From 5d0b180f798ca53cc04be4cec82c7c56b6c25d97 Mon Sep 17 00:00:00 2001
From: Mathias Kresin <dev@kresin.me>
Date: Tue, 9 Aug 2016 08:22:24 +0200
Subject: [PATCH] tools: flock: add NFSv4 compatibility
This patch fixes the LEDE build on mounted NFSv4 shares.
The lock file cannot be opened in read-write mode by default, because
then we cannot use flock(1) to lock executable files.
The read-write mode for lock files is necessary on NFSv4 where
flock(2) is emulated by by fcntl() -- this situation is possible to
detect by flock(2) EBADF error.
The patch consist of the following util-linux/flock commits
http://git.kernel.org/cgit/utils/util-linux/util-linux.git/commit/?id=eb742a1f66d5e3a7c5b43efce741c113f51bef3b
http://git.kernel.org/cgit/utils/util-linux/util-linux.git/commit/?id=caf1ba11a367ad702fb774653daf9ebdcca49d7b
without including the pre kernel 3.4 support.
Signed-off-by: Mathias Kresin <dev@kresin.me>
Signed-off-by: Felix Fietkau <nbd@nbd.name> [minor cleanup]
---
tools/flock/src/flock.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/tools/flock/src/flock.c b/tools/flock/src/flock.c
index 3ac3a4bebc..37ab0ea72d 100644
--- a/tools/flock/src/flock.c
+++ b/tools/flock/src/flock.c
@@ -133,6 +133,7 @@ int main(int argc, char *argv[])
int do_close = 0;
int err;
int status;
+ int open_flags = 0;
char *eon;
char **cmd_argv = NULL, *sh_c_argv[4];
const char *filename = NULL;
@@ -266,6 +267,21 @@ int main(int argc, char *argv[])
if ( timeout_expired )
exit(1); /* -w option set and failed to lock */
continue; /* otherwise try again */
+ case EBADF: /* since Linux 3.4 (commit 55725513) */
+ /* Probably NFSv4 where flock() is emulated by fcntl().
+ * Let's try to reopen in read-write mode.
+ */
+ if (!(open_flags & O_RDWR) &&
+ type != LOCK_SH &&
+ filename &&
+ access(filename, R_OK | W_OK) == 0) {
+
+ close(fd);
+ open_flags = O_RDWR;
+ fd = open(filename, open_flags);
+ break;
+ }
+ /* go through */
default: /* Other errors */
if ( filename )
fprintf(stderr, "%s: %s: %s\n", program, filename, strerror(err));
--
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