Nick Piggin wrote:
@@ -1878,31 +1889,88 @@ generic_file_buffered_write(struct kiocb
break;
}
+ /*
+ * non-uptodate pages cannot cope with short copies, and we
+ * cannot take a pagefault with the destination page locked.
+ * So pin the source page to copy it.
+ */
+ if (!PageUptodate(page)) {
+ unlock_page(page);
+
+ bytes = min(bytes, PAGE_CACHE_SIZE -
+ ((unsigned long)buf & ~PAGE_CACHE_MASK));
+
+ /*
+ * Cannot get_user_pages with a page locked for the
+ * same reason as we can't take a page fault with a
+ * page locked (as explained below).
+ */
+ status = get_user_pages(current, current->mm,
+ (unsigned long)buf & PAGE_CACHE_MASK, 1,
+ 0, 0, &src_page, NULL);
Thinko... get_user_pages needs to be called with mmap_sem held, obviously.
--
SUSE Labs, Novell Inc.
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