[PATCH v2] db: increase metadump's default overly long extent discard threshold

["Darrick J. Wong" <darrick.wong@oracle.com>]

Back in 88b8e1d6d7 ("Make xfs_metadump more robust against bad data"),
metadump grew the ability to ignore a directory extent if it was longer
than 20 blocks.  Presumably this was to protect metadump from dumping
absurdly long extents resulting from bmbt corruption, but it's certainly
possible to create a directory with an extent longer than 20 blocks.
Hilariously, the discards happen with no warning unless the caller
explicitly set -w.

This was raised to 1000 blocks in 7431d134fe8 ("Increase default maximum
extent size for xfs_metadump when copying..."), but it's still possible
to create a directory with an extent longer than 1000 blocks.

Increase the threshold to MAXEXTLEN blocks because it's totally valid
for the filesystem to create extents up to that length.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
v2: update manpage
---
 db/metadump.c           |    2 +-
 man/man8/xfs_metadump.8 |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/db/metadump.c b/db/metadump.c
index 6dd06c3..8ffb90f 100644
--- a/db/metadump.c
+++ b/db/metadump.c
@@ -32,7 +32,7 @@
 #include "field.h"
 #include "dir2.h"
 
-#define DEFAULT_MAX_EXT_SIZE	1000
+#define DEFAULT_MAX_EXT_SIZE	MAXEXTLEN
 
 /*
  * It's possible that multiple files in a directory (or attributes
diff --git a/man/man8/xfs_metadump.8 b/man/man8/xfs_metadump.8
index 3731d6a..b6af4b6 100644
--- a/man/man8/xfs_metadump.8
+++ b/man/man8/xfs_metadump.8
@@ -114,7 +114,7 @@ copied.
 .B \-m
 Set the maximum size of an allowed metadata extent.  Extremely large metadata
 extents are likely to be corrupt, and will be skipped if they exceed
-this value.  The default size is 1000 blocks.
+this value.  The default size is 2097151 blocks.
 .TP
 .B \-o
 Disables obfuscation of file names and extended attributes.