Re: [PATCH] [RFC]: fs: claw back a few FMODE_* bits

[Christian Brauner <brauner@kernel.org>]

On Thu, Mar 28, 2024 at 06:35:33AM +0100, Christoph Hellwig wrote:
> On Wed, Mar 27, 2024 at 05:45:09PM +0100, Christian Brauner wrote:
> > There's a bunch of flags that are purely based on what the file
> > operations support while also never being conditionally set or unset.
> > IOW, they're not subject to change for individual file opens. Imho, such
> > flags don't need to live in f_mode they might as well live in the fops
> > structs itself.
> 
> Yes.  I actually have a half-finished patch doing the same lying around,
> which I've not found time to rabse.
> 
> > (Fwiw, FMODE_NOACCOUNT and FMODE_BACKING could live in fops_flags as
> >  well because they're also completely static but they aren't really
> >  about file operations so they're better suited for FMODE_* imho.)
> 
> I'd still move them there.  I've also simply called fops_flags flags
> so maybe it didn't bother me too much :)

Possible that we can do that as well but I'd keep calling it fop_flags
for the sake of grepping. If you git grep \\.fop_flags you get a nice
unique match and you get an overview who uses what. I'm not married to
this but I'll keep it for now.

> 
> > +/* File ops support async buffered reads */
> > +#define FOP_BUF_RASYNC		BIT(0)
> > +/* File ops support async nowait buffered writes */
> > +#define FOP_BUF_WASYNC		BIT(1)
> 
> Can we spell out BUFFERED here when changing things?  BUF always confuses
> me as it let's me thing of the buffer cache.

Ok.

> 
> And can be please avoid this silly BIT() junk?  1u << N is shorter
> and a lot more obvious than this random macro.

Everyone and their grandmother has an opinion on this hex, <<, BIT(). :)
Fine, I don't care enough and my grandmothers aren't around anymore.

> 
> > +#define FOP_MMAP_SYNC		BIT(2)
> 
> Please throw in a comment for this one while you're at it.

Ok.

> 
> > +/* File ops support non-exclusive O_DIRECT writes from multiple threads */
> > +#define FOP_DIO_PARALLEL_WRITE	BIT(3)
> > +
> > +#define __fops_supported(f_op, flag) ((f_op)->fops_flags & (flag))
> > +#define fops_buf_rasync(file) __fops_supported((file)->f_op, FOP_BUF_RASYNC)
> > +#define fops_buf_wasync(file) __fops_supported((file)->f_op, FOP_BUF_WASYNC)
> > +#define fops_mmap_sync(file) __fops_supported((file)->f_op, FOP_MMAP_SYNC)
> > +#define fops_dio_parallel_write(file) __fops_supported((file)->f_op, FOP_DIO_PARALLEL_WRITE)
> 
> And please drop these helpers.  They just make grepping for the flags
> a complete pain.

Ok.