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[PATCH] xfs: limit superblock corruption errors to probable corruption

To: xfs-oss <xfs@xxxxxxxxxxx>
Subject: [PATCH] xfs: limit superblock corruption errors to probable corruption
From: Eric Sandeen <sandeen@xxxxxxxxxx>
Date: Tue, 28 Jan 2014 23:11:39 -0600
Delivered-to: xfs@xxxxxxxxxxx
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.2.0
Today, if

xfs_sb_read_verify
  xfs_sb_verify
    xfs_mount_validate_sb

detects superblock corruption, it'll be extremely noisy, dumping
2 stacks, 2 hexdumps, etc.

This is because we call XFS_CORRUPTION_ERROR in xfs_mount_validate_sb
as well as in xfs_sb_read_verify.

Also, *any* errors in xfs_mount_validate_sb which are not corruption
per se; things like too-big-blocksize, bad version, bad magic, v1 dirs,
rw-incompat etc - things which do not return EFSCORRUPTED - will
still do the whole XFS_CORRUPTION_ERROR spew when xfs_sb_read_verify
sees any error at all.  And it suggests to the user that they 
should run xfs_repair, even if the root cause of the mount failure
is a simple incompatibility.

I'll submit that the probably-not-corrupted errors don't warrant
this much noise, so this patch removes the high-level
XFS_CORRUPTION_ERROR which was firing for every error return
except EWRONGFS.

It also adds one to the path which detects a failed checksum.

The idea is, if it's really _corruption_ we can call
XFS_CORRUPTION_ERROR at the point of detection.  More benign
incompatibilities can do a little printk & fail the mount without
so much drama.

Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
---

I could see an argument where we might still want the hexdump
for things like bad magic - ok, just what *was* the magic?  But
I think we do need to reserve the oops-mimicing-backtraces for
the most severe problems.  Discuss.  ;)

diff --git a/fs/xfs/xfs_sb.c b/fs/xfs/xfs_sb.c
index 511cce9..b575317 100644
--- a/fs/xfs/xfs_sb.c
+++ b/fs/xfs/xfs_sb.c
@@ -617,6 +617,8 @@ xfs_sb_read_verify(
                        /* Only fail bad secondaries on a known V5 filesystem */
                        if (bp->b_bn != XFS_SB_DADDR &&
                            xfs_sb_version_hascrc(&mp->m_sb)) {
+                               XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW,
+                                                    mp, bp->b_addr);
                                error = EFSCORRUPTED;
                                goto out_error;
                        }
@@ -625,12 +627,8 @@ xfs_sb_read_verify(
        error = xfs_sb_verify(bp, true);
 
 out_error:
-       if (error) {
-               if (error != EWRONGFS)
-                       XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW,
-                                            mp, bp->b_addr);
+       if (error)
                xfs_buf_ioerror(bp, error);
-       }
 }
 
 /*

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