linux-kernel - Re: [PATCH] vfs: shave work on failed file open

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Date:   Tue, 26 Sep 2023 16:01:50 +0200
From:   Christian Brauner <brauner@...nel.org>
To:     Mateusz Guzik <mjguzik@...il.com>
Cc:     viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, torvalds@...ux-foundation.org
Subject: Re: [PATCH] vfs: shave work on failed file open

> +void fput_badopen(struct file *file)
> +{
> +	if (unlikely(file->f_mode & (FMODE_BACKING | FMODE_OPENED))) {
> +		fput(file);
> +		return;
> +	}
> +
> +	if (WARN_ON(atomic_long_read(&file->f_count) != 1)) {
> +		fput(file);
> +		return;
> +	}
> +
> +	/* zero out the ref count to appease possible asserts */
> +	atomic_long_set(&file->f_count, 0);

Afaict this could just be:

if (WARN_ON_ONCE(atomic_long_cmpxchg(&file->f_count, 1, 0) != 1)) {

> +	file_free_badopen(file);
> +}
> +EXPORT_SYMBOL(fput_badopen);

Should definitely not be exported and only be available to core vfs
code. So this should go into fs/internal.h.