Re: [PATCH] include/linux/pipe_fs_i: Add htmldoc annotation for "head_tail" member

[K Prateek Nayak]

Hello Linus,

On 3/5/2025 11:05 PM, Linus Torvalds wrote:
> On Wed, 5 Mar 2025 at 01:24, K Prateek Nayak <kprateek.nayak@xxxxxxx> wrote:
> > Add htmldoc annotation for the newly introduced "head_tail" member
> > describing it to be a union of the pipe_inode_info's @head and @tail
> > members.
>
> Applied.

Thank you.

> I also committed the pipe_occupancy() fix for 32-bit, but did so
> without testing - it was ObviouslyCorrect(tm), but considering that
> everybody missed it in the original patch, "obvious" is all relative.
>
> And it turns out my worry about pipe_discard_from() was unnecessary.
> Yes, the code is buggy. But no, it doesn't matter. Why? There are no
> callers of that function ;)

On the topic of pipe_discard_from(), Al had added that helper in commit
c3497fd009ef ("fix short copy handling in copy_mc_pipe_to_iter()") to
discard unused buffer for copy_mc_to_iter()

Its usage in copy_mc_pipe_to_iter() was later removed in commit
8fad7767edcf ("ITER_PIPE: allocate buffers as we go in copy-to-pipe
primitives) in favor of iov_iter_revert()

pipe_advance() started using it in from commit 2c855de93314 ("ITER_PIPE:
clean pipe_advance() up") however all of that was nuked in commit
3fc40265ae2b ("iov_iter: Kill ITER_PIPE")

generic_file_splice_read() started using it from commit 0d9649341363
("splice: stop abusing iov_iter_advance() to flush a pipe") but
generic_file_splice_read() was later removed in commit c6585011bc1d
("splice: Remove generic_file_splice_read()")

I don't see any in kernel user of this helper currently so can the
wrap-around issue be addressed and the helper be removed later?

> That said, I still hope people will take a look at the code and see if
> there's anything else I missed.
>
> Oh, and testing. Testing would be good.
>
>          Linus

--
Thanks and Regards,
Prateek