linux-kernel - Re: [PATCH] vfs: replace WARN(down_read_trylock, ...) abuse with proper asserts

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Date: Mon, 3 Jun 2024 13:09:57 +0200
From: Jan Kara <jack@...e.cz>
To: Mateusz Guzik <mjguzik@...il.com>
Cc: brauner@...nel.org, viro@...iv.linux.org.uk, jack@...e.cz,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] vfs: replace WARN(down_read_trylock, ...) abuse with
 proper asserts

On Sun 02-06-24 14:37:19, Mateusz Guzik wrote:
> Note the macro used here works regardless of LOCKDEP.
> 
> Signed-off-by: Mateusz Guzik <mjguzik@...il.com>

Nice cleanup. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/dcache.c      | 2 +-
>  fs/quota/dquot.c | 8 ++------
>  2 files changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/dcache.c b/fs/dcache.c
> index 407095188f83..a0a944fd3a1c 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -1548,7 +1548,7 @@ void shrink_dcache_for_umount(struct super_block *sb)
>  {
>  	struct dentry *dentry;
>  
> -	WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
> +	rwsem_assert_held_write(&sb->s_umount);
>  
>  	dentry = sb->s_root;
>  	sb->s_root = NULL;
> diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> index 627eb2f72ef3..a2b256dac36e 100644
> --- a/fs/quota/dquot.c
> +++ b/fs/quota/dquot.c
> @@ -2246,9 +2246,7 @@ int dquot_disable(struct super_block *sb, int type, unsigned int flags)
>  	int cnt;
>  	struct quota_info *dqopt = sb_dqopt(sb);
>  
> -	/* s_umount should be held in exclusive mode */
> -	if (WARN_ON_ONCE(down_read_trylock(&sb->s_umount)))
> -		up_read(&sb->s_umount);
> +	rwsem_assert_held_write(&sb->s_umount);
>  
>  	/* Cannot turn off usage accounting without turning off limits, or
>  	 * suspend quotas and simultaneously turn quotas off. */
> @@ -2510,9 +2508,7 @@ int dquot_resume(struct super_block *sb, int type)
>  	int ret = 0, cnt;
>  	unsigned int flags;
>  
> -	/* s_umount should be held in exclusive mode */
> -	if (WARN_ON_ONCE(down_read_trylock(&sb->s_umount)))
> -		up_read(&sb->s_umount);
> +	rwsem_assert_held_write(&sb->s_umount);
>  
>  	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
>  		if (type != -1 && cnt != type)
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR