libe2p: add a thread-safe variant of e2p_feature2string

This commit adds the function e2p_feature_to_string() which allows the
caller to pass in a preallocated buffer.

Google-Bug-Id: 16978603
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

2 files changed, 16 insertions, 4 deletions

diff --git a/lib/e2p/e2p.h b/lib/e2p/e2p.h
index c3a6b2587..ae7dd74dd 100644
--- a/lib/e2p/e2p.h
+++ b/lib/e2p/e2p.h
@@ -50,6 +50,8 @@ int setversion (int fd, unsigned long version);
 void e2p_list_journal_super(FILE *f, char *journal_sb_buf,
 			    int exp_block_size, int flags);
 
+void e2p_feature_to_string(int compat, unsigned int mask, char *buf,
+                           size_t buf_len);
 const char *e2p_feature2string(int compat, unsigned int mask);
 const char *e2p_jrnl_feature2string(int compat, unsigned int mask);
 int e2p_string2feature(char *string, int *compat, unsigned int *mask);
diff --git a/lib/e2p/feature.c b/lib/e2p/feature.c
index ae7f7f0aa..515a0f881 100644
--- a/lib/e2p/feature.c
+++ b/lib/e2p/feature.c
@@ -135,17 +135,20 @@ static struct feature jrnl_feature_list[] = {
        {       0, 0, 0 },
 };
 
-const char *e2p_feature2string(int compat, unsigned int mask)
+void e2p_feature_to_string(int compat, unsigned int mask, char *buf,
+                           size_t buf_len)
 {
 	struct feature  *f;
-	static char buf[20];
 	char	fchar;
 	int	fnum;
 
 	for (f = feature_list; f->string; f++) {
 		if ((compat == f->compat) &&
-		    (mask == f->mask))
-			return f->string;
+		    (mask == f->mask)) {
+			strncpy(buf, f->string, buf_len);
+			buf[buf_len - 1] = 0;
+			return;
+		}
 	}
 	switch (compat) {
 	case  E2P_FEATURE_COMPAT:
@@ -163,6 +166,13 @@ const char *e2p_feature2string(int compat, unsigned int mask)
 	}
 	for (fnum = 0; mask >>= 1; fnum++);
 	sprintf(buf, "FEATURE_%c%d", fchar, fnum);
+}
+
+const char *e2p_feature2string(int compat, unsigned int mask)
+{
+	static char buf[20];
+
+	e2p_feature_to_string(compat, mask, buf, sizeof(buf) / sizeof(buf[0]));
 	return buf;
 }