linux-kernel - Re: [PATCH v5 6/6] docs/mm: document latest changes to vm

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Message-ID: <CAJuCfpFgZUG28md9K=WZjUFoihOUSd4aBSuW-4V6JNdQS_8c9w@mail.gmail.com>
Date: Sat, 7 Dec 2024 09:33:56 -0800
From: Suren Baghdasaryan <surenb@...gle.com>
To: Akira Yokosawa <akiyks@...il.com>, lorenzo.stoakes@...cle.com
Cc: rdunlap@...radead.org, akpm@...ux-foundation.org, brauner@...nel.org, 
	corbet@....net, dave@...olabs.net, david@...hat.com, dhowells@...hat.com, 
	hannes@...xchg.org, hdanton@...a.com, hughd@...gle.com, jannh@...gle.com, 
	kernel-team@...roid.com, liam.howlett@...cle.com, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, mgorman@...hsingularity.net, 
	mhocko@...e.com, minchan@...gle.com, mjguzik@...il.com, oleg@...hat.com, 
	oliver.sang@...el.com, pasha.tatashin@...een.com, paulmck@...nel.org, 
	peterx@...hat.com, shakeel.butt@...ux.dev, souravpanda@...gle.com, 
	vbabka@...e.cz, willy@...radead.org
Subject: Re: [PATCH v5 6/6] docs/mm: document latest changes to vm_lock

On Fri, Dec 6, 2024 at 8:24 PM Akira Yokosawa <akiyks@...il.com> wrote:
>
> On Fri, 6 Dec 2024 19:23:59 -0800, Randy Dunlap wrote:
> > Hi,
> >
> > Can someone explain what the (consistent) usage of '!' does in this file?
> > This is the only file in Documentation/ that uses this syntax.
> >
> >
> > E.g.:
> >
> >> diff --git a/Documentation/mm/process_addrs.rst b/Documentation/mm/process_addrs.rst
> >> index 81417fa2ed20..92cf497a9e3c 100644
> >> --- a/Documentation/mm/process_addrs.rst
> >> +++ b/Documentation/mm/process_addrs.rst
> >> @@ -716,7 +716,11 @@ calls :c:func:`!rcu_read_lock` to ensure that the VMA is looked up in an RCU
> >>  critical section, then attempts to VMA lock it via :c:func:`!vma_start_read`,
> >>  before releasing the RCU lock via :c:func:`!rcu_read_unlock`.
> >>
> >> -VMA read locks hold the read lock on the :c:member:`!vma->vm_lock` semaphore for
> >> +In cases when the user already holds mmap read lock, :c:func:`!vma_start_read_locked`
> >> +and :c:func:`!vma_start_read_locked_nested` can be used. These functions always
> >> +succeed in acquiring VMA read lock.
> >
>
> Quoting from https://www.sphinx-doc.org/en/master/usage/referencing.html#syntax
>
>   * Suppressed link: Prefixing with an exclamation mark (!) prevents the
>     creation of a link but otherwise keeps the visual output of the role.
>
>     For example, writing :py:func:`!target` displays target(), with no link
>     generated.
>
>     This is helpful for cases in which the link target does not exist; e.g.
>     changelog entries that describe removed functionality, or third-party
>     libraries that don’t support intersphinx. Suppressing the link prevents
>     warnings in nitpicky mode.
>
> But in kernel documentation, there is a preferred alternative.
> Referencing by function names is the way to go.  For example:
>
>   calls rcu_read_lock() to ensure that the VMA is looked up in an RCU
>   critical section, then attempts to VMA lock it via vma_start_read(),
>   before releasing the RCU lock via rcu_read_unlock().
>
>   In cases when the user already holds mmap read lock, vma_start_read_locked()
>   and vma_start_read_locked_nested() can be used. These functions always
>   succeed in acquiring VMA read lock.
>
> They work regardless of link target's existence.
> Kernel-specific Sphinx extension named "automarkup" does conversions
> for you.

Thanks for the information. I was simply following the same style the
document was written in. Sounds like converting it to the preferred
alternative in a separate patch would be best. Lorenzo, WDYT?

>
> HTH, Akira
>
> > thanks.
> > --
> > ~Randy
>