[Libguestfs] [PATCH v2] lib: Use qemu-img info -U option to avoid locking error.

https://bugs.launchpad.net/qemu/+bug/1740364 --- lib/guestfs-internal.h | 3 +++ lib/handle.c | 2 ++ lib/info.c | 39 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 44 insertions(+) diff --git a/lib/guestfs-internal.h b/lib/guestfs-internal.h index adeb9478a..c66c55e70 100644 --- a/lib/guestfs-internal.h +++ b/lib/guestfs-internal.h @@ -510,6 +510,9 @@ struct guestfs_h { /* Cached features. */ struct cached_feature *features; size_t nr_features; + + /* Used by lib/info.c. -1 = not tested or error; else 0 or 1. */ + int qemu_img_supports_U_option; }; /** diff --git a/lib/handle.c b/lib/handle.c index a47aaafab..297ff6d67 100644 --- a/lib/handle.c +++ b/lib/handle.c @@ -101,6 +101,8 @@ guestfs_create_flags (unsigned flags, ...) g->memsize = DEFAULT_MEMSIZE; + g->qemu_img_supports_U_option = -1; /* not tested, see lib/info.c */ + /* Start with large serial numbers so they are easy to spot * inside the protocol. */ diff --git a/lib/info.c b/lib/info.c index 2eadc1c11..74e4424b8 100644 --- a/lib/info.c +++ b/lib/info.c @@ -57,6 +57,7 @@ cleanup_json_t_decref (void *ptr) #endif static json_t *get_json_output (guestfs_h *g, const char *filename); +static int qemu_img_supports_U_option (guestfs_h *g); static void set_child_rlimits (struct command *); char * @@ -149,6 +150,11 @@ get_json_output (guestfs_h *g, const char *filename) guestfs_int_cmd_add_arg (cmd, "qemu-img"); guestfs_int_cmd_add_arg (cmd, "info"); + switch (qemu_img_supports_U_option (g)) { + case -1: return NULL; + case 0: break; + default: guestfs_int_cmd_add_arg (cmd, "-U"); + } guestfs_int_cmd_add_arg (cmd, "--output"); guestfs_int_cmd_add_arg (cmd, "json"); if (filename[0] == '/') @@ -218,3 +224,36 @@ set_child_rlimits (struct command *cmd) guestfs_int_cmd_set_child_rlimit (cmd, RLIMIT_CPU, 10 /* seconds */); #endif } + +/** + * Test if the qemu-img info command supports the C<-U> option to + * disable locking. The result is memoized in the handle. + * + * Note this option was added in qemu 2.11. We can remove this test + * when we can assume everyone is using qemu >= 2.11. + */ +static int +qemu_img_supports_U_option (guestfs_h *g) +{ + if (g->qemu_img_supports_U_option >= 0) + return g->qemu_img_supports_U_option; + + CLEANUP_CMD_CLOSE struct command *cmd = guestfs_int_new_command (g); + int r; + + guestfs_int_cmd_add_string_unquoted (cmd, + "qemu-img info --help | " + "grep -sq -- 'info.*-U'"); + r = guestfs_int_cmd_run (cmd); + if (r == -1) + return -1; + if (!WIFEXITED (r)) { + guestfs_int_external_command_failed (g, r, + "qemu-img info -U option test", + NULL); + return -1; + } + + g->qemu_img_supports_U_option = WEXITSTATUS (r) == 0; + return g->qemu_img_supports_U_option; +} -- 2.19.0.rc0