+ * The following macros optimize certain frequently calculated
+ * quantities by using shifts and masks in place of divisions
+ * modulos and multiplications.
+ */
+#define blkoff(fs, loc) /* calculates (loc % fs->fs_bsize) */ \
+ ((loc) & ~(fs)->fs_bmask)
+#define fragoff(fs, loc) /* calculates (loc % fs->fs_fsize) */ \
+ ((loc) & ~(fs)->fs_fmask)
+#define lblkno(fs, loc) /* calculates (loc / fs->fs_bsize) */ \
+ ((loc) >> (fs)->fs_bshift)
+#define numfrags(fs, loc) /* calculates (loc / fs->fs_fsize) */ \
+ ((loc) >> (fs)->fs_fshift)
+#define blkroundup(fs, size) /* calculates roundup(size, fs->fs_bsize) */ \
+ (((size) + (fs)->fs_bsize - 1) & (fs)->fs_bmask)
+#define fragroundup(fs, size) /* calculates roundup(size, fs->fs_fsize) */ \
+ (((size) + (fs)->fs_fsize - 1) & (fs)->fs_fmask)
+
+/*
+ * Determining the size of a file block in the file system.