -877,6 +877,8 @@ 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, > + 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, > unsigned long flags); > diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h > index 33f3856a9c3c..4bcd8d366f38 100644 > --- a/include/uapi/asm-generic/unistd.h > +++ b/include/uapi/asm-generic/unistd.h > @@ -856,8 +856,11 @@ __SYSCALL(__NR_watch_devices, sys_watch_devices) > #define __NR_openat2 437 > __SYSCALL(__NR_openat2, sys_openat2) > > +#define __NR_openat2 438 > +__SYSCALL(__NR_process_madvise, sys_process_madvise) > + > #undef __NR_syscalls > -#define __NR_syscalls 438 > +#define __NR_syscalls 439 > > /* > * 32 bit systems traditionally used different > diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c > index 0e9b275260f8..10ce5eac8b4b 100644 > --- a/kernel/sys_ni.c > +++ b/kernel/sys_ni.c > @@ -281,6 +281,7 @@ 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 0c901de531e4..e15dfb4df7bf 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -17,6 +17,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -993,6 +994,18 @@ madvise_behavior_valid(int behavior) > } > } > > +static bool > +process_madvise_behavior_valid(int behavior) > +{ > + switch (behavior) { > + case MADV_COLD: > + case MADV_PAGEOUT: > + return true; > + default: > + return false; > + } > +} > + > /* > * madvise_common - request behavior hint to address range of the target process > * > @@ -1169,3 +1182,54 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) > { > return madvise_common(current, current->mm, start, len_in, behavior); > } > + > +SYSCALL_DEFINE5(process_madvise, int, pidfd, unsigned long, start, > + size_t, len_in, int, behavior, unsigned long, flags) I don't like the interface. The fact we have pidfd does not mean, we have to use it for new syscalls always. A user may want to set madvise for specific pid from console and pass pid as argument. pidfd would be an overkill in this case. We usually call "kill -9 pid" from console. Why shouldn't process_madvise() allow this? I suggent to extend first argument to work with both pid and pidfd. Look at what we have for waitid(idtype, id_t id, ...) for example: idtype == P_PID Wait for the child whose process ID matches id. idtype == P_PIDFD (since Linux 5.4) Wait for the child referred to by the PID file descriptor specified in id. (See pidfd_open(2) for further information on PID file descriptors.) We may use @flags argument for this. > +{ > + int ret; > + struct fd f; > + struct pid *pid; > + struct task_struct *task; > + struct mm_struct *mm; > + > + if (flags != 0) > + return -EINVAL; > + > + if (!process_madvise_behavior_valid(behavior)) > + return -EINVAL; > + > + f = fdget(pidfd); > + if (!f.file) > + return -EBADF; > + > + pid = pidfd_pid(f.file); > + if (IS_ERR(pid)) { > + ret = PTR_ERR(pid); > + goto err; > + } From here: > + rcu_read_lock(); > + task = pid_task(pid, PIDTYPE_PID); > + if (!task) { > + rcu_read_unlock(); > + ret = -ESRCH; > + goto err; > + } > + > + get_task_struct(task); > + rcu_read_unlock(); to here your code is a copy of existing get_pid_task(). We should the primitive instead. > + > + mm = mm_access(task, PTRACE_MODE_ATTACH_FSCREDS); > + if (IS_ERR_OR_NULL(mm)) { > + ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; > + goto release_task; > + } > + > + ret = madvise_common(task, mm, start, len_in, behavior); > + mmput(mm); > +release_task: > + put_task_struct(task); > +err: Maybe s/err:/fdput:/ for uniformity with the above "release_task:"? > + fdput(f); > + return ret; > +} >