linux-kernel - Re: [PATCH 4/4] change sb_writers to use percpu_rw

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Message-ID: <20150807195401.GA28529@redhat.com>
Date:	Fri, 7 Aug 2015 21:54:01 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Al Viro <viro@...iv.linux.org.uk>,
	Dave Chinner <david@...morbit.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Jan Kara <jack@...e.cz>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] change sb_writers to use percpu_rw_semaphore

On 07/22, Oleg Nesterov wrote:
>
> +static void sb_freeze_unlock(struct super_block *sb)
> +{
> +	int level;
> +
> +	for (level = 0; level < SB_FREEZE_LEVELS; ++level)
> +		percpu_up_write(sb->s_writers.rw_sem + level);
>  }

OK, this is not exactly right, see the fix below.

Otherwise seems to work, but see another email I'll send in reply to 0/4.

Oleg.

--- a/fs/super.c
+++ b/fs/super.c
@@ -1237,7 +1237,7 @@ static void sb_freeze_unlock(struct super_block *sb)
 {
 	int level;
 
-	for (level = 0; level < SB_FREEZE_LEVELS; ++level)
+	for (level = SB_FREEZE_LEVELS; --level >= 0; )
 		percpu_up_write(sb->s_writers.rw_sem + level);
 }
 

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