On Mon, May 05, 2025 at 12:55:34PM +0200, Jan Kara wrote:
> > if (!type)
> > return NULL;
> > - mnt = vfs_submount(mntpt, type, "tracefs", NULL);
> > +
> > + fc = fs_context_for_submount(type, mntpt);
> > + if (IS_ERR(fc))
> > + return ERR_CAST(fc);
>
> Missing put_filesystem() here?
Actually, I'd rather have it done unconditionally right after
fc_context_for_submount() - fs_context allocation grabs
a reference and it's held until put_fs_context, so...
[PATCH] kill vfs_submount()
The last remaining user of vfs_submount() (tracefs) is easy to convert
to fs_context_for_submount(); do that and bury that thing, along with
SB_SUBMOUNT
Signed-off-by: Al Viro <v...@zeniv.linux.org.uk>
---
diff --git a/fs/namespace.c b/fs/namespace.c
index 018e95fe5459..0577a9fb6050 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1329,21 +1329,6 @@ struct vfsmount *vfs_kern_mount(struct file_system_type
*type,
}
EXPORT_SYMBOL_GPL(vfs_kern_mount);
-struct vfsmount *
-vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
- const char *name, void *data)
-{
- /* Until it is worked out how to pass the user namespace
- * through from the parent mount to the submount don't support
- * unprivileged mounts with submounts.
- */
- if (mountpoint->d_sb->s_user_ns != &init_user_ns)
- return ERR_PTR(-EPERM);
-
- return vfs_kern_mount(type, SB_SUBMOUNT, name, data);
-}
-EXPORT_SYMBOL_GPL(vfs_submount);
-
static struct mount *clone_mnt(struct mount *old, struct dentry *root,
int flag)
{
diff --git a/fs/super.c b/fs/super.c
index 97a17f9d9023..1886e4c930e0 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -823,13 +823,6 @@ struct super_block *sget(struct file_system_type *type,
struct super_block *old;
int err;
- /* We don't yet pass the user namespace of the parent
- * mount through to here so always use &init_user_ns
- * until that changes.
- */
- if (flags & SB_SUBMOUNT)
- user_ns = &init_user_ns;
-
retry:
spin_lock(&sb_lock);
if (test) {
@@ -849,7 +842,7 @@ struct super_block *sget(struct file_system_type *type,
}
if (!s) {
spin_unlock(&sb_lock);
- s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
+ s = alloc_super(type, flags, user_ns);
if (!s)
return ERR_PTR(-ENOMEM);
goto retry;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 016b0fe1536e..515e702d98ae 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1240,7 +1240,6 @@ extern int send_sigurg(struct file *file);
/* These sb flags are internal to the kernel */
#define SB_DEAD BIT(21)
#define SB_DYING BIT(24)
-#define SB_SUBMOUNT BIT(26)
#define SB_FORCE BIT(27)
#define SB_NOSEC BIT(28)
#define SB_BORN BIT(29)
diff --git a/include/linux/mount.h b/include/linux/mount.h
index dcc17ce8a959..d4eb90a367af 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -98,9 +98,6 @@ extern struct vfsmount *vfs_create_mount(struct fs_context
*fc);
extern struct vfsmount *vfs_kern_mount(struct file_system_type *type,
int flags, const char *name,
void *data);
-extern struct vfsmount *vfs_submount(const struct dentry *mountpoint,
- struct file_system_type *type,
- const char *name, void *data);
extern void mnt_set_expiry(struct vfsmount *mnt, struct list_head
*expiry_list);
extern void mark_mounts_for_expiry(struct list_head *mounts);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e22aacb0028a..936a615e8c56 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -51,6 +51,7 @@
#include <linux/workqueue.h>
#include <linux/sort.h>
#include <linux/io.h> /* vmap_page_range() */
+#include <linux/fs_context.h>
#include <asm/setup.h> /* COMMAND_LINE_SIZE */
@@ -10075,6 +10076,8 @@ static struct vfsmount *trace_automount(struct dentry
*mntpt, void *ingore)
{
struct vfsmount *mnt;
struct file_system_type *type;
+ struct fs_context *fc;
+ int ret;
/*
* To maintain backward compatibility for tools that mount
@@ -10084,10 +10087,20 @@ static struct vfsmount *trace_automount(struct dentry
*mntpt, void *ingore)
type = get_fs_type("tracefs");
if (!type)
return NULL;
- mnt = vfs_submount(mntpt, type, "tracefs", NULL);
+
+ fc = fs_context_for_submount(type, mntpt);
put_filesystem(type);
- if (IS_ERR(mnt))
- return NULL;
+ if (IS_ERR(fc))
+ return ERR_CAST(fc);
+
+ ret = vfs_parse_fs_string(fc, "source",
+ "tracefs", strlen("tracefs"));
+ if (!ret)
+ mnt = fc_mount(fc);
+ else
+ mnt = ERR_PTR(ret);
+
+ put_fs_context(fc);
return mnt;
}
