linux-kernel - [ 111/149] jbd2: clear BH_Delay & BH_Unwritten in journal_unmap

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Message-Id: <20120330194858.073158709@linuxfoundation.org>
Date:	Fri, 30 Mar 2012 12:50:24 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Eric Sandeen <sandeen@...hat.com>,
	"Theodore Tso" <tytso@....edu>
Subject: [ 111/149] jbd2: clear BH_Delay & BH_Unwritten in journal_unmap_buffer

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Sandeen <sandeen@...hat.com>

commit 15291164b22a357cb211b618adfef4fa82fc0de3 upstream.

journal_unmap_buffer()'s zap_buffer: code clears a lot of buffer head
state ala discard_buffer(), but does not touch _Delay or _Unwritten as
discard_buffer() does.

This can be problematic in some areas of the ext4 code which assume
that if they have found a buffer marked unwritten or delay, then it's
a live one.  Perhaps those spots should check whether it is mapped
as well, but if jbd2 is going to tear down a buffer, let's really
tear it down completely.

Without this I get some fsx failures on sub-page-block filesystems
up until v3.2, at which point 4e96b2dbbf1d7e81f22047a50f862555a6cb87cb
and 189e868fa8fdca702eb9db9d8afc46b5cb9144c9 make the failures go
away, because buried within that large change is some more flag
clearing.  I still think it's worth doing in jbd2, since
->invalidatepage leads here directly, and it's the right place
to clear away these flags.

Signed-off-by: Eric Sandeen <sandeen@...hat.com>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/jbd2/transaction.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1948,6 +1948,8 @@ zap_buffer_unlocked:
 	clear_buffer_mapped(bh);
 	clear_buffer_req(bh);
 	clear_buffer_new(bh);
+	clear_buffer_delay(bh);
+	clear_buffer_unwritten(bh);
 	bh->b_bdev = NULL;
 	return may_free;
 }


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