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Re: [PATCH 1/5] metadump: sanitise write_buf/index return values

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 1/5] metadump: sanitise write_buf/index return values
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Fri, 14 Feb 2014 14:54:31 -0600
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <52FE73B3.1020804@xxxxxxx>
References: <1390472635-17225-1-git-send-email-david@xxxxxxxxxxxxx> <1390472635-17225-2-git-send-email-david@xxxxxxxxxxxxx> <52FD1D38.1010006@xxxxxxx> <20140214022053.GQ13997@dastard> <52FE73B3.1020804@xxxxxxx>
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On 02/14/14 13:51, Mark Tinguely wrote:
On 02/13/14 20:20, Dave Chinner wrote:
On Thu, Feb 13, 2014 at 01:30:00PM -0600, Mark Tinguely wrote:
On 01/23/14 04:23, Dave Chinner wrote:
From: Dave Chinner<dchinner@xxxxxxxxxx>

Write_buf/write_index use confusing boolean values for return,
meaning that it's hard to tell what the correct error return is
supposed to be. Convert them to return zero on success or a
negative errno otherwise so that it's clear what the error case is.

Signed-off-by: Dave Chinner<dchinner@xxxxxxxxxx>
---

Looks like this patch broke metadumps on some corrupted filesystems.
This is a legacy filesystem that has zeroes overwriting the
SB/AGF/AGI on AG 1/2/3:


# xfs_metadump -wgo /dev/sda8 myfile.metadata
xfs_agf_read_verify: XFS_CORRUPTION_ERROR
xfs_metadump: cannot init perag data (117). Continuing anyway.
Copied 64 of 64 inodes (0 of 4 AGs) xfs_agf_write_verify: XF
S_CORRUPTION_ERROR
write_buf: write verifer failed on bno 0x1100919/0x200
(no output)

Where did it crash? Can you post the stack trace from gdb? Even
better, can you send a patch to fix the problem? ;)

Cheers,

Dave.

No crash, just exits without performing the dump.

--Mark.


The error from the verifier prevents the metadump from completing.
You will want to fix it another way...

--Mark.

---
 db/metadump.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: b/db/metadump.c
===================================================================
--- a/db/metadump.c
+++ b/db/metadump.c
@@ -209,7 +209,7 @@ write_buf(
        _("%s: write verifer failed on bno 0x%llx/0x%x\n"),
                                __func__, (long long)buf->bp->b_bn,
                                buf->bp->b_bcount);
-                       return -buf->bp->b_error;
+                       return 0;
                }
        }

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