ARM: 6890/1: memmap: only free allocated memmap entries when using SPARSEMEM
authorWill Deacon <will.deacon@arm.com>
Thu, 28 Apr 2011 17:44:31 +0000 (18:44 +0100)
committerRussell King <rmk+kernel@arm.linux.org.uk>
Thu, 12 May 2011 09:52:00 +0000 (10:52 +0100)
The SPARSEMEM code allocates memmap entries only for sections which are
present (i.e. those which contain some valid memory). The membank checks
in free_unused_memmap do not take this into account and can incorrectly
attempt to free memory which is not allocated, resulting in a BUG() in
the bootmem code.

However, if memory is configured as follows:

    |<----section---->|<----hole---->|<----section---->|
    +--------+--------+--------------+--------+--------+
    | bank 0 | unused |              | bank 1 | unused |
    +--------+--------+--------------+--------+--------+

where a bank only occupies part of a section, the memmap allocated for
the remainder of the section *can* be freed.

This patch modifies the checks in free_unused_memmap so that only valid
memmap entries are considered for removal.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
arch/arm/mm/init.c

index e5f6fc4..e591513 100644 (file)
@@ -392,7 +392,7 @@ free_memmap(unsigned long start_pfn, unsigned long end_pfn)
         * Convert start_pfn/end_pfn to a struct page pointer.
         */
        start_pg = pfn_to_page(start_pfn - 1) + 1;
-       end_pg = pfn_to_page(end_pfn);
+       end_pg = pfn_to_page(end_pfn - 1) + 1;
 
        /*
         * Convert to physical addresses, and
@@ -426,6 +426,14 @@ static void __init free_unused_memmap(struct meminfo *mi)
 
                bank_start = bank_pfn_start(bank);
 
+#ifdef CONFIG_SPARSEMEM
+               /*
+                * Take care not to free memmap entries that don't exist
+                * due to SPARSEMEM sections which aren't present.
+                */
+               bank_start = min(bank_start,
+                                ALIGN(prev_bank_end, PAGES_PER_SECTION));
+#endif
                /*
                 * If we had a previous bank, and there is a space
                 * between the current bank and the previous, free it.
@@ -440,6 +448,12 @@ static void __init free_unused_memmap(struct meminfo *mi)
                 */
                prev_bank_end = ALIGN(bank_pfn_end(bank), MAX_ORDER_NR_PAGES);
        }
+
+#ifdef CONFIG_SPARSEMEM
+       if (!IS_ALIGNED(prev_bank_end, PAGES_PER_SECTION))
+               free_memmap(prev_bank_end,
+                           ALIGN(prev_bank_end, PAGES_PER_SECTION));
+#endif
 }
 
 static void __init free_highpages(void)