--- wikisrc/projects/project/ffs-discard.mdwn	2015/11/25 07:23:21	1.1
+++ wikisrc/projects/project/ffs-discard.mdwn	2016/08/26 19:35:19	1.2
@@ -14,7 +14,7 @@ difficulty="medium"
 duration="2-3 months"
 
 description="""
-The fdiscard system call, and the file-system-level discard operation
+The fdiscard system call, and the file-system-level VOP_DISCARD operation
 backing it, allow dropping ranges of blocks from files to create
 sparse files with holes.
 This is a simple generalization of truncate.
@@ -24,6 +24,9 @@ Discard is not currently implemented for
 It should be possible to do so by generalizing the existing truncate
 code; this should be not super-difficult, but somewhat messy.
 
+Note that it's important (for both the WAPBL and non-WAPBL cases) to
+preserve the on-disk invariants needed for successful crash recovery.
+
 """
 
 ]]