criu: pagemap: split read_pagemap_page into smaller chunks

Introduce helper functions for reading pages from parent snapshot and for
reading pages from local pages*img

travis-ci: success for criu: pagemap: minor improvements
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/pagemap.c

@@ -208,16 +208,11 @@ static inline void pagemap_bound_check(PagemapEntry *pe, unsigned long vaddr, in
 	}
 }
 
-static int read_pagemap_page(struct page_read *pr, unsigned long vaddr, int nr, void *buf)
+static int read_parent_page(struct page_read *pr, unsigned long vaddr,
+			    int nr, void *buf)
 {
-	int ret;
-	unsigned long len = nr * PAGE_SIZE;
-
-	pr_info("pr%u Read %lx %u pages\n", pr->id, vaddr, nr);
-	pagemap_bound_check(pr->pe, vaddr, nr);
-
-	if (pr->pe->in_parent) {
 	struct page_read *ppr = pr->parent;
+	int ret;
 
 	/*
 	 * Parent pagemap at this point entry may be shorter
@@ -245,7 +240,7 @@ static int read_pagemap_page(struct page_read *pr, unsigned long vaddr, int nr,
 		if (p_nr > nr)
 			p_nr = nr;
 
-			ret = read_pagemap_page(ppr, vaddr, p_nr, buf);
+		ret = ppr->read_pages(ppr, vaddr, p_nr, buf);
 		if (ret == -1)
 			return ret;
 
@@ -258,9 +253,16 @@ static int read_pagemap_page(struct page_read *pr, unsigned long vaddr, int nr,
 		vaddr += p_nr * PAGE_SIZE;
 		buf += p_nr * PAGE_SIZE;
 	} while (nr);
-	} else {
+
+	return 0;
+}
+
+static int read_local_page(struct page_read *pr, unsigned long vaddr,
+			   unsigned long len, void *buf)
+{
 	int fd = img_raw_fd(pr->pi);
 	off_t current_vaddr = lseek(fd, pr->pi_off, SEEK_SET);
+	int ret;
 
 	pr_debug("\tpr%u Read page from self %lx/%"PRIx64"\n", pr->id, pr->cvaddr, current_vaddr);
 	ret = read(fd, buf, len);
@@ -277,6 +279,23 @@ static int read_pagemap_page(struct page_read *pr, unsigned long vaddr, int nr,
 			return -1;
 		}
 	}
+
+	return 0;
+}
+
+static int read_pagemap_page(struct page_read *pr, unsigned long vaddr, int nr, void *buf)
+{
+	unsigned long len = nr * PAGE_SIZE;
+
+	pr_info("pr%u Read %lx %u pages\n", pr->id, vaddr, nr);
+	pagemap_bound_check(pr->pe, vaddr, nr);
+
+	if (pr->pe->in_parent) {
+		if (read_parent_page(pr, vaddr, nr, buf) < 0)
+			return -1;
+	} else {
+		if (read_local_page(pr, vaddr, len, buf) < 0)
+			return -1;
 	}
 
 	pr->cvaddr += len;