New subject: [PATCH] kdump.conf: introduce new "nfs_mntopts" in "/etc/kdump.conf"

5 May 2016

There are some complaints about nfs kdump that users must mount
nfs beforehand, which can also cause some overhead to NFS server.
To solve it, we added a new "nfs_mntopts" in "/etc/kdump.conf" to
allow users to specify the nfs options instead of mounting it. The
general rule about "nfs_mntopts" is:
1) "nfs_mntopts" has the highest priority, if it is specified, we
   always use it as the final mount option even if it is invalid
   (kdump will fail to start).
2) When no nfs mounted beforehand:
   a) If "nfs_mntopts" is specifed, do a temporary mount using it
      as the mount options.
   b) If "nfs_mntopts" is not specifed, do a temporary mount using
      no options(default option).
   If the temporary mount fails, kdump restart fails.
3) When nfs was mounted beforehand, parsing mounted nfs as before,
   but with the following extra logic:
   a) If "nfs_mntopts" is specified, validate it by doing a temporary
      mount: If it is valid, make it as the options passed to dracut
      instead of the mounted nfs(overridding it); If it is invalid,
      kdump restart fails.
   b) If "nfs_mntopts" is not specified, parsing mounted nfs as before.
4) After kdump is finished(started or failed), umount the temporary nfs
   mount immediately if any.
The patch introduced three new functions to do the implementation:
nfs_mount_prepare(), nfs_mount_finish(), and nfs_mount_cleanup().
Signed-off-by: Xunlei Pang xlpang@redhat.com
---
 kdump.conf |  4 ++++
 kdumpctl   |  4 ++--
 mkdumprd   | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 3 files changed, 81 insertions(+), 7 deletions(-)

diff --git a/kdump.conf b/kdump.conf
index 54b581d..f56556b 100644
--- a/kdump.conf
+++ b/kdump.conf
@@ -18,6 +18,9 @@
 # nfs <nfs mount>	- Will mount fs and copy /proc/vmcore to
 #			  <mnt>/var/crash/%HOST-%DATE/, supports DNS.
 #
+# nfs_mntopts <mount options> - Will mount nfs using this options
+#			  even if there's a mounted nfs with different options.
+#
 # ssh user@server	- Will scp /proc/vmcore to
 #			  user@server:/var/crash/%HOST-%DATE/, supports DNS
 #			  NOTE: make sure user has necessary write
@@ -147,6 +150,7 @@
 #ext4 LABEL=/boot
 #ext4 UUID=03138356-5e61-4ab3-b58e-27507ac41937
 #nfs my.server.com:/export/tmp
+#nfs_mntopts rw,relatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,timeo=500
 #ssh user@my.server.com
 #sshkey /root/.ssh/kdump_id_rsa
 path /var/crash
diff --git a/kdumpctl b/kdumpctl
index ef18a2d..8be82c7 100755
--- a/kdumpctl
+++ b/kdumpctl
@@ -235,7 +235,7 @@ check_config()
 {
    local nr
-	nr=$(awk 'BEGIN{cnt=0} /^raw|^ssh[[:blank:]]|^nfs|^ext[234]|^xfs|^btrfs|^minix/{cnt++} END{print cnt}' $KDUMP_CONFIG_FILE)
+	nr=$(awk 'BEGIN{cnt=0} /^raw|^ssh[[:blank:]]|^nfs[[:blank:]]|^ext[234]|^xfs|^btrfs|^minix/{cnt++} END{print cnt}' $KDUMP_CONFIG_FILE)
    [ $nr -gt 1 ] && {
    	echo "More than one dump targets specified."
    	return 1
@@ -247,7 +247,7 @@ check_config()
    	case "$config_opt" in
    	#* | "")
    		;;
-		raw|ext2|ext3|ext4|minix|btrfs|xfs|nfs|ssh|sshkey|path|core_collector|kdump_post|kdump_pre|extra_bins|extra_modules|default|force_rebuild|dracut_args|fence_kdump_args|fence_kdump_nodes)
+		raw|ext2|ext3|ext4|minix|btrfs|xfs|nfs|nfs_mntopts|ssh|sshkey|path|core_collector|kdump_post|kdump_pre|extra_bins|extra_modules|default|force_rebuild|dracut_args|fence_kdump_args|fence_kdump_nodes)
    		[ -z "$config_val" ] && {
    			echo "Invalid kdump config value for option $config_opt."
    			return 1;
diff --git a/mkdumprd b/mkdumprd
index 6e3d975..aca8573 100644
--- a/mkdumprd
+++ b/mkdumprd
@@ -13,6 +13,8 @@ conf_file="/etc/kdump.conf"
 SSH_KEY_LOCATION="/root/.ssh/kdump_id_rsa"
 SAVE_PATH=$(grep ^path $conf_file| cut -d' '  -f2)
 [ -z "$SAVE_PATH" ] && SAVE_PATH=$DEFAULT_PATH
+NFS_MNTOPTS=$(grep ^nfs_mntopts $conf_file| cut -d' '  -f2 | head -1)
+mntopts_override=""
 # strip the duplicated "/"
 SAVE_PATH=$(echo $SAVE_PATH | tr -s /)
@@ -21,6 +23,7 @@ dracut_args=("--hostonly" "-o" "plymouth dash resume ifcfg")
 OVERRIDE_RESETTABLE=0
perror_exit() {
+    nfs_mount_cleanup
     echo $@ >&2
     exit 1
 }
@@ -135,7 +138,15 @@ to_mount() {
     if ! is_nfs_dump_target; then
        _options="$_options,x-initrd.mount"
     fi
-    _mntopts="$_target $_fstype $_options"
+
+    # use $mntopts_override instead, if non-empty
+    if [ -n "$mntopts_override" ]; then
+        mntopts_override=${mntopts_override/#ro/rw} #mount fs target as rw in 2nd kernel
+        _mntopts="$_target $_fstype $mntopts_override"
+    else
+        _mntopts="$_target $_fstype $_options"
+    fi
+
     #for non-nfs _dev converting to use udev persistent name
     if [ -b "$_source" ]; then
         _pdev="$(get_persistent_dev $_source)"
@@ -352,6 +363,61 @@ get_block_dump_target()
     [ -b "$_target" ] && echo $(to_dev_name $_target)
 }
+# handle "nfs_mntopts"
+# 1) if no nfs mounted: temporarily mount it using "nfs_mntopts" if specifed, else do a default mount.
+# 2) if nfs is mounted: if "nfs_mntopts" is specified and valid, use it as the options passed to dracut.
+nfs_mount_prepare()
+{
+    local config_val=$1
+
+    NFS_MNTPOINT=$(mktemp -d /tmp/nfs_MPXXXXXX)
+    if ! findmnt $config_val >/dev/null; then
+        # nfs needn't to be mounted beforehand, mount it temporarily
+        if [ -z "$NFS_MNTOPTS" ]; then
+            # Empty implies to use default mount option
+            echo "default nfs mount option used."
+        else
+            echo "nfs_mntopts mount option used."
+            NFS_MNTOPTS="-o $NFS_MNTOPTS"
+        fi
+
+        if ! mount $config_val $NFS_MNTOPTS $NFS_MNTPOINT; then
+            perror_exit "Mount nfs $config_val failed. Please specify proper nfs_mntopts in /etc/kdump.conf"
+        fi
+    elif [ -n "$NFS_MNTOPTS" ]; then
+        echo "nfs_mntopts mount option used."
+        # Validate $NFS_MNTOPTS
+        if ! mount $config_val -o $NFS_MNTOPTS $NFS_MNTPOINT; then
+            perror_exit "Validate nfs $config_val failed. Please check nfs_mntopts in /etc/kdump.conf"
+        fi
+        # if nfs_mntopts is specified and valid, also there is a mounted nfs by users with
+        # different options, nfs_mntopts has the priority to be used by dracut.
+        mntopts_override=$(findmnt -f -n -r -o OPTIONS $NFS_MNTPOINT)
+
+        # after validation, umount it so as not to conflict with the previously mounted one.
+        umount $NFS_MNTPOINT
+    else
+        echo "Mounted nfs mount option used."
+    fi
+
+    add_dracut_module "nfs"
+}
+
+# umount temporary nfs mount if there is
+nfs_mount_finish()
+{
+    if [ -d "$NFS_MNTPOINT" ]; then
+        umount $NFS_MNTPOINT 2>/dev/null
+        rmdir $NFS_MNTPOINT
+    fi
+}
+
+# if error happens, we check to clean up temporary nfs mount.
+nfs_mount_cleanup()
+{
+    nfs_mount_finish
+}
+
 #handle the case user does not specify the dump target explicitly
 handle_default_dump_target()
 {
@@ -540,12 +606,12 @@ do
         extra_modules="$extra_modules $config_val"
         ;;
     ext[234]|xfs|btrfs|minix|nfs)
-        if ! findmnt $config_val >/dev/null; then
-            perror_exit "Dump target $config_val is probably not mounted."
+        if [ "$config_opt" = "nfs" ]; then
+            nfs_mount_prepare $config_val
         fi
-        if [ "$config_opt" = "nfs" ]; then
-            add_dracut_module "nfs"
+        if ! findmnt $config_val >/dev/null; then
+            perror_exit "Dump target $config_val is probably not mounted."
         fi
_absolute_save_path=$(make_absolute_save_path $config_val)
@@ -559,6 +625,10 @@ do
         add_mount "$config_val"
         check_save_path_fs $_absolute_save_path
         check_size fs $config_val
+
+        if [ "$config_opt" = "nfs" ]; then
+            nfs_mount_finish
+        fi
         ;;
     raw)
         #checking raw disk writable
-- 
1.8.3.1

    