From patchwork Fri Mar 10 08:16:57 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cyrill Gorcunov X-Patchwork-Id: 9615189 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 DF2A260415 for ; Fri, 10 Mar 2017 08:23:49 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CE313286E3 for ; Fri, 10 Mar 2017 08:23:49 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C11AD28706; Fri, 10 Mar 2017 08:23:49 +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=-6.3 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI, RCVD_IN_SORBS_SPAM, T_DKIM_INVALID 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 3A1AF286E3 for ; Fri, 10 Mar 2017 08:23:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755230AbdCJIXh (ORCPT ); Fri, 10 Mar 2017 03:23:37 -0500 Received: from mail-lf0-f67.google.com ([209.85.215.67]:35137 "EHLO mail-lf0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755166AbdCJIXg (ORCPT ); Fri, 10 Mar 2017 03:23:36 -0500 Received: by mail-lf0-f67.google.com with SMTP id v2so6297939lfi.2; Fri, 10 Mar 2017 00:23:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:message-id:user-agent:date:from:to:cc:subject:mime-version :content-disposition; bh=bPJMi3ONMLcX2iHjKeVgovjaIZB8FWGoh6oY0y9sqvs=; b=Usn9qm6uPd/Lt0MAJlk93kDl8SoxBMgscC+yQ0tCB48mB3RdzT5RM+UJEmo0sg3cUe eGizHbPy/3J0drNkrWqSxvV1C2dbEBVmXglE/vlnvnDIm6PzMIvnenYZMXNsvYdQCAks JAx/9hc+giropAlaLpFCNZxvPoyRVWh96sfADyxGbFbmdgf382LfXPamzwlH/D2EBW4A kEGQqCp8BBqT7qO61mJD38EZCDBeSOJO1eRJ+lHLbh/XTfBVqTz6S2Zked0zkt+7jDTP h329hkoSe2Hq4gd+HpRcs4OxosucouC3OfDBtSaYYXCJlyvBMi51TqDqalqAMDGakGkB lYgA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:message-id:user-agent:date:from:to:cc :subject:mime-version:content-disposition; bh=bPJMi3ONMLcX2iHjKeVgovjaIZB8FWGoh6oY0y9sqvs=; b=LMLVU0SXUtWAOU70EgyuKwhri0jtzSQEinj80rhHB5ehn50cqVosz3L6FVg/I32a7j AOqVWbg95h6K110KYOhTkODrjVOoKEFgIgieHD9AibLsZZyVbqBpPOdzReRnAi/cIIwc o9CAYCJxNbu7J0SfW7HsRYx7/1staQA2tKMTvBHX15k541758lfOxGiCpPTbt5v1Ou2O SfE+qI2evC5eSCIgGPAllbndkZa4LHEXyFHkMKtmKg78zpRx1wbN7xRJjHf2Q6zGoWDU 027/OkzfpC0M9kIed4/4u6+sB1bi/L37jAykPhpU7Fwd6d5zaLcvLcA9+YT2iGRWcBUT QZww== X-Gm-Message-State: AMke39n1bF7OJE3ZOFnW2OWYlpCUVEpAqqjCSvmQ1Fk8rii0SVqBvTgrQqZpPW53jE8LBw== X-Received: by 10.46.0.80 with SMTP id 77mr5748726lja.1.1489134213462; Fri, 10 Mar 2017 00:23:33 -0800 (PST) Received: from uranus.localdomain ([5.18.238.201]) by smtp.gmail.com with ESMTPSA id f28sm1721261lfi.52.2017.03.10.00.23.32 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 10 Mar 2017 00:23:32 -0800 (PST) Received: by uranus.localdomain (Postfix, from userid 1000) id 7B2A624932; Fri, 10 Mar 2017 11:21:46 +0300 (MSK) Message-Id: <20170310082146.103151106@openvz.org> User-Agent: quilt/0.64 Date: Fri, 10 Mar 2017 11:16:57 +0300 From: Cyrill Gorcunov To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Cc: viro@zeniv.linux.org.uk, akpm@linuxfoundation.org, avagin@virtuozzo.com, xemul@virtuozzo.com, mtk.manpages@gmail.com, kir@openvz.org, gorcunov@openvz.org, Andrey Vagin , Jason Baron , Andy Lutomirski Subject: [patch 2/3] kcmp: Add KCMP_EPOLL_TFD mode to compare epoll target files MIME-Version: 1.0 Content-Disposition: inline; filename=kcmp-epoll-3 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 the target file is present to add it into 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. 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 v3: - Use less if()s in kcmp_epoll_target for readability sake (by avagin@) - Use u32 for kcmp_epoll_slot::toff instead of u64, which makes the less memory pressue 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 Acked-by: Andrei Vagin --- fs/eventpoll.c | 42 +++++++++++++++++++++++++++++++++++ include/linux/eventpoll.h | 3 ++ include/uapi/linux/kcmp.h | 10 ++++++++ kernel/kcmp.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 110 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 +98,54 @@ 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; + + if (copy_from_user(&slot, uslot, sizeof(slot))) + return -EFAULT; + + filp = get_file_raw_ptr(task1, idx1); + if (!filp) + return -EBADF; + + files = get_files_struct(task2); + if (!files) + return -EBADF; + + spin_lock(&files->file_lock); + filp_epoll = fcheck_files(files, slot.efd); + if (filp_epoll) + get_file(filp_epoll); + else + filp_tgt = ERR_PTR(-EBADF); + spin_unlock(&files->file_lock); + put_files_struct(files); + + if (filp_epoll) { + filp_tgt = get_epoll_tfile_raw_ptr(filp_epoll, slot.tfd, slot.toff); + fput(filp_epoll); + } + + return IS_ERR(filp_tgt) ? PTR_ERR(filp_tgt) : + kcmp_ptr(filp, filp_tgt, KCMP_FILES); +} +#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 +217,9 @@ 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;