posix_fallocate can be interrupted by a signal #451
Description
Every now and then, use of any Pacemaker cmdline tool fails and results in Pacemaker logging errors:
(pcmk__new_client) debug: New IPC client 3efdbecf-c2d9-44bc-b4a6-9bcd48021ba1 for PID 27492 with uid 0 and gid 0
(handle_new_connection) debug: IPC credentials authenticated (/dev/shm/qb-7271-27492-12-hfPbKY/qb)
(qb_ipcs_shm_connect) debug: connecting to client [27492]
(qb_rb_open_2) debug: shm size:524301; real_size:528384; rb->word_size:132096
(qb_rb_open_2) debug: shm size:524301; real_size:528384; rb->word_size:132096
(qb_sys_mmap_file_open) error: couldn't allocate file /dev/shm/qb-7271-27492-12-hfPbKY/qb-event-cib_rw-data: Interrupted system call (4)
(qb_rb_open_2) error: couldn't create file for mmap
(qb_ipcs_shm_rb_open) error: qb_rb_open:/dev/shm/qb-7271-27492-12-hfPbKY/qb-event-cib_rw: Interrupted system call (4)
(qb_rb_close_helper) debug: Free'ing ringbuffer: /dev/shm/qb-7271-27492-12-hfPbKY/qb-response-cib_rw-header
(qb_rb_close_helper) debug: Free'ing ringbuffer: /dev/shm/qb-7271-27492-12-hfPbKY/qb-request-cib_rw-header
(qb_ipcs_shm_connect) error: shm connection FAILED: Interrupted system call (4)
(handle_new_connection) error: Error in connection setup (/dev/shm/qb-7271-27492-12-hfPbKY/qb): Interrupted system call (4)
The way we worked around it is with a silly "retry" logic in qb_sys_mmap_file_open(). Not sure if this is the best solution, but it proved to be "good enough":
--- a/lib/unix.c 2020-07-29 08:37:35.000000000 +0200
+++ b/lib/unix.c 2021-01-28 21:01:43.984432610 +0100
@@ -79,6 +79,9 @@
ssize_t written;
char *buffer = NULL;
char *is_absolute = strchr(file, '/');
+#ifdef HAVE_POSIX_FALLOCATE
+ int32_t fallocate_retry = 5;
+#endif
if (is_absolute) {
(void)strlcpy(path, file, PATH_MAX);
@@ -116,12 +119,22 @@
}
#ifdef HAVE_POSIX_FALLOCATE
- if ((res = posix_fallocate(fd, 0, bytes)) != 0) {
- errno = res;
- res = -1 * res;
- qb_util_perror(LOG_ERR, "couldn't allocate file %s", path);
- goto unlink_exit;
- }
+ /* posix_fallocate(3) can be interrupted by a signal,
+ so retry few times before giving up */
+ do {
+ fallocate_retry--;
+ res = posix_fallocate(fd, 0, bytes);
+ if (res == EINTR) {
+ qb_util_log(LOG_DEBUG, "got EINTR trying to allocate file %s, retrying...", path);
+ continue;
+ } else if (res != 0) {
+ errno = res;
+ res = -1 * res;
+ qb_util_perror(LOG_ERR, "couldn't allocate file %s", path);
+ goto unlink_exit;
+ }
+ break;
+ } while (fallocate_retry > 0);
#else
if (file_flags & O_CREAT) {
long page_size = sysconf(_SC_PAGESIZE);