[GFS2] Make journaled data files identical to normal files on disk

This is a very large patch, with a few still to be resolved issues
so you might want to check out the previous head of the tree since
this is known to be unstable. Fixes for the various bugs will be
forthcoming shortly.

This patch removes the special data format which has been used
up till now for journaled data files. Directories still retain the
old format so that they will remain on disk compatible with earlier
releases. As a result you can now do the following with journaled
data files:

 1) mmap them
 2) export them over NFS
 3) convert to/from normal files whenever you want to (the zero length
    restriction is gone)

In addition the level at which GFS' locking is done has changed for all
files (since they all now use the page cache) such that the locking is
done at the page cache level rather than the level of the fs operations.
This should mean that things like loopback mounts and other things which
touch the page cache directly should now work.

Current known issues:

 1. There is a lock mode inversion problem related to the resource
    group hold function which needs to be resolved.
 2. Any significant amount of I/O causes an oops with an offset of hex 320
    (NULL pointer dereference) which appears to be related to a journaled data
    buffer appearing on a list where it shouldn't be.
 3. Direct I/O writes are disabled for the time being (will reappear later)
 4. There is probably a deadlock between the page lock and GFS' locks under
    certain combinations of mmap and fs operation I/O.
 5. Issue relating to ref counting on internally used inodes causes a hang
    on umount (discovered before this patch, and not fixed by it)
 6. One part of the directory metadata is different from GFS1 and will need
    to be resolved before next release.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/gfs2_ondisk.h b/include/linux/gfs2_ondisk.h
index f1302e2616da..99d7ae4f6b7e 100644
--- a/include/linux/gfs2_ondisk.h
+++ b/include/linux/gfs2_ondisk.h
@@ -336,6 +336,10 @@ struct gfs2_log_header {
 /* ld_data1 is the number of revoke blocks in the descriptor.
    ld_data2 is unused. */
 
+#define GFS2_LOG_DESC_JDATA     302
+/* ld_data1 is the number of data blocks in the descriptor.
+   ld_data2 is unused. */
+
 struct gfs2_log_descriptor {
         struct gfs2_meta_header ld_header;
 
@@ -400,6 +404,7 @@ struct gfs2_quota_change {
         __be32 qc_id;
 };
 
+#ifdef __KERNEL__
 /* Translation functions */
 
 extern void gfs2_inum_in(struct gfs2_inum *no, char *buf);
@@ -444,4 +449,6 @@ extern void gfs2_statfs_change_print(struct gfs2_statfs_change *sc);
 extern void gfs2_unlinked_tag_print(struct gfs2_unlinked_tag *ut);
 extern void gfs2_quota_change_print(struct gfs2_quota_change *qc);
 
+#endif /* __KERNEL__ */
+
 #endif /* __GFS2_ONDISK_DOT_H__ */