[PATCH v2] Btrfs-progs: avoid using btrfs internal subvolume path to send

[Wang Shilong <wangshilong1991@gmail.com>]

From: Wang Shilong <wangsl.fnst@cn.fujitsu.com>

Steps to reproduce:
	# mkfs.btrfs -f /dev/sda
	# mount /dev/sda /mnt
	# btrfs subvolume create /mnt/foo
	# umount /mnt
	# mount -o subvol=foo /dev/sda /mnt
	# btrfs sub snapshot -r /mnt /mnt/snap
	# btrfs send /mnt/snap > /dev/null

We will fail to send '/mnt/snap',this is because btrfs send try to
open '/mnt/snap' by btrfs internal subvolume path 'foo/snap' rather
than relative path based on mounted point, this will return us 'no
such file or directory',this is not right, fix it.

Reported-by: Thomas Scheiblauer <tom@sharkbay.at>
Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
---
v1->v2:
	code cleanups(thanks to Stefan)
---
 cmds-send.c | 34 ++++++----------------------------
 1 file changed, 6 insertions(+), 28 deletions(-)

diff --git a/cmds-send.c b/cmds-send.c
index 53e9a53..6fdfd7f 100644
--- a/cmds-send.c
+++ b/cmds-send.c
@@ -282,31 +282,21 @@ out:
 	return ERR_PTR(ret);
 }
 
-static int do_send(struct btrfs_send *send, u64 root_id, u64 parent_root_id,
-		   int is_first_subvol, int is_last_subvol)
+static int do_send(struct btrfs_send *send, u64 parent_root_id,
+		   int is_first_subvol, int is_last_subvol, char *subvol)
 {
 	int ret;
 	pthread_t t_read;
 	pthread_attr_t t_attr;
 	struct btrfs_ioctl_send_args io_send;
-	struct subvol_info *si;
 	void *t_err = NULL;
 	int subvol_fd = -1;
 	int pipefd[2] = {-1, -1};
 
-	si = subvol_uuid_search(&send->sus, root_id, NULL, 0, NULL,
-			subvol_search_by_root_id);
-	if (!si) {
-		ret = -ENOENT;
-		fprintf(stderr, "ERROR: could not find subvol info for %llu",
-				root_id);
-		goto out;
-	}
-
-	subvol_fd = openat(send->mnt_fd, si->path, O_RDONLY | O_NOATIME);
+	subvol_fd = openat(send->mnt_fd, subvol, O_RDONLY | O_NOATIME);
 	if (subvol_fd < 0) {
 		ret = -errno;
-		fprintf(stderr, "ERROR: open %s failed. %s\n", si->path,
+		fprintf(stderr, "ERROR: open %s failed. %s\n", subvol,
 				strerror(-ret));
 		goto out;
 	}
@@ -385,10 +375,6 @@ out:
 		close(pipefd[0]);
 	if (pipefd[1] != -1)
 		close(pipefd[1]);
-	if (si) {
-		free(si->path);
-		free(si);
-	}
 	return ret;
 }
 
@@ -664,14 +650,6 @@ int cmd_send(int argc, char **argv)
 			goto out;
 		}
 
-		ret = get_root_id(&send, get_subvol_name(send.root_path, subvol),
-				&root_id);
-		if (ret < 0) {
-			fprintf(stderr, "ERROR: could not resolve root_id "
-					"for %s\n", subvol);
-			goto out;
-		}
-
 		if (!full_send && !parent_root_id) {
 			ret = find_good_parent(&send, root_id, &parent_root_id);
 			if (ret < 0) {
@@ -700,8 +678,8 @@ int cmd_send(int argc, char **argv)
 			is_first_subvol = 1;
 			is_last_subvol = 1;
 		}
-		ret = do_send(&send, root_id, parent_root_id,
-			      is_first_subvol, is_last_subvol);
+		ret = do_send(&send, parent_root_id, is_first_subvol,
+			      is_last_subvol, subvol);
 		if (ret < 0)
 			goto out;
 
-- 
1.8.4