On Tue, Nov 07, 2017 at 05:27:18PM -0500, Jeff Cody wrote:
> We don't need libssh2 failure to be fatal (we could just opt to not
> register the driver on failure). But, it is probably a good idea to
> avoid external library calls during the block_init(), and call the
> libssh2 global init function on the first usage, returning any errors.
>
> Signed-off-by: Jeff Cody <jc...@redhat.com>
> ---
> block/ssh.c | 37 ++++++++++++++++++++++++++-----------
> 1 file changed, 26 insertions(+), 11 deletions(-)
>
> diff --git a/block/ssh.c b/block/ssh.c
> index b049a16..de81ec8 100644
> --- a/block/ssh.c
> +++ b/block/ssh.c
> @@ -83,12 +83,28 @@ typedef struct BDRVSSHState {
> bool unsafe_flush_warning;
> } BDRVSSHState;
>
> -static void ssh_state_init(BDRVSSHState *s)
> +static bool ssh_libinit_called;
> +
> +static int ssh_state_init(BDRVSSHState *s, Error **errp)
> {
> + int ret;
> +
> + if (!ssh_libinit_called) {
> + ret = libssh2_init(0);
> + if (ret) {
> + error_setg(errp, "libssh2 initialization failed with %d", ret);
> + return ret;
> + }
> + ssh_libinit_called = true;
> + }
> +
> +
> memset(s, 0, sizeof *s);
> s->sock = -1;
> s->offset = -1;
> qemu_co_mutex_init(&s->lock);
> +
> + return 0;
Is this thread safe? Is there a case where multiple ssh URL opens
could race off against each other and we could end up calling
libssh2_init in parallel? (According to the libssh2_init
documentation, the function is not thread-safe so should not be called
in parallel on multiple threads)
Rich.
> }
>
> static void ssh_state_free(BDRVSSHState *s)
> @@ -773,7 +789,9 @@ static int ssh_file_open(BlockDriverState *bs, QDict
> *options, int bdrv_flags,
> int ret;
> int ssh_flags;
>
> - ssh_state_init(s);
> + if (ssh_state_init(s, errp)) {
> + return -EIO;
> + }
>
> ssh_flags = LIBSSH2_FXF_READ;
> if (bdrv_flags & BDRV_O_RDWR) {
> @@ -821,8 +839,13 @@ static int ssh_create(const char *filename, QemuOpts
> *opts, Error **errp)
> BDRVSSHState s;
> ssize_t r2;
> char c[1] = { '\0' };
> + Error *local_err = NULL;
>
> - ssh_state_init(&s);
> + ret = ssh_state_init(&s, &local_err);
> + if (local_err) {
> + error_propagate(errp, local_err);
> + return ret;
> + }
>
> /* Get desired file size. */
> total_size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
> @@ -1213,14 +1236,6 @@ static BlockDriver bdrv_ssh = {
>
> static void bdrv_ssh_init(void)
> {
> - int r;
> -
> - r = libssh2_init(0);
> - if (r != 0) {
> - fprintf(stderr, "libssh2 initialization failed, %d\n", r);
> - exit(EXIT_FAILURE);
> - }
> -
> bdrv_register(&bdrv_ssh);
> }
>
> --
> 2.9.5
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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