If we change our default subvolume, btrfs receive will fail to find
subvolume. To fix this problem, i have two ideas.
1.make btrfs snapshot ioctl support passing source subvolume's objectid
2.when we want to using interval subvolume path, we mount it other place
that use subvolume 5 as its default subvolume.
We'd better use the second approach because it won't bother kernel change.
Reported-by: Michael Welsh Duggan <mwd@xxxxxxxx>
Signed-off-by: Wang Shilong <wangsl.fnst@xxxxxxxxxxxxxx>
Signed-off-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
---
cmds-receive.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++----
utils.c | 28 ++++++++++++++++++++++++++++
utils.h | 1 +
3 files changed, 76 insertions(+), 4 deletions(-)
diff --git a/cmds-receive.c b/cmds-receive.c
index ed44107..c2cf8a3 100644
--- a/cmds-receive.c
+++ b/cmds-receive.c
@@ -40,6 +40,7 @@
#include <sys/types.h>
#include <sys/xattr.h>
#include <uuid/uuid.h>
+#include <sys/mount.h>
#include "ctree.h"
#include "ioctl.h"
@@ -199,6 +200,10 @@ static int process_snapshot(const char *path, const u8 *uuid, u64 ctransid,
char uuid_str[BTRFS_UUID_UNPARSED_SIZE];
struct btrfs_ioctl_vol_args_v2 args_v2;
struct subvol_info *parent_subvol = NULL;
+ char *dev = NULL;
+ char tmp_name[15] = "btrfs-XXXXXX";
+ char tmp_dir[30] = "/tmp";
+ char *full_path = NULL;
ret = finish_subvol(r);
if (ret < 0)
@@ -253,13 +258,47 @@ static int process_snapshot(const char *path, const u8 *uuid, u64 ctransid,
}
}*/
- args_v2.fd = openat(r->mnt_fd, parent_subvol->path,
- O_RDONLY | O_NOATIME);
+ ret = mnt_to_dev(r->root_path, &dev);
+ if (ret)
+ goto out;
+ if (!mktemp(tmp_name)) {
+ fprintf(stderr, "ERROR: fail to generate a tmp file\n");
+ goto out;
+ }
+ strncat(tmp_dir, "/", 1);
+ strncat(tmp_dir, tmp_name, strlen(tmp_name));
+
+ ret = mkdir(tmp_dir, 0777);
+ if (ret) {
+ fprintf(stderr, "ERROR: fail to make dir: %s\n", tmp_dir);
+ goto out;
+ }
+ /* if we change default subvolume, using btrfs interval
+ * subvolume path to lookup may return us ENOENT.To handle
+ * such case, we mount this btrfs filesystem other place
+ * where we use fs tree as our default subvolume.
+ */
+ ret = mount(dev, tmp_dir, "btrfs", 0, "-o subvolid=5");
+ if (ret) {
+ fprintf(stderr, "ERROR: fail to mount dev: %s", dev);
+ goto out;
+ }
+
+ full_path = calloc(1, strlen(parent_subvol->path) + strlen(tmp_dir));
+ if (!full_path) {
+ ret = -ENOMEM;
+ goto out_umount;
+ }
+ strncat(full_path, tmp_dir, strlen(tmp_dir));
+ strncat(full_path, "/", 1);
+ strncat(full_path, parent_subvol->path, strlen(parent_subvol->path));
+
+ args_v2.fd = open(full_path, O_RDONLY | O_NOATIME);
if (args_v2.fd < 0) {
ret = -errno;
fprintf(stderr, "ERROR: open %s failed. %s\n",
parent_subvol->path, strerror(-ret));
- goto out;
+ goto out_umount;
}
ret = ioctl(r->dest_dir_fd, BTRFS_IOC_SNAP_CREATE_V2, &args_v2);
@@ -269,10 +308,14 @@ static int process_snapshot(const char *path, const u8 *uuid, u64 ctransid,
fprintf(stderr, "ERROR: creating snapshot %s -> %s "
"failed. %s\n", parent_subvol->path,
path, strerror(-ret));
- goto out;
}
+out_umount:
+ umount(tmp_dir);
+ rmdir(tmp_dir);
out:
+ free(full_path);
+ free(dev);
if (parent_subvol) {
free(parent_subvol->path);
free(parent_subvol);
diff --git a/utils.c b/utils.c
index a92696e..da5291b 100644
--- a/utils.c
+++ b/utils.c
@@ -2194,6 +2194,34 @@ out:
return ret;
}
+/*
+ * Given mount point, this function will return
+ * its corresponding device
+ */
+int mnt_to_dev(const char *mnt_dir, char **dev)
+{
+ struct mntent *mnt;
+ FILE *f;
+ int ret = -1;
+
+ f = setmntent("/proc/self/mounts", "r");
+ if (f == NULL)
+ return ret;
+ while ((mnt = getmntent(f)) != NULL) {
+ if (strcmp(mnt->mnt_type, "btrfs"))
+ continue;
+ if (strcmp(mnt->mnt_dir, mnt_dir))
+ continue;
+ *dev = strdup(mnt->mnt_fsname);
+ if (*dev)
+ ret = 0;
+ break;
+ }
+ endmntent(f);
+
+ return ret;
+}
+
/* This finds the mount point for a given fsid,
* subvols of the same fs/fsid can be mounted
* so here this picks and lowest subvol id
diff --git a/utils.h b/utils.h
index 00f1c18..9b2f79c 100644
--- a/utils.h
+++ b/utils.h
@@ -98,5 +98,6 @@ int btrfs_scan_lblkid(int update_kernel);
int get_btrfs_mount(const char *dev, char *mp, size_t mp_size);
int get_fslist(struct btrfs_ioctl_fslist **out_fslist, u64 *out_count);
int fsid_to_mntpt(__u8 *fsid, char *mntpt, int *mnt_cnt);
+int mnt_to_dev(const char *mnt, char **dev);
#endif
--
1.8.3.1
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
