linux-kernel - Re: mmotm 2009-01-05-12-50 uploaded (ubifs)

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Message-Id: <1231243904.6608.47.camel@localhost.localdomain>
Date:	Tue, 06 Jan 2009 14:11:44 +0200
From:	Artem Bityutskiy <dedekind@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Randy Dunlap <randy.dunlap@...cle.com>,
	linux-kernel@...r.kernel.org,
	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>,
	Nick Piggin <nickpiggin@...oo.com.au>
Subject: Re: mmotm 2009-01-05-12-50 uploaded (ubifs)

On Mon, 2009-01-05 at 14:24 -0800, Andrew Morton wrote:
> WB_SYNC_HOLD got removed by
> http://userweb.kernel.org/~akpm/mmotm/broken-out/fs-remove-wb_sync_hold.patch
> 
> I think I'll just switch that to WB_SYNC_NONE.  The `wait==0' mode is
> just an advisory thing to help the fs shove lots of data into the
> queues.  If some gets missed then it'll be picked up on the second
> ->sync_fs call, with wait==1.

Sorry for the problems caused by this patch. Here is a fix for your
convenience. Will you send it to Linus or I should do this?

From: Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
Subject: [PATCH] UBIFS: do not use WB_SYNC_HOLD

WB_SYNC_HOLD is going to be zapped so we should not use it. Use
%WB_SYNC_NONE instead. Here is what akpm said:

"I think I'll just switch that to WB_SYNC_NONE.  The `wait==0' mode is
just an advisory thing to help the fs shove lots of data into the
queues.  If some gets missed then it'll be picked up on the second
->sync_fs call, with wait==1."

Thanks to Randy Dunlap <randy.dunlap@...cle.com> for catching this.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
---
 fs/ubifs/super.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 0d7564b..89556ee 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -432,12 +432,19 @@ static int ubifs_sync_fs(struct super_block *sb, int wait)
 	int i, err;
 	struct ubifs_info *c = sb->s_fs_info;
 	struct writeback_control wbc = {
-		.sync_mode   = wait ? WB_SYNC_ALL : WB_SYNC_HOLD,
+		.sync_mode   = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
 		.range_start = 0,
 		.range_end   = LLONG_MAX,
 		.nr_to_write = LONG_MAX,
 	};
 
+	/*
+	 * Note by akpm about WB_SYNC_NONE used above: zero @wait is just an
+	 * advisory thing to help the file system shove lots of data into the
+	 * queues. If some gets missed then it'll be picked up on the second
+	 * '->sync_fs()' call, with non-zero @wait.
+	 */
+
 	if (sb->s_flags & MS_RDONLY)
 		return 0;
 
-- 
1.6.0.6

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

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