iov_iter: get rid of 'copy_mc' flag

[linux-2.6-block.git] / fs / coredump.c

diff --git a/fs/coredump.c b/fs/coredump.c
index f258c17c18411284b9725ed88110de32fadc8993..be6403b4b14b6a26e611398f0903244d1af96343 100644 (file)
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -872,6 +872,9 @@ static int dump_emit_page(struct coredump_params *cprm, struct page *page)
        loff_t pos;
        ssize_t n;
 
+       if (!page)
+               return 0;
+
        if (cprm->to_skip) {
                if (!__dump_skip(cprm, cprm->to_skip))
                        return 0;
@@ -884,7 +887,6 @@ static int dump_emit_page(struct coredump_params *cprm, struct page *page)
        pos = file->f_pos;
        bvec_set_page(&bvec, page, PAGE_SIZE, 0);
        iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE);
-       iov_iter_set_copy_mc(&iter);
        n = __kernel_write_iter(cprm->file, &iter, &pos);
        if (n != PAGE_SIZE)
                return 0;
@@ -895,10 +897,44 @@ static int dump_emit_page(struct coredump_params *cprm, struct page *page)
        return 1;
 }
 
+/*
+ * If we might get machine checks from kernel accesses during the
+ * core dump, let's get those errors early rather than during the
+ * IO. This is not performance-critical enough to warrant having
+ * all the machine check logic in the iovec paths.
+ */
+#ifdef copy_mc_to_kernel
+
+#define dump_page_alloc() alloc_page(GFP_KERNEL)
+#define dump_page_free(x) __free_page(x)
+static struct page *dump_page_copy(struct page *src, struct page *dst)
+{
+       void *buf = kmap_local_page(src);
+       size_t left = copy_mc_to_kernel(page_address(dst), buf, PAGE_SIZE);
+       kunmap_local(buf);
+       return left ? NULL : dst;
+}
+
+#else
+
+/* We just want to return non-NULL; it's never used. */
+#define dump_page_alloc() ERR_PTR(-EINVAL)
+#define dump_page_free(x) ((void)(x))
+static inline struct page *dump_page_copy(struct page *src, struct page *dst)
+{
+       return src;
+}
+#endif
+
 int dump_user_range(struct coredump_params *cprm, unsigned long start,
                    unsigned long len)
 {
        unsigned long addr;
+       struct page *dump_page;
+
+       dump_page = dump_page_alloc();
+       if (!dump_page)
+               return 0;
 
        for (addr = start; addr < start + len; addr += PAGE_SIZE) {
                struct page *page;
@@ -912,14 +948,17 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
                 */
                page = get_dump_page(addr);
                if (page) {
-                       int stop = !dump_emit_page(cprm, page);
+                       int stop = !dump_emit_page(cprm, dump_page_copy(page, dump_page));
                        put_page(page);
-                       if (stop)
+                       if (stop) {
+                               dump_page_free(dump_page);
                                return 0;
+                       }
                } else {
                        dump_skip(cprm, PAGE_SIZE);
                }
        }
+       dump_page_free(dump_page);
        return 1;
 }
 #endif