[PATCH 03/21] make btree root in inode support generic

[Christoph Hellwig <hch@xxxxxx>]

The bmap btree is rooted in the inode and not in a single disk block.  Make
the support for this feature more generic by:

 (a) adding a btree flag to check for instead of the XFS_BTNUM_BMAP type
 (b) add a get_root_from_inode btree operation to get a btree block from
     the inode, with the implementation details left to the individual btree.

Also clean up xfs_btree_get_block, which is the place these two features
are used.

The XFS_BTREE_ROOT_IN_INODE is based upon a patch from Dave Chinner.


Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Index: linux-2.6-xfs/fs/xfs/xfs_bmap_btree.c
===================================================================
--- linux-2.6-xfs.orig/fs/xfs/xfs_bmap_btree.c  2008-07-08 20:05:01.000000000 
+0200
+++ linux-2.6-xfs/fs/xfs/xfs_bmap_btree.c       2008-07-08 20:41:49.000000000 
+0200
@@ -2630,8 +2630,19 @@ xfs_bmbt_dup_cursor(
        return new;
 }
 
+STATIC struct xfs_btree_block *
+xfs_bmbt_get_root_from_inode(
+       struct xfs_btree_cur    *cur)
+{
+       struct xfs_ifork        *ifp;
+
+       ifp = XFS_IFORK_PTR(cur->bc_private.b.ip, cur->bc_private.b.whichfork);
+       return (struct xfs_btree_block *)ifp->if_broot;
+}
+
 static const struct xfs_btree_ops xfs_bmbt_ops = {
        .dup_cursor             = xfs_bmbt_dup_cursor,
+       .get_root_from_inode    = xfs_bmbt_get_root_from_inode,
 };
 
 /*
@@ -2656,6 +2667,7 @@ xfs_bmbt_init_cursor(
        cur->bc_blocklog = mp->m_sb.sb_blocklog;
 
        cur->bc_ops = &xfs_bmbt_ops;
+       cur->bc_flags = XFS_BTREE_ROOT_IN_INODE;
 
        cur->bc_private.b.forksize = XFS_IFORK_SIZE(ip, whichfork);
        cur->bc_private.b.ip = ip;
Index: linux-2.6-xfs/fs/xfs/xfs_btree.c
===================================================================
--- linux-2.6-xfs.orig/fs/xfs/xfs_btree.c       2008-07-08 20:05:01.000000000 
+0200
+++ linux-2.6-xfs/fs/xfs/xfs_btree.c    2008-07-08 20:42:43.000000000 +0200
@@ -425,29 +425,20 @@ xfs_btree_dup_cursor(
  * Retrieve the block pointer from the cursor at the given level.
  * This may be a bmap btree root or from a buffer.
  */
-STATIC xfs_btree_block_t *             /* generic btree block pointer */
+STATIC struct xfs_btree_block *                /* generic btree block pointer 
*/
 xfs_btree_get_block(
-       xfs_btree_cur_t         *cur,   /* btree cursor */
+       struct xfs_btree_cur    *cur,   /* btree cursor */
        int                     level,  /* level in btree */
-       xfs_buf_t               **bpp)  /* buffer containing the block */
+       struct xfs_buf          **bpp)  /* buffer containing the block */
 {
-       xfs_btree_block_t       *block; /* return value */
-       xfs_buf_t               *bp;    /* return buffer */
-       xfs_ifork_t             *ifp;   /* inode fork pointer */
-       int                     whichfork; /* data or attr fork */
-
-       if (cur->bc_btnum == XFS_BTNUM_BMAP && level == cur->bc_nlevels - 1) {
-               whichfork = cur->bc_private.b.whichfork;
-               ifp = XFS_IFORK_PTR(cur->bc_private.b.ip, whichfork);
-               block = (xfs_btree_block_t *)ifp->if_broot;
-               bp = NULL;
-       } else {
-               bp = cur->bc_bufs[level];
-               block = XFS_BUF_TO_BLOCK(bp);
+       if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) &&
+           (level == cur->bc_nlevels - 1)) {
+               *bpp = NULL;
+               return cur->bc_ops->get_root_from_inode(cur);
        }
-       ASSERT(block != NULL);
-       *bpp = bp;
-       return block;
+
+       *bpp = cur->bc_bufs[level];
+       return XFS_BUF_TO_BLOCK(*bpp);
 }
 
 /*
Index: linux-2.6-xfs/fs/xfs/xfs_btree.h
===================================================================
--- linux-2.6-xfs.orig/fs/xfs/xfs_btree.h       2008-07-08 20:06:55.000000000 
+0200
+++ linux-2.6-xfs/fs/xfs/xfs_btree.h    2008-07-08 20:41:49.000000000 +0200
@@ -164,6 +164,9 @@ extern const __uint32_t     xfs_magics[];
 struct xfs_btree_ops {
        /* cursor operations */
        struct xfs_btree_cur *(*dup_cursor)(struct xfs_btree_cur *);
+
+       /* get inode rooted btree root */
+       struct xfs_btree_block *(*get_root_from_inode)(struct xfs_btree_cur *);
 };
 
 /*
@@ -175,6 +178,7 @@ typedef struct xfs_btree_cur
        struct xfs_trans        *bc_tp; /* transaction we're in, if any */
        struct xfs_mount        *bc_mp; /* file system mount struct */
        const struct xfs_btree_ops *bc_ops;
+       uint                    bc_flags; /* btree features - below */
        union {
                xfs_alloc_rec_incore_t  a;
                xfs_bmbt_irec_t         b;
@@ -206,6 +210,10 @@ typedef struct xfs_btree_cur
        }               bc_private;     /* per-btree type data */
 } xfs_btree_cur_t;
 
+/* cursor flags */
+#define XFS_BTREE_ROOT_IN_INODE                (1<<1)  /* root may be variable 
size */
+
+
 #define        XFS_BTREE_NOERROR       0
 #define        XFS_BTREE_ERROR         1
 

--