[PATCH] fadump: fix dump capture failure to root disk

[Hari Bathini]

If the dump target is the root disk, kdump scripts add an entry in
/etc/fstab for root disk with /sysroot as the mount point. The root
disk, passed through root=<> kernel commandline parameter, is mounted
at /sysroot in read-only mode before switching from initial ramdisk.
So, in fadump mode, a remount of /sysroot to read-write mode is needed
to capture dump successfully, because /sysroot is already mounted as
read-only based on root=<> boot parameter.

Commit e8ef4db8ff91 ("Fix dump_fs mount point detection and fallback
mount") removed initialization of $_op variable, the variable holding
the options the dump target was mounted with, leading to the below
error as remount was skipped:

  kdump[586]: saving to /sysroot/var/crash/127.0.0.1-2021-04-22-07:22:08/
  kdump.sh[587]: mkdir: cannot create directory
'/sysroot/var/crash/127.0.0.1-2021-04-22-07:22:08/': Read-only file system
  kdump[589]: saving vmcore failed

Restore $_op variable initialization in dump_fs() function to fix this.

Fixes: e8ef4db8ff91 ("Fix dump_fs mount point detection and fallback mount")
Signed-off-by: Hari Bathini <hbathini(a)linux.ibm.com&gt;
---
 kdump-lib-initramfs.sh |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kdump-lib-initramfs.sh b/kdump-lib-initramfs.sh
index 5cb0223..15bbd85 100755
--- a/kdump-lib-initramfs.sh
+++ b/kdump-lib-initramfs.sh
@@ -119,7 +119,8 @@ dump_fs()
 {
     local _exitcode
     local _mp=$1
-    ddebug "dump_fs _mp=$_mp"
+    local _op=$(get_mount_info OPTIONS target $_mp -f)
+    ddebug "dump_fs _mp=$_mp _opts=$_op"
 
     if ! is_mounted "$_mp"; then
         dinfo "dump path \"$_mp\" is not mounted, trying to
mount..."
@@ -139,8 +140,8 @@ dump_fs()
 
     # Only remount to read-write mode if the dump target is mounted read-only.
     if [[ "$_op" = "ro"* ]]; then
-       dinfo "Mounting Dump target $_dev in rw mode."
-       mount -o remount,rw $_dev $_mp || return 1
+       dinfo "Remounting the dump target in rw mode."
+       mount -o remount,rw $_mp || return 1
     fi
 
     mkdir -p $_dump_path || return 1

[Kairui Song]

On Thu, Apr 22, 2021 at 8:52 PM Hari Bathini <hbathini(a)linux.ibm.com&gt; wrote:
>  If the dump target is the root disk, kdump scripts add an entry in
>  /etc/fstab for root disk with /sysroot as the mount point. The root
>  disk, passed through root=<> kernel commandline parameter, is mounted
>  at /sysroot in read-only mode before switching from initial ramdisk.
>  So, in fadump mode, a remount of /sysroot to read-write mode is needed
>  to capture dump successfully, because /sysroot is already mounted as
>  read-only based on root=<> boot parameter.
>
>  Commit e8ef4db8ff91 ("Fix dump_fs mount point detection and fallback
>  mount") removed initialization of $_op variable, the variable holding
>  the options the dump target was mounted with, leading to the below
>  error as remount was skipped:
>
>    kdump[586]: saving to /sysroot/var/crash/127.0.0.1-2021-04-22-07:22:08/
>    kdump.sh[587]: mkdir: cannot create directory
> '/sysroot/var/crash/127.0.0.1-2021-04-22-07:22:08/': Read-only file system
>    kdump[589]: saving vmcore failed
>
>  Restore $_op variable initialization in dump_fs() function to fix this.
>
>  Fixes: e8ef4db8ff91 ("Fix dump_fs mount point detection and fallback mount")
>  Signed-off-by: Hari Bathini <hbathini(a)linux.ibm.com&gt;
>  ---
>   kdump-lib-initramfs.sh |    7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
>
>  diff --git a/kdump-lib-initramfs.sh b/kdump-lib-initramfs.sh
>  index 5cb0223..15bbd85 100755
>  --- a/kdump-lib-initramfs.sh
>  +++ b/kdump-lib-initramfs.sh
>  @@ -119,7 +119,8 @@ dump_fs()
>   {
>       local _exitcode
>       local _mp=$1
>  -    ddebug "dump_fs _mp=$_mp"
>  +    local _op=$(get_mount_info OPTIONS target $_mp -f)
>  +    ddebug "dump_fs _mp=$_mp _opts=$_op"
>
>       if ! is_mounted "$_mp"; then
>           dinfo "dump path \"$_mp\" is not mounted, trying to
> mount..."
>  @@ -139,8 +140,8 @@ dump_fs()
>
>       # Only remount to read-write mode if the dump target is mounted read-only.
>       if [[ "$_op" = "ro"* ]]; then
>  -       dinfo "Mounting Dump target $_dev in rw mode."
>  -       mount -o remount,rw $_dev $_mp || return 1
>  +       dinfo "Remounting the dump target in rw mode."
>  +       mount -o remount,rw $_mp || return 1
>       fi
>
>       mkdir -p $_dump_path || return 1
>
>  
Thanks for the fix!

Acked-by: Kairui Song <kasong(a)redhat.com&gt;


--
Best Regards,
Kairui Song