[XFS] refactor xfs_btree_readahead

From: Dave Chinner <dgc@sgi.com>

Refactor xfs_btree_readahead to make it more readable:

(a) remove the inline xfs_btree_readahead wrapper and move all checks out

of line into the main routine.

(b) factor out helpers for short/long form btrees

(c) move check for root in inodes from the callers into
xfs_btree_readahead

[hch: split out from a big patch and minor cleanups]

SGI-PV: 985583

SGI-Modid: xfs-linux-melb:xfs-kern:32182a

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>

3 files changed, 76 insertions, 72 deletions

diff --git a/fs/xfs/xfs_bmap_btree.c b/fs/xfs/xfs_bmap_btree.c
index 1ec494e111b5..519249e20536 100644
--- a/fs/xfs/xfs_bmap_btree.c
+++ b/fs/xfs/xfs_bmap_btree.c
@@ -1721,8 +1721,9 @@ xfs_bmbt_decrement(
         XFS_BMBT_TRACE_CURSOR(cur, ENTRY);
         XFS_BMBT_TRACE_ARGI(cur, level);
         ASSERT(level < cur->bc_nlevels);
-        if (level < cur->bc_nlevels - 1)
-                xfs_btree_readahead(cur, level, XFS_BTCUR_LEFTRA);
+
+        xfs_btree_readahead(cur, level, XFS_BTCUR_LEFTRA);
+
         if (--cur->bc_ptrs[level] > 0) {
                 XFS_BMBT_TRACE_CURSOR(cur, EXIT);
                 *stat = 1;
@@ -1743,8 +1744,7 @@ xfs_bmbt_decrement(
         for (lev = level + 1; lev < cur->bc_nlevels; lev++) {
                 if (--cur->bc_ptrs[lev] > 0)
                         break;
-                if (lev < cur->bc_nlevels - 1)
-                        xfs_btree_readahead(cur, lev, XFS_BTCUR_LEFTRA);
+                xfs_btree_readahead(cur, lev, XFS_BTCUR_LEFTRA);
         }
         if (lev == cur->bc_nlevels) {
                 XFS_BMBT_TRACE_CURSOR(cur, EXIT);
@@ -1995,8 +1995,8 @@ xfs_bmbt_increment(
         XFS_BMBT_TRACE_CURSOR(cur, ENTRY);
         XFS_BMBT_TRACE_ARGI(cur, level);
         ASSERT(level < cur->bc_nlevels);
-        if (level < cur->bc_nlevels - 1)
-                xfs_btree_readahead(cur, level, XFS_BTCUR_RIGHTRA);
+
+        xfs_btree_readahead(cur, level, XFS_BTCUR_RIGHTRA);
         block = xfs_bmbt_get_block(cur, level, &bp);
 #ifdef DEBUG
         if ((error = xfs_btree_check_lblock(cur, block, level, bp))) {
@@ -2024,8 +2024,7 @@ xfs_bmbt_increment(
 #endif
                 if (++cur->bc_ptrs[lev] <= be16_to_cpu(block->bb_numrecs))
                         break;
-                if (lev < cur->bc_nlevels - 1)
-                        xfs_btree_readahead(cur, lev, XFS_BTCUR_RIGHTRA);
+                xfs_btree_readahead(cur, lev, XFS_BTCUR_RIGHTRA);
         }
         if (lev == cur->bc_nlevels) {
                 XFS_BMBT_TRACE_CURSOR(cur, EXIT);
diff --git a/fs/xfs/xfs_btree.c b/fs/xfs/xfs_btree.c
index 59796b42e9c4..4d793e4ccdcc 100644
--- a/fs/xfs/xfs_btree.c
+++ b/fs/xfs/xfs_btree.c
@@ -725,66 +725,84 @@ xfs_btree_reada_bufs(
         xfs_baread(mp->m_ddev_targp, d, mp->m_bsize * count);
 }
 
+STATIC int
+xfs_btree_readahead_lblock(
+        struct xfs_btree_cur    *cur,
+        int                     lr,
+        struct xfs_btree_block  *block)
+{
+        int                     rval = 0;
+        xfs_fsblock_t           left = be64_to_cpu(block->bb_u.l.bb_leftsib);
+        xfs_fsblock_t           right = be64_to_cpu(block->bb_u.l.bb_rightsib);
+
+        if ((lr & XFS_BTCUR_LEFTRA) && left != NULLDFSBNO) {
+                xfs_btree_reada_bufl(cur->bc_mp, left, 1);
+                rval++;
+        }
+
+        if ((lr & XFS_BTCUR_RIGHTRA) && right != NULLDFSBNO) {
+                xfs_btree_reada_bufl(cur->bc_mp, right, 1);
+                rval++;
+        }
+
+        return rval;
+}
+
+STATIC int
+xfs_btree_readahead_sblock(
+        struct xfs_btree_cur    *cur,
+        int                     lr,
+        struct xfs_btree_block *block)
+{
+        int                     rval = 0;
+        xfs_agblock_t           left = be32_to_cpu(block->bb_u.s.bb_leftsib);
+        xfs_agblock_t           right = be32_to_cpu(block->bb_u.s.bb_rightsib);
+
+
+        if ((lr & XFS_BTCUR_LEFTRA) && left != NULLAGBLOCK) {
+                xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.a.agno,
+                                     left, 1);
+                rval++;
+        }
+
+        if ((lr & XFS_BTCUR_RIGHTRA) && right != NULLAGBLOCK) {
+                xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.a.agno,
+                                     right, 1);
+                rval++;
+        }
+
+        return rval;
+}
+
 /*
  * Read-ahead btree blocks, at the given level.
  * Bits in lr are set from XFS_BTCUR_{LEFT,RIGHT}RA.
  */
 int
-xfs_btree_readahead_core(
-        xfs_btree_cur_t         *cur,           /* btree cursor */
+xfs_btree_readahead(
+        struct xfs_btree_cur    *cur,           /* btree cursor */
         int                     lev,            /* level in btree */
         int                     lr)             /* left/right bits */
 {
-        xfs_alloc_block_t       *a;
-        xfs_bmbt_block_t        *b;
-        xfs_inobt_block_t       *i;
-        int                     rval = 0;
+        struct xfs_btree_block  *block;
+
+        /*
+         * No readahead needed if we are at the root level and the
+         * btree root is stored in the inode.
+         */
+        if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) &&
+            (lev == cur->bc_nlevels - 1))
+                return 0;
+
+        if ((cur->bc_ra[lev] | lr) == cur->bc_ra[lev])
+                return 0;
 
-        ASSERT(cur->bc_bufs[lev] != NULL);
         cur->bc_ra[lev] |= lr;
-        switch (cur->bc_btnum) {
-        case XFS_BTNUM_BNO:
-        case XFS_BTNUM_CNT:
-                a = XFS_BUF_TO_ALLOC_BLOCK(cur->bc_bufs[lev]);
-                if ((lr & XFS_BTCUR_LEFTRA) && be32_to_cpu(a->bb_leftsib) != NULLAGBLOCK) {
-                        xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.a.agno,
-                                be32_to_cpu(a->bb_leftsib), 1);
-                        rval++;
-                }
-                if ((lr & XFS_BTCUR_RIGHTRA) && be32_to_cpu(a->bb_rightsib) != NULLAGBLOCK) {
-                        xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.a.agno,
-                                be32_to_cpu(a->bb_rightsib), 1);
-                        rval++;
-                }
-                break;
-        case XFS_BTNUM_BMAP:
-                b = XFS_BUF_TO_BMBT_BLOCK(cur->bc_bufs[lev]);
-                if ((lr & XFS_BTCUR_LEFTRA) && be64_to_cpu(b->bb_leftsib) != NULLDFSBNO) {
-                        xfs_btree_reada_bufl(cur->bc_mp, be64_to_cpu(b->bb_leftsib), 1);
-                        rval++;
-                }
-                if ((lr & XFS_BTCUR_RIGHTRA) && be64_to_cpu(b->bb_rightsib) != NULLDFSBNO) {
-                        xfs_btree_reada_bufl(cur->bc_mp, be64_to_cpu(b->bb_rightsib), 1);
-                        rval++;
-                }
-                break;
-        case XFS_BTNUM_INO:
-                i = XFS_BUF_TO_INOBT_BLOCK(cur->bc_bufs[lev]);
-                if ((lr & XFS_BTCUR_LEFTRA) && be32_to_cpu(i->bb_leftsib) != NULLAGBLOCK) {
-                        xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.a.agno,
-                                be32_to_cpu(i->bb_leftsib), 1);
-                        rval++;
-                }
-                if ((lr & XFS_BTCUR_RIGHTRA) && be32_to_cpu(i->bb_rightsib) != NULLAGBLOCK) {
-                        xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.a.agno,
-                                be32_to_cpu(i->bb_rightsib), 1);
-                        rval++;
-                }
-                break;
-        default:
-                ASSERT(0);
-        }
-        return rval;
+        block = XFS_BUF_TO_BLOCK(cur->bc_bufs[lev]);
+
+        if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
+                return xfs_btree_readahead_lblock(cur, lr, block);
+        return xfs_btree_readahead_sblock(cur, lr, block);
 }
 
 /*
diff --git a/fs/xfs/xfs_btree.h b/fs/xfs/xfs_btree.h
index dd93fd39c56a..8be838f0154a 100644
--- a/fs/xfs/xfs_btree.h
+++ b/fs/xfs/xfs_btree.h
@@ -421,23 +421,10 @@ xfs_btree_reada_bufs(
  * Bits in lr are set from XFS_BTCUR_{LEFT,RIGHT}RA.
  */
 int                                     /* readahead block count */
-xfs_btree_readahead_core(
-        xfs_btree_cur_t         *cur,   /* btree cursor */
-        int                     lev,    /* level in btree */
-        int                     lr);    /* left/right bits */
-
-static inline int                       /* readahead block count */
 xfs_btree_readahead(
         xfs_btree_cur_t         *cur,   /* btree cursor */
         int                     lev,    /* level in btree */
-        int                     lr)     /* left/right bits */
-{
-        if ((cur->bc_ra[lev] | lr) == cur->bc_ra[lev])
-                return 0;
-
-        return xfs_btree_readahead_core(cur, lev, lr);
-}
-
+        int                     lr);    /* left/right bits */
 
 /*
  * Set the buffer for level "lev" in the cursor to bp, releasing