Re: [Qemu-devel] [PATCH RFC for-2.3 2/6] qga: introduce three help functions for memory block functions

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting zhanghailiang (2014-12-06 00:59:15)
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> ---
>  qga/commands-posix.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 130 insertions(+)
> 
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index b0d6a5d..8917dca 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -1875,6 +1875,136 @@ int64_t qmp_guest_set_vcpus(GuestLogicalProcessorList *vcpus, Error **errp)
>      return processed;
>  }

I think these would break build bisectability. Please move these into the
patches which introduce the first users.

> 
> +static void ga_read_sysfs_file(int dirfd, const char *pathname, char *buf,
> +                               int size, Error **errp)
> +{
> +    int fd;
> +    int res;
> +
> +    errno = 0;
> +    fd = openat(dirfd, pathname, O_RDONLY);
> +    if (fd == -1) {
> +        error_setg_errno(errp, errno, "open sysfs file \"%s\"", pathname);
> +        return;
> +    }
> +
> +    res = pread(fd, buf, size, 0);
> +    if (res == -1) {
> +        error_setg_errno(errp, errno, "pread sysfs file \"%s\"", pathname);
> +    } else if (res == 0) {
> +        error_setg(errp, "pread sysfs file \"%s\": unexpected EOF", pathname);
> +    }
> +    res = close(fd);
> +    g_assert(res == 0);

This should also be propagated up as an error, killing the guest agent should be
avoided when possible.

> +}
> +
> +static void ga_write_sysfs_file(int dirfd, const char *pathname,
> +                                const char *buf, int size, Error **errp)
> +{
> +    int fd;
> +    int res;
> +
> +    errno = 0;
> +    fd = openat(dirfd, pathname, O_WRONLY);
> +    if (fd == -1) {
> +        error_setg_errno(errp, errno, "open sysfs file \"%s\"", pathname);
> +        return;
> +    }
> +
> +    if (pwrite(fd, buf, size, 0) == -1) {
> +        error_setg_errno(errp, errno, "pwrite sysfs file \"%s\"", pathname);
> +    }
> +
> +    res = close(fd);
> +    g_assert(res == 0);
> +}
> +
> +/* Transfer online/offline status between @mem_blk and the guest system.
> + *
> + * On input either @errp or *@errp must be NULL.
> + *
> + * In system-to-@mem_blk direction, the following @mem_blk fields are accessed:
> + * - R: mem_blk->phys_index
> + * - W: mem_blk->online
> + * - W: mem_blk->can_offline
> + *
> + * In @mem_blk-to-system direction, the following @mem_blk fields are accessed:
> + * - R: mem_blk->phys_index
> + * - R: mem_blk->online
> + *-  R: mem_blk->can_offline
> + * Written members remain unmodified on error.
> + */
> +static void transfer_memory_block(GuestMemoryBlock *mem_blk, bool sys2memblk,
> +                                  Error **errp)
> +{
> +    char *dirpath;
> +    int dirfd;
> +    int res;
> +    char *status;
> +    Error *local_err = NULL;
> +
> +    dirpath = g_strdup_printf("/sys/devices/system/memory/memory%" PRId64 "/",
> +                              mem_blk->phys_index);
> +    dirfd = open(dirpath, O_RDONLY | O_DIRECTORY);
> +    if (dirfd == -1) {
> +        error_setg_errno(errp, errno, "open(\"%s\")", dirpath);
> +        g_free(dirpath);
> +        return;
> +    }
> +    g_free(dirpath);
> +
> +    status = g_malloc0(10);
> +    ga_read_sysfs_file(dirfd, "state", status, 10, &local_err);
> +    if (local_err) {
> +        /* treat with sysfs file that not exist in old kernel */
> +        if (errno == ENOENT) {
> +            error_free(local_err);
> +            if (sys2memblk) {
> +                mem_blk->online = true;
> +                mem_blk->can_offline = false;
> +            } else if (!mem_blk->online) {
> +                error_setg(errp, "memory block #%" PRId64 " can't be "
> +                           "offlined", mem_blk->phys_index);
> +            }
> +        } else {
> +            error_propagate(errp, local_err);
> +        }
> +        return;

Need to free 'status' here, and close 'dirfd'. perhaps just a goto
to the end of the function since you already have common cleanup there.
And, if you use 'local_err' in place of 'err' for error_set, you can
maybe move all your error_propagate calls there as well.

> +    }
> +
> +    if (sys2memblk) {
> +        char removable = '0';
> +
> +        mem_blk->online = (strncmp(status, "online", 6) == 0);
> +
> +        ga_read_sysfs_file(dirfd, "removable", &removable, 1, &local_err);
> +        if (local_err) {
> +            /* if no 'removable' file, it does't support offline mem blk */
> +            if (errno == ENOENT) {
> +                error_free(local_err);
> +                mem_blk->can_offline = false;
> +            } else {
> +                error_propagate(errp, local_err);
> +            }
> +        } else {
> +            mem_blk->can_offline = (removable != '0');
> +        }
> +    } else {
> +        if (mem_blk->online != (strncmp(status, "online", 6) == 0)) {
> +            char *new_state = mem_blk->online ? g_strdup("online") :
> +                                                g_strdup("offline");
> +
> +            ga_write_sysfs_file(dirfd, "state", new_state, strlen(new_state),
> +                                errp);
> +            g_free(new_state);
> +        } /* otherwise pretend successful re-(on|off)-lining */
> +    }
> +
> +    g_free(status);
> +    res = close(dirfd);
> +    g_assert(res == 0);
> +}
> +
>  #else /* defined(__linux__) */
> 
>  void qmp_guest_suspend_disk(Error **errp)
> -- 
> 1.7.12.4