[PATCH v3] kexec: Make a pair of map and unmap reserved pages when kdump fails to start

[Minfei Huang <mnfhuang@gmail.com>]

For some arch, kexec shall map the reserved pages, then use them, when
we try to start the kdump service.

Now kexec will never unmap the reserved pages, once it fails to continue
starting the kdump service.

Make a pair of reserved pages in kdump starting path, whatever kexec
fails or not.

Signed-off-by: Minfei Huang <mnfhuang@gmail.com>
---
v2:
- replace the "failure" label with "fail_unmap_pages"
v1:
- reconstruct the patch code
---
 kernel/kexec.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 4589899..9cb09d9 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1291,35 +1291,37 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 			 */
 
 			kimage_free(xchg(&kexec_crash_image, NULL));
-			result = kimage_alloc_init(&image, entry, nr_segments,
-						   segments, flags);
-			crash_map_reserved_pages();
-		} else {
-			/* Loading another kernel to reboot into. */
-
-			result = kimage_alloc_init(&image, entry, nr_segments,
-						   segments, flags);
 		}
+
+		result = kimage_alloc_init(&image, entry, nr_segments,
+				segments, flags);
 		if (result)
 			goto out;
 
+		if (flags & KEXEC_ON_CRASH)
+			crash_map_reserved_pages();
+
 		if (flags & KEXEC_PRESERVE_CONTEXT)
 			image->preserve_context = 1;
 		result = machine_kexec_prepare(image);
 		if (result)
-			goto out;
+			goto fail_unmap_pages;
 
 		for (i = 0; i < nr_segments; i++) {
 			result = kimage_load_segment(image, &image->segment[i]);
 			if (result)
-				goto out;
+				goto fail_unmap_pages;
 		}
 		kimage_terminate(image);
+
+fail_unmap_pages:
 		if (flags & KEXEC_ON_CRASH)
 			crash_unmap_reserved_pages();
 	}
-	/* Install the new kernel, and  Uninstall the old */
-	image = xchg(dest_image, image);
+
+	if (result == 0)
+		/* Install the new kernel, and  Uninstall the old */
+		image = xchg(dest_image, image);
 
 out:
 	mutex_unlock(&kexec_mutex);
-- 
2.2.2