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authorSteven Whitehouse <swhiteho@redhat.com>2009-11-06 16:20:51 +0000
committerSteven Whitehouse <swhiteho@redhat.com>2009-12-03 11:58:47 +0000
commit0ab7d13fcbd7ce1658c563e345990ba453719deb (patch)
tree5db7f97c264883765da4a9c6324019f0cf746e44 /include
parent2c77634965ee28c8b4790ffb5e83dd5ff7ac8988 (diff)
GFS2: Tag all metadata with jid
There are two spare field in the header common to all GFS2 metadata. One is just the right size to fit a journal id in it, and this patch updates the journal code so that each time a metadata block is modified, we tag it with the journal id of the node which is performing the modification. The reason for this is that it should make it much easier to debug issues which arise if we can tell which node was the last to modify a particular metadata block. Since the field is updated before the block is written into the journal, each journal should only contain metadata which is tagged with its own journal id. The one exception to this is the journal header block, which might have a different node's id in it, if that journal was recovered by another node in the cluster. Thus each journal will contain a record of which nodes recovered it, via the journal header. The other field in the metadata header could potentially be used to hold information about what kind of operation was performed, but for the time being we just zero it on each transaction so that if we use it for that in future, we'll know that the information (where it exists) is reliable. I did consider using the other field to hold the journal sequence number, however since in GFS2's journaling we write the modified data into the journal and not the original data, this gives no information as to what action caused the modification, so I think we can probably come up with a better use for those 64 bits in the future. Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Diffstat (limited to 'include')
-rw-r--r--include/linux/gfs2_ondisk.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/include/linux/gfs2_ondisk.h b/include/linux/gfs2_ondisk.h
index b80c88dedbb..81f90a59cda 100644
--- a/include/linux/gfs2_ondisk.h
+++ b/include/linux/gfs2_ondisk.h
@@ -81,7 +81,11 @@ struct gfs2_meta_header {
__be32 mh_type;
__be64 __pad0; /* Was generation number in gfs1 */
__be32 mh_format;
- __be32 __pad1; /* Was incarnation number in gfs1 */
+ /* This union is to keep userspace happy */
+ union {
+ __be32 mh_jid; /* Was incarnation number in gfs1 */
+ __be32 __pad1;
+ };
};
/*