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

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 <[email protected]>

---
 kernel/kexec.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

kernel/kexec.c +14 -12

index 4589899..68f6dfb 100644
@@ -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 failure;
 
 		for (i = 0; i < nr_segments; i++) {
 			result = kimage_load_segment(image, &image->segment[i]);
 			if (result)
-				goto out;
+				goto failure;
 		}
 		kimage_terminate(image);
+
+failure:
 		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);

Hello Minfei,

Regarding functionality your patch looks ok for me. But the code is not easy to read.

What about replacing the "failure" label with "fail_unmap_pages"?

Michael

Quoted 68 lines · On Tue, 30 Jun 2015 13:44:46 +0800 Minfei Huang <[email protected]> wrote:

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 <[email protected]>

---
 kernel/kexec.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

kernel/kexec.c +14 -12

index 4589899..68f6dfb 100644
@@ -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 failure;
 
 		for (i = 0; i < nr_segments; i++) {
 			result = kimage_load_segment(image, &image->segment[i]);
 			if (result)
-				goto out;
+				goto failure;
 		}
 		kimage_terminate(image);
+
+failure:
 		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);