[XFS] implement generic xfs_btree_increment

From: Dave Chinner <dgc@sgi.com>

Because this is the first major generic btree routine this patch includes
some infrastrucure, first a few routines to deal with a btree block that
can be either in short or long form, second xfs_btree_read_buf_block,
which is the new central routine to read a btree block given a cursor, and
third the new xfs_btree_ptr_addr routine to calculate the address for a
given btree pointer record.

[hch: split out from bigger patch and minor adaptions]

SGI-PV: 985583

SGI-Modid: xfs-linux-melb:xfs-kern:32190a

Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
Signed-off-by: Bill O'Donnell <billodo@sgi.com>
Signed-off-by: David Chinner <david@fromorbit.com>

1 files changed, 222 insertions, 0 deletions

diff --git a/fs/xfs/xfs_btree.c b/fs/xfs/xfs_btree.c
index 4aec7c7d5ba9..e9ab86b7990e 100644
--- a/fs/xfs/xfs_btree.c
+++ b/fs/xfs/xfs_btree.c
@@ -35,6 +35,7 @@
 #include "xfs_dinode.h"
 #include "xfs_inode.h"
 #include "xfs_btree.h"
+#include "xfs_btree_trace.h"
 #include "xfs_ialloc.h"
 #include "xfs_error.h"
 
@@ -949,3 +950,224 @@ xfs_btree_setbuf(
                         cur->bc_ra[lev] |= XFS_BTCUR_RIGHTRA;
         }
 }
+
+STATIC int
+xfs_btree_ptr_is_null(
+        struct xfs_btree_cur    *cur,
+        union xfs_btree_ptr     *ptr)
+{
+        if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
+                return be64_to_cpu(ptr->l) == NULLFSBLOCK;
+        else
+                return be32_to_cpu(ptr->s) == NULLAGBLOCK;
+}
+
+/*
+ * Get/set/init sibling pointers
+ */
+STATIC void
+xfs_btree_get_sibling(
+        struct xfs_btree_cur    *cur,
+        struct xfs_btree_block  *block,
+        union xfs_btree_ptr     *ptr,
+        int                     lr)
+{
+        ASSERT(lr == XFS_BB_LEFTSIB || lr == XFS_BB_RIGHTSIB);
+
+        if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
+                if (lr == XFS_BB_RIGHTSIB)
+                        ptr->l = block->bb_u.l.bb_rightsib;
+                else
+                        ptr->l = block->bb_u.l.bb_leftsib;
+        } else {
+                if (lr == XFS_BB_RIGHTSIB)
+                        ptr->s = block->bb_u.s.bb_rightsib;
+                else
+                        ptr->s = block->bb_u.s.bb_leftsib;
+        }
+}
+
+STATIC xfs_daddr_t
+xfs_btree_ptr_to_daddr(
+        struct xfs_btree_cur    *cur,
+        union xfs_btree_ptr     *ptr)
+{
+        if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
+                ASSERT(be64_to_cpu(ptr->l) != NULLFSBLOCK);
+
+                return XFS_FSB_TO_DADDR(cur->bc_mp, be64_to_cpu(ptr->l));
+        } else {
+                ASSERT(cur->bc_private.a.agno != NULLAGNUMBER);
+                ASSERT(be32_to_cpu(ptr->s) != NULLAGBLOCK);
+
+                return XFS_AGB_TO_DADDR(cur->bc_mp, cur->bc_private.a.agno,
+                                        be32_to_cpu(ptr->s));
+        }
+}
+
+STATIC void
+xfs_btree_set_refs(
+        struct xfs_btree_cur    *cur,
+        struct xfs_buf          *bp)
+{
+        switch (cur->bc_btnum) {
+        case XFS_BTNUM_BNO:
+        case XFS_BTNUM_CNT:
+                XFS_BUF_SET_VTYPE_REF(*bpp, B_FS_MAP, XFS_ALLOC_BTREE_REF);
+                break;
+        case XFS_BTNUM_INO:
+                XFS_BUF_SET_VTYPE_REF(*bpp, B_FS_INOMAP, XFS_INO_BTREE_REF);
+                break;
+        case XFS_BTNUM_BMAP:
+                XFS_BUF_SET_VTYPE_REF(*bpp, B_FS_MAP, XFS_BMAP_BTREE_REF);
+                break;
+        default:
+                ASSERT(0);
+        }
+}
+
+/*
+ * Read in the buffer at the given ptr and return the buffer and
+ * the block pointer within the buffer.
+ */
+STATIC int
+xfs_btree_read_buf_block(
+        struct xfs_btree_cur    *cur,
+        union xfs_btree_ptr     *ptr,
+        int                     level,
+        int                     flags,
+        struct xfs_btree_block  **block,
+        struct xfs_buf          **bpp)
+{
+        struct xfs_mount        *mp = cur->bc_mp;
+        xfs_daddr_t             d;
+        int                     error;
+
+        /* need to sort out how callers deal with failures first */
+        ASSERT(!(flags & XFS_BUF_TRYLOCK));
+
+        d = xfs_btree_ptr_to_daddr(cur, ptr);
+        error = xfs_trans_read_buf(mp, cur->bc_tp, mp->m_ddev_targp, d,
+                                   mp->m_bsize, flags, bpp);
+        if (error)
+                return error;
+
+        ASSERT(*bpp != NULL);
+        ASSERT(!XFS_BUF_GETERROR(*bpp));
+
+        xfs_btree_set_refs(cur, *bpp);
+        *block = XFS_BUF_TO_BLOCK(*bpp);
+
+        error = xfs_btree_check_block(cur, *block, level, *bpp);
+        if (error)
+                xfs_trans_brelse(cur->bc_tp, *bpp);
+        return error;
+}
+
+/*
+ * Increment cursor by one record at the level.
+ * For nonzero levels the leaf-ward information is untouched.
+ */
+int                                             /* error */
+xfs_btree_increment(
+        struct xfs_btree_cur    *cur,
+        int                     level,
+        int                     *stat)          /* success/failure */
+{
+        struct xfs_btree_block  *block;
+        union xfs_btree_ptr     ptr;
+        struct xfs_buf          *bp;
+        int                     error;          /* error return value */
+        int                     lev;
+
+        XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
+        XFS_BTREE_TRACE_ARGI(cur, level);
+
+        ASSERT(level < cur->bc_nlevels);
+
+        /* Read-ahead to the right at this level. */
+        xfs_btree_readahead(cur, level, XFS_BTCUR_RIGHTRA);
+
+        /* Get a pointer to the btree block. */
+        block = xfs_btree_get_block(cur, level, &bp);
+
+#ifdef DEBUG
+        error = xfs_btree_check_block(cur, block, level, bp);
+        if (error)
+                goto error0;
+#endif
+
+        /* We're done if we remain in the block after the increment. */
+        if (++cur->bc_ptrs[level] <= xfs_btree_get_numrecs(block))
+                goto out1;
+
+        /* Fail if we just went off the right edge of the tree. */
+        xfs_btree_get_sibling(cur, block, &ptr, XFS_BB_RIGHTSIB);
+        if (xfs_btree_ptr_is_null(cur, &ptr))
+                goto out0;
+
+        XFS_BTREE_STATS_INC(cur, increment);
+
+        /*
+         * March up the tree incrementing pointers.
+         * Stop when we don't go off the right edge of a block.
+         */
+        for (lev = level + 1; lev < cur->bc_nlevels; lev++) {
+                block = xfs_btree_get_block(cur, lev, &bp);
+
+#ifdef DEBUG
+                error = xfs_btree_check_block(cur, block, lev, bp);
+                if (error)
+                        goto error0;
+#endif
+
+                if (++cur->bc_ptrs[lev] <= xfs_btree_get_numrecs(block))
+                        break;
+
+                /* Read-ahead the right block for the next loop. */
+                xfs_btree_readahead(cur, lev, XFS_BTCUR_RIGHTRA);
+        }
+
+        /*
+         * If we went off the root then we are either seriously
+         * confused or have the tree root in an inode.
+         */
+        if (lev == cur->bc_nlevels) {
+                if (cur->bc_flags & XFS_BTREE_ROOT_IN_INODE)
+                        goto out0;
+                ASSERT(0);
+                error = EFSCORRUPTED;
+                goto error0;
+        }
+        ASSERT(lev < cur->bc_nlevels);
+
+        /*
+         * Now walk back down the tree, fixing up the cursor's buffer
+         * pointers and key numbers.
+         */
+        for (block = xfs_btree_get_block(cur, lev, &bp); lev > level; ) {
+                union xfs_btree_ptr     *ptrp;
+
+                ptrp = xfs_btree_ptr_addr(cur, cur->bc_ptrs[lev], block);
+                error = xfs_btree_read_buf_block(cur, ptrp, --lev,
+                                                        0, &block, &bp);
+                if (error)
+                        goto error0;
+
+                xfs_btree_setbuf(cur, lev, bp);
+                cur->bc_ptrs[lev] = 1;
+        }
+out1:
+        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
+        *stat = 1;
+        return 0;
+
+out0:
+        XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
+        *stat = 0;
+        return 0;
+
+error0:
+        XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
+        return error;
+}