From patchwork Tue Feb 28 17:12:46 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cyrill Gorcunov X-Patchwork-Id: 9596319 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id E5013601D7 for ; Tue, 28 Feb 2017 17:13:29 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CE7D520009 for ; Tue, 28 Feb 2017 17:13:29 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C35282854E; Tue, 28 Feb 2017 17:13:29 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RCVD_IN_SORBS_SPAM autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7163628552 for ; Tue, 28 Feb 2017 17:13:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751734AbdB1RNL (ORCPT ); Tue, 28 Feb 2017 12:13:11 -0500 Received: from mail-lf0-f67.google.com ([209.85.215.67]:36004 "EHLO mail-lf0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751639AbdB1RMz (ORCPT ); Tue, 28 Feb 2017 12:12:55 -0500 Received: by mail-lf0-f67.google.com with SMTP id g70so487532lfh.3; Tue, 28 Feb 2017 09:12:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=dJzu7w9HRY9qplle8Z+COyhdDAaOiashLs87Ys9yVO0=; b=E5mJo/NxN6y8vxcztij3tOILtLJLaO4Qv5ZLViiYMfEQLrudi5U/yxsUCKBDvk1KxK uJPsmVMOy3kq3/BquiQnLChP+a1X3DUZjW5/8p1PEP223pIAK/Ru43OBpJz+rPjuZ1HC VSKvElplR8//oznskGfgjXXbFu74I2RkUivWYWYNKK65m1uTtB6WSc3yrhtLWOR1XOx2 5bEpLblNAC0Fv6zOriMbYmcmR3FxG7DgUF0vwlwU6VJUAyTh6YPf8yOAgjYabEtOCXCa O/DAHvRedhUeqjup/7RDsb1zvkND6qYyDAEHt4uKwBucAT0PR91k6ma0dJvzcvI9fDR1 SJ2g== 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=dJzu7w9HRY9qplle8Z+COyhdDAaOiashLs87Ys9yVO0=; b=MIkxiSQg6ukGZsCZTo5Rq1d1W+2WOSWazroktROkFt5asm4t/jWF16Q2HmmHcrQ89r svEUSuyNh3fFHfMSPprCr4htSIYhINjt8XhUmSZdqWQs30EbwBbyXAzK++arsK/G6mUQ DKhQEC5Qp/+LxTFvgLz1F2/RRPj3gvWQeWH+P4US+rbc0wNNuRSIujip3wP/RHMsNzMX WTPdSYu7G2/sDZcIaO0LE5uiXmaexU1lWfxa5mG4kgMrdbmKUuef9ZNoqzzSi5P9PGKx YgrES3eHTb+/X904LBVxiCisiZOmcbnDNEbUY/yMkTcq2jqrB4OXmsk89rq+e2bkE8l0 ugzw== X-Gm-Message-State: AMke39n901bu2FkW0ekWwq/L8Qs2kNgmDBQg6m9IiMzklm7oF+3deecPVw1wKw6iVLr1BQ== X-Received: by 10.25.125.11 with SMTP id y11mr1247618lfc.101.1488301968406; Tue, 28 Feb 2017 09:12:48 -0800 (PST) Received: from uranus.localdomain ([5.19.3.67]) by smtp.gmail.com with ESMTPSA id l14sm494825ljb.66.2017.02.28.09.12.47 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 28 Feb 2017 09:12:47 -0800 (PST) Received: by uranus.localdomain (Postfix, from userid 1000) id CA2F722725; Tue, 28 Feb 2017 20:12:46 +0300 (MSK) Date: Tue, 28 Feb 2017 20:12:46 +0300 From: Cyrill Gorcunov To: Andrei Vagin Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, viro@zeniv.linux.org.uk, akpm@linuxfoundation.org, xemul@virtuozzo.com, mtk.manpages@gmail.com, kir@openvz.org, luto@amacapital.net, jbaron@akamai.com, Andrey Vagin Subject: [RFC v2 2/3] kcmp: Add KCMP_EPOLL_TFD mode to compare epoll target files Message-ID: <20170228171246.GC28817@uranus.lan> References: <20170221171255.023016858@openvz.org> <20170227224346.GA7101@outlook.office365.com> <20170228065306.GH22938@uranus> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20170228065306.GH22938@uranus> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP With current epoll architecture target files are addressed with file_struct and file descriptor number, where the last is not unique. Moreover files can be transferred from another process via unix socket, added into queue and closed then so we won't find this descriptor in the task fdinfo list. Thus to checkpoint and restore such processes CRIU needs to find out where exactly target file is present to add it into the epoll queue. For this sake one can use kcmp call where some particular target file from the queue is compared with arbitrary file passed as an argument. Because epoll target files can have same file descriptor number but different file_struct a caller should explicitly specify the offset within such entries. To test if some particular file is matching entry inside epoll one have to - fill kcmp_epoll_slot structure with epoll file descriptor, target file number and target file offset (in case if only one target is present then it should be 0) - call kcmp as kcmp(pid1, pid2, KCMP_EPOLL_TFD, fd, &kcmp_epoll_slot) - the kernel fetch file pointer matching file descriptor @fd of pid1 - lookups for file struct in epoll queue of pid2 and returns traditional 0,1,2 result for sorting purpose v2: - Use KCMP_FILES salt for files comparision (for convenience sake, since the pointers are file structs so user can lookup over previously collected files tree) - Make kcmp_epoll_target as a separate helper instead of opencoding it with #ifdef Signed-off-by: Cyrill Gorcunov CC: Al Viro CC: Andrew Morton CC: Andrey Vagin CC: Pavel Emelyanov CC: Michael Kerrisk CC: Kir Kolyshkin CC: Jason Baron CC: Andy Lutomirski --- fs/eventpoll.c | 42 +++++++++++++++++++++++++++++++++ include/linux/eventpoll.h | 3 ++ include/uapi/linux/kcmp.h | 10 +++++++ kernel/kcmp.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 113 insertions(+) Index: linux-ml.git/fs/eventpoll.c =================================================================== --- linux-ml.git.orig/fs/eventpoll.c +++ linux-ml.git/fs/eventpoll.c @@ -1000,6 +1000,48 @@ static struct epitem *ep_find(struct eve return epir; } +static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long toff) +{ + struct rb_node *rbp; + struct epitem *epi; + + for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { + epi = rb_entry(rbp, struct epitem, rbn); + if (epi->ffd.fd == tfd) { + if (toff == 0) + return epi; + else + toff--; + } + cond_resched(); + } + + return NULL; +} + +struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, + unsigned long toff) +{ + struct file *file_raw; + struct eventpoll *ep; + struct epitem *epi; + + if (!is_file_epoll(file)) + return ERR_PTR(-EINVAL); + + ep = file->private_data; + + mutex_lock(&ep->mtx); + epi = ep_find_tfd(ep, tfd, toff); + if (epi) + file_raw = epi->ffd.file; + else + file_raw = ERR_PTR(-ENOENT); + mutex_unlock(&ep->mtx); + + return file_raw; +} + /* * This is the callback that is passed to the wait queue wakeup * mechanism. It is called by the stored file descriptors when they Index: linux-ml.git/include/linux/eventpoll.h =================================================================== --- linux-ml.git.orig/include/linux/eventpoll.h +++ linux-ml.git/include/linux/eventpoll.h @@ -14,6 +14,7 @@ #define _LINUX_EVENTPOLL_H #include +#include /* Forward declarations to avoid compiler errors */ @@ -22,6 +23,8 @@ struct file; #ifdef CONFIG_EPOLL +struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff); + /* Used to initialize the epoll bits inside the "struct file" */ static inline void eventpoll_init_file(struct file *file) { Index: linux-ml.git/include/uapi/linux/kcmp.h =================================================================== --- linux-ml.git.orig/include/uapi/linux/kcmp.h +++ linux-ml.git/include/uapi/linux/kcmp.h @@ -1,6 +1,8 @@ #ifndef _UAPI_LINUX_KCMP_H #define _UAPI_LINUX_KCMP_H +#include + /* Comparison type */ enum kcmp_type { KCMP_FILE, @@ -10,8 +12,16 @@ enum kcmp_type { KCMP_SIGHAND, KCMP_IO, KCMP_SYSVSEM, + KCMP_EPOLL_TFD, KCMP_TYPES, }; +/* Slot for KCMP_EPOLL_TFD */ +struct kcmp_epoll_slot { + __u32 efd; /* epoll file descriptor */ + __u32 tfd; /* target file number */ + __u32 toff; /* target offset within same numbered sequence */ +}; + #endif /* _UAPI_LINUX_KCMP_H */ Index: linux-ml.git/kernel/kcmp.c =================================================================== --- linux-ml.git.orig/kernel/kcmp.c +++ linux-ml.git/kernel/kcmp.c @@ -11,6 +11,10 @@ #include #include #include +#include +#include +#include +#include #include @@ -94,6 +98,57 @@ static int kcmp_lock(struct mutex *m1, s return err; } +#ifdef CONFIG_EPOLL +static int kcmp_epoll_target(struct task_struct *task1, + struct task_struct *task2, + unsigned long idx1, + struct kcmp_epoll_slot __user *uslot) +{ + struct file *filp, *filp_epoll, *filp_tgt; + struct kcmp_epoll_slot slot; + struct files_struct *files; + int ret; + + if (copy_from_user(&slot, uslot, sizeof(slot))) + return -EFAULT; + + filp = get_file_raw_ptr(task1, idx1); + + files = get_files_struct(task2); + if (files) { + spin_lock(&files->file_lock); + filp_epoll = fcheck_files(files, slot.efd); + if (filp_epoll) + get_file(filp_epoll); + spin_unlock(&files->file_lock); + put_files_struct(files); + } else + filp_epoll = NULL; + + if (filp && filp_epoll) { + filp_tgt = get_epoll_tfile_raw_ptr(filp_epoll, slot.tfd, slot.toff); + if (IS_ERR(filp_tgt)) + ret = PTR_ERR(filp_tgt); + else + ret = kcmp_ptr(filp, filp_tgt, KCMP_FILES); + } else + ret = -EBADF; + + if (filp_epoll) + fput(filp_epoll); + + return ret; +} +#else +static int kcmp_epoll_target(struct task_struct *task1, + struct task_struct *task2, + unsigned long idx1, + struct kcmp_epoll_slot __user *uslot) +{ + return -EOPNOTSUPP; +} +#endif + SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type, unsigned long, idx1, unsigned long, idx2) { @@ -165,6 +220,9 @@ SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t ret = -EOPNOTSUPP; #endif break; + case KCMP_EPOLL_TFD: + ret = kcmp_epoll_target(task1, task2, idx1, (void *)idx2); + break; default: ret = -EINVAL; break;