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));
+ 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;
+ /* 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;
+ }
+
+ close(fd);
+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;
--
2.8.2
