Merge branch 'master' of ssh://github.com/abbbi/nullfsvfs

Author: abbbi

README.md

@@ -1,19 +1,20 @@
-![ci](https://github.com/abbbi/nullfsvfs/actions/workflows/ci-ubuntu-latest.yml/badge.svg)
+[![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)
 
 ## Index
 
  - [About](#nullfs)
  - [Usage](#usage)
+ - [Installation](#installation)
  - [Use Cases](#usecases)
  - [Keeping data](#keep)
  - [Mount options](#supported)
 
 # nullfs
-a virtual file system that behaves like /dev/null
+A virtual file system that behaves like /dev/null
 
 It can handle regular file operations like mkdir/rmdir/ln but writing to files
-does not store any data. The file size is however saved, so reading from the
-files behaves like reading from /dev/zero with a fixed size.
+does not store any data. The file size is however saved, reading from the
+files behaves like reading from /dev/zero.
 
 Writing and reading is basically an NOOP, so it can be used for performance
 testing with applications that require directory structures.  Implemented as
@@ -71,6 +72,35 @@ makes it behave like reading from /dev/zero:
 ```
 
 
+## installation
+
+To install the module for the running linux kernel use:
+
+```
+ # make -C /lib/modules/$(uname -r)/build M=$PWD modules_install INSTALL_MOD_DIR=kernel/fs/nullfs
+ # depmod
+```
+
+Running `depmod` is mandatory. Now the module can be loaded via:
+
+```
+ modprobe  nullfs
+``` 
+
+To automatically load filesystem module during boot time, create a configuration
+file suitable for your distribution, usually located in */etc/modules-load.d*
+
+```
+echo nullfs > /etc/modules-load.d/nullfs.conf
+```
+
+Example entry for `/etc/fstab`, mounting the filesystem to `/nullfs`:
+
+
+```
+none    /nullfs nullfs auto
+```
+
 ### keep
 
 There is the possiblity to exclude certain files from beeing sent into the void.
@@ -103,6 +133,9 @@ nulled.
 It is possible to set POSIX ACL attributes via `setfacl` so it appears the
 filesystem supports them, they are not saved.
 
+Works with recent linux kernels (5.x), nullfs builds fine with older kernels
+(4.x, 3.x) but setting ACL information fails with "Operation not supported".
+
 ### usecases
 
 See: [Use Cases ](https://github.com/abbbi/nullfsvfs/labels/Usecase)

debian/changelog

@@ -1,4 +1,19 @@
-nullfsvfs (0.10) UNRELEASED; urgency=medium
+nullfsvfs (0.12) unstable; urgency=medium
+
+  * Fix build on SLES based kernels, add #ifdef for RHEL_MAJOR.
+  Module now builds on RHEL/Centos7,SLES12,SLES15 and newer.
+
+ -- Michael Ablassmeier <[email protected]>  Wed, 29 Sep 2021 10:45:37 +0200
+
+nullfsvfs (0.11) unstable; urgency=medium
+
+  * Re-Add support for older linux kernel versions (3.10.x) used
+  by RHEL7 and Centos7 and SLES15, which was broken by adding Posix ACL
+  and O_DIRECT support.
+
+ -- Michael Ablassmeier <[email protected]>  Tue, 28 Sep 2021 16:37:59 +0200
+
+nullfsvfs (0.10) unstable; urgency=medium
 
   * Add support for kernel versions >= 5.14
 

nullfs.c

@@ -42,7 +42,7 @@
 #define NULLFS_MAGIC 0x19980123
 #define NULLFS_DEFAULT_MODE  0755
 #define NULLFS_SYSFS_MODE  0644
-#define NULLFS_VERSION "0.11"
+#define NULLFS_VERSION "0.12"
 
 MODULE_AUTHOR("Michael Ablassmeier");
 MODULE_LICENSE("GPL");
@@ -51,8 +51,16 @@ MODULE_VERSION(NULLFS_VERSION);
 /*
  * POSIX ACL
  * setfacl is possible, but acls are not stored, of course
+ *
+ * For older kernel versions (3.x, used on rhel7/centos7 its required to 
+ * redefine some non-public functions to make it "work", so we skip..
  */
-
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 0, 0)
+static const struct xattr_handler *nullfs_xattr_handlers[] = {
+    &posix_acl_access_xattr_handler,
+    &posix_acl_default_xattr_handler,
+    NULL
+};
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0)
 static int nullfs_set_acl(struct user_namespace *mnt_userns,
         struct inode *inode, struct posix_acl *acl, int type)
@@ -62,12 +70,7 @@ static int nullfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 {
     return 0;
 }
-static const struct xattr_handler *nullfs_xattr_handlers[] = {
-    &posix_acl_access_xattr_handler,
-    &posix_acl_default_xattr_handler,
-    NULL
-};
-
+#endif
 
 /*
  * sysfs handlers
@@ -191,19 +194,32 @@ const struct file_operations nullfs_real_file_operations = {
 const struct inode_operations nullfs_file_inode_operations = {
     .setattr    = simple_setattr,
     .getattr    = nullfs_getattr,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 0, 0)
     .set_acl    = nullfs_set_acl,
+#endif
 };
 const struct inode_operations nullfs_special_inode_operations = {
     .setattr    = simple_setattr,
     .getattr    = nullfs_getattr,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 0, 0)
     .set_acl    = nullfs_set_acl,
+#endif
 };
 #if LINUX_VERSION_CODE < KERNEL_VERSION(5, 14, 0)
 static const struct address_space_operations nullfs_aops = {
     .readpage    = simple_readpage,
     .write_begin = simple_write_begin,
     .write_end   = simple_write_end,
+/**
+ * RHEL kernel exports noop_direct_IO, SLES15 does not
+ **/
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(5, 0, 0)
+#ifdef RHEL_MAJOR
     .direct_IO   = noop_direct_IO
+#endif
+#else
+    .direct_IO   = noop_direct_IO
+#endif
 };
 #endif
 
@@ -462,6 +478,7 @@ static int nullfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 #endif
 }
 
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 11, 0)
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 12, 0)
 static int nullfs_tmpfile(struct user_namespace *mnt_userns, struct inode *dir, struct dentry *dentry, umode_t mode)
 #else
@@ -475,6 +492,7 @@ static int nullfs_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode
     d_tmpfile(dentry, inode);
     return 0;
 }
+#endif
 
 static const struct inode_operations nullfs_dir_inode_operations = {
     .create     = nullfs_create,
@@ -487,7 +505,9 @@ static const struct inode_operations nullfs_dir_inode_operations = {
     .mknod      = nullfs_mknod,
     .rename     = simple_rename,
     .getattr    = nullfs_getattr,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 0, 0)
     .set_acl    = nullfs_set_acl,
+#endif
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 11, 0)
     .tmpfile	= nullfs_tmpfile,
 #endif
@@ -539,8 +559,10 @@ int nullfs_fill_super(struct super_block *sb, void *data, int silent)
     sb->s_magic          = NULLFS_MAGIC;
     sb->s_op             = &nullfs_ops;
     sb->s_time_gran      = 1;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 0, 0)
     sb->s_xattr          = nullfs_xattr_handlers;
     sb->s_flags         |= SB_POSIXACL;
+#endif
 
     inode = nullfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0, sb->s_root);
     sb->s_root = d_make_root(inode);

rpm/README.md

@@ -5,9 +5,9 @@ Examples how to build rpm package from source.
 ### RHEL 8.4 
 ```
  yum install git rpm-build elfutils-libelf-devel kernel-abi-stablelists kernel-rpm-macros -y
- git clone http://github.com/abbbi/nullfsvfs nullfsvfs-0.9
- tar -czvf /root/rpmbuild/SOURCES/nullfsvfs-kmod-0.9.tar.gz nullfsvfs-0.9
- rpmbuild -ba nullfsvfs-0.9/rpm/nullfsvfs-kmod.spec
- rpm -i /root/rpmbuild/RPMS/x86_64/kmod-nullfsvfs-0.9-1.el8.x86_64.rpm
+ git clone http://github.com/abbbi/nullfsvfs nullfsvfs-0.12
+ tar -czvf /root/rpmbuild/SOURCES/nullfsvfs-kmod-0.12.tar.gz nullfsvfs-0.12
+ rpmbuild -ba nullfsvfs-0.12/rpm/nullfsvfs-kmod.spec
+ rpm -i /root/rpmbuild/RPMS/x86_64/kmod-nullfsvfs-0.12-1.el8.x86_64.rpm
  modprobe nullfs
 ```

rpm/nullfsvfs-kmod.spec

@@ -19,7 +19,7 @@
 %{!?kversion: %global kversion %(uname -r)}
 
 Name:           %{kmod_name}-kmod
-Version:        0.10
+Version:        0.11
 Release:        1%{?dist}
 Summary:        A virtual file system that behaves like /dev/null
 License:        GPLv3+