On 26.05.2016 08:15, Fam Zheng wrote:
> This is sometimes a useful value we should count in.
>
> Signed-off-by: Fam Zheng <f...@redhat.com>
> ---
> block/raw-posix.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 47 insertions(+)
>
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index a4f5a1b..d3796ad 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -729,9 +729,56 @@ static void raw_reopen_abort(BDRVReopenState *state)
> state->opaque = NULL;
> }
>
> +static int hdev_get_max_transfer_length(dev_t dev)
> +{
> + int ret;
> + int fd;
> + char *path;
> + const char *end;
> + char buf[32];
> + long len;
> +
> + path = g_strdup_printf("/sys/dev/block/%u:%u/queue/max_sectors_kb",
> + major(dev), minor(dev));
I can't say I like this very much, but well, it won't do any harm on any
systems that do not offer this path (i.e. any non-Linux system, I
suppose). So I'm fine with it.
> + fd = open(path, O_RDONLY);
> + if (fd < 0) {
> + ret = -errno;
> + goto out;
> + }
> + ret = read(fd, buf, sizeof(buf));
> + if (ret < 0) {
> + ret = -errno;
> + goto out;
> + } else if (ret == 0) {
> + ret = -EIO;
> + goto out;
> + }
> + buf[ret] = 0;
Potential buffer overflow if ret == sizeof(buf).
> + /* The file is ended with '\n', pass 'end' to accept that. */
> + ret = qemu_strtol(buf, &end, 10, &len);
> + if (ret == 0 && end && *end == '\n') {
> + ret = len * 1024 / BDRV_SECTOR_SIZE;
Maybe there should be an overflow check here.
> + }
> +
> + close(fd);
This belongs in some error path, because otherwise the FD is leaked if
the read() failed.
Max
> +out:
> + g_free(path);
> + return ret;
> +}
> +
> static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
> {
> BDRVRawState *s = bs->opaque;
> + struct stat st;
> +
> + if (!fstat(s->fd, &st)) {
> + if (S_ISBLK(st.st_mode)) {
> + int ret = hdev_get_max_transfer_length(st.st_rdev);
> + if (ret >= 0) {
> + bs->bl.max_transfer_length = ret;
> + }
> + }
> + }
>
> raw_probe_alignment(bs, s->fd, errp);
> bs->bl.min_mem_alignment = s->buf_align;
>
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