linux-kernel - Re: [PATCH v2 5/5] fs: Add inode_assert_locked() and inode_assert_locked

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Message-ID: <CAGudoHGVa2qjkOB25whVquRtgUN7sJtEuqUGDoVe_18RdYwSTw@mail.gmail.com>
Date:   Sun, 8 Oct 2023 23:21:34 +0200
From:   Mateusz Guzik <mjguzik@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Chandan Babu R <chandan.babu@...cle.com>,
        "Darrick J . Wong" <djwong@...nel.org>,
        linux-xfs <linux-xfs@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Christian Brauner <brauner@...nel.org>
Subject: Re: [PATCH v2 5/5] fs: Add inode_assert_locked() and inode_assert_locked_excl()

On 10/8/23, Matthew Wilcox <willy@...radead.org> wrote:
> On Sun, Oct 08, 2023 at 10:26:40PM +0200, Mateusz Guzik wrote:
>> On 10/7/23, Matthew Wilcox (Oracle) <willy@...radead.org> wrote:
>> > +static inline void inode_assert_locked_excl(const struct inode *inode)
>> > +{
>> > +	rwsem_assert_held_write(&inode->i_rwsem);
>> > +}
>> > +
>> >  static inline void inode_lock_nested(struct inode *inode, unsigned
>> > subclass)
>> >  {
>> >  	down_write_nested(&inode->i_rwsem, subclass);
>>
>> Why "excl" instead of "write"? Apart from looking weird, it is
>> inconsistent with "prior art" in the file: i_mmap_assert_write_locked.
>
> Yes, but that pairs with i_mmap_lock_write() / i_mmap_lock_read().
>
> The problem is that we have inode_lock() / inode_lock_shared()
> inode_assert_locked_read/write doesn't make sense with them.  But
> inode_assert_locked() doesn't make sense as the assertion for
> inode_lock() because you'd expect it to assert whether the inode lock
> is held at all.  So I went with inode_assert_locked_excl().
>
> I wouldn't mind if we converted all the inode_lock()/shared to
> inode_lock_read() / inode_lock_write(), and then added
> inode_assert_read_locked() / inode_assert_write_locked().  That's
> a bit of a bigger job than I want to take on today.
>

I agree it is rather messy and I'm not going to spend time arguing as
it is not my call anyway.

Speaking of that, I just noticed the vfs folk are not CC'ed, which I'm
rectifying with this e-mail.

-- 
Mateusz Guzik <mjguzik gmail.com>