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Tue, 3 Sep 2024 23:23:17 GMT Received: from pps.reinject (localhost [127.0.0.1]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTPS id 41bsmfmn7q-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 03 Sep 2024 23:23:17 +0000 Received: from iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 483NMkf8040456; Tue, 3 Sep 2024 23:23:16 GMT Received: from localhost.us.oracle.com (dhcp-10-159-133-114.vpn.oracle.com [10.159.133.114]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTP id 41bsmfmmwr-2; Tue, 03 Sep 2024 23:23:15 +0000 From: Anthony Yznaga To: akpm@linux-foundation.org, willy@infradead.org, markhemm@googlemail.com, viro@zeniv.linux.org.uk, david@redhat.com, khalid@kernel.org Cc: anthony.yznaga@oracle.com, andreyknvl@gmail.com, dave.hansen@intel.com, luto@kernel.org, brauner@kernel.org, arnd@arndb.de, ebiederm@xmission.com, catalin.marinas@arm.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhiramat@kernel.org, rostedt@goodmis.org, vasily.averin@linux.dev, xhao@linux.alibaba.com, pcc@google.com, neilb@suse.de, maz@kernel.org Subject: [RFC PATCH v3 01/10] mm: Add msharefs filesystem Date: Tue, 3 Sep 2024 16:22:32 -0700 Message-ID: <20240903232241.43995-2-anthony.yznaga@oracle.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20240903232241.43995-1-anthony.yznaga@oracle.com> References: <20240903232241.43995-1-anthony.yznaga@oracle.com> MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.60.29 definitions=2024-09-03_11,2024-09-03_01,2024-09-02_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxscore=0 mlxlogscore=876 suspectscore=0 phishscore=0 bulkscore=0 adultscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2407110000 definitions=main-2409030187 X-Proofpoint-GUID: AbPuJa1pBRboO3bqigacEes6kB0erZoG X-Proofpoint-ORIG-GUID: AbPuJa1pBRboO3bqigacEes6kB0erZoG X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 3F16B12000A X-Stat-Signature: oyeb89i7ksn9arr54bf13wmqnti85xkr X-Rspam-User: X-HE-Tag: 1725405813-659108 X-HE-Meta: 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 grFRSW8r k5fjGtuCAgtN3935NVyuWJ9kD3x49O60CjGRFYw/TypsYbAv4CUedSWeNf1w1t8BdAtn/V2Q53x9CbtIyezKmIIsrx2TqQAK/OK/ckPe9Hr/VV7DLg9+T1DEAhZqzjdNv5Ec5ht9aBC5IMHpmjz2DP1lSNFCXIcmnsi4wkNPaEPwl7OT4W2aLk2m2Eu4mpYQ03+EMrJ4lJKUnqiLQUnYwOPj4T1P58Yolrw7ZhkZdeVfGlksftwh0hsy0b/XA2gVTBOBrTYmMgGXlOX4mgY+V4xUBVTIduNOjEOugNdTxxTIj15I= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Khalid Aziz Add a ram-based filesystem that contains page table sharing information and files that enables processes to share page tables. This patch adds the basic filesystem that can be mounted. Signed-off-by: Khalid Aziz Signed-off-by: Anthony Yznaga --- Documentation/filesystems/msharefs.rst | 107 +++++++++++++++++++++++++ include/uapi/linux/magic.h | 1 + mm/Makefile | 2 +- mm/mshare.c | 97 ++++++++++++++++++++++ 4 files changed, 206 insertions(+), 1 deletion(-) create mode 100644 Documentation/filesystems/msharefs.rst create mode 100644 mm/mshare.c diff --git a/Documentation/filesystems/msharefs.rst b/Documentation/filesystems/msharefs.rst new file mode 100644 index 000000000000..727cda663b0b --- /dev/null +++ b/Documentation/filesystems/msharefs.rst @@ -0,0 +1,107 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================================================== +msharefs - a filesystem to support shared page tables +===================================================== + +msharefs is a ram-based filesystem that allows multiple processes to +share page table entries for shared pages. + +msharefs is typically mounted like this:: + + mount -t msharefs none /sys/fs/mshare + +A file created on msharefs creates a new shared region where all +processes mapping that region will map it using shared page table +entries. ioctls are used to initialize or retrieve the start address +and size of a shared region and to map objects in the shared +region. It is important to note that an msharefs file is a control +file for the shared region and does not contain the contents +of the region itself. + +Here are the basic steps for using mshare:: + +1. Mount msharefs on /sys/fs/mshare:: + + mount -t msharefs msharefs /sys/fs/mshare + +2. mshare regions have alignment and size requirements. Start + address for the region must be aligned to an address boundary and + be a multiple of fixed size. This alignment and size requirement + can be obtained by reading the file ``/sys/fs/mshare/mshare_info`` + which returns a number in text format. mshare regions must be + aligned to this boundary and be a multiple of this size. + +3. For the process creating an mshare region:: + +a. Create a file on /sys/fs/mshare, for example: + +.. code-block:: c + + fd = open("/sys/fs/mshare/shareme", + O_RDWR|O_CREAT|O_EXCL, 0600); + +b. Establish the starting address and size of the region: + +.. code-block:: c + + struct mshare_info minfo; + + minfo.start = TB(2); + minfo.size = BUFFER_SIZE; + ioctl(fd, MSHAREFS_SET_SIZE, &minfo); + +c. Map some memory in the region: + +.. code-block:: c + + struct mshare_create mcreate; + + mcreate.addr = TB(2); + mcreate.size = BUFFER_SIZE; + mcreate.offset = 0; + mcreate.prot = PROT_READ | PROT_WRITE; + mcreate.flags = MAP_ANONYMOUS | MAP_SHARED | MAP_FIXED; + mcreate.fd = -1; + + ioctl(fd, MSHAREFS_CREATE_MAPPING, &mcreate); + +d. Map the mshare region into the process: + +.. code-block:: c + + mmap((void *)TB(2), BUF_SIZE, + PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + +e. Write and read to mshared region normally. + + +4. For processes attaching an mshare region:: + +a. Open the file on msharefs, for example: + +.. code-block:: c + + fd = open("/sys/fs/mshare/shareme", O_RDWR); + +b. Get information about mshare'd region from the file: + +.. code-block:: c + + struct mshare_info minfo; + + ioctl(fd, MSHAREFS_GET_SIZE, &minfo); + +c. Map the mshare'd region into the process: + +.. code-block:: c + + mmap(minfo.start, minfo.size, + PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + +5. To delete the mshare region: + +.. code-block:: c + + unlink("/sys/fs/mshare/shareme"); + diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h index bb575f3ab45e..e53dd6063cba 100644 --- a/include/uapi/linux/magic.h +++ b/include/uapi/linux/magic.h @@ -103,5 +103,6 @@ #define DEVMEM_MAGIC 0x454d444d /* "DMEM" */ #define SECRETMEM_MAGIC 0x5345434d /* "SECM" */ #define PID_FS_MAGIC 0x50494446 /* "PIDF" */ +#define MSHARE_MAGIC 0x4d534852 /* "MSHR" */ #endif /* __LINUX_MAGIC_H__ */ diff --git a/mm/Makefile b/mm/Makefile index d2915f8c9dc0..956137de9e1f 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -45,7 +45,7 @@ mmu-$(CONFIG_MMU) += process_vm_access.o endif ifdef CONFIG_64BIT -mmu-$(CONFIG_MMU) += mseal.o +mmu-$(CONFIG_MMU) += mseal.o mshare.o endif obj-y := filemap.o mempool.o oom_kill.o fadvise.o \ diff --git a/mm/mshare.c b/mm/mshare.c new file mode 100644 index 000000000000..d5d8e2530e5a --- /dev/null +++ b/mm/mshare.c @@ -0,0 +1,97 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Enable cooperating processes to share page table between + * them to reduce the extra memory consumed by multiple copies + * of page tables. + * + * This code adds an in-memory filesystem - msharefs. + * msharefs is used to manage page table sharing + * + * + * Copyright (C) 2024 Oracle Corp. All rights reserved. + * Author: Khalid Aziz + * + */ + +#include +#include +#include + +static const struct file_operations msharefs_file_operations = { + .open = simple_open, + .llseek = no_llseek, +}; + +static const struct super_operations mshare_s_ops = { + .statfs = simple_statfs, +}; + +static int +msharefs_fill_super(struct super_block *sb, struct fs_context *fc) +{ + struct inode *inode; + + sb->s_blocksize = PAGE_SIZE; + sb->s_blocksize_bits = PAGE_SHIFT; + sb->s_magic = MSHARE_MAGIC; + sb->s_op = &mshare_s_ops; + sb->s_time_gran = 1; + + inode = new_inode(sb); + if (!inode) + return -ENOMEM; + + inode->i_ino = 1; + inode->i_mode = S_IFDIR | 0777; + simple_inode_init_ts(inode); + inode->i_op = &simple_dir_inode_operations; + inode->i_fop = &simple_dir_operations; + set_nlink(inode, 2); + + sb->s_root = d_make_root(inode); + if (!sb->s_root) + return -ENOMEM; + + return 0; +} + +static int +msharefs_get_tree(struct fs_context *fc) +{ + return get_tree_nodev(fc, msharefs_fill_super); +} + +static const struct fs_context_operations msharefs_context_ops = { + .get_tree = msharefs_get_tree, +}; + +static int +mshare_init_fs_context(struct fs_context *fc) +{ + fc->ops = &msharefs_context_ops; + return 0; +} + +static struct file_system_type mshare_fs = { + .name = "msharefs", + .init_fs_context = mshare_init_fs_context, + .kill_sb = kill_litter_super, +}; + +static int __init +mshare_init(void) +{ + int ret; + + ret = sysfs_create_mount_point(fs_kobj, "mshare"); + if (ret) + return ret; + + ret = register_filesystem(&mshare_fs); + if (ret) + sysfs_remove_mount_point(fs_kobj, "mshare"); + + return ret; +} + +core_initcall(mshare_init);