linux-kernel - [PATCH 46/51] [GFS2] Data corruption fix

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Date:	Thu,  4 Oct 2007 09:49:39 +0100
From:	swhiteho@...hat.com
To:	linux-kernel@...r.kernel.org, cluster-devel@...hat.com
Cc:	Wendy Cheng <wcheng@...hat.com>,
	Steven Whitehouse <swhiteho@...hat.com>
Subject: [PATCH 46/51] [GFS2] Data corruption fix

From: Wendy Cheng <wcheng@...hat.com>

* GFS2 has been using i_cache array to store its indirect meta blocks.
Its flush routine doesn't correctly clean up all the entries. The
problem would show while multiple nodes do simultaneous writes to the
same file. Upon glock exclusive lock transfer, if the file is a sparse
file with large file size where the indirect meta blocks span multiple
array entries with "zero" entries in between. The flush routine
prematurely stops the flushing that leaves old (stale) entries around.
This leads to several nasty issues, including data corruption.
* Fix gfs2_get_block_noalloc checking to correctly return EIO upon
unmapped buffer.

Signed-off-by: Wendy Cheng <wcheng@...hat.com>
Signed-off-by: Steven Whitehouse <swhiteho@...hat.com>

diff --git a/fs/gfs2/meta_io.c b/fs/gfs2/meta_io.c
index 1d80f2d..4da4239 100644
--- a/fs/gfs2/meta_io.c
+++ b/fs/gfs2/meta_io.c
@@ -374,10 +374,10 @@ void gfs2_meta_cache_flush(struct gfs2_inode *ip)
 
 	for (x = 0; x < GFS2_MAX_META_HEIGHT; x++) {
 		bh_slot = &ip->i_cache[x];
-		if (!*bh_slot)
-			break;
-		brelse(*bh_slot);
-		*bh_slot = NULL;
+		if (*bh_slot) {
+			brelse(*bh_slot);
+			*bh_slot = NULL;
+		}
 	}
 
 	spin_unlock(&ip->i_spin);
diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index b7baf18..4002f41 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -90,7 +90,7 @@ static int gfs2_get_block_noalloc(struct inode *inode, sector_t lblock,
 	error = gfs2_block_map(inode, lblock, 0, bh_result);
 	if (error)
 		return error;
-	if (bh_result->b_blocknr == 0)
+	if (!buffer_mapped(bh_result))
 		return -EIO;
 	return 0;
 }
-- 
1.5.1.2

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