rear/rear-skip-useless-xfs-mount-options-RHEL-10478.patch

commit ed4c78d5fe493ea368989d0086a733653692f5cb
Merge: 3c9398bb 0cdcab02
Author: pcahyna <pcahyna@users.noreply.github.com>
Date:   Mon Oct 30 18:31:01 2023 +0100

    Merge pull request #3058 from pcahyna/skip-useless-xfs-mount-options
    
    Skip useless xfs mount options when mounting during recovery

    Cherry-picked-by: Lukáš Zaoral <lzaoral@redhat.com>

diff --git a/usr/share/rear/layout/prepare/GNU/Linux/133_include_mount_filesystem_code.sh b/usr/share/rear/layout/prepare/GNU/Linux/133_include_mount_filesystem_code.sh
index d5707779..f7115f55 100644
--- a/usr/share/rear/layout/prepare/GNU/Linux/133_include_mount_filesystem_code.sh
+++ b/usr/share/rear/layout/prepare/GNU/Linux/133_include_mount_filesystem_code.sh
@@ -29,6 +29,7 @@ mount_fs() {
         case $name in
             (options)
                 # Do not mount nodev, as chrooting later on would fail:
+                # FIXME: naive approach, will replace any "nodev" inside longer options/values
                 value=${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
@@ -36,13 +37,8 @@ mount_fs() {
                 # so that those mount options are removed here. All btrfs subvolume handling
                 # happens in the btrfs_subvolumes_setup_SLES function in 136_include_btrfs_subvolumes_SLES_code.sh
                 # or in the btrfs_subvolumes_setup_generic function in 135_include_btrfs_subvolumes_generic_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/%,/}
+                # Remove all subvolid= and subvol= mount options:
+                mountopts="$( remove_mount_options_values $value subvolid subvol )"
                 ;;
         esac
     done
@@ -147,6 +143,27 @@ mount_fs() {
             echo "mount $mountopts,remount,user_xattr $device $TARGET_FS_ROOT$mountpoint"
             ) >> "$LAYOUT_CODE"
             ;;
+        (xfs)
+            # remove logbsize=... mount option. It is a purely performance/memory usage optimization option,
+            # which can lead to mount failures, because it must be an integer multiple of the log stripe unit
+            # and the log stripe unit can be different in the recreated filesystem from the original filesystem
+            # (for example when using MKFS_XFS_OPTIONS, or in some exotic situations involving an old filesystem,
+            # see GitHub issue #2777 ).
+            # If logbsize is not an integer multiple of the log stripe unit, mount fails with the warning
+            # "XFS (...): logbuf size must be greater than or equal to log stripe size"
+            # in the kernel log
+            # (and a confusing error message
+            # "mount: ...: wrong fs type, bad option, bad superblock on ..., missing codepage or helper program, or other error."
+            # from the mount command), causing the layout restoration in the recovery process to fail.
+            # Wrong sunit/swidth can cause mount to fail as well, with this in the kernel log:
+            # "kernel: XFS (...): alignment check failed: sunit/swidth vs. agsize",
+            # so remove the sunit=.../swidth=... mount options as well.
+            mountopts="$( remove_mount_options_values "$mountopts" logbsize sunit swidth )"
+            (
+            echo "mkdir -p $TARGET_FS_ROOT$mountpoint"
+            echo "mount $mountopts $device $TARGET_FS_ROOT$mountpoint"
+            ) >> "$LAYOUT_CODE"
+            ;;
         (*)
             (
             echo "mkdir -p $TARGET_FS_ROOT$mountpoint"
diff --git a/usr/share/rear/lib/filesystems-functions.sh b/usr/share/rear/lib/filesystems-functions.sh
index f459c204..f0547706 100644
--- a/usr/share/rear/lib/filesystems-functions.sh
+++ b/usr/share/rear/lib/filesystems-functions.sh
@@ -256,3 +256,40 @@ function total_target_fs_used_disk_space() {
   # Output xfs options for further use
   echo "$xfs_opts"
 }
+
+
+# $1 is a mount command argument (string containing comma-separated
+# mount options). The remaining arguments to the function ($2 ... )
+# specify the mount options to remove from $1, together with a trailing "="
+# and any value that follows each option.
+# For example, the call
+# "remove_mount_options_values nodev,uid=1,rw,gid=1 uid gid"
+# returns "nodev,rw".
+# There is no support for removing a mount option without a value and "=",
+# so "remove_mount_options_values nodev,uid=1,rw,gid=1 rw" will not work.
+# The function will return the modified string on stdout.
+
+function remove_mount_options_values () {
+    local str="$1"
+
+    shift
+    # First add a comma at the end so that it is easier to remove a mount option at the end:
+    str="${str/%/,}"
+    for i in "$@" ; do
+        # FIXME this also removes trailing strings at the end of longer words
+        # For example if one wants to remove any id=... option,
+        # the function will also replace "uid=1" by "u" by removing
+        # the trailing "id=1", which is not intended.
+        # Not easy to fix because $str can contain prefixes which are not
+        # mount options but arguments to the mount command itself
+        # (in particluar, "-o ").
+        # FIXME this simple approach would fail in case of mount options
+        # containing commas, for example the "context" option values,
+        # see mount(8)
+
+        # the extglob shell option is enabled in rear
+        str="${str//$i=*([^,]),/}"
+    done
+    # Remove all commas at the end:
+    echo "${str/%,/}"
+}