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Fri, 24 Jan 2025 23:55:05 GMT Received: from pps.reinject (localhost [127.0.0.1]) by phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTPS id 44917u4a2t-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 24 Jan 2025 23:55:05 +0000 Received: from phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 50ONsxPi018051; Fri, 24 Jan 2025 23:55:04 GMT Received: from localhost.us.oracle.com (dhcp-10-65-130-174.vpn.oracle.com [10.65.130.174]) by phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTP id 44917u49ww-2; Fri, 24 Jan 2025 23:55:04 +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, jthoughton@google.com, corbet@lwn.net, dave.hansen@intel.com, kirill@shutemov.name, luto@kernel.org, brauner@kernel.org, arnd@arndb.de, ebiederm@xmission.com, catalin.marinas@arm.com, mingo@redhat.com, peterz@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, tglx@linutronix.de, cgroups@vger.kernel.org, x86@kernel.org, linux-doc@vger.kernel.org, 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: [PATCH 01/20] mm: Add msharefs filesystem Date: Fri, 24 Jan 2025 15:54:35 -0800 Message-ID: <20250124235454.84587-2-anthony.yznaga@oracle.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20250124235454.84587-1-anthony.yznaga@oracle.com> References: <20250124235454.84587-1-anthony.yznaga@oracle.com> MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-01-24_10,2025-01-23_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 phishscore=0 mlxscore=0 spamscore=0 mlxlogscore=999 bulkscore=0 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2411120000 definitions=main-2501240162 X-Proofpoint-ORIG-GUID: H3g567xUR2NiiHY65FwJbZPol2W-orgQ X-Proofpoint-GUID: H3g567xUR2NiiHY65FwJbZPol2W-orgQ X-Rspamd-Queue-Id: 1D744A0002 X-Stat-Signature: 9efkne5shm497i8kj5hq4eufn11db3wc X-Rspamd-Server: rspam08 X-Rspam-User: X-HE-Tag: 1737762930-555433 X-HE-Meta: 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 VrxBf6oy Bs8V9tPCJ24FPpe2XnNsZnKVs1SiJivEyJPTGK1Zm9nGkaqG4FL/seGqcKAfq/xHnt3qCIMQyjLBtBW19A1E/i/zFItRDU9EYdsfy/2N2Q6wWRjbd9SWz8lE2IARmbzywVd1SqiO7A/FvyX+lvsIE44sYzBy6WNznTUquF604bPFpHgn0gWgyXwI7xcbaQ2QKxsZ+m0bf6SEaS2IUjPWI5hBjbVhJ9BwPBpaj4+blA/AqZ34AxjKavDM7JutI0jaF22G/ithR+A1SsyqrrsugIVNrjA== 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 and a CONFIG_MSHARE option for compiling support in a kernel. Signed-off-by: Khalid Aziz Signed-off-by: Anthony Yznaga --- Documentation/filesystems/msharefs.rst | 107 +++++++++++++++++++++++++ include/uapi/linux/magic.h | 1 + mm/Kconfig | 9 +++ mm/Makefile | 4 + mm/mshare.c | 96 ++++++++++++++++++++++ 5 files changed, 217 insertions(+) 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..c3c7168aa18f --- /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. To enable support for +msharefs the kernel must be compiled with CONFIG_MSHARE set. + +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/Kconfig b/mm/Kconfig index 1b501db06417..ba3dbe31f86a 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -1358,6 +1358,15 @@ config PT_RECLAIM Note: now only empty user PTE page table pages will be reclaimed. +config MSHARE + bool "Mshare" + depends on MMU + help + Enable msharefs: A ram-based filesystem that allows multiple + processes to share page table entries for shared pages. A file + created on msharefs represents a shared region where all processes + mapping that region will map objects within it with shared PTEs. + Ioctls are used to configure and map objects into the shared region source "mm/damon/Kconfig" diff --git a/mm/Makefile b/mm/Makefile index 850386a67b3e..68bc967863f9 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -48,6 +48,10 @@ ifdef CONFIG_64BIT mmu-$(CONFIG_MMU) += mseal.o endif +ifdef CONFIG_MSHARE +mmu-$(CONFIG_MMU) += mshare.o +endif + obj-y := filemap.o mempool.o oom_kill.o fadvise.o \ maccess.o page-writeback.o folio-compat.o \ readahead.o swap.o truncate.o vmscan.o shrinker.o \ diff --git a/mm/mshare.c b/mm/mshare.c new file mode 100644 index 000000000000..49d32e0c20d2 --- /dev/null +++ b/mm/mshare.c @@ -0,0 +1,96 @@ +// 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, +}; + +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);