[SPARC64]: Fix "mem=xxx" handling.

We were not being careful enough.  When we trim the physical
memory areas, we have to make sure we don't remove the kernel
image or initial ramdisk image ranges.
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc64/mm/init.c

@@ -872,6 +872,115 @@ static unsigned long __init choose_bootmap_pfn(unsigned long start_pfn,
 	prom_halt();
 }
 
+static void __init trim_pavail(unsigned long *cur_size_p,
+			       unsigned long *end_of_phys_p)
+{
+	unsigned long to_trim = *cur_size_p - cmdline_memory_size;
+	unsigned long avoid_start, avoid_end;
+	int i;
+
+	to_trim = PAGE_ALIGN(to_trim);
+
+	avoid_start = avoid_end = 0;
+#ifdef CONFIG_BLK_DEV_INITRD
+	avoid_start = initrd_start;
+	avoid_end = PAGE_ALIGN(initrd_end);
+#endif
+
+	/* Trim some pavail[] entries in order to satisfy the
+	 * requested "mem=xxx" kernel command line specification.
+	 *
+	 * We must not trim off the kernel image area nor the
+	 * initial ramdisk range (if any).  Also, we must not trim
+	 * any pavail[] entry down to zero in order to preserve
+	 * the invariant that all pavail[] entries have a non-zero
+	 * size which is assumed by all of the code in here.
+	 */
+	for (i = 0; i < pavail_ents; i++) {
+		unsigned long start, end, kern_end;
+		unsigned long trim_low, trim_high, n;
+
+		kern_end = PAGE_ALIGN(kern_base + kern_size);
+
+		trim_low = start = pavail[i].phys_addr;
+		trim_high = end = start + pavail[i].reg_size;
+
+		if (kern_base >= start &&
+		    kern_base < end) {
+			trim_low = kern_base;
+			if (kern_end >= end)
+				continue;
+		}
+		if (kern_end >= start &&
+		    kern_end < end) {
+			trim_high = kern_end;
+		}
+		if (avoid_start &&
+		    avoid_start >= start &&
+		    avoid_start < end) {
+			if (trim_low > avoid_start)
+				trim_low = avoid_start;
+			if (avoid_end >= end)
+				continue;
+		}
+		if (avoid_end &&
+		    avoid_end >= start &&
+		    avoid_end < end) {
+			if (trim_high < avoid_end)
+				trim_high = avoid_end;
+		}
+
+		if (trim_high <= trim_low)
+			continue;
+
+		if (trim_low == start && trim_high == end) {
+			/* Whole chunk is available for trimming.
+			 * Trim all except one page, in order to keep
+			 * entry non-empty.
+			 */
+			n = (end - start) - PAGE_SIZE;
+			if (n > to_trim)
+				n = to_trim;
+
+			if (n) {
+				pavail[i].phys_addr += n;
+				pavail[i].reg_size -= n;
+				to_trim -= n;
+			}
+		} else {
+			n = (trim_low - start);
+			if (n > to_trim)
+				n = to_trim;
+
+			if (n) {
+				pavail[i].phys_addr += n;
+				pavail[i].reg_size -= n;
+				to_trim -= n;
+			}
+			if (to_trim) {
+				n = end - trim_high;
+				if (n > to_trim)
+					n = to_trim;
+				if (n) {
+					pavail[i].reg_size -= n;
+					to_trim -= n;
+				}
+			}
+		}
+
+		if (!to_trim)
+			break;
+	}
+
+	/* Recalculate.  */
+	*cur_size_p = 0UL;
+	for (i = 0; i < pavail_ents; i++) {
+		*end_of_phys_p = pavail[i].phys_addr +
+			pavail[i].reg_size;
+		*cur_size_p += pavail[i].reg_size;
+	}
+}
+
 static unsigned long __init bootmem_init(unsigned long *pages_avail,
 					 unsigned long phys_base)
 {
@@ -889,31 +998,13 @@ static unsigned long __init bootmem_init(unsigned long *pages_avail,
 		end_of_phys_memory = pavail[i].phys_addr +
 			pavail[i].reg_size;
 		bytes_avail += pavail[i].reg_size;
-		if (cmdline_memory_size) {
-			if (bytes_avail > cmdline_memory_size) {
-				unsigned long slack = bytes_avail - cmdline_memory_size;
-
-				bytes_avail -= slack;
-				end_of_phys_memory -= slack;
-
-				pavail[i].reg_size -= slack;
-				if ((long)pavail[i].reg_size <= 0L) {
-					pavail[i].phys_addr = 0xdeadbeefUL;
-					pavail[i].reg_size = 0UL;
-					pavail_ents = i;
-				} else {
-					pavail[i+1].reg_size = 0Ul;
-					pavail[i+1].phys_addr = 0xdeadbeefUL;
-					pavail_ents = i + 1;
-				}
-				break;
-			}
-		}
 	}
 
-	*pages_avail = bytes_avail >> PAGE_SHIFT;
-
-	end_pfn = end_of_phys_memory >> PAGE_SHIFT;
+	/* Determine the location of the initial ramdisk before trying
+	 * to honor the "mem=xxx" command line argument.  We must know
+	 * where the kernel image and the ramdisk image are so that we
+	 * do not trim those two areas from the physical memory map.
+	 */
 
 #ifdef CONFIG_BLK_DEV_INITRD
 	/* Now have to check initial ramdisk, so that bootmap does not overwrite it */
@@ -932,6 +1023,16 @@ static unsigned long __init bootmem_init(unsigned long *pages_avail,
 		}
 	}
 #endif	
+
+	if (cmdline_memory_size &&
+	    bytes_avail > cmdline_memory_size)
+		trim_pavail(&bytes_avail,
+			    &end_of_phys_memory);
+
+	*pages_avail = bytes_avail >> PAGE_SHIFT;
+
+	end_pfn = end_of_phys_memory >> PAGE_SHIFT;
+
 	/* Initialize the boot-time allocator. */
 	max_pfn = max_low_pfn = end_pfn;
 	min_low_pfn = (phys_base >> PAGE_SHIFT);