xfs: swap extents operations for CRC filesystems
For CRC enabled filesystems, we can't just swap inode forks from one
inode to another when defragmenting a file - the blocks in the inode
fork bmap btree contain pointers back to the owner inode. Hence if
we are to swap the inode forks we have to atomically modify every
block in the btree during the transaction.
We are doing an entire fork swap here, so we could create a new
transaction item type that indicates we are changing the owner of a
certain structure from one value to another. If we combine this with
ordered buffer logging to modify all the buffers in the tree, then
we can change the buffers in the tree without needing log space for
the operation. However, this then requires log recovery to perform
the modification of the owner information of the objects/structures
in question.
This does introduce some interesting ordering details into recovery:
we have to make sure that the owner change replay occurs after the
change that moves the objects is made, not before. Hence we can't
use a separate log item for this as we have no guarantee of strict
ordering between multiple items in the log due to the relogging
action of asynchronous transaction commits. Hence there is no
"generic" method we can use for changing the ownership of arbitrary
metadata structures.
For inode forks, however, there is a simple method of communicating
that the fork contents need the owner rewritten - we can pass a
inode log format flag for the fork for the transaction that does a
fork swap. This flag will then follow the inode fork through
relogging actions so when the swap actually gets replayed the
ownership can be changed immediately by log recovery. So that gives
us a simple method of "whole fork" exchange between two inodes.
This is relatively simple to implement, so it makes sense to do this
as an initial implementation to support xfs_fsr on CRC enabled
filesytems in the same manner as we do on existing filesystems. This
commit introduces the swapext driven functionality, the recovery
functionality will be in a separate patch.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
diff --git a/fs/xfs/xfs_btree.h b/fs/xfs/xfs_btree.h
index c8473c7..544b209 100644
--- a/fs/xfs/xfs_btree.h
+++ b/fs/xfs/xfs_btree.h
@@ -121,15 +121,18 @@
/*
* For logging record fields.
*/
-#define XFS_BB_MAGIC 0x01
-#define XFS_BB_LEVEL 0x02
-#define XFS_BB_NUMRECS 0x04
-#define XFS_BB_LEFTSIB 0x08
-#define XFS_BB_RIGHTSIB 0x10
-#define XFS_BB_BLKNO 0x20
+#define XFS_BB_MAGIC (1 << 0)
+#define XFS_BB_LEVEL (1 << 1)
+#define XFS_BB_NUMRECS (1 << 2)
+#define XFS_BB_LEFTSIB (1 << 3)
+#define XFS_BB_RIGHTSIB (1 << 4)
+#define XFS_BB_BLKNO (1 << 5)
+#define XFS_BB_LSN (1 << 6)
+#define XFS_BB_UUID (1 << 7)
+#define XFS_BB_OWNER (1 << 8)
#define XFS_BB_NUM_BITS 5
#define XFS_BB_ALL_BITS ((1 << XFS_BB_NUM_BITS) - 1)
-#define XFS_BB_NUM_BITS_CRC 8
+#define XFS_BB_NUM_BITS_CRC 9
#define XFS_BB_ALL_BITS_CRC ((1 << XFS_BB_NUM_BITS_CRC) - 1)
/*
@@ -442,6 +445,7 @@
int xfs_btree_insert(struct xfs_btree_cur *, int *);
int xfs_btree_delete(struct xfs_btree_cur *, int *);
int xfs_btree_get_rec(struct xfs_btree_cur *, union xfs_btree_rec **, int *);
+int xfs_btree_change_owner(struct xfs_btree_cur *cur, __uint64_t new_owner);
/*
* btree block CRC helpers