+/*
+ * Assembles a buffer covering the specified range. The code is optimised for
+ * cache hits, as metadata intensive workloads will see 3 orders of magnitude
+ * more hits than misses.
+ */
+int
+xfs_buf_get_map(
+ struct xfs_buftarg *btp,
+ struct xfs_buf_map *map,
+ int nmaps,
+ xfs_buf_flags_t flags,
+ struct xfs_buf **bpp)
+{
+ struct xfs_perag *pag;
+ struct xfs_buf *bp = NULL;
+ struct xfs_buf_map cmap = { .bm_bn = map[0].bm_bn };
+ int error;
+ int i;
+
+ for (i = 0; i < nmaps; i++)
+ cmap.bm_len += map[i].bm_len;
+
+ error = xfs_buf_map_verify(btp, &cmap);
+ if (error)
+ return error;
+
+ pag = xfs_perag_get(btp->bt_mount,
+ xfs_daddr_to_agno(btp->bt_mount, cmap.bm_bn));
+
+ error = xfs_buf_lookup(pag, &cmap, flags, &bp);
+ if (error && error != -ENOENT)
+ goto out_put_perag;
+
+ /* cache hits always outnumber misses by at least 10:1 */
+ if (unlikely(!bp)) {
+ XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
+
+ if (flags & XBF_INCORE)
+ goto out_put_perag;
+
+ /* xfs_buf_find_insert() consumes the perag reference. */
+ error = xfs_buf_find_insert(btp, pag, &cmap, map, nmaps,
+ flags, &bp);
+ if (error)
+ return error;
+ } else {
+ XFS_STATS_INC(btp->bt_mount, xb_get_locked);
+ xfs_perag_put(pag);
+ }
+
+ /* We do not hold a perag reference anymore. */