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

[Eric Sandeen <sandeen@redhat.com>]

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@redhat.com>
---

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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