[PATCH] Early writeback initialisation

Patch from Anders Gustafsson <andersg@0x63.nu>

We're getting a division-by-zero in the writeback code during early rootfs
population, because writeback has not yet been initialised.

Fix that by performing an explicit initialisation rather than relying on
initcall ordering.

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 620f18f5ceeb4542982402077c64bdc519d8d474..f316169bb1f7499d79ad9cf786dd50741fb0ade8 100644 (file)
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -79,6 +79,7 @@ extern int dirty_writeback_centisecs;
 extern int dirty_expire_centisecs;
 
 
+void page_writeback_init(void);
 void balance_dirty_pages(struct address_space *mapping);
 void balance_dirty_pages_ratelimited(struct address_space *mapping);
 int pdflush_operation(void (*fn)(unsigned long), unsigned long arg0);

diff --git a/init/main.c b/init/main.c
index 55d1c0595e85110c85e41e280b24205b3d6be1da..c6367147fe29350031a2b1cc4540bc2a40e0ac24 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -35,6 +35,7 @@
 #include <linux/profile.h>
 #include <linux/rcupdate.h>
 #include <linux/moduleparam.h>
+#include <linux/writeback.h>
 
 #include <asm/io.h>
 #include <asm/bugs.h>
@@ -439,6 +440,8 @@ asmlinkage void __init start_kernel(void)
        vfs_caches_init(num_physpages);
        radix_tree_init();
        signals_init();
+       /* rootfs populating might need page-writeback */
+       page_writeback_init();
        populate_rootfs();
 #ifdef CONFIG_PROC_FS
        proc_root_init();

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 7348c97a4b255ef805b0e34b81d00d426d7f5680..28a7e425664b299841a1ac506db2bfbea04a2754 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -369,7 +369,7 @@ static struct notifier_block ratelimit_nb = {
  * dirty memory thresholds: allowing too much dirty highmem pins an excessive
  * number of buffer_heads.
  */
-static int __init page_writeback_init(void)
+void __init page_writeback_init(void)
 {
        long buffer_pages = nr_free_buffer_pages();
        long correction;
@@ -392,9 +392,7 @@ static int __init page_writeback_init(void)
        add_timer(&wb_timer);
        set_ratelimit();
        register_cpu_notifier(&ratelimit_nb);
-       return 0;
 }
-module_init(page_writeback_init);
 
 int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
 {