On Mon, Feb 01, 2021 at 03:49:20PM -0800, Amy Parker wrote:
> Hello filesystem developers!
>
> I was scouting through the FreeVXFS code, when I came across this in
> fs/freevxfs/vxfs.h:
>
> enum vxfs_mode {
> VXFS_ISUID = 0x00000800, /* setuid */
> VXFS_ISGID = 0x00000400, /* setgid */
> VXFS_ISVTX = 0x00000200, /* sticky bit */
> VXFS_IREAD = 0x00000100, /* read */
> VXFS_IWRITE = 0x00000080, /* write */
> VXFS_IEXEC = 0x00000040, /* exec */
>
> Especially in an expanded form like this, these are ugly to read, and
> a pain to work with.
I would personally just change those to use the constants in
include/uapi/linux/stat.h. They're userspace ABI and I don't think
anyone's going to come up with a good reason to change the numbering
after nearly 50 years.
That said, on the general principle of "anything you touch you get to
QA" I would leave it alone.
--D
>
> An example of potentially a better method, from fs/dax.c:
>
> #define DAX_SHIFT (4)
> #define DAX_LOCKED (1UL << 0)
> #define DAX_PMD (1UL << 1)
> #define DAX_ZERO_PAGE (1UL << 2)
> #define DAX_EMPTY (1UL << 3)
>
> Pardon the space condensation - my email client is not functioning properly.
>
> Anyways, I believe using bit shifts to represent different file modes
> would be a much better idea - no runtime penalty as they get
> calculated into constants at compile time, and significantly easier
> for the average user to read.
>
> Any thoughts on this?
>
> Best regards,
> Amy Parker
> (she/her/hers)
