The kernel root filesystem may use the rootflags parameters
when mount, especially for tmpfs, to setup a variety of features.
For example:
1. Add 'rootflags=huge=always' to boot args.
2. When the OS bootup:
rootfs on / type rootfs (..., huge=always)
Then we can get the hugepage performance improvement of tmpfs.
Signed-off-by: Weilong Chen <[email protected]>
---
fs/namespace.c | 5 +++--
include/linux/init.h | 2 +-
init/do_mounts.c | 4 +++-
3 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index c3f1a78ba369..318ad4fbc20b 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4184,6 +4184,7 @@ SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path,
return err;
}
+static char * __initdata rootfs_flags;
static void __init init_mount_tree(void)
{
struct vfsmount *mnt;
@@ -4191,7 +4192,7 @@ static void __init init_mount_tree(void)
struct mnt_namespace *ns;
struct path root;
- mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
+ mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", rootfs_flags);
if (IS_ERR(mnt))
panic("Can't create rootfs");
@@ -4245,7 +4246,7 @@ void __init mnt_init(void)
if (!fs_kobj)
printk(KERN_WARNING "%s: kobj create error\n", __func__);
shmem_init();
- init_rootfs();
+ init_rootfs(&rootfs_flags);
init_mount_tree();
}
diff --git a/include/linux/init.h b/include/linux/init.h
index d82b4b2e1d25..d8d46d3c73fb 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -148,7 +148,7 @@ extern unsigned int reset_devices;
/* used by init/main.c */
void setup_arch(char **);
void prepare_namespace(void);
-void __init init_rootfs(void);
+void __init init_rootfs(char **rootfs_flags);
extern struct file_system_type rootfs_fs_type;
#if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_STRICT_MODULE_RWX)
diff --git a/init/do_mounts.c b/init/do_mounts.c
index a78e44ee6adb..42019b5fbf45 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -632,9 +632,11 @@ struct file_system_type rootfs_fs_type = {
.kill_sb = kill_litter_super,
};
-void __init init_rootfs(void)
+void __init init_rootfs(char **rootfs_flags)
{
if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] &&
(!root_fs_names || strstr(root_fs_names, "tmpfs")))
is_tmpfs = true;
+
+ *rootfs_flags = root_mount_data;
}
--
2.31.GIT
On Sat, Jun 26, 2021 at 09:16:55AM +0800, Weilong Chen wrote:
> The kernel root filesystem may use the rootflags parameters
> when mount, especially for tmpfs, to setup a variety of features.
>
> For example:
> 1. Add 'rootflags=huge=always' to boot args.
> 2. When the OS bootup:
> rootfs on / type rootfs (..., huge=always)
> Then we can get the hugepage performance improvement of tmpfs.
>
> Signed-off-by: Weilong Chen <[email protected]>
> ---
> fs/namespace.c | 5 +++--
> include/linux/init.h | 2 +-
> init/do_mounts.c | 4 +++-
> 3 files changed, 7 insertions(+), 4 deletions(-)
No documentation update for this new user/kernel api you added?
On 2021/6/27 18:46, Greg KH wrote:
> On Sat, Jun 26, 2021 at 09:16:55AM +0800, Weilong Chen wrote:
>> The kernel root filesystem may use the rootflags parameters
>> when mount, especially for tmpfs, to setup a variety of features.
>>
>> For example:
>> 1. Add 'rootflags=huge=always' to boot args.
>> 2. When the OS bootup:
>> rootfs on / type rootfs (..., huge=always)
>> Then we can get the hugepage performance improvement of tmpfs.
>>
>> Signed-off-by: Weilong Chen <[email protected]>
>> ---
>> fs/namespace.c | 5 +++--
>> include/linux/init.h | 2 +-
>> init/do_mounts.c | 4 +++-
>> 3 files changed, 7 insertions(+), 4 deletions(-)
> No documentation update for this new user/kernel api you added?
There is already relevant documents (Documentation/admin-guide/kernel-parameters.txt)
description:
rootflags= [KNL] Set root filesystem mount option string
This patch make it work for tmpfs.
> .