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

[Jens Axboe <axboe@kernel.dk>]

On 3/27/24 10:45 AM, 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. And the fops struct already has that lonely
> mmap_supported_flags member. We might as well turn that into a generic
> fops_flags member and move a few flags from FMODE_* space into FOP_*
> space. That gets us four FMODE_* bits back and the ability for new
> static flags that are about file ops to not have to live in FMODE_*
> space but in their own FOP_* space. It's not the most beautiful thing
> ever but it gets the job done. Yes, there'll be an additional pointer
> chase but hopefully that won't matter for these flags.

Not doing that extra dereference is kind of the point of the FMODE_*
flags, at least the ones that I care about. Probably not a huge deal for
these cases though, as we're generally going to call one of the f_op
handlers shortly anyway. The cases where we don't, at least for
io_uring, we already cache the state separately.

Hence more of a general observation than an objection to the patch. I do
like freeing up FMODE space, as it's (pretty) full.

-- 
Jens Axboe