vma: Don't lookup file_desc for vma twice

We do it first -- on collect, second -- on restore. The
2nd lookup is excessive, we can put fd pointer on vm_area
at lookup and reuse one later.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -226,7 +226,7 @@ static int map_private_vma(pid_t pid, struct vma_area *vma, void *tgt_addr,
 	struct vma_area *p = *pvma;
 
 	if (vma_area_is(vma, VMA_FILE_PRIVATE)) {
-		ret = get_filemap_fd(pid, vma->e);
+		ret = get_filemap_fd(vma);
 		if (ret < 0) {
 			pr_err("Can't fixup VMA's fd\n");
 			return -1;
@@ -583,7 +583,7 @@ static int open_vmas(int pid)
 		else if (vma_area_is(vma, VMA_ANON_SHARED))
 			ret = get_shmem_fd(pid, vma->e);
 		else if (vma_area_is(vma, VMA_FILE_SHARED))
-			ret = get_filemap_fd(pid, vma->e);
+			ret = get_filemap_fd(vma);
 		else if (vma_area_is(vma, VMA_AREA_SOCKET))
 			ret = get_socket_fd(pid, vma->e);
 		else

fifo.c

@@ -118,7 +118,7 @@ static void collect_fifo_fd(struct file_desc *d,
 	struct fifo_info *info;
 
 	info = container_of(d, struct fifo_info, d);
-	if (collect_special_file(info->fe->id))
+	if (collect_special_file(info->fe->id) == NULL)
 		BUG();
 
 	collect_gen_fd(fle, ri);

files-reg.c

@@ -672,14 +672,26 @@ static int open_fe_fd(struct file_desc *fd)
 int open_reg_by_id(u32 id)
 {
 	/*
-	 * This one gets called by exe link, chroot,
-	 * cwd and file vmas restoring code. No need
-	 * in calling lseek on either of them.
+	 * This one gets called by exe link, chroot and cwd
+	 * restoring code. No need in calling lseek on either
+	 * of them.
 	 */
 
 	return open_path_by_id(id, do_open_reg_noseek, NULL);
 }
 
+int get_filemap_fd(struct vma_area *vma)
+{
+	/*
+	 * Thevma->fd should have been assigned in collect_filemap
+	 *
+	 * We open file w/o lseek, as mappings don't care about it
+	 */
+
+	BUG_ON(vma->fd == NULL);
+	return open_path(vma->fd, do_open_reg_noseek, NULL);
+}
+
 static void remap_get(struct file_desc *fdesc, char typ)
 {
 	struct reg_file_info *rfi;
@@ -708,7 +720,7 @@ static struct file_desc_ops reg_desc_ops = {
 	.collect_fd = collect_reg_fd,
 };
 
-int collect_special_file(u32 id)
+struct file_desc *collect_special_file(u32 id)
 {
 	struct file_desc *fdesc;
 
@@ -722,11 +734,11 @@ int collect_special_file(u32 id)
 	fdesc = find_file_desc_raw(FD_TYPES__REG, id);
 	if (fdesc == NULL) {
 		pr_err("No entry for reg-file-ID %#x\n", id);
-		return -1;
+		return NULL;
 	}
 
 	remap_get(fdesc, 's');
-	return 0;
+	return fdesc;
 }
 
 static int collect_one_regfile(void *o, ProtobufCMessage *base)

files.c

@@ -1087,11 +1087,6 @@ out:
 	return ret;
 }
 
-int get_filemap_fd(int pid, VmaEntry *vma_entry)
-{
-	return open_reg_by_id(vma_entry->shmid);
-}
-
 int shared_fdt_prepare(struct pstree_item *item)
 {
 	struct pstree_item *parent = item->parent;

include/files-reg.h

@@ -34,7 +34,7 @@ extern int dump_one_reg_file(int lfd, u32 id, const struct fd_parms *p);
 
 extern struct file_remap *lookup_ghost_remap(u32 dev, u32 ino);
 extern void remap_put(struct file_remap *remap);
-extern int collect_special_file(u32 id);
+extern struct file_desc *collect_special_file(u32 id);
 
 extern struct collect_image_info reg_file_cinfo;
 extern struct collect_image_info remap_cinfo;

include/files.h

@@ -145,7 +145,7 @@ extern int prepare_fds(struct pstree_item *me);
 extern int prepare_fd_pid(struct pstree_item *me);
 extern int prepare_ctl_tty(int pid, struct rst_info *rst_info, u32 ctl_tty_id);
 extern int prepare_shared_fdinfo(void);
-extern int get_filemap_fd(int pid, VmaEntry *vma_entry);
+extern int get_filemap_fd(struct vma_area *);
 extern int prepare_fs(int pid);
 extern int set_fd_flags(int fd, int flags);
 

include/vma.h

@@ -21,6 +21,8 @@ static inline void vm_area_list_init(struct vm_area_list *vml)
 	vml->longest = 0;
 }
 
+struct file_desc;
+
 struct vma_area {
 	struct list_head	list;
 	VmaEntry		*e;
@@ -28,6 +30,7 @@ struct vma_area {
 	union {
 		int		vm_file_fd;
 		int		vm_socket_id;
+		struct file_desc *fd;
 	};
 	unsigned long		*page_bitmap;  /* existent pages */
 	unsigned long		*ppage_bitmap; /* parent's existent pages */

mem.c

@@ -342,9 +342,16 @@ int parasite_dump_pages_seized(struct parasite_ctl *ctl,
 	return ret;
 }
 
-static inline int collect_filemap(VmaEntry *vme)
+static inline int collect_filemap(struct vma_area *vma)
 {
-	return collect_special_file(vme->shmid);
+	struct file_desc *fd;
+
+	fd = collect_special_file(vma->e->shmid);
+	if (!fd)
+		return -1;
+
+	vma->fd = fd;
+	return 0;
 }
 
 int prepare_mm_pid(struct pstree_item *i)
@@ -365,7 +372,7 @@ int prepare_mm_pid(struct pstree_item *i)
 	if (ret < 0)
 		return -1;
 
-	if (collect_special_file(ri->mm->exe_file_id))
+	if (collect_special_file(ri->mm->exe_file_id) == NULL)
 		return -1;
 
 	pr_debug("Found %zd VMAs in image\n", ri->mm->n_vmas);
@@ -415,7 +422,7 @@ int prepare_mm_pid(struct pstree_item *i)
 			ret = collect_shmem(pid, vma->e);
 		else if (vma_area_is(vma, VMA_FILE_PRIVATE) ||
 				vma_area_is(vma, VMA_FILE_SHARED))
-			ret = collect_filemap(vma->e);
+			ret = collect_filemap(vma);
 		else
 			ret = 0;
 		if (ret)