util: Add fd parameter to vaddr_to_pfn()

Expand vaddr_to_pfn() so it can read and translate to PFN
from already opened fd. This can be used as optimization
if one need to translate a couple of addresses and
also to read other task's PFN.

I'll use it in the next patch for reading other tasks's
vdso's PFN.
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/include/util.h

@@ -193,7 +193,7 @@ extern int read_fd_link(int lfd, char *buf, size_t size);
 #define USEC_PER_SEC	1000000L
 #define NSEC_PER_SEC    1000000000L
 
-int vaddr_to_pfn(unsigned long vaddr, u64 *pfn);
+int vaddr_to_pfn(int fd, unsigned long vaddr, u64 *pfn);
 
 /*
  * Check whether @str starts with @sub and report the

criu/kerndat.c

@@ -354,7 +354,7 @@ static int init_zero_page_pfn()
 		return -1;
 	}
 
-	ret = vaddr_to_pfn((unsigned long)addr, &kdat.zero_page_pfn);
+	ret = vaddr_to_pfn(-1, (unsigned long)addr, &kdat.zero_page_pfn);
 	munmap(addr, PAGE_SIZE);
 
 	if (kdat.zero_page_pfn == 0)

criu/util.c

@@ -784,14 +784,23 @@ out:
 	return ret;
 }
 
-int vaddr_to_pfn(unsigned long vaddr, u64 *pfn)
+/*
+ * Get PFN from pagemap file for virtual address vaddr.
+ * Optionally if fd >= 0, it's used as pagemap file descriptor
+ * (may be other task's pagemap)
+ */
+int vaddr_to_pfn(int fd, unsigned long vaddr, u64 *pfn)
 {
-	int fd, ret = -1;
+	int ret = -1;
 	off_t off;
+	bool close_fd = false;
 
-	fd = open_proc(PROC_SELF, "pagemap");
-	if (fd < 0)
-		return -1;
+	if (fd < 0) {
+		fd = open_proc(PROC_SELF, "pagemap");
+		if (fd < 0)
+			return -1;
+		close_fd = true;
+	}
 
 	off = (vaddr / page_size()) * sizeof(u64);
 	ret = pread(fd, pfn, sizeof(*pfn), off);
@@ -803,7 +812,9 @@ int vaddr_to_pfn(unsigned long vaddr, u64 *pfn)
 		ret = 0;
 	}
 
-	close(fd);
+	if (close_fd)
+		close(fd);
+
 	return ret;
 }
 

criu/vdso.c

@@ -493,7 +493,7 @@ int vdso_init_dump(void)
 
 	if (kdat.pmap != PM_FULL)
 		pr_info("VDSO detection turned off\n");
-	else if (vaddr_to_pfn(vdso_maps.vdso_start, &vdso_pfn))
+	else if (vaddr_to_pfn(-1, vdso_maps.vdso_start, &vdso_pfn))
 		return -1;
 
 	return 0;