Re: [RFC 1/3] include/linux.h: Factor out generic platform_test_fs_fd() helper

From: Ojaswin Mujoo
Date: Thu Dec 12 2024 - 07:07:09 EST


On Wed, Dec 11, 2024 at 10:09:02AM -0800, Darrick J. Wong wrote:
> On Wed, Dec 11, 2024 at 01:24:02PM +0530, Ojaswin Mujoo wrote:
> > Factor our the generic code to detect the FS type out of
> > platform_test_fs_fd(). This can then be used to detect different file
> > systems types based on magic number.
> >
> > Also, add a helper to detect if the fd is from an ext4 filesystem.
> >
> > Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
> > ---
> > include/linux.h | 25 +++++++++++++++++--------
> > 1 file changed, 17 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/linux.h b/include/linux.h
> > index e9eb7bfb26a1..52c64014c57f 100644
> > --- a/include/linux.h
> > +++ b/include/linux.h
> > @@ -43,13 +43,7 @@ static __inline__ int xfsctl(const char *path, int fd, int cmd, void *p)
> > return ioctl(fd, cmd, p);
> > }
> >
> > -/*
> > - * platform_test_xfs_*() implies that xfsctl will succeed on the file;
> > - * on Linux, at least, special files don't get xfs file ops,
> > - * so return 0 for those
> > - */
> > -
> > -static __inline__ int platform_test_xfs_fd(int fd)
> > +static __inline__ int platform_test_fs_fd(int fd, long type)
> > {
> > struct statfs statfsbuf;
> > struct stat statbuf;
> > @@ -60,7 +54,22 @@ static __inline__ int platform_test_xfs_fd(int fd)
> > return 0;
> > if (!S_ISREG(statbuf.st_mode) && !S_ISDIR(statbuf.st_mode))
> > return 0;
> > - return (statfsbuf.f_type == 0x58465342); /* XFSB */
> > + return (statfsbuf.f_type == type);
> > +}
> > +
> > +/*
> > + * platform_test_xfs_*() implies that xfsctl will succeed on the file;
> > + * on Linux, at least, special files don't get xfs file ops,
> > + * so return 0 for those
> > + */
> > +static __inline__ int platform_test_xfs_fd(int fd)
> > +{
> > + return platform_test_fs_fd(fd, 0x58465342); /* XFSB */
> > +}
> > +
> > +static __inline__ int platform_test_ext4_fd(int fd)
> > +{
> > + return platform_test_fs_fd(fd, 0xef53); /* EXT4 magic number */
>
> Should this be pulling EXT4_SUPER_MAGIC from linux/magic.h?

Oh right, thanks for pointing out. I'll use that for the magic numbers.

Thanks,
ojaswin

>
> --D
>
> > }
> >
> > static __inline__ int platform_test_xfs_path(const char *path)
> > --
> > 2.43.5
> >
> >