+/*
+ * This cancels just the dirty bit on the kernel page itself, it
+ * does NOT actually remove dirty bits on any mmap's that may be
+ * around. It also leaves the page tagged dirty, so any sync
+ * activity will still find it on the dirty lists, and in particular,
+ * clear_page_dirty_for_io() will still look at the dirty bits in
+ * the VM.
+ *
+ * Doing this should *normally* only ever be done when a page
+ * is truncated, and is not actually mapped anywhere at all. However,
+ * fs/buffer.c does this when it notices that somebody has cleaned
+ * out all the buffers on a page without actually doing it through
+ * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
+ */
+void cancel_dirty_page(struct page *page, unsigned int account_size)
+{
+ if (TestClearPageDirty(page)) {
+ struct address_space *mapping = page->mapping;
+ if (mapping && mapping_cap_account_dirty(mapping)) {
+ dec_zone_page_state(page, NR_FILE_DIRTY);
+ if (account_size)
+ task_io_account_cancelled_write(account_size);
+ }
+ }
+}
+EXPORT_SYMBOL(cancel_dirty_page);
+