diff --git a/tests/xfs/779 b/tests/xfs/779
new file mode 100755
index 00000000..f064879c
--- /dev/null
+++ b/tests/xfs/779
@@ -0,0 +1,112 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2021 Oracle.  All Rights Reserved.
+#
+# FS QA Test 779
+#
+# Test for xfs_growfs to make sure that we can add a realtime device and set
+# its extent size hint at the same time.  This also checks for the presence of
+# these patches:
+#
+#	xfs: improve FSGROWFSRT precondition checking
+#	xfs: fix an integer overflow error in xfs_growfs_rt
+#	xfs: correct the narrative around misaligned rtinherit/extszinherit dirs
+#	xfs: don't expose misaligned extszinherit hints to userspace
+#
+. ./common/preamble
+_begin_fstest auto quick realtime growfs
+
+# Import common functions.
+. ./common/filter
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs generic
+_require_realtime
+_require_scratch
+
+# Format scratch fs with no realtime section.
+SCRATCH_RTDEV="" _scratch_mkfs | _filter_mkfs 2> $tmp.mkfs >> $seqres.full
+_scratch_mount
+
+# Check that there's no realtime section.
+source $tmp.mkfs
+test $rtblocks -eq 0 || echo "expected 0 rtblocks, got $rtblocks"
+
+# Compute a new rt extent size and a separate rt extent size hint to exercise
+# the code that ignores hints that aren't a multiple of the extent size.
+XFS_MAX_RTEXTSIZE=$((1024 * 1024 * 1024))
+new_rtextsz=$((rtextsz + dbsize))
+if [ $new_rtextsz -gt $XFS_MAX_RTEXTSIZE ]; then
+	new_rtextsz=$((rtextsz - dbsize))
+fi
+new_rtextsz_blocks=$(( new_rtextsz / dbsize ))
+
+new_extszhint=$((rtextsz * 2))
+if [ $new_extszhint -eq $new_rtextsz ]; then
+	new_extszhint=$((rtextsz * 3))
+fi
+
+# Set the inheritable extent size hint and rt status.
+$XFS_IO_PROG -c 'chattr +t' -c "extsize $new_extszhint" $SCRATCH_MNT
+
+# Check that the hint was set correctly
+after_extszhint=$($XFS_IO_PROG -c 'stat' $SCRATCH_MNT | \
+	grep 'fsxattr.extsize' | cut -d ' ' -f 3)
+test $after_extszhint -eq $new_extszhint || \
+	echo "expected extszhint $new_extszhint, got $after_extszhint"
+
+# Add a realtime section and change the extent size.
+echo $XFS_GROWFS_PROG -e $new_rtextsz_blocks -r $SCRATCH_MNT >> $seqres.full
+$XFS_GROWFS_PROG -e $new_rtextsz_blocks -r $SCRATCH_MNT >> $seqres.full 2> $tmp.growfs
+res=$?
+cat $tmp.growfs
+
+# If the growfs failed, skip the post-test check because the scratch fs does
+# not have SCRATCH_RTDEV configured.  If the kernel didn't support adding the
+# rt volume, skip everything else.
+if [ $res -ne 0 ]; then
+	rm -f ${RESULT_DIR}/require_scratch
+	if grep -q "Operation not supported" $tmp.growfs; then
+		_notrun "growfs not supported on rt volume"
+	fi
+fi
+
+# Now that the root directory's extsize hint is no longer aligned to the rt
+# extent size, check that we don't report it to userspace any more.
+grow_extszhint=$($XFS_IO_PROG -c 'stat' $SCRATCH_MNT | \
+	grep 'fsxattr.extsize' | cut -d ' ' -f 3)
+test $grow_extszhint -eq 0 || \
+	echo "expected post-grow extszhint 0, got $grow_extszhint"
+
+# Check that we now have rt extents.
+rtextents=$($XFS_IO_PROG -c 'statfs' $SCRATCH_MNT | \
+	grep 'geom.rtextents' | cut -d ' ' -f 3)
+test $rtextents -gt 0 || echo "expected rtextents > 0"
+
+# Check the new rt extent size.
+after_rtextsz_blocks=$($XFS_IO_PROG -c 'statfs' $SCRATCH_MNT | \
+	grep 'geom.rtextsize' | cut -d ' ' -f 3)
+test $after_rtextsz_blocks -eq $new_rtextsz_blocks || \
+	echo "expected rtextsize $new_rtextsz_blocks, got $after_rtextsz_blocks"
+
+# Create a new realtime file to prove that we can.
+echo moo > $SCRATCH_MNT/a
+sync
+$XFS_IO_PROG -c 'lsattr -v' $SCRATCH_MNT/a | \
+	cut -d ' ' -f 1 | \
+	grep -q realtime || \
+	echo "$SCRATCH_MNT/a is not a realtime file?"
+
+# Check that the root directory's hint (which was aligned before the grow and
+# misaligned after) did not propagate to the new realtime file.
+file_extszhint=$($XFS_IO_PROG -c 'stat' $SCRATCH_MNT/a | \
+	grep 'fsxattr.extsize' | cut -d ' ' -f 3)
+test $file_extszhint -eq 0 || \
+	echo "expected file extszhint 0, got $file_extszhint"
+
+# success, all done
+echo Silence is golden
+status=0
+exit
diff --git a/tests/xfs/779.out b/tests/xfs/779.out
new file mode 100644
index 00000000..1f79fae2
--- /dev/null
+++ b/tests/xfs/779.out
@@ -0,0 +1,2 @@
+QA output created by 779
+Silence is golden
