Eryu,
btrfs dev scan -d option is there for legacy reasons. The new method
is using libblkid to find btrfs devs.
David/Zach, is it time to remove -d option ? or mention deprecated.
But your test case show problem using btrfsck as well. thats nice!
The fix for this is in the kernel, which would return busy
if the device path is being updated when the device is mounted.
Can you try with Chris integration branch ? mainly the patch..
-------------
commit 4e5c146442b23437d23a2bd81b95f13dfeaffe88
Author: Anand Jain <anand.jain@xxxxxxxxxx>
Date: Thu Jul 3 18:22:05 2014 +0800
Btrfs: device_list_add() should not update list when mounted
-------------
Thanks, Anand
On 14/08/2014 19:40, Eryu Guan wrote:
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);
}
}
--
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