comments below
On 08/03/14 17:28, Chen Gang wrote:
> In dump_init(), when failure occurs, need notice about 'fd' and memory
> mapping. So call dump_cleanup() for it (need let all initializations at
> front).
>
> Also simplify dump_cleanup(): remove redundant 'ret' and redundant 'fd'
> checking.
>
> Signed-off-by: Chen Gang <gang.chen.5...@gmail.com>
> ---
> dump.c | 18 +++++-------------
> 1 file changed, 5 insertions(+), 13 deletions(-)
Please explain what is leaked and how.
The only possibility I can see (without digging very hard) is that
qemu_get_guest_memory_mapping() succeeds and lzo_init() fails (which
should never happen in practice).
Regarding s->fd itself, I'm beyond trying to understand its lifecycle.
Qemu uses a bad ownership model wherein functions, in case of an
internal error, release resources they got from their callers. I'm
unable to reason in such a model. The only function to close fd *ever*
should be qmp_dump_guest_memory() (and that one should close fd with a
direct close() call). Currently fd is basically a global variable,
because the entire dump function tree has access to it (and closes it if
there's an error).
Anyway I guess it's OK to call dump_cleanup() to close s->fd just in case.
If you have a Coverity report, please share it.
Then,
> diff --git a/dump.c b/dump.c
> index ce646bc..71d3e94 100644
> --- a/dump.c
> +++ b/dump.c
> @@ -71,18 +71,14 @@ uint64_t cpu_to_dump64(DumpState *s, uint64_t val)
>
> static int dump_cleanup(DumpState *s)
> {
> - int ret = 0;
> -
I agree with this change.
> guest_phys_blocks_free(&s->guest_phys_blocks);
> memory_mapping_list_free(&s->list);
> - if (s->fd != -1) {
> - close(s->fd);
> - }
> + close(s->fd);
I disagree. It clobbers errno if s->fd is -1. Even though we don't
particularly care about errno, it sort of disturbs be. Or can you prove
s->fd is never -1 here?
> if (s->resume) {
> vm_start();
> }
>
> - return ret;
> + return 0;
> }
>
> static void dump_error(DumpState *s, const char *reason)
> @@ -1499,6 +1495,8 @@ static int dump_init(DumpState *s, int fd, bool
> has_format,
> s->begin = begin;
> s->length = length;
>
> + memory_mapping_list_init(&s->list);
> +
> guest_phys_blocks_init(&s->guest_phys_blocks);
> guest_phys_blocks_append(&s->guest_phys_blocks);
>
> @@ -1526,7 +1524,6 @@ static int dump_init(DumpState *s, int fd, bool
> has_format,
> }
>
> /* get memory mapping */
> - memory_mapping_list_init(&s->list);
> if (paging) {
> qemu_get_guest_memory_mapping(&s->list, &s->guest_phys_blocks, &err);
> if (err != NULL) {
> @@ -1622,12 +1619,7 @@ static int dump_init(DumpState *s, int fd, bool
> has_format,
> return 0;
>
> cleanup:
> - guest_phys_blocks_free(&s->guest_phys_blocks);
> -
> - if (s->resume) {
> - vm_start();
> - }
> -
> + dump_cleanup(s);
> return -1;
> }
>
>
This code is ripe for a generic lifecycle tracking overhaul, but since
my view of ownership tracking is marginal in the qemu developer
community, I'm not motivated.
NB: I'm not nacking your patch, just please explain it better.
Thanks
Laszlo
