raw-posix: implement write_zeroes with MAY_UNMAP for block devices
See the next commit for the description of the Linux kernel problem
that is worked around in raw_open_common.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 7f3f47d..b3feed6 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -334,6 +334,22 @@
if (S_ISREG(st.st_mode)) {
s->discard_zeroes = true;
}
+ if (S_ISBLK(st.st_mode)) {
+#ifdef BLKDISCARDZEROES
+ unsigned int arg;
+ if (ioctl(s->fd, BLKDISCARDZEROES, &arg) == 0 && arg) {
+ s->discard_zeroes = true;
+ }
+#endif
+#ifdef __linux__
+ /* On Linux 3.10, BLKDISCARD leaves stale data in the page cache. Do
+ * not rely on the contents of discarded blocks unless using O_DIRECT.
+ */
+ if (!(bs->open_flags & BDRV_O_NOCACHE)) {
+ s->discard_zeroes = false;
+ }
+#endif
+ }
#ifdef CONFIG_XFS
if (platform_test_xfs_fd(s->fd)) {
@@ -1586,6 +1602,26 @@
cb, opaque, QEMU_AIO_DISCARD|QEMU_AIO_BLKDEV);
}
+static coroutine_fn int hdev_co_write_zeroes(BlockDriverState *bs,
+ int64_t sector_num, int nb_sectors, BdrvRequestFlags flags)
+{
+ BDRVRawState *s = bs->opaque;
+ int rc;
+
+ rc = fd_open(bs);
+ if (rc < 0) {
+ return rc;
+ }
+ if (!(flags & BDRV_REQ_MAY_UNMAP)) {
+ return -ENOTSUP;
+ }
+ if (!s->discard_zeroes) {
+ return -ENOTSUP;
+ }
+ return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
+ QEMU_AIO_DISCARD|QEMU_AIO_BLKDEV);
+}
+
static int hdev_create(const char *filename, QEMUOptionParameter *options,
Error **errp)
{
@@ -1638,6 +1674,7 @@
.bdrv_reopen_abort = raw_reopen_abort,
.bdrv_create = hdev_create,
.create_options = raw_create_options,
+ .bdrv_co_write_zeroes = hdev_co_write_zeroes,
.bdrv_aio_readv = raw_aio_readv,
.bdrv_aio_writev = raw_aio_writev,
