linux-kernel - Re: Mount ext3 with barrier=1 doesn't send real barrier bio?

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Date:	Fri, 22 Aug 2008 08:38:24 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Cc:	Eric Sandeen <sandeen@...deen.net>, Milan Broz <mbroz@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Ric Wheeler <rwheeler@...hat.com>,
	"MASON,CHRISTOPHER" <CHRIS.MASON@...cle.com>
Subject: Re: Mount ext3 with barrier=1 doesn't send real barrier bio?

On Fri, Aug 22 2008, OGAWA Hirofumi wrote:
> Eric Sandeen <sandeen@...deen.net> writes:
> 
> >> --- a/fs/buffer.c
> >> +++ b/fs/buffer.c
> >> @@ -2926,16 +2926,16 @@ int submit_bh(int rw, struct buffer_head * bh)
> >>  	BUG_ON(!buffer_mapped(bh));
> >>  	BUG_ON(!bh->b_end_io);
> >>  
> >> -	if (buffer_ordered(bh) && (rw == WRITE))
> >> -		rw = WRITE_BARRIER;
> >> -
> >>  	/*
> >>  	 * Only clear out a write error when rewriting, should this
> >>  	 * include WRITE_SYNC as well?
> >>  	 */
> >> -	if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER))
> >> +	if (test_set_buffer_req(bh) && rw == WRITE)
> >>  		clear_buffer_write_io_error(bh);
> 
> This should be ((rw & RW_MASK) == WRITE) too?  Anyway, this seems change
> behavior of submit_bh(WRITE_BARRIER) (maybe reiserfs only), it wouldn't
> be your intent...

Yes, I believe the simpler and more correct fix is:

diff --git a/fs/buffer.c b/fs/buffer.c
index 38653e3..16b2263 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2926,14 +2926,13 @@ int submit_bh(int rw, struct buffer_head * bh)
 	BUG_ON(!buffer_mapped(bh));
 	BUG_ON(!bh->b_end_io);
 
-	if (buffer_ordered(bh) && (rw == WRITE))
+	if (buffer_ordered(bh) && (rw & WRITE))
 		rw = WRITE_BARRIER;
 
 	/*
-	 * Only clear out a write error when rewriting, should this
-	 * include WRITE_SYNC as well?
+	 * Only clear out a write error when rewriting
 	 */
-	if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER))
+	if (test_set_buffer_req(bh) && (rw & WRITE))
 		clear_buffer_write_io_error(bh);
 
 	/*

-- 
Jens Axboe

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