From d74d9789688fde1151ece6a751d1c549af87de84 Mon Sep 17 00:00:00 2001
From: Joey Hess <joeyh@joeyh.name>
Date: Mon, 5 Oct 2020 14:17:46 -0400
Subject: [PATCH] fully atomic LOCPATH populating

This fixes a race between two runshells from two different
bundles. One could have run the cache cleanup code, seen the
LOCPATH the other one was in the process of populating, which didn't
have a base or a buildid file written yet, and so the cache cleanup code
would delete it out from under the other process.

Also, doing it fully atomically simplifies where the races between two
runshell processes from the same bundle. Now that needs to be
dealt with to only the mv that puts it in place.

Note that, if the same bundle has 2 runshells run first thing, they will
both generate locales, which is unncessary work, but that should be a
very unusual circumstance and after the LOCPATH is set up, it won't
happen again anyway.
---
 standalone/linux/skel/runshell | 74 ++++++++++++++++------------------
 1 file changed, 34 insertions(+), 40 deletions(-)

diff --git a/standalone/linux/skel/runshell b/standalone/linux/skel/runshell
index 08661d3e21..e9170c0aac 100755
--- a/standalone/linux/skel/runshell
+++ b/standalone/linux/skel/runshell
@@ -142,51 +142,45 @@ if [ -z "${LOCPATH+set}" ] && [ -z "$GIT_ANNEX_PACKAGE_INSTALL" ]; then
 	export LOCPATH
 	
 	if [ ! -d "$LOCPATH" ]; then
-		if ! mkdir -p "$LOCPATH"; then
-			echo "Unable to write to $LOCPATH; can't continue!" >&2
+		if ! mkdir -p "$LOCPATH.$$"; then
+			echo "Unable to write to $LOCPATH.$$; can't continue!" >&2
 			exit 1
 		fi
-	fi
-	if [ ! -e "$LOCPATH/base" ]; then
-		echo "$base" > "$LOCPATH/base.$$"
-		mv -f "$LOCPATH/base.$$" "$LOCPATH/base"
-	fi
-	# Not using cp to avoid using the one bundled with git-annex
-	# before the environment is set up to run it.
-	if [ ! -e "$LOCPATH/buildid" ]; then
-		cat < "$base/buildid" > "$LOCPATH/buildid.$$"
-		mv -f "$LOCPATH/buildid.$$" "$LOCPATH/buildid"
-	fi
+		echo "$base" > "$LOCPATH.$$/base"
+		# Not using cp to avoid using the one bundled with git-annex
+		# before the environment is set up to run it.
+		cat < "$base/buildid" > "$LOCPATH.$$/buildid"
 
-	# Generate locale definition files for the locales in use,
-	# using the localedef and locale files from the bundle.
-	# Currently only utf-8 locales are handled.
-	lastlocaleenv=""
-	for localeenv in "$LANG" "$LANGUAGE" "$LC_CTYPE" "$LC_NUMERIC" "$LC_TIME" \
-			"$LC_COLLATE" "$LC_MONETARY" "$LC_MESSAGES" "$LC_PAPER" \
-			"$LC_NAME" "$LC_ADDRESS" "$LC_TELEPHONE" "$LC_MEASUREMENT" \
-			"$LC_IDENTIFICATION" "$LC_ALL"; do
-		if [ -n "$localeenv" ] && [ "$localeenv" != "$lastlocaleenv" ]; then
-			lastlocaleenv="$localeenv"
-			if [ ! -d "$LOCPATH/$localeenv" ]; then
-				if [ "${localeenv##[!.]*.}" = "utf8" ] || [ "${localeenv##[!.]*.}" = "UTF-8" ]; then
-					(
-						rm -rf "$LOCPATH/$localeenv.new.$$" &&
-						mkdir -p "$LOCPATH/$localeenv.new.$$" &&
-						# cd to $base since localedef reads files from pwd
-						cd "$base" &&
-						# Run localedef using the bundled i18n files;
-						# use LANG=C to avoid it reading the system locale archive.
-						I18NPATH="$base/i18n" LANG=C localedef -i "${localeenv%%.*}" -c -f UTF-8 "$LOCPATH/$localeenv.new.$$" &&
-						mv "$LOCPATH/$localeenv.new.$$" "$LOCPATH/$localeenv"
-						# In a race, LOCPATH may get created by another process,
-						# in which cache the mv above would put it here.
-						rm -rf "$LOCPATH/$localeenv/$localeenv.new.$$"
-					) >/dev/null 2>/dev/null || true
+		# Generate locale definition files for the locales in use,
+		# using the localedef and locale files from the bundle.
+		# Currently only utf-8 locales are handled.
+		lastlocaleenv=""
+		for localeenv in "$LANG" "$LANGUAGE" "$LC_CTYPE" "$LC_NUMERIC" "$LC_TIME" \
+				"$LC_COLLATE" "$LC_MONETARY" "$LC_MESSAGES" "$LC_PAPER" \
+				"$LC_NAME" "$LC_ADDRESS" "$LC_TELEPHONE" "$LC_MEASUREMENT" \
+				"$LC_IDENTIFICATION" "$LC_ALL"; do
+			if [ -n "$localeenv" ] && [ "$localeenv" != "$lastlocaleenv" ]; then
+				lastlocaleenv="$localeenv"
+				if [ ! -d "$LOCPATH.$$/$localeenv" ]; then
+					if [ "${localeenv##[!.]*.}" = "utf8" ] || [ "${localeenv##[!.]*.}" = "UTF-8" ]; then
+						(
+							mkdir -p "$LOCPATH.$$/$localeenv" &&
+							# cd to $base since localedef reads files from pwd
+							cd "$base" &&
+							# Run localedef using the bundled i18n files;
+							# use LANG=C to avoid it reading the system locale archive.
+							I18NPATH="$base/i18n" LANG=C localedef -i "${localeenv%%.*}" -c -f UTF-8 "$LOCPATH.$$/$localeenv"
+						) >/dev/null 2>/dev/null || true
+					fi
 				fi
 			fi
-		fi
-	done
+		done
+		
+		mv "$LOCPATH.$$" "$LOCPATH"
+		# In a race, LOCPATH may get created by another process,
+		# in which cache the mv above would put it here.
+		rm -rf "$LOCPATH/$LOCPATH.$$"
+	fi
 	
 	# Clean up locale caches when their standalone bundle no longer exists.
 	for localecache in $HOME/.cache/git-annex/locales/*; do