On Tue, 2026-11-10 at 10:14 +0100, Christian Brauner wrote: > Add a helper to check whether a file is a regular file on a pseudo > filesystem. Only regular files count. Device nodes on pseudo > filesystems > such as devpts, binderfs or the block devices on bdevfs are what they > are. > > Look at the inode that actually provides the data via d_real_inode(). > overlayfs accepts sysfs, cgroup2, debugfs, tracefs, configfs and > securityfs as lower layers and reads of such an overlayfs file are > served by the file on the pseudo filesystem. Checking the overlayfs > inode would miss that. > > No functional changes. > > Signed-off-by: Christian Brauner (Amutable) <[email protected]>
Reviewed-by: Alexander Mikhalitsyn <[email protected]> > --- > include/linux/fs.h | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 99caef43ff3c..407ffb6342ec 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -2553,6 +2553,18 @@ static inline const struct inode > *file_user_inode(const struct file *f) > return file_inode(f); > } > > +/* > + * Regular files on pseudo filesystems are kernel interfaces and > must not be > + * used as storage. Look through stacking filesystems at the inode > that > + * provides the data. > + */ > +static inline bool file_is_pseudo(const struct file *file) > +{ > + const struct inode *inode = d_real_inode(file- > >f_path.dentry); > + > + return S_ISREG(inode->i_mode) && (inode->i_sb->s_iflags & > SB_I_PSEUDO); > +} > + > static inline struct file *file_clone_open(struct file *file) > { > return dentry_open(&file->f_path, file->f_flags, file- > >f_cred);
