File SLE12-SP1-btrfs.patch of Package rear

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File SLE12-SP1-btrfs.patch of Package rear (Revision 7503f9eefc0673b15d14fda3e77b6f10)

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diff -rp -U17 rear-1.17.2/usr/share/rear/layout/prepare/GNU/Linux/13_include_mount_filesystem_code.sh rear-1.17.2.SLE12-SP1-btrfs/usr/share/rear/layout/prepare/GNU/Linux/13_include_mount_filesystem_code.sh
--- rear-1.17.2/usr/share/rear/layout/prepare/GNU/Linux/13_include_mount_filesystem_code.sh	2015-06-25 09:07:56.000000000 +0200
+++ rear-1.17.2.SLE12-SP1-btrfs/usr/share/rear/layout/prepare/GNU/Linux/13_include_mount_filesystem_code.sh	2015-10-02 12:33:46.000000000 +0200
@@ -1,41 +1,58 @@
 # code to mount a file system
 # 13_mount_filesystem_code.sh contains the generic function 'mount_fs'
 # each distro may overrule the 'mount_fs' function with its proper way to do it
 # especially the case for btrfs related file systems
 
 mount_fs() {
     Log "Begin mount_fs( $@ )"
     local fs device mp fstype uuid label options
     ## mp: mount point
     read fs device mp fstype uuid label options < <(grep "^fs.* ${1#fs:} " "$LAYOUT_FILE")
 
     label=${label#label=}
     uuid=${uuid#uuid=}
 
     # Extract mount options.
     local option mountopts
+    # An input line could look like this (an example from SLES12-SP1):
+    # fs /dev/sda2 / btrfs uuid=a2b2c3 label= options=rw,relatime,space_cache,subvolid=259,subvol=/@/.snapshots/1/snapshot
+    # which means by the above 'read' the variable (that is unfortunately) named 'options' gets the
+    # value 'options=rw,relatime,space_cache,subvolid=259,subvol=/@/.snapshots/1/snapshot'
+    # i.e. options='options=rw,relatime,space_cache,subvolid=259,subvol=/@/.snapshots/1/snapshot'
     for option in $options ; do
-        name=${option%%=*}     # options can contain more '=' signs
-        value=${option#*=}
+        name=${option%%=*}     # an option can contain more '=' signs (see the above example value)
+        value=${option#*=}     # therefore split the name from the actual value at the leftmost '='
 
         case $name in
             (options)
                 ### Do not mount nodev, as chrooting later on would fail.
-                mountopts=${value//nodev/dev}
+                value=${value//nodev/dev}
+                # btrfs mount options like subvolid=259 or subvol=/@/.snapshots/1/snapshot
+                # from the old system cannot work here for recovery because btrfs subvolumes
+                # are not yet created (and when created their subvolid is likely different)
+                # so that those mount options are removed here. All btrfs subvolume handling
+                # happens in the btrfs_subvolumes_setup function in 13_include_mount_subvolumes_code.sh
+                # First add a comma at the end so that it is easier to remove a mount option at the end:
+                value=${value/%/,}
+                # Remove all subvolid= and subvol= mount options (the extglob shell option is enabled in rear):
+                value=${value//subvolid=*([^,]),/}
+                value=${value//subvol=*([^,]),/}
+                # Remove all commas at the end:
+                mountopts=${value/%,/}
                 ;;
         esac
     done
 
     if [ -n "$mountopts" ] ; then
         mountopts="-o $mountopts"
     fi
 
     echo "LogPrint \"Mounting filesystem $mp\"" >> "$LAYOUT_CODE"
 
     case $fstype in
         (btrfs)
             # The following commands are basically the same as in the default/fallback case.
             # The explicite case for btrfs is only there to be prepared for special adaptions for btrfs related file systems.
             # Because the btrfs filesystem was created anew just before by the create_fs function in 13_include_filesystem_code.sh
             # the code here mounts the whole btrfs filesystem because by default when creating a btrfs filesystem
             # its top-level/root subvolume is the btrfs default subvolume which gets mounted when no other subvolume is specified.
diff -rp -U17 rear-1.17.2/usr/share/rear/layout/prepare/GNU/Linux/13_include_mount_subvolumes_code.sh rear-1.17.2.SLE12-SP1-btrfs/usr/share/rear/layout/prepare/GNU/Linux/13_include_mount_subvolumes_code.sh
--- rear-1.17.2/usr/share/rear/layout/prepare/GNU/Linux/13_include_mount_subvolumes_code.sh	2015-06-08 09:50:38.000000000 +0200
+++ rear-1.17.2.SLE12-SP1-btrfs/usr/share/rear/layout/prepare/GNU/Linux/13_include_mount_subvolumes_code.sh	2015-10-16 12:09:06.000000000 +0200
@@ -19,206 +19,309 @@ btrfs_subvolumes_setup() {
     # where $device is the device node where the filesystem was already created by 13_include_filesystem_code.sh
     # (usually a harddisk partition like e.g. /dev/sda1):
     device=$1
     mountpoint=$2
     # mountopts are of the form "-o foo,bar,baz" (see 13_include_mount_filesystem_code.sh)
     # which means $3 is '-o' and 'foo,bar,baz' is $4:
     mountopts="$3 $4"
     # Empty device or mountpoint may indicate an error. In this case be verbose and inform the user:
     if test -z "$device" -o -z "$mountpoint" ; then
         LogPrint "Empty device='$device' or mountpoint='$mountpoint' may indicate an error, skipping btrfs_subvolumes_setup( $@ )."
         Log "Return 0 from btrfs_subvolumes_setup( $@ )"
         return 0
     fi
     # FIXME: The following avoids to have '/mnt/local' hardcoded at many places in the code only here.
     # The root of the filesysten tree of the to-be-recovered-system in the recovery system should be in a global variable:
     recovery_system_root=/mnt/local
     ###########################################
+    # SLES 12 SP1 special btrfs subvolumes setup detection:
+    SLES12SP1_btrfs_detection_string="@/.snapshots/"
+    if grep "^btrfsdefaultsubvol $device $mountpoint [0-9]* $SLES12SP1_btrfs_detection_string" "$LAYOUT_FILE" ; then
+        info_message="Detected SLES 12 SP1 special btrfs subvolumes setup because the default subvolume path contains '$SLES12SP1_btrfs_detection_string'"
+        Log $info_message
+        echo "# $info_message" >> "$LAYOUT_CODE"
+        # For SLES 12 SP1 a btrfsdefaultsubvol entry in disklayout.conf looks like
+        #   btrfsdefaultsubvol /dev/sda2 / 259 @/.snapshots/1/snapshot
+        # where "@/.snapshots/" should be fixed but "1/snapshot" may vary.
+        # This requires special setup because the btrfs default subvolume on SLES 12 SP1
+        # is not a normal btrfs subvolume (as it was on SLES 12 (without SP1))
+        # but on SLES 12 SP1 it is a snapper controlled btrfs snapshot subvolume, see
+        # https://github.com/rear/rear/issues/556
+        # https://fate.suse.com/318701 (SUSE internal feature request)
+        # https://bugzilla.suse.com/show_bug.cgi?id=946006 (SUSE internal issue)
+        SLES12SP1_btrfs_subvolumes_setup="yes"
+        # Because that very special btrfs default subvolume on SLES 12 SP1
+        # has to be controlled by snapper it must be set up by snapper
+        # which means that snapper is needed in the rear recovery system.
+        # For this special setup during installation a special SUSE tool
+        # /usr/lib/snapper/installation-helper is used:
+        SLES12SP1_installation_helper_executable="/usr/lib/snapper/installation-helper"
+        # What "snapper/installation-helper --step 1" basically does is
+        # creating a snapshot of the first root filesystem
+        # where the first root filesystem must have the btrfs subvolume '@' mounted at '/'
+        # which means the btrfs subvolume '@' must be the initial btrfs default subvolume:
+        SLES12SP1_initial_default_subvolume_path="@"
+    fi
+    ###########################################
     # Btrfs snapshot subvolumes handling:
     # Remember all btrfs snapshot subvolumes to exclude them when mounting all btrfs normal subvolumes below.
     # The btrfs snapshot subvolumes entries that are created by 23_filesystem_layout.sh
     # are deactivated (as '#btrfssnapshotsubvol ...') in the LAYOUT_FILE (disklayout.conf).
     # When there are active btrfs snapshot subvolumes entries, the user has manually
     # activated them (as 'btrfssnapshotsubvol ...') in the LAYOUT_FILE (disklayout.conf).
     # Because any btrfssnapshotsubvol entries are needed to exclude all btrfs snapshot subvolumes
     # 'grep "btrfssnapshotsubvol ..." ... | sed ...' is used.
     while read keyword dummy dummy dummy subvolume_path junk ; do
         if test -z "$subvolume_path" ; then
            continue
         fi
         # When there is a non-empty subvolume_path, btrfs snapshot subvolume handling is needed:
         Log "Handling snapshot subvolume $subvolume_path for $device at $mountpoint"
         # Remember btrfs snapshot subvolumes to exclude them when mounting all btrfs normal subvolumes below:
         snapshot_subvolumes_devices_and_paths="$snapshot_subvolumes_devices_and_paths $device,$subvolume_path"
         # Be verbose if there are active btrfs snapshot subvolumes entries (snapshot subvolumes cannot be recreated).
         # In this case inform the user that nothing can be done for activated snapshot subvolumes entries:
         if test "btrfssnapshotsubvol" = "$keyword" ; then
             info_message="It is not possible to recreate btrfs snapshot subvolumes, skipping $subvolume_path on $device at $mountpoint"
             LogPrint $info_message
             echo "# $info_message" >> "$LAYOUT_CODE"
          fi
     done < <( grep "btrfssnapshotsubvol $device $mountpoint " "$LAYOUT_FILE" | sed -e 's/.*#.*btrfssnapshotsubvol/#btrfssnapshotsubvol/' )
     ###########################################
     # Btrfs normal subvolumes setup:
     # Create the normal btrfs subvolumes before the btrfs default subvolume setup
     # because currently the whole btrfs filesystem (i.e. its top-level/root subvolume) is mounted at the mountpoint
     # so that currently normal btrfs subvolumes can be created using the subvolume path relative to the btrfs toplevel/root subvolume
     # and that subvolume path relative to the btrfs toplevel/root subvolume is stored in the LAYOUT_FILE.
     # In contrast after the btrfs default subvolume setup only the btrfs filesystem default subvolume is mounted at the mountpoint and
     # then it would be no longer possible to create btrfs subvolumes with the subvolume path that is stored in the LAYOUT_FILE.
     # In particular a special btrfs default subvolume (i.e. when the btrfs default subvolume is not the toplevel/root subvolume)
-    # is also listed as a normal subvolume so that also the subvolume that is later used as default subvolume is hereby created.
+    # is also listed as a normal subvolume so that also the subvolume that is later used as default subvolume is hereby created
+    # provided the btrfs default subvolume is not a btrfs snapshot subvolume as in SLES 12 SP1 - but not in SLES 12 (without SP1):
     while read dummy dummy dummy dummy subvolume_path junk ; do
         # Empty subvolume_path may indicate an error. In this case be verbose and inform the user:
         if test -z "$subvolume_path" ; then
             LogPrint "btrfsnormalsubvol entry with empty subvolume_path for $device at $mountpoint may indicate an error, skipping subvolume setup for it."
             continue
         fi
+        # In case of SLES 12 SP1 special btrfs subvolumes setup
+        # skip setup of the normal btrfs subvolume '@/.snapshots' because
+        # that one will be created by "snapper/installation-helper --step 1"
+        # which fails if it already exists:
+        if test -n "$SLES12SP1_btrfs_subvolumes_setup" ; then
+            test "$subvolume_path" = "@/.snapshots" && continue
+        fi
         # When there is a non-empty subvolume_path, btrfs normal subvolume setup is needed:
         Log "Setup normal subvolume $subvolume_path for $device at $mountpoint"
         # E.g. for 'btrfs subvolume create /foo/bar/subvol' the directory path /foo/bar/ must already exist
         # but 'subvol' must not exist because 'btrfs subvolume create' creates the subvolume 'subvol' itself.
         # When 'subvol' already exists (e.g. as normal directory), it fails with ERROR: '/foo/bar/subvol' exists.
         subvolume_directory_path=${subvolume_path%/*}
         if test "$subvolume_directory_path" = "$subvolume_path" ; then
             # When subvolume_path is only plain 'mysubvol' then also subvolume_directory_path becomes 'mysubvol'
             # but 'mysubvol' must not be made as a normal directory by 'mkdir' below:
             subvolume_directory_path=""
         fi
         recovery_system_mountpoint=$recovery_system_root$mountpoint
         info_message="Creating normal btrfs subvolume $subvolume_path on $device at $mountpoint"
         Log $info_message
         (
         echo "# $info_message"
         if test -n "$subvolume_directory_path" ; then
             # Test in the recovery system if the directory path already exists to avoid that
             # useless 'mkdir -p' commands are run which look confusing in the "rear recover" log
             # regardless that 'mkdir -p' does nothing when its argument already exists:
             echo "if ! test -d $recovery_system_mountpoint/$subvolume_directory_path ; then"
             echo "    mkdir -p $recovery_system_mountpoint/$subvolume_directory_path"
             echo "fi"
         fi
         echo "btrfs subvolume create $recovery_system_mountpoint/$subvolume_path"
         ) >> "$LAYOUT_CODE"
+        # Btrfs subvolumes 'no copy on write' attribute setup:
+        if grep -q "^btrfsnocopyonwrite $subvolume_path\$" "$LAYOUT_FILE" ; then
+            info_message="Setting 'no copy on write' attribute for subvolume $subvolume_path"
+            Log $info_message
+            (
+            echo "# $info_message"
+            echo "chattr +C $recovery_system_mountpoint/$subvolume_path"
+            ) >> "$LAYOUT_CODE"
+        fi
     done < <( grep "^btrfsnormalsubvol $device $mountpoint " "$LAYOUT_FILE" )
     ###########################################
     # Btrfs default subvolume setup:
-    # There is exactly one default subvolume for one btrfs filesystem on one specific device (usually a harddisk partition like e.g. /dev/sda1):
+    # No outer 'while read ...' loop because there is exactly one default subvolume for one btrfs filesystem
+    # on one specific device (usually a harddisk partition like e.g. /dev/sda1):
     read dummy dummy dummy dummy subvolume_path junk < <( grep "^btrfsdefaultsubvol $device $mountpoint " "$LAYOUT_FILE" )
     # Artificial 'for' clause that is run only once to be able to 'continue' in the same syntactical way as in the 'while' loops
     # (because the 'for' loop is run only once 'continue' is the same as 'break'):
     for dummy in "once" ; do
         # Empty subvolume_path may indicate an error. In this case be verbose and inform the user:
         if test -z "$subvolume_path" ; then
             LogPrint "btrfsdefaultsubvol entry with empty subvolume_path for $device at $mountpoint may indicate an error, skipping default subvolume setup for it."
             continue
         fi
         # When there is a non-empty subvolume_path, btrfs default subvolume setup is needed:
         Log "Setup default subvolume $subvolume_path for $device at $mountpoint"
         # Remember the btrfs default subvolume on that specific device which is needed when mounting all btrfs normal subvolumes below
         # (also needed when the default subvolume path is "/" to avoid that it gets remounted when mounting normal subvolumes below):
         default_subvolume_path="$subvolume_path"
         # When subvolume_path is "/", the default for the btrfs default subvolume is used
         # (i.e. the btrfs default subvolume is the toplevel/root subvolume):
         if test "/" = "$subvolume_path" ; then
             info_message="No special btrfs default subvolume is used on $device at $mountpoint, no default subvolume setup needed"
             Log $info_message
             echo "# $info_message" >> "$LAYOUT_CODE"
             continue
         fi
-        # When in the original system the btrfs filesystem had a special different default subvolume,
+        # When in the original system the btrfs filesystem had a special different default subvolume
+        # (i.e. when the btrfs default subvolume is not the toplevel/root subvolume), then
         # that different subvolume needs to be set to be the default subvolume:
         recovery_system_mountpoint=$recovery_system_root$mountpoint
         Log "Setting $subvolume_path as btrfs default subvolume for $device at $mountpoint"
-        (
-        echo "# Begin btrfs default subvolume setup on $device at $mountpoint"
-        echo "# Making the $subvolume_path subvolume the default subvolume"
-        echo "# Get the ID of the $subvolume_path subvolume"
-        echo "subvolumeID=\$( btrfs subvolume list -a $recovery_system_mountpoint | sed -e 's/<FS_TREE>\///' | grep ' $subvolume_path\$' | tr -s '[:blank:]' ' ' | cut -d ' ' -f 2 )"
-        echo "# Set the $subvolume_path subvolume as default subvolume using its subvolume ID"
-        echo "btrfs subvolume set-default \$subvolumeID $recovery_system_mountpoint"
-        ) >> "$LAYOUT_CODE"
+        if test -n "$SLES12SP1_btrfs_subvolumes_setup" ; then
+            (
+            echo "# Begin btrfs default subvolume setup on $device at $mountpoint"
+            echo "# Doing special SLES 12 SP1 btrfs default snapper snapshot subvolume setup"
+            echo "# because the default subvolume path '$subvolume_path' contains '@/.snapshots/'"
+            echo "# Making the $SLES12SP1_initial_default_subvolume_path subvolume the initial default subvolume"
+            echo "# Get the ID of the $initial_default_subvolume_path subvolume"
+            echo "subvolumeID=\$( btrfs subvolume list -a $recovery_system_mountpoint | sed -e 's/<FS_TREE>\///' | grep ' $SLES12SP1_initial_default_subvolume_path\$' | tr -s '[:blank:]' ' ' | cut -d ' ' -f 2 )"
+            echo "# Set the $SLES12SP1_initial_default_subvolume_path subvolume as initial default subvolume using its subvolume ID"
+            echo "btrfs subvolume set-default \$subvolumeID $recovery_system_mountpoint"
+            echo "# Begin step 1 of special SLES 12 SP1 btrfs default snapper snapshot subvolume setup"
+            echo "umount $recovery_system_mountpoint"
+            echo "# Configuring snapper for root filesystem - step 1:"
+            echo "# - temporarily mounting device"
+            echo "# - copying/modifying config-file"
+            echo "# - creating filesystem config"
+            echo "# - creating snapshot of first root filesystem"
+            echo "# - setting default subvolume"
+            echo "if test -x $SLES12SP1_installation_helper_executable"
+            echo "then $SLES12SP1_installation_helper_executable --step 1 --device $device --description 'first root filesystem'"
+            echo "else LogPrint '$SLES12SP1_installation_helper_executable not executable may indicate an error with btrfs default subvolume setup for $subvolume_path on $device'"
+            echo "fi"
+            echo " mount -t btrfs -o subvolid=0 $mountopts $device $recovery_system_mountpoint"
+            echo "# End step 1 of special SLES 12 SP1 btrfs default snapper snapshot subvolume setup"
+            ) >> "$LAYOUT_CODE"
+        else
+            (
+            echo "# Begin btrfs default subvolume setup on $device at $mountpoint"
+            echo "# Making the $subvolume_path subvolume the default subvolume"
+            echo "# Get the ID of the $subvolume_path subvolume"
+            echo "subvolumeID=\$( btrfs subvolume list -a $recovery_system_mountpoint | sed -e 's/<FS_TREE>\///' | grep ' $subvolume_path\$' | tr -s '[:blank:]' ' ' | cut -d ' ' -f 2 )"
+            echo "# Set the $subvolume_path subvolume as default subvolume using its subvolume ID"
+            echo "btrfs subvolume set-default \$subvolumeID $recovery_system_mountpoint"
+            ) >> "$LAYOUT_CODE"
+        fi
         # When the btrfs filesystem has a special default subvolume (one that is not the toplevel/root subvolume)
         # then a reasonable assumption is that this one was mounted in the original system and not something else.
         # FIXME: It is possible that the admin has actually mounted something else in his original system
         # which would result a wrong recovery because currently such an awkward setup is not supported.
         # Under the above assumption the btrfs filesystem needs to be umonted and mounted again so that
         # the special default subvolume gets mounted in the recovery system at /mnt/local$mountpoint.
         Log "Remounting the btrfs default subvolume $subvolume_path for $device at $mountpoint"
         (
         echo "# Remounting the $subvolume_path default subvolume at $recovery_system_mountpoint"
         echo "umount $recovery_system_mountpoint"
         echo "mount -t btrfs $mountopts $device $recovery_system_mountpoint"
         echo "# End btrfs default subvolume setup on $device at $mountpoint"
         ) >> "$LAYOUT_CODE"
     done
     ###########################################
     # Mounting all btrfs normal subvolumes:
     # After the btrfs default subvolume setup now the btrfs default subvolume is mounted and then it is possible
     # to mount the other btrfs normal subvolumes at their mountpoints in the tree of the mounted filesystems:
     while read dummy dummy subvolume_mountpoint subvolume_mount_options subvolume_path junk ; do
         # Empty subvolume_mountpoint or subvolume_mount_options or subvolume_path may indicate an error.
         # E.g. missing subvolume mount options result that the subvolume path is read into subvolume_mount_options and subvolume_path becomes empty.
         # Therefore be verbose and inform the user:
         if test -z "$subvolume_mountpoint" -o -z "$subvolume_mount_options" -o -z "$subvolume_path" ; then
             LogPrint "btrfsmountedsubvol entry for $device where subvolume_mountpoint='$subvolume_mountpoint' or subvolume_mount_options='$subvolume_mount_options' or subvolume_path='$subvolume_path' is empty may indicate an error, skipping mounting it."
             continue
         fi
         # When there are non-empty values, mounting normal subvolume is needed:
         Log "Mounting normal subvolume $subvolume_path at $subvolume_mountpoint for $device"
+        # btrfs mount options like subvolid=259 or subvol=/@/.snapshots/1/snapshot
+        # from the old system cannot work here or are not needed here for recovery
+        # because for new created btrfs subvolumes their subvolid is likely different
+        # and the subvol=... value is already explicitly available via subvolume_path
+        # so that those mount options are removed here:
+        # First add a comma at the end so that it is easier to remove a mount option at the end:
+        subvolume_mount_options=${subvolume_mount_options/%/,}
+        # Remove all subvolid= and subvol= mount options (the extglob shell option is enabled in rear):
+        subvolume_mount_options=${subvolume_mount_options//subvolid=*([^,]),/}
+        subvolume_mount_options=${subvolume_mount_options//subvol=*([^,]),/}
+        # Remove all commas at the end:
+        subvolume_mount_options=${subvolume_mount_options/%,/}
         # Do not mount btrfs snapshot subvolumes:
         for snapshot_subvolume_device_and_path in $snapshot_subvolumes_devices_and_paths ; do
             # Assume $snapshot_subvolume_device_and_path is "/dev/sdX99,my/subvolume,path" then split
             # at the first comma because device nodes (e.g. /dev/sdX99) do not contain a comma
             # but a subvolume path may contain a comma (e.g. my/subvolume,path).
             # If a subvolume path contains space or tab characters it will break here
             # because space tab and newline are standard bash internal field separators ($IFS)
             # so that admins who use such characters for their subvolume paths get hereby
             # an exercise in using fail-safe names and/or how to enhance standard bash scripts:
             snapshot_subvolume_device=${snapshot_subvolume_device_and_path%%,*}
             snapshot_subvolume_path=${snapshot_subvolume_device_and_path#*,}
             if test "$device" = "$snapshot_subvolume_device" -a "$subvolume_path" = "$snapshot_subvolume_path" ; then
                 info_message="It is not possible to recreate btrfs snapshot subvolumes, skipping mounting $subvolume_path on $device at $subvolume_mountpoint"
                 Log $info_message
                 echo "# $info_message" >> "$LAYOUT_CODE"
                 # If one snapshot_subvolume_device_and_path matches,
                 # continue with the next btrfsmountedsubvol line from the LAYOUT_FILE
                 # (i.e. continue with the while loop which is the 2th enclosing loop):
                 continue 2
             fi
         done
         recovery_system_mountpoint=$recovery_system_root$subvolume_mountpoint
         # Remounting is needed when at the '/' mountpoint not the btrfs default subvolume is mounted:
         # On Fedora 21 what is mounted at the root of the filesystem tree (i.e. at the '/' mountpoint)
         # is not the btrfs default subvolume (the default subvolume is the toplevel/root subvolume).
         # On Fedora 21 there is a btrfs subvolume "root" which is mounted at the '/' mountpoint.
         # I (jsmeix@suse.de) am not a btrfs expert but from my point of view it looks like
         # a misconfiguration (a.k.a. bug) in Fedora 21 how they set up btrfs. I think Fedora
-        # should specify as btrfs default subvolume what is mounted at the '/' mountpoint.
-        # Regardless if it is really a misconfiguration or not I like to have rear working fail-safe
-        # because an admin could manually create such an awkward btrfs setup.
+        # should specify as btrfs default subvolume what is mounted by default at the '/' mountpoint.
+        # On the other hand I noticed an openSUSE user who presented arguments that
+        # the btrfs default subvolume setting only belongs to the user and
+        # should not be used by the system to specify what is mounted by default,
+        # see what Chris Murphy wrote on the "Default btrfs subvolume after a rollback"
+        # and "systemd, btrfs, /var/lib/machines" mail threads on opensuse-factory@opensuse.org
+        # http://lists.opensuse.org/opensuse-factory/2015-07/msg00517.html
+        # http://lists.opensuse.org/opensuse-factory/2015-07/msg00591.html
+        # and his GitHub snapper issue and openSUSE feature request
+        # "snapper improperly usurps control of the default subvolume from the user"
+        # https://github.com/openSUSE/snapper/issues/178
+        # https://features.opensuse.org/319292
+        # Regardless who or what is right or wrong here I like to have rear working fail-safe
+        # because an admin could manually create any kind of awkward btrfs setup.
         # Therefore remounting is needed when the subvolume_mountpoint is '/'
         # but the subvolume_path is neither '/' nor the default subvolume.
         # Examples: disklayout.conf contains
         # on openSUSE 13.2 at '/' the default subvolume which is the root subvolume (ID 5 '/') is mounted:
         #   btrfsdefaultsubvol /dev/sda2 / 5 /
         #   btrfsmountedsubvol /dev/sda2 / rw,relatime,space_cache /
         # on SLES 12 at '/' the default subvolume '@' is mounted:
         #   btrfsdefaultsubvol /dev/sda2 / 257 @
         #   btrfsmountedsubvol /dev/sda2 / rw,relatime,space_cache @
+        # on SLES 12 SP1 at '/' the default subvolume '@/.snapshots/1/snapshot' is mounted:
+        #   btrfsdefaultsubvol /dev/sda2 / 259 @/.snapshots/1/snapshot
+        #   #btrfssnapshotsubvol /dev/sda2 / 259 @/.snapshots/1/snapshot
+        #   btrfsnormalsubvol /dev/sda2 / 258 @/.snapshots
+        #   btrfsmountedsubvol /dev/sda2 / rw,relatime,space_cache,subvolid=259,subvol=/@/.snapshots/1/snapshot @/.snapshots/1/snapshot
         # on Fedora 21 at '/' not the default subvolume which is the root subvolume (ID 5 '/') but the subvolume 'root' is mounted:
         #   btrfsdefaultsubvol /dev/sda3 / 5 /
         #   btrfsmountedsubvol /dev/sda3 / rw,relatime,seclabel,space_cache root
         # FIXME: Currently only for the mountpoint '/' there is this special handling.
         # In general the subvolume_mountpoint could be anything.
         # For example for a second disk /dev/sdb1 the disklayout.conf file could contain those entries:
         #   btrfsdefaultsubvol /dev/sdb1 /data 5 /
         #   btrfsmountedsubvol /dev/sdb1 /data rw,relatime,seclabel,space_cache datasubvol
         # This would mean for /dev/sdb1 what is mounted at its mountpoint /data
         # is not its btrfs default subvolume but the btrfs subvolume "datasubvol".
         # Currently such a setup is not supported for mountpoints other than '/'.
         if test '/' = "$subvolume_mountpoint" ; then
             # No remounting needed when the subvolume_path is the default_subvolume_path for this device
             # because then the default subvolume is already mounted by the "Btrfs default subvolume setup" above:
             if test "$subvolume_path" = "$default_subvolume_path" ; then
                Log "On $device btrfs default subvolume $default_subvolume_path already mounted at $subvolume_mountpoint, no remounting needed"
                continue
diff -rp -U17 rear-1.17.2/usr/share/rear/layout/save/GNU/Linux/23_filesystem_layout.sh rear-1.17.2.SLE12-SP1-btrfs/usr/share/rear/layout/save/GNU/Linux/23_filesystem_layout.sh
--- rear-1.17.2/usr/share/rear/layout/save/GNU/Linux/23_filesystem_layout.sh	2015-06-25 09:07:56.000000000 +0200
+++ rear-1.17.2.SLE12-SP1-btrfs/usr/share/rear/layout/save/GNU/Linux/23_filesystem_layout.sh	2015-10-16 12:06:18.000000000 +0200
@@ -256,23 +256,49 @@ read_filesystems_command="$read_filesyst
                 if test -z "$btrfs_subvolume_path" ; then
                     # When btrfs_subvolume_path is empty (in particular when the traditional mount command is used)
                     # try to find the mountpoint in /etc/fstab and try to read the subvol=... option value if exists
                     # (using subvolid=... can fail because the subvolume ID can be different during system recovery).
                     # Because both "mount ... -o subvol=/path/to/subvolume" and "mount ... -o subvol=path/to/subvolume" work
                     # the subvolume path can be specified with or without leading '/':
                     btrfs_subvolume_path=$( grep " $subvolume_mountpoint btrfs " /etc/fstab | grep -o 'subvol=[^ ]*' | cut -s -d '=' -f 2 )
                 fi
                 # Remove leading '/' from btrfs_subvolume_path (except it is only '/') to have same syntax for all entries and
                 # without leading '/' is more clear that it is not an absolute path in the currently mounted tree of filesystems
                 # instead the subvolume path is relative to the toplevel/root subvolume of the particular btrfs filesystem
                 # (i.e. a subvolume path is an absolute path in the particular btrfs filesystem)
                 # see https://btrfs.wiki.kernel.org/index.php/Mount_options
                 test "/" != "$btrfs_subvolume_path" && btrfs_subvolume_path=${btrfs_subvolume_path#/}
                 echo "btrfsmountedsubvol $device $subvolume_mountpoint $mount_options $btrfs_subvolume_path"
             fi
         done < <( eval $read_mounted_btrfs_subvolumes_command )
+        ########################################
+        # No copy on write attributes of mounted btrfs subvolumes:
+        echo "# Mounted btrfs subvolumes that have the 'no copy on write' attribute set."
+        echo "# Format: btrfsnocopyonwrite <btrfs_subvolume_path>"
+        lsattr_command="$( type -P lsattr )"
+        if test -x "$lsattr_command" -a -x "$findmnt_command" ; then
+            for subvolume_mountpoint in $( $findmnt_command -nrv -o TARGET -t btrfs ) ; do
+                # The 'no copy on write' attribute is shown as 'C' in the lsattr output (see "man chattr"):
+                if $lsattr_command -d $subvolume_mountpoint | cut -d ' ' -f 1 | grep -q 'C' ; then
+                    btrfs_subvolume_path=$( $findmnt_command -nrv -o FSROOT $subvolume_mountpoint )
+                    # Remove leading '/' from btrfs_subvolume_path (except it is only '/') to have same syntax for all entries and
+                    # without leading '/' is more clear that it is not an absolute path in the currently mounted tree of filesystems
+                    # instead the subvolume path is relative to the toplevel/root subvolume of the particular btrfs filesystem
+                    # (i.e. a subvolume path is an absolute path in the particular btrfs filesystem)
+                    # see https://btrfs.wiki.kernel.org/index.php/Mount_options
+                    test "/" != "$btrfs_subvolume_path" && btrfs_subvolume_path=${btrfs_subvolume_path#/}
+                    if test -n "btrfs_subvolume_path" ; then
+                        echo "btrfsnocopyonwrite $btrfs_subvolume_path"
+                    else
+                        echo "# $subvolume_mountpoint has the 'no copy on write' attribute set but $findmnt_command does not show its btrfs subvolume path"
+                    fi
+                fi
+            done
+        else
+            echo "# Attributes cannot be determined because no executable 'lsattr' and/or 'findmnt' command(s) found."
+        fi
     fi
 
 ) >> $DISKLAYOUT_FILE
 # End writing output to DISKLAYOUT_FILE.
 Log "End saving filesystem layout"

Places

File SLE12-SP1-btrfs.patch of Package rear (Revision 7503f9eefc0673b15d14fda3e77b6f10)

Places