linux-kernel - Re: [PATCH] include/linux/pipe_fs_i: Add htmldoc annotation for "head

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Message-ID: <e6cb4e60-9525-4d42-8912-7ce3f7fa4abb@amd.com>
Date: Wed, 5 Mar 2025 23:38:42 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Oleg Nesterov <oleg@...hat.com>, Stephen Rothwell <sfr@...b.auug.org.au>,
	<linux-kernel@...r.kernel.org>, Linux Next Mailing List
	<linux-next@...r.kernel.org>, Swapnil Sapkal <swapnil.sapkal@....com>
Subject: Re: [PATCH] include/linux/pipe_fs_i: Add htmldoc annotation for
 "head_tail" member

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@....com> 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