[PATCH] sstate: A third fix for for touching files inside pseudo

[Peter Kjellerstedt <pkj@axis.com>]

This continues where commit676757f "sstate: fix touching files inside
pseudo" and commit 29fc8599 "sstate: another fix for touching files
inside pseudo" left off.

The previous changes switched from trying to check if the sstate file is
writable before touching it, to always touching the sstate file and
ignoring any errors. However, if the sstate file is actually a symbolic
link that links to nothing, this would actually result in an empty
sstate file being created. And this in turn leads to that future
setscene tasks will fail when they try to unpack the empty file.

Change the code so that if an sstate file linking to nothing already
exists, it is overwritten with the new sstate file. Also change it so
that the temporary file that is used is always removed, even if ln
fails to link the sstate file to it.

Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
---
 meta/classes/sstate.bbclass | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/meta/classes/sstate.bbclass b/meta/classes/sstate.bbclass
index b45da4fb23..17dcf4cc17 100644
--- a/meta/classes/sstate.bbclass
+++ b/meta/classes/sstate.bbclass
@@ -862,14 +862,18 @@ sstate_create_package () {
 	fi
 	chmod 0664 $TFILE
 	# Skip if it was already created by some other process
-	if [ ! -e ${SSTATE_PKG} ]; then
+	if [ -h ${SSTATE_PKG} ] && [ ! -e ${SSTATE_PKG} ]; then
+		# There is a symbolic link, but it links to nothing.
+		# Forcefully replace it with the new file.
+		ln -f $TFILE ${SSTATE_PKG} || true
+	elif [ ! -e ${SSTATE_PKG} ]; then
 		# Move into place using ln to attempt an atomic op.
 		# Abort if it already exists
-		ln $TFILE ${SSTATE_PKG} && rm $TFILE
+		ln $TFILE ${SSTATE_PKG} || true
 	else
-		rm $TFILE
+		touch ${SSTATE_PKG} 2>/dev/null || true
 	fi
-	touch ${SSTATE_PKG} 2>/dev/null || true
+	rm $TFILE
 }
 
 python sstate_sign_package () {
@@ -905,7 +909,7 @@ sstate_unpack_package () {
 
 	tar -I "$ZSTD" -xvpf ${SSTATE_PKG}
 	# update .siginfo atime on local/NFS mirror if it is a symbolic link
-	[ ! -h ${SSTATE_PKG}.siginfo ] || touch -a ${SSTATE_PKG}.siginfo 2>/dev/null || true
+	[ ! -h ${SSTATE_PKG}.siginfo ] || [ ! -e ${SSTATE_PKG}.siginfo ] || touch -a ${SSTATE_PKG}.siginfo 2>/dev/null || true
 	# update each symbolic link instead of any referenced file
 	touch --no-dereference ${SSTATE_PKG} 2>/dev/null || true
 	[ ! -e ${SSTATE_PKG}.sig ] || touch --no-dereference ${SSTATE_PKG}.sig 2>/dev/null || true