[PATCH v2] mkdumprd: Fix the bug to get persistent device correctly

[Minfei Huang]

Persistent device name is an uuid in directory /dev/disk/by-uuid which
can determine the unique devices by soft link. The uuid is created, once
the device are formated by command mkfs, and one filesystem has an
unique uuid to detect itself.

For btrfs, one filesystem may contain several devices. So it may fail to
find the device from the /dev/disk/by-uuid as usual, because
/dev/disk/by-uuid/* only points to the one of the several devices by the
soft link, although there is a filesystem on the devices.

In order to get the persistent device, we can use command "blkid",
instead of finding it in directory /dev/disk/by-uuid directly.

Signed-off-by: Minfei Huang <mhuang(a)redhat.com&gt;
---
v1:
- describe the commit log more detail
---
 mkdumprd | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/mkdumprd b/mkdumprd
index 8cf3c7b..52d560e 100644
--- a/mkdumprd
+++ b/mkdumprd
@@ -30,14 +30,14 @@ perror() {
 }
 
 get_persistent_dev() {
-    local i _tmp _dev
+    local i _tmp _dev _uuid
 
     _dev=$(udevadm info --query=name --name="$1" 2>/dev/null)
     [ -z "$_dev" ] && {
         perror_exit "Kernel dev name of $1 is not found."
     }
 
-    for i in /dev/mapper/* /dev/disk/by-uuid/* /dev/disk/by-id/*; do
+    for i in /dev/mapper/* /dev/disk/by-id/*; do
         _tmp=$(udevadm info --query=name --name="$i" 2>/dev/null)
         if [ "$_tmp" = "$_dev" ]; then
             echo $i
@@ -45,6 +45,18 @@ get_persistent_dev() {
         fi
     done
 
+    if [ "x" != "x""$(blkid $1 | grep "UUID")" ];
then
+        _uuid=`blkid $1 | grep "UUID" | awk '{print $2}'`
+        _uuid=${_uuid#*\"}
+        _uuid=${_uuid%\"*}
+        _dev=/dev/disk/by-uuid/$_uuid
+        _tmp=$(udevadm info --query=name --name=$_dev 2>/dev/null)
+        if [ "x" != "x"$_tmp ]; then
+            echo $_dev
+            return
+        fi
+    fi
+
     perror "WARNING: Persistent device name of $1 not found. Using $1 as dump target
name"
     echo $1
 }
-- 
1.9.3

[Baoquan He]

On 06/02/15 at 05:04pm, Minfei Huang wrote:
>  Persistent device name is an uuid in directory /dev/disk/by-uuid
> which
>  can determine the unique devices by soft link. The uuid is created, once
>  the device are formated by command mkfs, and one filesystem has an
>  unique uuid to detect itself.
>  
>  For btrfs, one filesystem may contain several devices. So it may fail to
>  find the device from the /dev/disk/by-uuid as usual, because
>  /dev/disk/by-uuid/* only points to the one of the several devices by the
>  soft link, although there is a filesystem on the devices.
>  
>  In order to get the persistent device, we can use command "blkid",
>  instead of finding it in directory /dev/disk/by-uuid directly. 
Hi Minfei,

Could you please give an example in your testing environment? If you
don't like the specific inforamtion, you can use things like a btrfs is
built on /dev/{a,b,c}, then how problems happened and how you fixed it.
Otherwise I need build a btrfs and execute your shell command line by
line to understand your patch.

Giving example can accelerate people's review, seriously.

Thanks
Baoquan



>  
>  Signed-off-by: Minfei Huang <mhuang(a)redhat.com&gt;
>  ---
>  v1:
>  - describe the commit log more detail
>  ---
>   mkdumprd | 16 ++++++++++++++--
>   1 file changed, 14 insertions(+), 2 deletions(-)
>  
>  diff --git a/mkdumprd b/mkdumprd
>  index 8cf3c7b..52d560e 100644
>  --- a/mkdumprd
>  +++ b/mkdumprd
>  @@ -30,14 +30,14 @@ perror() {
>   }
>   
>   get_persistent_dev() {
>  -    local i _tmp _dev
>  +    local i _tmp _dev _uuid
>   
>       _dev=$(udevadm info --query=name --name="$1" 2>/dev/null)
>       [ -z "$_dev" ] && {
>           perror_exit "Kernel dev name of $1 is not found."
>       }
>   
>  -    for i in /dev/mapper/* /dev/disk/by-uuid/* /dev/disk/by-id/*; do
>  +    for i in /dev/mapper/* /dev/disk/by-id/*; do
>           _tmp=$(udevadm info --query=name --name="$i" 2>/dev/null)
>           if [ "$_tmp" = "$_dev" ]; then
>               echo $i
>  @@ -45,6 +45,18 @@ get_persistent_dev() {
>           fi
>       done
>   
>  +    if [ "x" != "x""$(blkid $1 | grep "UUID")"
> ]; then
>  +        _uuid=`blkid $1 | grep "UUID" | awk '{print $2}'`
>  +        _uuid=${_uuid#*\"}
>  +        _uuid=${_uuid%\"*}
>  +        _dev=/dev/disk/by-uuid/$_uuid
>  +        _tmp=$(udevadm info --query=name --name=$_dev 2>/dev/null)
>  +        if [ "x" != "x"$_tmp ]; then
>  +            echo $_dev
>  +            return
>  +        fi
>  +    fi
>  +
>       perror "WARNING: Persistent device name of $1 not found. Using $1 as dump
> target name"
>       echo $1
>   }
>  -- 
>  1.9.3
>  
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