[lxc-devel] [lxcfs/master] Fix `get_min_memlimit()` on non-glibc

[devplayer0 on Github]

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From db36731bf3598d0f6fe5f493b1df59ed6edd16ce Mon Sep 17 00:00:00 2001
From: Jack O'Sullivan <jackos1998 at gmail.com>
Date: Thu, 3 Sep 2020 22:39:05 +0100
Subject: [PATCH] Fix `get_min_memlimit()` on non-glibc

Signed-off-by: Jack O'Sullivan <j at ckos.ie>
---
 src/proc_fuse.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/proc_fuse.c b/src/proc_fuse.c
index a99162c..7e957d0 100644
--- a/src/proc_fuse.c
+++ b/src/proc_fuse.c
@@ -213,6 +213,25 @@ static uint64_t get_memlimit(const char *cgroup, bool swap)
 	return memlimit;
 }
 
+/*
+ * dirname() behaves differently on musl than glibc, so implement the bits we
+ * need (the path in this case is always absolute and never ends in a `/`)
+ */
+static char *cgroup_parent(char *cgroup)
+{
+	if (strcmp(cgroup, "/") == 0) {
+		return cgroup;
+	}
+
+	char *last_slash = strrchr(cgroup, '/');
+	if (last_slash == cgroup) {
+		last_slash++;
+	}
+	*last_slash = '\0';
+
+	return cgroup;
+}
+
 static uint64_t get_min_memlimit(const char *cgroup, bool swap)
 {
 	__do_free char *copy = NULL;
@@ -227,7 +246,7 @@ static uint64_t get_min_memlimit(const char *cgroup, bool swap)
 	while (strcmp(copy, "/") != 0) {
 		char *it = copy;
 
-		it = dirname(it);
+		it = cgroup_parent(it);
 		memlimit = get_memlimit(it, swap);
 		if (memlimit > 0 && memlimit < retlimit)
 			retlimit = memlimit;