Re: [PATCH v8 00/10] fs: interface for directly reading/writing compressed data

[Omar Sandoval <osandov@osandov.com>]

On Fri, Mar 19, 2021 at 05:31:18PM -0700, Linus Torvalds wrote:
> On Fri, Mar 19, 2021 at 3:46 PM Omar Sandoval <osandov@osandov.com> wrote:
> >
> > Not much shorter, but it is easier to follow.
> 
> Yeah, that looks about right to me.
> 
> You should probably use kmap_local_page() rather than kmap_atomic()
> these days, but other than that this looks fairly straightforward, and
> I much prefer the model where we very much force that "must be the
> first iovec entry".

To be exact, this code only enforces that the iov_iter is at the
beginning of the current entry. As far as I can tell, iov_iter doesn't
track its position overall, so there's no way to tell whether the
current entry is the first one.

> As you say, maybe not shorter, but a lot more straightforward.
> 
> That said, looking through the patch series, I see at least one other
> issue. Look at parisc:
> 
>     +#define O_ALLOW_ENCODED 100000000
> 
> yeah, that's completely wrong. I see how it happened, but that's _really_ wrong.

Ugh, that's embarrassing. It also happens to add exactly one new bit to
VALID_OPEN_FLAGS, so the BUILD_BUG_ON() in fcntl_init() didn't catch it.

> I would want others to take a look in case there's something else. I'm
> not qualified to comment about (nor do I deeply care) about the btrfs
> parts, but the generic interface parts should most definitely get more
> attention.
> 
> By Al, if possible, but other fs people too..

That's all I ask. I'll fix your comments and wait a few days to get some
more feedback on the fs side before I resend the patch bomb.

Thanks,
Omar