A btrfsck or btrfs device scan -d operation could change the device
name of other mounted btrfs in kernel, if the other btrfs is on lvm
device.
Assume that we have two btrfs filesystems, kernel is 3.16.0-rc4+
[root@hp-dl388eg8-01 btrfs-progs]# btrfs fi show
Label: none uuid: 1aba7da5-ce2b-4af0-a716-db732abc60b2
Total devices 1 FS bytes used 384.00KiB
devid 1 size 15.00GiB used 2.04GiB path /dev/mapper/rhel_hp--dl388eg8--01-testlv1
Label: none uuid: 26ff4f12-f6d9-4cbc-aae2-57febeefde37
Total devices 2 FS bytes used 112.00KiB
devid 1 size 15.00GiB used 2.03GiB path /dev/mapper/rhel_hp--dl388eg8--01-testlv2
devid 2 size 15.00GiB used 2.01GiB path /dev/mapper/rhel_hp--dl388eg8--01-testlv3
Btrfs v3.14.2
And testlv1 was mounted at /mnt/btrfs
[root@hp-dl388eg8-01 btrfs-progs]# df -TP /mnt/btrfs
Filesystem Type 1024-blocks Used Available Capacity Mounted on
/dev/mapper/rhel_hp--dl388eg8--01-testlv1 btrfs 15728640 512 13602560 1% /mnt/btrfs
Now run btrfsck on testlv2 or btrfs device scan -d, which will scan
all btrfs devices and somehow change the device name.
[root@hp-dl388eg8-01 btrfs-progs]# btrfsck /dev/mapper/rhel_hp--dl388eg8--01-testlv2 >/dev/null 2>&1
[root@hp-dl388eg8-01 btrfs-progs]# df -TP /mnt/btrfs
Filesystem Type 1024-blocks Used Available Capacity Mounted on
/dev/dm-3 btrfs 15728640 512 13602560 1% /mnt/btrfs
[root@hp-dl388eg8-01 btrfs-progs]# btrfs fi show
Label: none uuid: 1aba7da5-ce2b-4af0-a716-db732abc60b2
Total devices 1 FS bytes used 384.00KiB
devid 1 size 15.00GiB used 2.04GiB path /dev/dm-3
Label: none uuid: 26ff4f12-f6d9-4cbc-aae2-57febeefde37
Total devices 2 FS bytes used 112.00KiB
devid 1 size 15.00GiB used 2.03GiB path /dev/mapper/rhel_hp--dl388eg8--01-testlv2
devid 2 size 15.00GiB used 2.01GiB path /dev/mapper/rhel_hp--dl388eg8--01-testlv3
Btrfs v3.14.2
Now calling btrfs_register_one_device with canonicalized dm device name.
Signed-off-by: Eryu Guan <guaneryu@xxxxxxxxx>
---
With patch 1 applied, btrfsck won't change the device name,
but btrfs device scan -d still does.
utils.c | 44 +++++++++++++++++++++++++++++++++++++++++---
1 file changed, 41 insertions(+), 3 deletions(-)
diff --git a/utils.c b/utils.c
index f54e749..3567094 100644
--- a/utils.c
+++ b/utils.c
@@ -985,6 +985,32 @@ static int blk_file_in_dev_list(struct btrfs_fs_devices* fs_devices,
}
/*
+ * Convert dm-N device name to /dev/mapper/name
+ */
+static void canonicalize_dm_name(char *devnode, char *path, int len)
+{
+ char *buf = NULL;
+ FILE *sysfsp = NULL;
+
+ buf = malloc(PATH_MAX);
+ if (!buf)
+ return;
+
+ snprintf(buf, PATH_MAX, "/sys/block/%s/dm/name", devnode);
+ sysfsp = fopen(buf, "r");
+ if (!sysfsp)
+ goto out;
+
+ if (fgets(buf, PATH_MAX, sysfsp)) {
+ buf[strlen(buf) - 1] = '\0';
+ snprintf(path, len - 1, "/dev/mapper/%s", buf);
+ }
+ fclose(sysfsp);
+out:
+ free(buf);
+}
+
+/*
* returns 1 if the device was mounted, < 0 on error or 0 if everything
* is safe to continue.
*/
@@ -1189,6 +1215,9 @@ again:
if (fsid && memcmp(fsid, tmp_devices->fsid, BTRFS_FSID_SIZE))
continue;
if (run_ioctl > 0) {
+ if (!strncmp(fullpath, "/dev/dm-", strlen("/dev/dm-")))
+ canonicalize_dm_name(dirent->d_name,
+ fullpath, PATH_MAX);
btrfs_register_one_device(fullpath);
}
close(fd);
@@ -1475,8 +1504,11 @@ int btrfs_scan_block_devices(u8 *fsid, int run_ioctl)
int i;
char buf[1024];
char fullpath[110];
+ char devnode[64];
+ char *dirname = "/dev/";
int scans = 0;
int special;
+ int is_dm;
scan_again:
proc_partitions = fopen("/proc/partitions","r");
@@ -1493,9 +1525,11 @@ scan_again:
return -ENOENT;
}
- strcpy(fullpath,"/dev/");
- while(fgets(buf, 1023, proc_partitions)) {
- i = sscanf(buf," %*d %*d %*d %99s", fullpath+5);
+ strcpy(fullpath, dirname);
+ while (fgets(buf, sizeof(buf) - 1, proc_partitions)) {
+ i = sscanf(buf, " %*d %*d %*d %99s", devnode);
+ strncpy(fullpath + strlen(dirname), devnode,
+ sizeof(fullpath) - strlen(dirname));
/*
* multipath and MD devices may register as a btrfs filesystem
@@ -1504,6 +1538,7 @@ scan_again:
* This scans the special entries last
*/
special = strncmp(fullpath, "/dev/dm-", strlen("/dev/dm-")) == 0;
+ is_dm = special;
if (!special)
special = strncmp(fullpath, "/dev/md", strlen("/dev/md")) == 0;
@@ -1538,6 +1573,9 @@ scan_again:
if (fsid && memcmp(fsid, tmp_devices->fsid, BTRFS_FSID_SIZE))
continue;
if (run_ioctl > 0) {
+ if (is_dm)
+ canonicalize_dm_name(devnode, fullpath,
+ sizeof(fullpath));
btrfs_register_one_device(fullpath);
}
}
