Add kernel module auto-loading

Historically a dynamic misc minor number was registered for the
/dev/zfs device in order to prevent minor number collisions.  This
was fine but it prevented us from being able to use the kernel
module auto-loaded which requires a known reserved value.

Resolve this issue by adding a configure test to find an available
misc minor number which can then be used in MODULE_ALIAS_MISCDEV at
build time.  By adding this alias the zfs kmod is added to the list
of known static-nodes and the systemd-tmpfiles-setup-dev service
will create a /dev/zfs character device at boot time.

This in turn allows us to update the 90-zfs.rules file to make it
aware this is a static node.  The upshot of this is that whenever
a process (zpool, zfs, zed) opens the /dev/zfs the kmods will be
automatic loaded.  This even works for unprivileged users so there
is no longer a need to manually load the modules at boot time.

As an additional bonus the zed now no longer needs to start after
the zfs-import.service since it will trigger the module load.

In the unlikely event the minor number we selected conflicts with
another out of tree unregistered minor number the code falls back
to dynamically allocating it.  In this case the modules again
must be manually loaded.

Note that due to the change in the method of registering the minor
number the zimport.sh test case may incorrectly fail when the
static node for the installed packages is created instead of the
dynamic one.  This issue will only transiently impact zimport.sh
for this single commit when we transition and are mixing and
matching methods.

Reviewed-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
TEST_ZIMPORT_SKIP="yes"
Closes #7287

diff --git a/config/kernel-misc-minor.m4 b/config/kernel-misc-minor.m4
new file mode 100644 (file)
index 0000000..3917e28
--- /dev/null
+++ b/config/kernel-misc-minor.m4
@@ -0,0 +1,26 @@
+dnl #
+dnl # Determine an available miscellaneous minor number which can be used
+dnl # for the /dev/zfs device.  This is needed because kernel module
+dnl # auto-loading depends on registering a reserved non-conflicting minor
+dnl # number.  Start with a large known available unreserved minor and work
+dnl # our way down to lower value if a collision is detected.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_MISC_MINOR], [
+       AC_MSG_CHECKING([for available /dev/zfs minor])
+
+       for i in $(seq 249 -1 200); do
+               if ! grep -q "^#define\s\+.*_MINOR\s\+.*$i" \
+                   ${LINUX}/include/linux/miscdevice.h; then
+                       ZFS_MINOR="$i"
+                       AC_MSG_RESULT($ZFS_MINOR)
+                       AC_DEFINE_UNQUOTED([ZFS_MINOR], [$ZFS_MINOR],
+                           [/dev/zfs minor])
+                       break
+               fi
+       done
+
+       AS_IF([ test -z "$ZFS_MINOR"], [
+               AC_MSG_ERROR([
+       *** No available misc minor numbers available for use.])
+       ])
+])

diff --git a/config/kernel.m4 b/config/kernel.m4
index 8f0a65666c9b498b8f3123e619107af613769e7f..dfc509d6ae7205038c1140d277979323173b797f 100644 (file)
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -6,6 +6,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
        ZFS_AC_SPL
        ZFS_AC_QAT
        ZFS_AC_TEST_MODULE
+       ZFS_AC_KERNEL_MISC_MINOR
        ZFS_AC_KERNEL_OBJTOOL
        ZFS_AC_KERNEL_CONFIG
        ZFS_AC_KERNEL_DECLARE_EVENT_CLASS

diff --git a/etc/modules-load.d/zfs.conf.in b/etc/modules-load.d/zfs.conf.in
index 8b41baa300cbfb80f1b68d324a993e683670ec45..44e1bb3ed906b18eaafb6376471380b669590357 100644 (file)
--- a/etc/modules-load.d/zfs.conf.in
+++ b/etc/modules-load.d/zfs.conf.in
@@ -1,3 +1,3 @@
-# Always load kernel modules at boot.  The default behavior is to load the
-# kernel modules in the zfs-import-*.service or when blkid(8) detects a pool.
+# The default behavior is to allow udev to load the kernel modules on demand.
+# Uncomment the following line to unconditionally load them at boot.
 #zfs

diff --git a/etc/systemd/system/zfs-import-cache.service.in b/etc/systemd/system/zfs-import-cache.service.in
index 726c468ca30c5f96d778a38b3c817dd9e2705b80..97808dee7ed50f2c3ab193873c9891f72afbec48 100644 (file)
--- a/etc/systemd/system/zfs-import-cache.service.in
+++ b/etc/systemd/system/zfs-import-cache.service.in
@@ -12,7 +12,6 @@ ConditionPathExists=@sysconfdir@/zfs/zpool.cache
 [Service]
 Type=oneshot
 RemainAfterExit=yes
-ExecStartPre=-/sbin/modprobe zfs
 ExecStart=@sbindir@/zpool import -c @sysconfdir@/zfs/zpool.cache -aN
 
 [Install]

diff --git a/etc/systemd/system/zfs-import-scan.service.in b/etc/systemd/system/zfs-import-scan.service.in
index abc8e8e6d94a92a23bde6762aa03aec4579f1189..c097e38528a7a4738c281f3d93f2a6468bf01f85 100644 (file)
--- a/etc/systemd/system/zfs-import-scan.service.in
+++ b/etc/systemd/system/zfs-import-scan.service.in
@@ -11,7 +11,6 @@ ConditionPathExists=!@sysconfdir@/zfs/zpool.cache
 [Service]
 Type=oneshot
 RemainAfterExit=yes
-ExecStartPre=-/sbin/modprobe zfs
 ExecStart=@sbindir@/zpool import -aN -o cachefile=none
 
 [Install]

diff --git a/lib/libzfs/libzfs_util.c b/lib/libzfs/libzfs_util.c
index bc51a76a8ecb3475292430bf8b21e3ee99f827bb..9703f844f6eec7f929e0af5ba4d0daf0dd97873b 100644 (file)
--- a/lib/libzfs/libzfs_util.c
+++ b/lib/libzfs/libzfs_util.c
@@ -963,13 +963,14 @@ libzfs_load_module(const char *module)
                                load = 0;
                }
 
-               if (load && libzfs_run_process("/sbin/modprobe", argv, 0))
-                       return (ENOEXEC);
-       }
+               if (load) {
+                       if (libzfs_run_process("/sbin/modprobe", argv, 0))
+                               return (ENOEXEC);
 
-       /* Module loading is synchronous it must be available */
-       if (!libzfs_module_loaded(module))
-               return (ENXIO);
+                       if (!libzfs_module_loaded(module))
+                               return (ENXIO);
+               }
+       }
 
        /*
         * Device creation by udev is asynchronous and waiting may be

diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index b8783e54a984f3a2d33438f608878cd7c564a8d5..a79decb966efe04411087bb56ba9b3eb6a60fb7b 100644 (file)
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -6634,11 +6634,14 @@ static const struct file_operations zfsdev_fops = {
 };
 
 static struct miscdevice zfs_misc = {
-       .minor          = MISC_DYNAMIC_MINOR,
+       .minor          = ZFS_MINOR,
        .name           = ZFS_DRIVER,
        .fops           = &zfsdev_fops,
 };
 
+MODULE_ALIAS_MISCDEV(ZFS_MINOR);
+MODULE_ALIAS("devname:zfs");
+
 static int
 zfs_attach(void)
 {
@@ -6649,12 +6652,24 @@ zfs_attach(void)
        zfsdev_state_list->zs_minor = -1;
 
        error = misc_register(&zfs_misc);
-       if (error != 0) {
-               printk(KERN_INFO "ZFS: misc_register() failed %d\n", error);
-               return (error);
+       if (error == -EBUSY) {
+               /*
+                * Fallback to dynamic minor allocation in the event of a
+                * collision with a reserved minor in linux/miscdevice.h.
+                * In this case the kernel modules must be manually loaded.
+                */
+               printk(KERN_INFO "ZFS: misc_register() with static minor %d "
+                   "failed %d, retrying with MISC_DYNAMIC_MINOR\n",
+                   ZFS_MINOR, error);
+
+               zfs_misc.minor = MISC_DYNAMIC_MINOR;
+               error = misc_register(&zfs_misc);
        }
 
-       return (0);
+       if (error)
+               printk(KERN_INFO "ZFS: misc_register() failed %d\n", error);
+
+       return (error);
 }
 
 static void

diff --git a/rpm/generic/zfs.spec.in b/rpm/generic/zfs.spec.in
index f28793a833b421741de17120484691230f0c21ad..87c6f5e25926876616220dceb99a681965dd97c4 100644 (file)
--- a/rpm/generic/zfs.spec.in
+++ b/rpm/generic/zfs.spec.in
@@ -283,6 +283,15 @@ fi
 %endif
 exit 0
 
+# On RHEL/CentOS 7 the static nodes aren't refreshed by default after
+# installing a package.  This is the default behavior for Fedora.
+%posttrans
+%if 0%{?rhel} == 7 || 0%{?centos} == 7
+systemctl restart kmod-static-nodes
+systemctl restart systemd-tmpfiles-setup-dev
+udevadm trigger
+%endif
+
 %preun
 %if 0%{?_systemd}
 %if 0%{?systemd_preun:1}

diff --git a/udev/rules.d/90-zfs.rules.in b/udev/rules.d/90-zfs.rules.in
index 855c154040f5a9b17fe67c8d6e22f15c1f0cf3d3..82f8cf1cf5ec2877f925592fa76367925336fe6a 100644 (file)
--- a/udev/rules.d/90-zfs.rules.in
+++ b/udev/rules.d/90-zfs.rules.in
@@ -7,6 +7,6 @@ ENV{ID_FS_TYPE}=="zfs_member", RUN+="/sbin/modprobe zfs"
 KERNEL=="null", SYMLINK+="root"
 SYMLINK=="null", SYMLINK+="root"
 
-SUBSYSTEM=="misc", KERNEL=="zfs", MODE="0666"
+KERNEL=="zfs", MODE="0666", OPTIONS+="static_node=zfs"
 
 LABEL="zfs_end"