From c57be0b4d6a5a9e6a54cf30acbb9cedf597ae899 Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andriin@fb.com>
Date: Mon, 10 Aug 2020 21:51:53 -0700
Subject: [PATCH] vmtests: speed up fetching of bpf-next sources

Attempt to first fetch bpf-next tree from a snapshot, falling back to shallow
clone, and if that is not enough, doing a full bpf-next clone. This should
both improve a speed and (because of full clone fallback) improve test
reliability if libbpf wasn't synced in a while.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 travis-ci/vmtest/checkout_latest_kernel.sh | 30 ++++++++++++++++------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/travis-ci/vmtest/checkout_latest_kernel.sh b/travis-ci/vmtest/checkout_latest_kernel.sh
index b108e7b..2bfcd3e 100755
--- a/travis-ci/vmtest/checkout_latest_kernel.sh
+++ b/travis-ci/vmtest/checkout_latest_kernel.sh
@@ -8,17 +8,31 @@ REPO_PATH=$1
 
 BPF_NEXT_ORIGIN=https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git
 LINUX_SHA=$(cat ${LIBBPF_PATH}/CHECKPOINT-COMMIT)
+SNAPSHOT_URL=https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/snapshot/bpf-next-${LINUX_SHA}.tar.gz
 
 echo REPO_PATH = ${REPO_PATH}
 echo LINUX_SHA = ${LINUX_SHA}
 
 if [ ! -d "${REPO_PATH}" ]; then
-	mkdir -p ${REPO_PATH}
-	cd ${REPO_PATH}
-	git init
-	git remote add bpf-next ${BPF_NEXT_ORIGIN}
-	for depth in 32 64 128; do
-		git fetch --depth ${depth} bpf-next
-		git reset --hard ${LINUX_SHA} && break
-	done
+	mkdir -p $(dirname "${REPO_PATH}")
+	cd $(dirname "${REPO_PATH}")
+	# attempt to fetch desired bpf-next repo snapshot
+	if wget ${SNAPSHOT_URL} ; then
+		tar xf bpf-next-${LINUX_SHA}.tar.gz
+		mv bpf-next-${LINUX_SHA} $(basename ${REPO_PATH})
+	else
+		# but fallback to git fetch approach if that fails
+		mkdir -p ${REPO_PATH}
+		cd ${REPO_PATH}
+		git init
+		git remote add bpf-next ${BPF_NEXT_ORIGIN}
+		# try shallow clone first
+		git fetch --depth 32 bpf-next
+		# check if desired SHA exists
+		if ! git cat-file -e ${LINUX_SHA}^{commit} ; then
+			# if not, fetch all of bpf-next; slow and painful
+			git fetch bpf-next
+		fi
+		git reset --hard ${LINUX_SHA}
+	fi
 fi