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[PATCH 1/4] xfs: catch buffers written without verifiers attached

To: xfs@xxxxxxxxxxx
Subject: [PATCH 1/4] xfs: catch buffers written without verifiers attached
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 30 Jul 2014 11:48:46 +1000
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1406684929-11133-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1406684929-11133-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

We recently had a bug where buffers were slipping through log
recovery without any verifier attached to them. This was resulting
in on-disk CRC mismatches for valid data. Add some warning code to
catch this occurrence so that we catch such bugs durin development
rather than not being aware they exist.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 fs/xfs/xfs_buf.c | 6 ++++++
 fs/xfs/xfs_log.c | 7 ++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index a6dc83e..95e5516 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1330,6 +1330,12 @@ _xfs_buf_ioapply(
                                                   SHUTDOWN_CORRUPT_INCORE);
                                return;
                        }
+               } else if (bp->b_bn != -1LL) {
+                       xfs_warn(bp->b_target->bt_mount,
+                               "%s: no ops on block 0x%llx/0x%llx",
+                               __func__, bp->b_bn, bp->b_maps[0].bm_bn);
+                       xfs_hex_dump(bp->b_addr, 64);
+                       dump_stack();
                }
        } else if (bp->b_flags & XBF_READ_AHEAD) {
                rw = READA;
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 149a4a5..9dc92b3 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1378,8 +1378,13 @@ xlog_alloc_log(
 
        xlog_get_iclog_buffer_size(mp, log);
 
+       /*
+        * Use a block number of -1 for the extra log buffer used during splits
+        * so that it will trigger errors if we ever try to do IO on it without
+        * first having set it up properly.
+        */
        error = -ENOMEM;
-       bp = xfs_buf_alloc(mp->m_logdev_targp, 0, BTOBB(log->l_iclog_size), 0);
+       bp = xfs_buf_alloc(mp->m_logdev_targp, -1LL, BTOBB(log->l_iclog_size), 
0);
        if (!bp)
                goto out_free_log;
 
-- 
2.0.0

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