[CRIU] [PATCH] uffd.c: do not call unneeded functions

[Adrian Reber]

From: Adrian Reber <areber at redhat.com>

For a lazy restore via userfaultfd the lazy-pages daemon
needs to know which pages exist, so that it knows when all
pages have finally been migrated so that the restored process
has all of its memory. Therefore it needs to know which pages
exist and it needs to parse the files in the dump result directory.

The existing criu functions are designed to be used by a 'normal'
restore and thus a lot of assumptions are made what has to be set up.

For the lazy-pages restore the complete 'restore' initialization is
not necessary and therefore the criu common code dependencies are
minimized with this commit.

Signed-off-by: Adrian Reber <areber at redhat.com>
---
 criu/uffd.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 68 insertions(+), 12 deletions(-)

diff --git a/criu/uffd.c b/criu/uffd.c
index 3beae79..69403dd 100644
--- a/criu/uffd.c
+++ b/criu/uffd.c
@@ -19,6 +19,7 @@
 #include "include/criu-plugin.h"
 #include "include/page-read.h"
 #include "include/files-reg.h"
+#include "include/kerndat.h"
 #include "include/mem.h"
 #include "include/uffd.h"
 #include "include/util-pie.h"
@@ -425,18 +426,69 @@ static int handle_vdso_pages(int uffd, struct list_head *uffd_list, unsigned lon
 }
 
 /*
- *  Setting up criu infrastructure to easily
- *  access the dump results.
+ *  Setting up criu infrastructure and scan for VMAs.
  */
-static void criu_init()
+static int find_vmas()
 {
-	/* TODO: return code checking */
-	check_img_inventory();
-	prepare_task_entries();
-	prepare_pstree();
-	collect_remaps_and_regfiles();
-	prepare_shared_reg_files();
-	prepare_mm_pid(root_item);
+	struct cr_img *img;
+	int ret;
+	struct vm_area_list vmas;
+	int vn = 0;
+	struct rst_info *ri;
+
+	LIST_HEAD(uffd_list);
+
+	if (check_img_inventory() == -1)
+		return -1;
+
+	vm_area_list_init(&vmas);
+
+	/* Allocate memory for task_entries */
+	if (prepare_task_entries() == -1)
+		return -1;
+
+	if (prepare_pstree() == -1)
+		return -1;
+
+	ri = rsti(root_item);
+	if (!ri)
+		return -1;
+
+	img = open_image(CR_FD_MM, O_RSTR, pid);
+	if (!img)
+		return -1;
+
+	ret = pb_read_one_eof(img, &ri->mm, PB_MM);
+	close_image(img);
+	if (ret == -1)
+		return -1;
+
+	pr_debug("Found %zd VMAs in image\n", ri->mm->n_vmas);
+
+	while (vn < ri->mm->n_vmas) {
+		struct vma_area *vma;
+
+		ret = -1;
+		vma = alloc_vma_area();
+		if (!vma)
+			break;
+
+		ret = 0;
+		ri->vmas.nr++;
+		vma->e = ri->mm->vmas[vn++];
+
+		list_add_tail(&vma->list, &ri->vmas.h);
+
+		if (vma_area_is_private(vma, kdat.task_size)) {
+			vmas.priv_size += vma_area_len(vma);
+			if (vma->e->flags & MAP_GROWSDOWN)
+				vmas.priv_size += PAGE_SIZE;
+		}
+
+		pr_info("vma 0x%"PRIx64" 0x%"PRIx64"\n", vma->e->start, vma->e->end);
+	}
+
+	return ret;
 }
 
 int uffd_listen()
@@ -476,8 +528,12 @@ int uffd_listen()
 	uffd_flags = fcntl(uffd, F_GETFD, NULL);
 	pr_debug("uffd_flags are 0x%x\n", uffd_flags);
 
-	/* Setting up criu infrastructure to easily access the dump results */
-	criu_init();
+	/*
+	 * Find the memory pages belonging to the restored process
+	 * so that it is trackable when all pages have been transferred.
+	 */
+	if (find_vmas() == -1)
+		return -1;
 
 	/* Initialize FD sets for read() with timeouts (using select()) */
 	FD_ZERO(&set);
-- 
1.8.3.1