linux-kernel - [PATCH] fs: nobh_truncate

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Message-Id: <1173128289.9109.36.camel@kleikamp.austin.ibm.com>
Date:	Mon, 05 Mar 2007 20:58:09 +0000
From:	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Will Trives <will@...vescon.com.au>, linux-kernel@...r.kernel.org,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Chuck Ebbert <cebbert@...hat.com>
Subject: [PATCH] fs: nobh_truncate_page() fix

Adding Linus and Andrew since this patch looks obviously correct and
Will and Nick are in another timezone.

On Mon, 2007-03-05 at 09:50 -0600, Dave Kleikamp wrote:
> On Mon, 2007-03-05 at 09:36 -0600, Dave Kleikamp wrote:
> > On Mon, 2007-03-05 at 09:59 -0500, Chuck Ebbert wrote:
> > > Will Trives wrote:
> > > 
> > > [adding JFS maintainer to cc:]
> > 
> > Thanks for adding me to the thread.
> > 
> > > Some kind of JFS problem?
> > 
> > I don' t know yet.  I was notified of the problem through bugzilla:
> > http://bugzilla.kernel.org/show_bug.cgi?id=8128
> > 
> > The problem appears that a non-uptodate page has been marked dirty.  I
> > haven't found much in the way of changes between 2.6.20 and the current
> > git tree to explain this.  There's this one:
> > http://git.kernel.org/gitweb.cgi?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=22c8ca78f20724676b6006232bf06cc3e9299539
> > 
> > I'm looking for for a caller to ->prepare_write() which marks the page
> > dirty without calling ->commit_write().
> 
> I think I just found it:
> 
> nobh_truncate_page():
> 
> 	ret = a_ops->prepare_write(NULL, page, offset, to);
> 	if (ret == 0) {
> 		kaddr = kmap_atomic(page, KM_USER0);
> 		memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
> 		flush_dcache_page(page);
> 		kunmap_atomic(kaddr, KM_USER0);
> 		set_page_dirty(page);
> 	}
> 	unlock_page(page);
> 	page_cache_release(page);
> 
> > 
> > Will, could you try reverting that patch?  If that fails, narrowing the
> > problem down with git-bisect would be helpful, if you have the time.
> 
> Better yet, try this patch:

This fixes a regression caused by 22c8ca78f20724676b6006232bf06cc3e9299539.

nobh_prepare_write() no longer marks the page uptodate, so
nobh_truncate_page() needs to do it.

Signed-off-by: Dave Kleikamp <shaggy@...ux.vnet.ibm.com>

diff -Nurp linux-orig/fs/buffer.c linux/fs/buffer.c
--- linux-orig/fs/buffer.c	2007-02-22 07:59:01.000000000 -0600
+++ linux/fs/buffer.c	2007-03-05 09:47:07.000000000 -0600
@@ -2466,6 +2466,7 @@ int nobh_truncate_page(struct address_sp
 		memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
 		flush_dcache_page(page);
 		kunmap_atomic(kaddr, KM_USER0);
+		SetPageUptodate(page);
 		set_page_dirty(page);
 	}
 	unlock_page(page);

-- 
David Kleikamp
IBM Linux Technology Center

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