├── .github ├── FUNDING.yml └── workflows │ └── ci-ubuntu-latest.yml ├── LICENSE ├── Makefile ├── README.md ├── debian ├── changelog ├── compat ├── control ├── copyright ├── nullfsvfs.dkms ├── rules └── source │ └── format ├── nullfs.c ├── nullfs.jpg └── rpm ├── README.md └── nullfsvfs-kmod.spec /.github/FUNDING.yml: -------------------------------------------------------------------------------- 1 | github: abbbi 2 | buy_me_a_coffee: abbbi 3 | -------------------------------------------------------------------------------- /.github/workflows/ci-ubuntu-latest.yml: -------------------------------------------------------------------------------- 1 | name: nullfsvfs CI on ubuntu-latest 2 | 3 | on: [push, pull_request] 4 | 5 | jobs: 6 | build: 7 | runs-on: ubuntu-latest 8 | steps: 9 | - uses: actions/checkout@v2 10 | - uses: abbbi/github-actions-tune@v1 11 | - name: apt update 12 | run: sudo apt-get update 13 | - name: Install build-essential and devscripts 14 | run: sudo apt-get install build-essential devscripts equivs acl codespell dh-dkms 15 | - name: Run codespell 16 | run: codespell -L filp,iput . 17 | - name: Install Kernel Build Dependencies 18 | run: sudo mk-build-deps --install debian/control 19 | - name: Remove dependency package 20 | run: rm -f nullfsvfs-build-deps*.deb 21 | - name: Build Debian package 22 | run: sudo -E dpkg-buildpackage -uc -us -b 23 | - name: Install generated Package 24 | run: sudo dpkg -i ../nullfsvfs_*_amd64.deb 25 | - name: Modprobe kernel module 26 | run: sudo modprobe nullfs 27 | - name: Mount nullfs 28 | run: sudo mount -t nullfs none /mnt 29 | - name: Test filecopy 30 | run: sudo cp -r /etc/ /mnt/ 31 | - name: Test mknod 32 | run: sudo mknod /mnt/nod c 1 8 33 | - name: Test acl 34 | run: | 35 | sudo mkdir /mnt/acl_dir 36 | sudo touch /mnt/acl_file 37 | sudo setfacl -m d:u:root:r /mnt/acl_dir 38 | sudo setfacl -m u:root:r /mnt/acl_file 39 | sudo setfacl -m u:root:r /mnt/nod 40 | - name: Test file 41 | run: sudo dd if=/dev/zero of=/mnt/direct bs=1M count=1953 42 | - name: Test filesize 43 | run: sudo stat --printf '%s' /mnt/direct | grep 2047868928 44 | - name: Umount nullfs 45 | run: sudo umount /mnt 46 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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Limitation of Liability. 601 | 602 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 603 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS 604 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY 605 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE 606 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF 607 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD 608 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 609 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF 610 | SUCH DAMAGES. 611 | 612 | 17. Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /Makefile: -------------------------------------------------------------------------------- 1 | obj-m := nullfs.o 2 | 3 | all: ko 4 | ko: 5 | make -C /lib/modules/$(shell uname -r)/build M=$(shell pwd) modules 6 | 7 | clean: 8 | make -C /lib/modules/$(shell uname -r)/build M=$(shell pwd) clean 9 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | [![nullfsvfs CI on ubuntu-latest](https://github.com/abbbi/nullfsvfs/actions/workflows/ci-ubuntu-latest.yml/badge.svg?branch=master)](https://github.com/abbbi/nullfsvfs/actions/workflows/ci-ubuntu-latest.yml) 2 | 3 | 4 | 5 | 6 | - [nullfs](#nullfs) 7 | - [installation](#installation) 8 | - [manual installation](#manual-installation) 9 | - [debian package](#debian-package) 10 | - [Usage](#usage) 11 | - [Keeping file data](#keeping-file-data) 12 | - [ACL](#acl) 13 | - [usecases](#usecases) 14 | - [supported mount options](#supported-mount-options) 15 | - [todos/ideas](#todosideas) 16 | 17 | 18 | 19 | # nullfs 20 | A virtual file system that behaves like /dev/null 21 | 22 | It can handle regular file operations like mkdir/rmdir/ln but writing to files 23 | does not store any data. The file size is however saved, reading from the 24 | files behaves like reading from /dev/zero. 25 | 26 | Writing and reading is basically an NOOP, so it can be used for performance 27 | testing with applications that require directory structures. Implemented as 28 | kernel module, instead of using FUSE, there is absolutely no overhead for 29 | copying application data from user to kernel space while performing write or 30 | read operations. 31 | 32 | ![alt text](https://github.com/abbbi/nullfsvfs/raw/master/nullfs.jpg) 33 | 34 | ``` 35 | # sudo make 36 | make -C /lib/modules/4.18.5/build M=/home/abi/lwnfs modules 37 | make[1]: Entering directory '/usr/src/linux-headers-4.18.5' 38 | Building modules, stage 2. 39 | MODPOST 1 modules 40 | make[1]: Leaving directory '/usr/src/linux-headers-4.18.5' 41 | 42 | # insmod nullfs.ko 43 | # mkdir /sinkhole 44 | # mount -t nullfs none /sinkhole/ 45 | # mkdir /sinkhole/testdir 46 | # touch /sinkhole/testdir/myfile 47 | # echo foobar > /sinkhole/testdir/myfile 48 | # ls -lah /sinkhole/testdir/myfile 49 | -rw-r--r-- 1 root root 0 Nov 8 20:17 /sinkhole/testdir/myfile 50 | # cat /sinkhole/testdir/myfile 51 | # pv < /dev/zero > /sinkhole/testdir/myfile 52 | 11.1GiB 0:00:04 [3.85GiB/s] [ <=> ] 53 | # cat /sinkhole/testdir/myfile 54 | # 55 | ``` 56 | 57 | File size is preserved to work around applications that do size checks: 58 | 59 | ``` 60 | # dd if=/dev/zero of=/nullfs/DATA bs=1M count=20 61 | 20+0 records in 62 | 20+0 records out 63 | 20971520 bytes (21 MB, 20 MiB) copied, 0.00392452 s, 5.3 GB/s 64 | # stat -c%s /nullfs/DATA 65 | 20971520 66 | ``` 67 | 68 | Reading from the files does not copy anything to userspace and is an NOOP; 69 | makes it behave like reading from /dev/zero: 70 | 71 | ``` 72 | # dd if=/nullfs/DATA of=/tmp/REALFILE 73 | 40960+0 records in 74 | 40960+0 records out 75 | 20971520 bytes (21 MB, 20 MiB) copied, 0.0455288 s, 461 MB/s 76 | # hexdump -C /tmp/REALFILE 77 | 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 78 | ``` 79 | 80 | 81 | ## installation 82 | 83 | ### manual installation 84 | 85 | To install the module for the running linux kernel use: 86 | 87 | ``` 88 | # make -C /lib/modules/$(uname -r)/build M=$PWD modules_install INSTALL_MOD_DIR=kernel/fs/nullfs 89 | # depmod 90 | ``` 91 | 92 | Running `depmod` is mandatory. Now the module can be loaded via: 93 | 94 | ``` 95 | # modprobe nullfs 96 | ``` 97 | 98 | To automatically load the module during system boot, create a configuration 99 | file suitable for your distribution (usually located in */etc/modules-load.d*): 100 | 101 | ``` 102 | # echo nullfs > /etc/modules-load.d/nullfs.conf 103 | ``` 104 | 105 | Example entry for `/etc/fstab`, mounting the filesystem to `/nullfs`: 106 | 107 | 108 | ``` 109 | none /nullfs nullfs auto 110 | ``` 111 | 112 | ### debian package 113 | 114 | ``` 115 | # apt-get install debhelper dkms dh-dkms 116 | # dpkg-buildpackage -uc -us -rfakeroot 117 | # dpkg -i ../nullfsvfs__amd64.deb 118 | ``` 119 | 120 | ## Usage 121 | ### Keeping file data 122 | 123 | There is the possibility to exclude certain files from being sent into the 124 | void. If, for example, the file matching "fstab" should be kept in memory, 125 | mount nullfs with the "write=" option. 126 | 127 | ``` 128 | # mount -t nullfs none /sinkhole/ -o write=fstab 129 | # cp /etc/fstab /sinkhole/ 130 | # wc -l /sinkhole/fstab 131 | 14 /sinkhole/fstab 132 | # cp /etc/passwd /sinkhole/ 133 | # wc -l /sinkhole/passwd 134 | 0 /sinkhole/passwd 135 | ``` 136 | 137 | Another option is using the sysfs interface to change the exclude string 138 | after the module has been loaded: 139 | 140 | ``` 141 | # echo foo > /sys/fs/nullfs/exclude 142 | ``` 143 | 144 | Keep in mind that file data is kept in memory and no boundary checks are done, 145 | so this might fill up your RAM in case you exclude big files from being 146 | nulled. 147 | 148 | ### ACL 149 | 150 | It is possible to set POSIX ACL attributes via `setfacl` so it appears the 151 | filesystem supports them, they are not saved. 152 | 153 | Works with recent linux kernels (5.x), nullfs builds fine with older kernels 154 | (4.x, 3.x) but setting ACL information fails with "Operation not supported". 155 | 156 | ### usecases 157 | 158 | See: [Use Cases ](https://github.com/abbbi/nullfsvfs/labels/Usecase) 159 | 160 | The module has been used for performance testing with redis, see: 161 | 162 | https://www.usenix.org/system/files/atc20-george.pdf 163 | 164 | Please report usecases as regular issues! 165 | 166 | ### supported mount options 167 | 168 | The following mount options are supported: 169 | ``` 170 | -o mode= set permissions on mount directory ( mount .. -o mode=777 ) 171 | -o uid= set uid on mount directory ( mount .. -o uid=1000 ) 172 | -o gid= set gid on mount directory ( mount .. -o gid=1000 ) 173 | -o write=fn keep data for specific file ( mount .. -o write=fstab ) 174 | ``` 175 | 176 | ### todos/ideas 177 | 178 | * replace simple_statfs call with real one, show free space of a directory that 179 | can be passed during kernel module load 180 | * support multiple parameters for write= option 181 | * allow regex for write= option via trace.h 182 | * simulate xattr support? 183 | -------------------------------------------------------------------------------- /debian/changelog: -------------------------------------------------------------------------------- 1 | nullfsvfs (0.18) unstable; urgency=medium 2 | 3 | * Support for kernel versions 6.15 4 | 5 | -- Michael Ablassmeier Wed, 02 Apr 2025 08:48:43 +0200 6 | 7 | nullfsvfs (0.17) unstable; urgency=medium 8 | 9 | * Support for kernel versions 6.6/6.7 10 | 11 | -- Michael Ablassmeier Sat, 11 Nov 2023 20:27:10 +0100 12 | 13 | nullfsvfs (0.16) unstable; urgency=medium 14 | 15 | * Fix build on opensuse thumbleweed (kernel version 6.5.2) #20 16 | 17 | -- Michael Ablassmeier Thu, 14 Sep 2023 16:22:39 +0200 18 | 19 | nullfsvfs (0.15) unstable; urgency=medium 20 | 21 | * Adds support for kernel version 6.3, thanks Woody Suwalski 22 | 23 | -- Michael Ablassmeier Sun, 05 Mar 2023 18:23:08 +0100 24 | 25 | nullfsvfs (0.14) unstable; urgency=medium 26 | 27 | * Adds support for kernel version 6.2, thanks Woody Suwalski 28 | 29 | -- Michael Ablassmeier Tue, 27 Dec 2022 09:33:33 +0100 30 | 31 | nullfsvfs (0.13) unstable; urgency=medium 32 | 33 | * Adds support for kernel version 6.1, thanks Woody Suwalski 34 | 35 | -- Michael Ablassmeier Thu, 20 Oct 2022 20:54:13 +0200 36 | 37 | nullfsvfs (0.12) unstable; urgency=medium 38 | 39 | * Fix build on SLES based kernels, add #ifdef for RHEL_MAJOR. 40 | Module now builds on RHEL/Centos7,SLES12,SLES15 and newer. 41 | 42 | -- Michael Ablassmeier Wed, 29 Sep 2021 10:45:37 +0200 43 | 44 | nullfsvfs (0.11) unstable; urgency=medium 45 | 46 | * Re-Add support for older linux kernel versions (3.10.x) used 47 | by RHEL7 and Centos7 and SLES15, which was broken by adding Posix ACL 48 | and O_DIRECT support. 49 | 50 | -- Michael Ablassmeier Tue, 28 Sep 2021 16:37:59 +0200 51 | 52 | nullfsvfs (0.10) unstable; urgency=medium 53 | 54 | * Add support for kernel versions >= 5.14 55 | 56 | -- Michael Ablassmeier Fri, 10 Sep 2021 15:56:49 +0200 57 | 58 | nullfsvfs (0.9) unstable; urgency=medium 59 | 60 | * Raise version, new tarball with spec file included. 61 | * Simulates support for Posix ACL's 62 | 63 | -- Michael Ablassmeier Thu, 26 Aug 2021 15:57:22 +0200 64 | 65 | nullfsvfs (0.8) unstable; urgency=medium 66 | 67 | * Update Version 68 | * Add support for O_DIRECT flag 69 | * Print version information during filesystem initialization 70 | 71 | -- Michael Ablassmeier Mon, 12 Nov 2018 01:48:40 -0800 72 | 73 | nullfsvfs (0.6) unstable; urgency=medium 74 | 75 | * Update Version 76 | * Add support for O_TMPFILE flag 77 | 78 | -- Michael Ablassmeier Mon, 12 Nov 2018 01:48:40 -0800 79 | 80 | nullfsvfs (0.5) unstable; urgency=medium 81 | 82 | * Update Version 83 | 84 | -- Michael Ablassmeier Mon, 12 Nov 2018 01:48:40 -0800 85 | 86 | nullfsvfs (0.1) unstable; urgency=medium 87 | 88 | * Initial Release. 89 | 90 | -- Michael Ablassmeier Mon, 12 Nov 2018 01:48:40 -0800 91 | -------------------------------------------------------------------------------- /debian/compat: -------------------------------------------------------------------------------- 1 | 10 2 | -------------------------------------------------------------------------------- /debian/control: -------------------------------------------------------------------------------- 1 | Source: nullfsvfs 2 | Section: misc 3 | Priority: optional 4 | Maintainer: Michael Ablassmeier 5 | Build-Depends: debhelper (>= 9), dkms 6 | Standards-Version: 3.9.8 7 | Homepage: https://github.com/abbbi/nullfsvfs 8 | Vcs-Git: https://github.com/abbbi/nullfsvfs 9 | 10 | Package: nullfsvfs 11 | Architecture: any 12 | Depends: ${misc:Depends} 13 | Description: virtual file system that behaves like /dev/null 14 | Nullfsvfs is a virtual file system that can handle regular 15 | file operations like mkdir/rmdir/ln but won't store any data. 16 | -------------------------------------------------------------------------------- /debian/copyright: -------------------------------------------------------------------------------- 1 | Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/ 2 | Upstream-Name: nullfsvfs 3 | Source: https://github.com/abbbi/nullfsvfs 4 | 5 | Files: * 6 | License: GPL-2.0+ 7 | 8 | Files: debian/* 9 | Copyright: 2018 Michael Ablassmeier 10 | License: GPL-2.0+ 11 | 12 | License: GPL-2.0+ 13 | This package is free software; you can redistribute it and/or modify 14 | it under the terms of the GNU General Public License as published by 15 | the Free Software Foundation; either version 2 of the License, or 16 | (at your option) any later version. 17 | . 18 | This package is distributed in the hope that it will be useful, 19 | but WITHOUT ANY WARRANTY; without even the implied warranty of 20 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 21 | GNU General Public License for more details. 22 | . 23 | You should have received a copy of the GNU General Public License 24 | along with this program. If not, see 25 | . 26 | On Debian systems, the complete text of the GNU General 27 | Public License version 2 can be found in "/usr/share/common-licenses/GPL-2". 28 | 29 | # Please also look if there are files or directories which have a 30 | # different copyright/license attached and list them here. 31 | # Please avoid picking licenses with terms that are more restrictive than the 32 | # packaged work, as it may make Debian's contributions unacceptable upstream. 33 | -------------------------------------------------------------------------------- /debian/nullfsvfs.dkms: -------------------------------------------------------------------------------- 1 | PACKAGE_VERSION="#MODULE_VERSION#" 2 | PACKAGE_NAME="nullfsvfs" 3 | CLEAN="make clean" 4 | BUILT_MODULE_NAME[0]="nullfs" 5 | BUILT_MODULE_LOCATION[0]="./" 6 | DEST_MODULE_LOCATION[0]="/kernel/fs" 7 | MAKE[1]="make" 8 | AUTOINSTALL="yes" 9 | 10 | -------------------------------------------------------------------------------- /debian/rules: -------------------------------------------------------------------------------- 1 | #!/usr/bin/make -f 2 | 3 | VERSION=$(shell dpkg-parsechangelog |grep ^Version:|cut -d ' ' -f 2) 4 | 5 | %: 6 | dh $@ --with dkms 7 | 8 | override_dh_install: 9 | dh_install Makefile nullfs.c usr/src/nullfsvfs-$(VERSION)/ 10 | 11 | override_dh_dkms: 12 | dh_dkms -V $(VERSION) 13 | -------------------------------------------------------------------------------- /debian/source/format: -------------------------------------------------------------------------------- 1 | 3.0 (native) 2 | -------------------------------------------------------------------------------- /nullfs.c: -------------------------------------------------------------------------------- 1 | /* 2 | * Nullfs. 3 | * 4 | * 5 | * Copyright (C) 2018 Michael Ablassmeier 6 | * 7 | * This program is free software: you can redistribute it and/or modify 8 | * it under the terms of the GNU General Public License as published by 9 | * the Free Software Foundation, either version 3 of the License, or 10 | * (at your option) any later version. 11 | * 12 | * This program is distributed in the hope that it will be useful, 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 | * GNU General Public License for more details. 16 | * 17 | * You should have received a copy of the GNU General Public License 18 | * along with this program. If not, see . 19 | * 20 | * 21 | * 22 | * Create a file system that stores its structure in memory but 23 | * written data is sent to a blackhole. May be used for performance 24 | * testing etc.. 25 | */ 26 | #include 27 | #include 28 | #include 29 | #include 30 | #include 31 | #include 32 | #include 33 | #include 34 | #include 35 | #include 36 | #include 37 | #include 38 | #include 39 | #include 40 | #include 41 | 42 | #define NULLFS_MAGIC 0x19980123 43 | #define NULLFS_DEFAULT_MODE 0755 44 | #define NULLFS_SYSFS_MODE 0644 45 | #define NULLFS_VERSION "0.18" 46 | 47 | MODULE_AUTHOR("Michael Ablassmeier"); 48 | MODULE_LICENSE("GPL"); 49 | MODULE_VERSION(NULLFS_VERSION); 50 | 51 | struct inode *nullfs_get_inode(struct super_block*, const struct inode*, umode_t, dev_t, struct dentry*); 52 | int nullfs_statfs(struct dentry*, struct kstatfs*); 53 | int nullfs_fill_super(struct super_block*, void*, int); 54 | 55 | /* 56 | * POSIX ACL 57 | * setfacl is possible, but acls are not stored, of course 58 | * 59 | * For older kernel versions (3.x, used on rhel7/centos7 its required to 60 | * redefine some non-public functions to make it "work", so we skip.. 61 | */ 62 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 0, 0) 63 | static const struct xattr_handler *nullfs_xattr_handlers[] = { 64 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 5, 2) 65 | &nop_posix_acl_access, 66 | &nop_posix_acl_default, 67 | #else 68 | &posix_acl_access_xattr_handler, 69 | &posix_acl_default_xattr_handler, 70 | #endif 71 | NULL 72 | }; 73 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) 74 | static int nullfs_set_acl(struct mnt_idmap *idmap, 75 | struct dentry *dentry, struct posix_acl *acl, int type) 76 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(6, 2, 0) 77 | static int nullfs_set_acl(struct user_namespace *mnt_userns, 78 | struct dentry *dentry, struct posix_acl *acl, int type) 79 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) 80 | static int nullfs_set_acl(struct user_namespace *mnt_userns, 81 | struct inode *inode, struct posix_acl *acl, int type) 82 | #else 83 | static int nullfs_set_acl(struct inode *inode, struct posix_acl *acl, int type) 84 | #endif 85 | { 86 | return 0; 87 | } 88 | #endif 89 | 90 | /* 91 | * sysfs handlers 92 | */ 93 | static char exclude[100] = "\0"; 94 | static ssize_t exclude_show(struct kobject *kobj, struct kobj_attribute *attr, 95 | char *buf) 96 | { 97 | return sprintf(buf, "%s", exclude); 98 | } 99 | 100 | static ssize_t exclude_store(struct kobject *kobj, struct kobj_attribute *attr, 101 | const char *buf, size_t count) 102 | { 103 | char *p; 104 | p = strchr(buf,'\n'); 105 | if (p) 106 | *p = '\0'; 107 | strncpy(exclude, buf, sizeof(exclude)); 108 | printk(KERN_INFO "nullfs: will keep data for files matching: [%s]\n", 109 | exclude); 110 | return count; 111 | } 112 | 113 | static struct kobj_attribute exclude_attribute = 114 | __ATTR(exclude, NULLFS_SYSFS_MODE, exclude_show, exclude_store); 115 | 116 | static struct attribute *attrs[] = { 117 | &exclude_attribute.attr, 118 | NULL, /* need to NULL terminate the list of attributes */ 119 | }; 120 | 121 | static struct attribute_group attr_group = { 122 | .attrs = attrs, 123 | }; 124 | 125 | static struct kobject *exclude_kobj; 126 | 127 | /** 128 | * regular filesystem handlers, inode handling etc.. 129 | **/ 130 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) 131 | static int nullfs_getattr(struct mnt_idmap *idmap, 132 | const struct path *path, struct kstat *stat, u32 request_mask, unsigned int flags) 133 | { 134 | struct inode *inode = path->dentry->d_inode; 135 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) 136 | static int nullfs_getattr(struct user_namespace *mnt_userns, 137 | const struct path *path, struct kstat *stat, u32 request_mask, unsigned int flags) 138 | { 139 | struct inode *inode = path->dentry->d_inode; 140 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(4, 11, 0) 141 | static int nullfs_getattr(const struct path *path, struct kstat *stat, 142 | u32 request_mask, unsigned int flags) 143 | { 144 | struct inode *inode = path->dentry->d_inode; 145 | #else 146 | static int nullfs_getattr(struct vfsmount *mnt, 147 | struct dentry *dentry, struct kstat *stat) 148 | { 149 | struct inode *inode = dentry->d_inode; 150 | #endif 151 | 152 | unsigned long npages; 153 | 154 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 6, 0) 155 | generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat); 156 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) 157 | generic_fillattr(&nop_mnt_idmap, inode, stat); 158 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) 159 | generic_fillattr(&init_user_ns, inode, stat); 160 | #else 161 | generic_fillattr(inode, stat); 162 | #endif 163 | npages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT; 164 | stat->blocks = npages << (PAGE_SHIFT - 9); 165 | return 0; 166 | } 167 | 168 | static ssize_t write_null(struct file *filp, const char *buf, 169 | size_t count, loff_t *offset) { 170 | /** 171 | * keep track of size 172 | **/ 173 | struct inode *inode = file_inode(filp); 174 | i_size_write(inode, (inode->i_size + count)); 175 | return count; 176 | } 177 | 178 | static ssize_t read_null(struct file *filp, char *buf, 179 | size_t count, loff_t *offset) { 180 | 181 | /** 182 | * Pretend we have returned some data 183 | * during file read 184 | **/ 185 | int nbytes; 186 | struct inode * inode = filp->f_inode; 187 | 188 | if (*offset >= inode->i_size) { 189 | return 0; 190 | } 191 | 192 | nbytes = min((size_t) inode->i_size, count); 193 | *offset += nbytes; 194 | 195 | return nbytes; 196 | } 197 | 198 | const struct file_operations nullfs_file_operations = { 199 | .write = write_null, 200 | .read = read_null, 201 | .llseek = noop_llseek, 202 | .fsync = noop_fsync, 203 | }; 204 | 205 | const struct file_operations nullfs_real_file_operations = { 206 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 15, 0) 207 | .read_iter = generic_file_read_iter, 208 | .write_iter = generic_file_write_iter, 209 | #else 210 | .aio_read = generic_file_aio_read, 211 | .aio_write = generic_file_aio_write, 212 | #endif 213 | .mmap = generic_file_mmap, 214 | .fsync = noop_fsync, 215 | .llseek = generic_file_llseek, 216 | }; 217 | 218 | const struct inode_operations nullfs_file_inode_operations = { 219 | .setattr = simple_setattr, 220 | .getattr = nullfs_getattr, 221 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 0, 0) 222 | .set_acl = nullfs_set_acl, 223 | #endif 224 | }; 225 | const struct inode_operations nullfs_special_inode_operations = { 226 | .setattr = simple_setattr, 227 | .getattr = nullfs_getattr, 228 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 0, 0) 229 | .set_acl = nullfs_set_acl, 230 | #endif 231 | }; 232 | #if LINUX_VERSION_CODE < KERNEL_VERSION(5, 14, 0) 233 | static const struct address_space_operations nullfs_aops = { 234 | .readpage = simple_readpage, 235 | .write_begin = simple_write_begin, 236 | .write_end = simple_write_end, 237 | /** 238 | * RHEL kernel exports noop_direct_IO, SLES15 does not 239 | **/ 240 | #if LINUX_VERSION_CODE <= KERNEL_VERSION(5, 0, 0) 241 | #ifdef RHEL_MAJOR 242 | .direct_IO = noop_direct_IO 243 | #endif 244 | #else 245 | .direct_IO = noop_direct_IO 246 | #endif 247 | }; 248 | #endif 249 | 250 | static const struct inode_operations nullfs_dir_inode_operations; 251 | static const struct super_operations nullfs_ops; 252 | 253 | struct nullfs_mount_opts { 254 | char *write; 255 | umode_t mode; 256 | kuid_t uid; 257 | kgid_t gid; 258 | }; 259 | 260 | struct nullfs_fs_info { 261 | struct nullfs_mount_opts mount_opts; 262 | }; 263 | 264 | enum { 265 | Opt_write, 266 | Opt_mode, 267 | Opt_uid, 268 | Opt_gid, 269 | Opt_err 270 | }; 271 | 272 | static const match_table_t tokens = { 273 | {Opt_write, "write=%s"}, 274 | {Opt_mode, "mode=%s"}, 275 | {Opt_uid, "uid=%s"}, 276 | {Opt_gid, "gid=%s"}, 277 | {Opt_err, NULL} 278 | }; 279 | 280 | static int nullfs_parse_options(char *data, struct nullfs_mount_opts *opts) 281 | { 282 | substring_t args[MAX_OPT_ARGS]; 283 | char *option; 284 | int token; 285 | int opt; 286 | char *p; 287 | kuid_t uid; 288 | kgid_t gid; 289 | opts->write = NULL; 290 | opts->mode = NULLFS_DEFAULT_MODE; 291 | opts->uid = GLOBAL_ROOT_UID; 292 | opts->gid = GLOBAL_ROOT_GID; 293 | // maybe use fs_parse here? Not sure which kernel versions 294 | // support it 295 | while ((p = strsep(&data, ",")) != NULL) { 296 | if (!*p) 297 | continue; 298 | 299 | token = match_token(p, tokens, args); 300 | switch (token) { 301 | case Opt_write: 302 | option = match_strdup(&args[0]); 303 | opts->write = option; 304 | strncpy(exclude, option, sizeof(exclude)); 305 | break; 306 | case Opt_uid: 307 | if (match_int(&args[0], &opt)) 308 | return -EINVAL; 309 | uid = make_kuid(current_user_ns(), opt); 310 | if (!uid_valid(uid)) 311 | return -EINVAL; 312 | opts->uid = uid; 313 | break; 314 | case Opt_gid: 315 | if (match_int(&args[0], &opt)) 316 | return -EINVAL; 317 | gid = make_kgid(current_user_ns(), opt); 318 | if (!gid_valid(gid)) 319 | return -EINVAL; 320 | opts->gid = gid; 321 | break; 322 | case Opt_mode: 323 | if (match_octal(&args[0], &opt)) 324 | return -EINVAL; 325 | opts->mode = opt & S_IALLUGO; 326 | break; 327 | } 328 | } 329 | if(opts->write != NULL) 330 | printk(KERN_INFO "nullfs: will keep data for files matching: [%s]\n", 331 | opts->write); 332 | return 0; 333 | } 334 | 335 | static int nullfs_show_options(struct seq_file *m, struct dentry *root) 336 | { 337 | struct nullfs_fs_info *fsi = root->d_sb->s_fs_info; 338 | 339 | if(fsi->mount_opts.write != NULL) 340 | seq_printf(m, ",write=%s", fsi->mount_opts.write); 341 | if (!uid_eq(fsi->mount_opts.uid, GLOBAL_ROOT_UID)) 342 | seq_printf(m, ",uid=%u", 343 | from_kuid_munged(&init_user_ns, fsi->mount_opts.uid)); 344 | if (!gid_eq(fsi->mount_opts.gid, GLOBAL_ROOT_GID)) 345 | seq_printf(m, ",gid=%u", 346 | from_kgid_munged(&init_user_ns, fsi->mount_opts.gid)); 347 | if (fsi->mount_opts.mode != NULLFS_DEFAULT_MODE) 348 | seq_printf(m, ",mode=%o", fsi->mount_opts.mode); 349 | 350 | return 0; 351 | } 352 | 353 | struct inode *nullfs_get_inode(struct super_block *sb, 354 | const struct inode *dir, umode_t mode, dev_t dev, struct dentry *dentry) 355 | { 356 | struct inode * inode = new_inode(sb); 357 | struct nullfs_fs_info *fsi = sb->s_fs_info; 358 | 359 | if (inode) { 360 | inode->i_ino = get_next_ino(); 361 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) 362 | inode_init_owner(&nop_mnt_idmap, inode, dir, mode); 363 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) 364 | inode_init_owner(&init_user_ns, inode, dir, mode); 365 | #else 366 | inode_init_owner(inode, dir, mode); 367 | #endif 368 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 14, 0) 369 | inode->i_mapping->a_ops = &ram_aops; 370 | #else 371 | inode->i_mapping->a_ops = &nullfs_aops; 372 | #endif 373 | if (!uid_eq(fsi->mount_opts.uid, GLOBAL_ROOT_UID)) 374 | inode->i_uid = fsi->mount_opts.uid; 375 | if (!gid_eq(fsi->mount_opts.gid, GLOBAL_ROOT_GID)) 376 | inode->i_gid = fsi->mount_opts.gid; 377 | mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); 378 | mapping_set_unevictable(inode->i_mapping); 379 | #ifndef CURRENT_TIME 380 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 7, 0) 381 | simple_inode_init_ts(inode); 382 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(6, 6, 0) 383 | inode->i_atime = inode->i_mtime = inode_set_ctime_current(inode); 384 | #else 385 | inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); 386 | #endif 387 | #else 388 | inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 389 | #endif 390 | switch (mode & S_IFMT) { 391 | default: 392 | init_special_inode(inode, mode, dev); 393 | inode->i_op = &nullfs_special_inode_operations; 394 | break; 395 | case S_IFREG: 396 | inode->i_op = &nullfs_file_inode_operations; 397 | if(fsi->mount_opts.write != NULL && dentry != NULL) { 398 | if(strstr(dentry->d_iname, fsi->mount_opts.write) || 399 | strstr(dentry->d_iname, exclude)) { 400 | inode->i_fop = &nullfs_real_file_operations; 401 | break; 402 | } 403 | } 404 | inode->i_fop = &nullfs_file_operations; 405 | break; 406 | case S_IFDIR: 407 | inode->i_op = &nullfs_dir_inode_operations; 408 | inode->i_fop = &simple_dir_operations; 409 | 410 | /* directory inodes start off with i_nlink == 2 (for "." entry) */ 411 | inc_nlink(inode); 412 | break; 413 | case S_IFLNK: 414 | inode->i_op = &page_symlink_inode_operations; 415 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 15, 0) 416 | inode_nohighmem(inode); 417 | #endif 418 | break; 419 | } 420 | } 421 | return inode; 422 | } 423 | 424 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) 425 | static int nullfs_mknod(struct mnt_idmap *idmap, 426 | struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) 427 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) 428 | static int nullfs_mknod(struct user_namespace *mnt_userns, 429 | struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) 430 | # else 431 | static int nullfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) 432 | #endif 433 | { 434 | struct inode * inode; 435 | int error = -ENOSPC; 436 | 437 | inode = nullfs_get_inode(dir->i_sb, dir, mode, dev, dentry); 438 | 439 | if (inode) { 440 | /** 441 | * pretend created directories some size 442 | **/ 443 | if(mode & S_IFDIR) { 444 | inode->i_size = PAGE_SIZE; 445 | } 446 | d_instantiate(dentry, inode); 447 | dget(dentry); /* Extra count - pin the dentry in core */ 448 | error = 0; 449 | #ifndef CURRENT_TIME 450 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 7, 0) 451 | inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir)); 452 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(6, 6, 0) 453 | dir->i_mtime = inode_set_ctime_current(dir); 454 | #else 455 | dir->i_mtime = dir->i_ctime = current_time(dir); 456 | #endif 457 | #else 458 | dir->i_mtime = dir->i_ctime = CURRENT_TIME; 459 | #endif 460 | } 461 | return error; 462 | } 463 | 464 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 15, 0) 465 | static struct dentry *nullfs_mkdir(struct mnt_idmap *idmap, 466 | struct inode * dir, struct dentry * dentry, umode_t mode) 467 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) 468 | static int nullfs_mkdir(struct mnt_idmap *idmap, 469 | struct inode * dir, struct dentry * dentry, umode_t mode) 470 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) 471 | static int nullfs_mkdir(struct user_namespace *mnt_userns, 472 | struct inode * dir, struct dentry * dentry, umode_t mode) 473 | #else 474 | static int nullfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode) 475 | #endif 476 | { 477 | 478 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) 479 | int retval = nullfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFDIR, 0); 480 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) 481 | int retval = nullfs_mknod(&init_user_ns, dir, dentry, mode | S_IFDIR, 0); 482 | #else 483 | int retval = nullfs_mknod(dir, dentry, mode | S_IFDIR, 0); 484 | #endif 485 | 486 | if (!retval) 487 | inc_nlink(dir); 488 | 489 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 15, 0) 490 | return ERR_PTR(retval); 491 | #else 492 | return retval; 493 | #endif 494 | } 495 | 496 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) 497 | static int nullfs_symlink(struct mnt_idmap *idmap, 498 | struct inode * dir, struct dentry *dentry, const char * symname) 499 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) 500 | static int nullfs_symlink(struct user_namespace *mnt_userns, 501 | struct inode * dir, struct dentry *dentry, const char * symname) 502 | #else 503 | static int nullfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname) 504 | #endif 505 | { 506 | struct inode *inode; 507 | int error = -ENOSPC; 508 | 509 | inode = nullfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, dentry); 510 | if (inode) { 511 | int l = strlen(symname)+1; 512 | error = page_symlink(inode, symname, l); 513 | if (!error) { 514 | d_instantiate(dentry, inode); 515 | dget(dentry); 516 | #ifndef CURRENT_TIME 517 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 7, 0) 518 | inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir)); 519 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(6, 6, 0) 520 | dir->i_mtime = inode_set_ctime_current(dir); 521 | #else 522 | dir->i_mtime = dir->i_ctime = current_time(dir); 523 | #endif 524 | #else 525 | dir->i_mtime = dir->i_ctime = CURRENT_TIME; 526 | #endif 527 | } else 528 | iput(inode); 529 | } 530 | return error; 531 | } 532 | 533 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) 534 | static int nullfs_create(struct mnt_idmap *idmap, struct inode *dir, struct dentry *dentry, umode_t mode, bool excl) 535 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) 536 | static int nullfs_create(struct user_namespace *mnt_userns, struct inode *dir, struct dentry *dentry, umode_t mode, bool excl) 537 | #else 538 | static int nullfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl) 539 | #endif 540 | { 541 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) 542 | return nullfs_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0); 543 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) 544 | return nullfs_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0); 545 | #else 546 | return nullfs_mknod(dir, dentry, mode | S_IFREG, 0); 547 | #endif 548 | } 549 | 550 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 11, 0) 551 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) 552 | static int nullfs_tmpfile(struct mnt_idmap *idmap, struct inode *dir, 553 | struct file *file, umode_t mode) 554 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(6, 1, 0) 555 | static int nullfs_tmpfile(struct user_namespace *mnt_userns, struct inode *dir, 556 | struct file *file, umode_t mode) 557 | #elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0) 558 | static int nullfs_tmpfile(struct user_namespace *mnt_userns, struct inode *dir, struct dentry *dentry, umode_t mode) 559 | #else 560 | static int nullfs_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode) 561 | #endif 562 | { 563 | struct inode *inode; 564 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 1, 0) 565 | inode = nullfs_get_inode(dir->i_sb, dir, mode, 0, file->f_path.dentry); 566 | #else 567 | inode = nullfs_get_inode(dir->i_sb, dir, mode, 0, dentry); 568 | #endif 569 | if (!inode) 570 | return -ENOSPC; 571 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 1, 0) 572 | d_tmpfile(file, inode); 573 | #else 574 | d_tmpfile(dentry, inode); 575 | #endif 576 | return finish_open_simple(file, 0); 577 | } 578 | #endif 579 | 580 | static const struct inode_operations nullfs_dir_inode_operations = { 581 | .create = nullfs_create, 582 | .lookup = simple_lookup, 583 | .link = simple_link, 584 | .unlink = simple_unlink, 585 | .symlink = nullfs_symlink, 586 | .mkdir = nullfs_mkdir, 587 | .rmdir = simple_rmdir, 588 | .mknod = nullfs_mknod, 589 | .rename = simple_rename, 590 | .getattr = nullfs_getattr, 591 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 0, 0) 592 | .set_acl = nullfs_set_acl, 593 | #endif 594 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 11, 0) 595 | .tmpfile = nullfs_tmpfile, 596 | #endif 597 | }; 598 | 599 | int nullfs_statfs(struct dentry *dentry, struct kstatfs *buf) 600 | { 601 | /** 602 | * Software this is used with checks for free space 603 | * constantly, so we need to tell there is always free 604 | * space 605 | * 606 | * Filesystem Size Used Avail Use% Mounted on 607 | * none 382G 39G 344G 10% /my 608 | **/ 609 | buf->f_type = dentry->d_sb->s_magic; 610 | buf->f_bsize = dentry->d_sb->s_blocksize; 611 | buf->f_blocks = 100000000; 612 | buf->f_bfree = 90000000; 613 | buf->f_bavail = 90000000; 614 | buf->f_namelen = NAME_MAX; 615 | return 0; 616 | } 617 | 618 | static const struct super_operations nullfs_ops = { 619 | .statfs = nullfs_statfs, 620 | .drop_inode = generic_delete_inode, 621 | .show_options = nullfs_show_options 622 | }; 623 | 624 | int nullfs_fill_super(struct super_block *sb, void *data, int silent) 625 | { 626 | struct nullfs_fs_info *fsi; 627 | struct inode *inode; 628 | int err; 629 | 630 | fsi = kzalloc(sizeof(struct nullfs_fs_info), GFP_KERNEL); 631 | sb->s_fs_info = fsi; 632 | if (!fsi) 633 | return -ENOMEM; 634 | 635 | err = nullfs_parse_options(data, &fsi->mount_opts); 636 | if(err) 637 | return err; 638 | 639 | sb->s_maxbytes = MAX_LFS_FILESIZE; 640 | sb->s_blocksize = PAGE_SIZE; 641 | sb->s_blocksize_bits = PAGE_SHIFT; 642 | sb->s_magic = NULLFS_MAGIC; 643 | sb->s_op = &nullfs_ops; 644 | sb->s_time_gran = 1; 645 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 0, 0) 646 | sb->s_xattr = nullfs_xattr_handlers; 647 | sb->s_flags |= SB_POSIXACL; 648 | #endif 649 | 650 | inode = nullfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0, sb->s_root); 651 | sb->s_root = d_make_root(inode); 652 | if (!sb->s_root) 653 | return -ENOMEM; 654 | 655 | return 0; 656 | } 657 | 658 | /** 659 | * setup / register and destroy filesystem 660 | **/ 661 | static void nullfs_kill_sb(struct super_block *sb) 662 | { 663 | kfree(sb->s_fs_info); 664 | kill_litter_super(sb); 665 | } 666 | 667 | static struct dentry * nullfs_get_super(struct file_system_type *fst, 668 | int flags, const char *devname, void *data) 669 | { 670 | return mount_nodev(fst, flags, data, nullfs_fill_super); 671 | } 672 | 673 | static struct file_system_type nullfs_type = { 674 | .name = "nullfs", 675 | .mount = nullfs_get_super, 676 | .kill_sb = nullfs_kill_sb, 677 | .owner = THIS_MODULE 678 | }; 679 | 680 | static int __init nullfs_init(void) 681 | { 682 | int retval; 683 | exclude_kobj = kobject_create_and_add("nullfs", fs_kobj); 684 | if (!exclude_kobj) 685 | return -ENOMEM; 686 | 687 | retval = sysfs_create_group(exclude_kobj, &attr_group); 688 | if (retval) 689 | kobject_put(exclude_kobj); 690 | 691 | register_filesystem(&nullfs_type); 692 | printk(KERN_INFO "nullfs: version [%s] initialized\n", NULLFS_VERSION); 693 | return 0; 694 | } 695 | 696 | static void __exit nullfs_exit(void) 697 | { 698 | kobject_put(exclude_kobj); 699 | unregister_filesystem(&nullfs_type); 700 | } 701 | 702 | module_init(nullfs_init); 703 | module_exit(nullfs_exit); 704 | -------------------------------------------------------------------------------- /nullfs.jpg: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/abbbi/nullfsvfs/4a7da3a0e8cead12643164eaa819e6a169e1b863/nullfs.jpg -------------------------------------------------------------------------------- /rpm/README.md: -------------------------------------------------------------------------------- 1 | RPM Build 2 | 3 | Examples how to build rpm package from source. 4 | 5 | ### RHEL 8.4 6 | ``` 7 | yum install git rpm-build elfutils-libelf-devel kernel-abi-stablelists kernel-rpm-macros -y 8 | git clone http://github.com/abbbi/nullfsvfs nullfsvfs-0.12 9 | tar -czvf /root/rpmbuild/SOURCES/nullfsvfs-kmod-0.12.tar.gz nullfsvfs-0.12 10 | rpmbuild -ba nullfsvfs-0.12/rpm/nullfsvfs-kmod.spec 11 | rpm -i /root/rpmbuild/RPMS/x86_64/kmod-nullfsvfs-0.12-1.el8.x86_64.rpm 12 | modprobe nullfs 13 | ``` 14 | -------------------------------------------------------------------------------- /rpm/nullfsvfs-kmod.spec: -------------------------------------------------------------------------------- 1 | %global kmod_name nullfsvfs 2 | 3 | %global debug_package %{nil} 4 | 5 | %define __spec_install_post \ 6 | %{__arch_install_post}\ 7 | %{__os_install_post}\ 8 | %{__mod_compress_install_post} 9 | 10 | %define __mod_compress_install_post \ 11 | if [ $kernel_version ]; then \ 12 | find %{buildroot} -type f -name '*.ko' | xargs %{__strip} --strip-debug; \ 13 | find %{buildroot} -type f -name '*.ko' | xargs xz; \ 14 | fi 15 | 16 | # Generate kernel symbols requirements: 17 | %global _use_internal_dependency_generator 0 18 | 19 | %{!?kversion: %global kversion %(uname -r)} 20 | 21 | Name: %{kmod_name}-kmod 22 | Version: 0.18 23 | Release: 1%{?dist} 24 | Summary: A virtual file system that behaves like /dev/null 25 | License: GPLv3+ 26 | URL: https://github.com/abbbi/%{kmod_name} 27 | 28 | Source0: %{url}/archive/%{version}.tar.gz#/%{name}-%{version}.tar.gz 29 | 30 | BuildRequires: elfutils-libelf-devel 31 | BuildRequires: gcc 32 | BuildRequires: kernel-devel 33 | BuildRequires: kmod 34 | BuildRequires: redhat-rpm-config 35 | 36 | %if 0%{?rhel} == 7 37 | BuildRequires: kernel-abi-whitelists 38 | %else 39 | BuildRequires: kernel-abi-stablelists 40 | BuildRequires: kernel-rpm-macros 41 | %endif 42 | 43 | %description 44 | A virtual file system that behaves like /dev/null. It can handle regular file 45 | operations but writing to files does not store any data. The file size is 46 | however saved, so reading from the files behaves like reading from /dev/zero 47 | with a fixed size. 48 | 49 | Writing and reading is basically an NOOP, so it can be used for performance 50 | testing with applications that require directory structures. 51 | 52 | %package -n kmod-%{kmod_name} 53 | Summary: %{kmod_name} kernel module(s) 54 | 55 | Provides: kabi-modules = %{kversion}.%{_target_cpu} 56 | Provides: %{kmod_name}-kmod = %{?epoch:%{epoch}:}%{version}-%{release} 57 | Requires: module-init-tools 58 | 59 | %description -n kmod-%{kmod_name} 60 | This package provides the %{kmod_name} kernel module(s) built for the Linux kernel 61 | using the %{_target_cpu} family of processors. 62 | 63 | %post -n kmod-%{kmod_name} 64 | if [ -e "/boot/System.map-%{kversion}.%{_target_cpu}" ]; then 65 | /usr/sbin/depmod -aeF "/boot/System.map-%{kversion}.%{_target_cpu}" "%{kversion}.%{_target_cpu}" > /dev/null || : 66 | fi 67 | modules=( $(find /lib/modules/%{kversion}/extra/%{kmod_name} | grep '\.ko$') ) 68 | if [ -x "/usr/sbin/weak-modules" ]; then 69 | printf '%s\n' "${modules[@]}" | /usr/sbin/weak-modules --add-modules 70 | fi 71 | 72 | %preun -n kmod-%{kmod_name} 73 | rpm -ql kmod-%{kmod_name}-%{version}-%{release}.%{_target_cpu} | grep '\.ko$' > /var/run/rpm-kmod-%{kmod_name}-modules 74 | 75 | %postun -n kmod-%{kmod_name} 76 | if [ -e "/boot/System.map-%{kversion}.%{_target_cpu}" ]; then 77 | /usr/sbin/depmod -aeF "/boot/System.map-%{kversion}.%{_target_cpu}" "%{kversion}.%{_target_cpu}" > /dev/null || : 78 | fi 79 | modules=( $(cat /var/run/rpm-kmod-%{kmod_name}-modules) ) 80 | rm /var/run/rpm-kmod-%{kmod_name}-modules 81 | if [ -x "/usr/sbin/weak-modules" ]; then 82 | printf '%s\n' "${modules[@]}" | /usr/sbin/weak-modules --remove-modules 83 | fi 84 | 85 | %prep 86 | %autosetup -p1 -n %{kmod_name}-%{version} 87 | 88 | echo "override %{kmod_name} * weak-updates/%{kmod_name}" > kmod-%{kmod_name}.conf 89 | 90 | %build 91 | make -C %{_usrsrc}/kernels/%{kversion} M=$PWD modules 92 | 93 | %install 94 | export INSTALL_MOD_PATH=%{buildroot} 95 | export INSTALL_MOD_DIR=extra/%{kmod_name} 96 | make -C %{_usrsrc}/kernels/%{kversion} M=$PWD modules_install 97 | 98 | install -d %{buildroot}%{_sysconfdir}/depmod.d/ 99 | install kmod-%{kmod_name}.conf %{buildroot}%{_sysconfdir}/depmod.d/ 100 | 101 | # Remove the unrequired files. 102 | rm -f %{buildroot}/lib/modules/%{kversion}/modules.* 103 | 104 | %files -n kmod-%{kmod_name} 105 | %license LICENSE 106 | /lib/modules/%{kversion}/extra/* 107 | %config /etc/depmod.d/kmod-%{kmod_name}.conf 108 | 109 | %changelog 110 | * Tue Aug 24 2021 Michael Ablassmeier - 0.9-1 111 | - Add example spec file based on version by Simone Caronni 112 | --------------------------------------------------------------------------------