linux-ext4 - Re: [RFC 1/3] include/linux.h: Factor out generic platform_test_fs

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Message-ID: <Z1rRcFbDR4IbjyVl@li-bb2b2a4c-3307-11b2-a85c-8fa5c3a69313.ibm.com>
Date: Thu, 12 Dec 2024 17:35:04 +0530
From: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        Ritesh Harjani <ritesh.list@...il.com>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        Andrey Albershteyn <aalbersh@...nel.org>,
        John Garry <john.g.garry@...cle.com>
Subject: Re: [RFC 1/3] include/linux.h: Factor out generic
 platform_test_fs_fd() helper

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@...ux.ibm.com>
> > ---
> >  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
> > 
> >