Use dynamic file descriptor numbers in ztest.

Currently, ztest expects to get 3 and 4 as the file descriptors for
data and random files, respectively. This is quite fragile and breaks
easily if ztest is run with these file descriptors already opened
(e.g. in a complex shell script).

This patch fixes the issue by removing the assumptions on the file
descriptor numbers that open() returns.

For the random file (/dev/urandom), the new code doesn't rely on a
shared file descriptor; instead, it reopens the file in the child.

For the data file, the new code writes the file descriptor number into
a "ZTEST_FD_DATA" environment variable so that it can be recovered
after the execv() call.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index 9da15a1859adea90f6fff70b5bee760d74238e73..973e7b2f6a80c2454cd85bebabb7dbd3acc57dc0 100644 (file)
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -121,8 +121,8 @@
 #include <sys/fs/zfs.h>
 #include <libnvpair.h>
 
-#define        ZTEST_FD_DATA 3
-#define        ZTEST_FD_RAND 4
+static int ztest_fd_data = -1;
+static int ztest_fd_rand = -1;
 
 typedef struct ztest_shared_hdr {
        uint64_t        zh_hdr_size;
@@ -783,10 +783,12 @@ ztest_random(uint64_t range)
 {
        uint64_t r;
 
+       ASSERT3S(ztest_fd_rand, >=, 0);
+
        if (range == 0)
                return (0);
 
-       if (read(ZTEST_FD_RAND, &r, sizeof (r)) != sizeof (r))
+       if (read(ztest_fd_rand, &r, sizeof (r)) != sizeof (r))
                fatal(1, "short read from /dev/urandom");
 
        return (r % range);
@@ -5815,26 +5817,13 @@ ztest_init(ztest_shared_t *zs)
 }
 
 static void
-setup_fds(void)
+setup_data_fd(void)
 {
-       int fd;
-
        char *tmp = tempnam(NULL, NULL);
-       fd = open(tmp, O_RDWR | O_CREAT, 0700);
-       ASSERT3S(fd, >=, 0);
-       if (fd != ZTEST_FD_DATA) {
-               VERIFY3S(dup2(fd, ZTEST_FD_DATA), ==, ZTEST_FD_DATA);
-               close(fd);
-       }
+       ztest_fd_data = open(tmp, O_RDWR | O_CREAT, 0700);
+       ASSERT3S(ztest_fd_data, >=, 0);
        (void) unlink(tmp);
        free(tmp);
-
-       fd = open("/dev/urandom", O_RDONLY);
-       ASSERT3S(fd, >=, 0);
-       if (fd != ZTEST_FD_RAND) {
-               VERIFY3S(dup2(fd, ZTEST_FD_RAND), ==, ZTEST_FD_RAND);
-               close(fd);
-       }
 }
 
 static int
@@ -5858,10 +5847,10 @@ setup_hdr(void)
        ztest_shared_hdr_t *hdr;
 
        hdr = (void *)mmap(0, P2ROUNDUP(sizeof (*hdr), getpagesize()),
-           PROT_READ | PROT_WRITE, MAP_SHARED, ZTEST_FD_DATA, 0);
+           PROT_READ | PROT_WRITE, MAP_SHARED, ztest_fd_data, 0);
        ASSERT(hdr != MAP_FAILED);
 
-       VERIFY3U(0, ==, ftruncate(ZTEST_FD_DATA, sizeof (ztest_shared_hdr_t)));
+       VERIFY3U(0, ==, ftruncate(ztest_fd_data, sizeof (ztest_shared_hdr_t)));
 
        hdr->zh_hdr_size = sizeof (ztest_shared_hdr_t);
        hdr->zh_opts_size = sizeof (ztest_shared_opts_t);
@@ -5872,7 +5861,7 @@ setup_hdr(void)
        hdr->zh_ds_count = ztest_opts.zo_datasets;
 
        size = shared_data_size(hdr);
-       VERIFY3U(0, ==, ftruncate(ZTEST_FD_DATA, size));
+       VERIFY3U(0, ==, ftruncate(ztest_fd_data, size));
 
        (void) munmap((caddr_t)hdr, P2ROUNDUP(sizeof (*hdr), getpagesize()));
 }
@@ -5885,14 +5874,14 @@ setup_data(void)
        uint8_t *buf;
 
        hdr = (void *)mmap(0, P2ROUNDUP(sizeof (*hdr), getpagesize()),
-           PROT_READ, MAP_SHARED, ZTEST_FD_DATA, 0);
+           PROT_READ, MAP_SHARED, ztest_fd_data, 0);
        ASSERT(hdr != MAP_FAILED);
 
        size = shared_data_size(hdr);
 
        (void) munmap((caddr_t)hdr, P2ROUNDUP(sizeof (*hdr), getpagesize()));
        hdr = ztest_shared_hdr = (void *)mmap(0, P2ROUNDUP(size, getpagesize()),
-           PROT_READ | PROT_WRITE, MAP_SHARED, ZTEST_FD_DATA, 0);
+           PROT_READ | PROT_WRITE, MAP_SHARED, ztest_fd_data, 0);
        ASSERT(hdr != MAP_FAILED);
        buf = (uint8_t *)hdr;
 
@@ -5925,9 +5914,15 @@ exec_child(char *cmd, char *libpath, boolean_t ignorekill, int *statusp)
 
        if (pid == 0) { /* child */
                char *emptyargv[2] = { cmd, NULL };
+               char fd_data_str[12];
 
                struct rlimit rl = { 1024, 1024 };
                (void) setrlimit(RLIMIT_NOFILE, &rl);
+
+               (void) close(ztest_fd_rand);
+               VERIFY(11 >= snprintf(fd_data_str, 12, "%d", ztest_fd_data));
+               VERIFY(0 == setenv("ZTEST_FD_DATA", fd_data_str, 1));
+
                (void) enable_extended_FILE_stdio(-1, -1);
                if (libpath != NULL)
                        VERIFY(0 == setenv("LD_LIBRARY_PATH", libpath, 1));
@@ -6005,22 +6000,24 @@ main(int argc, char **argv)
        char cmd[MAXNAMELEN];
        boolean_t hasalt;
        int f;
-       boolean_t ischild = (0 == lseek(ZTEST_FD_DATA, 0, SEEK_CUR));
-
-       ASSERT(ischild || errno == EBADF || errno == ESPIPE);
+       char *fd_data_str = getenv("ZTEST_FD_DATA");
 
        (void) setvbuf(stdout, NULL, _IOLBF, 0);
 
-       if (!ischild) {
+       ztest_fd_rand = open("/dev/urandom", O_RDONLY);
+       ASSERT3S(ztest_fd_rand, >=, 0);
+
+       if (!fd_data_str) {
                dprintf_setup(&argc, argv);
                process_options(argc, argv);
 
-               setup_fds();
+               setup_data_fd();
                setup_hdr();
                setup_data();
                bcopy(&ztest_opts, ztest_shared_opts,
                    sizeof (*ztest_shared_opts));
        } else {
+               ztest_fd_data = atoi(fd_data_str);
                setup_data();
                bcopy(ztest_shared_opts, &ztest_opts, sizeof (ztest_opts));
        }
@@ -6029,12 +6026,12 @@ main(int argc, char **argv)
        /* Override location of zpool.cache */
        (void) asprintf((char **)&spa_config_path, "%s/zpool.cache",
            ztest_opts.zo_dir);
-       
+
        ztest_ds = umem_alloc(ztest_opts.zo_datasets * sizeof (ztest_ds_t),
            UMEM_NOFAIL);
        zs = ztest_shared;
 
-       if (ischild) {
+       if (fd_data_str) {
                metaslab_gang_bang = ztest_opts.zo_metaslab_gang_bang;
                metaslab_df_alloc_threshold =
                    zs->zs_metaslab_df_alloc_threshold;