raw-posix: add support for write_zeroes on XFS and block devices
The code is similar to the implementation of discard and write_zeroes
with UNMAP. However, failure must be propagated up to block.c.
The stale page cache problem can be reproduced as follows:
# modprobe scsi-debug lbpws=1 lbprz=1
# ./qemu-io /dev/sdXX
qemu-io> write -P 0xcc 0 2M
qemu-io> write -z 0 1M
qemu-io> read -P 0x00 0 512
Pattern verification failed at offset 0, 512 bytes
qemu-io> read -v 0 512
00000000: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
...
# ./qemu-io --cache=none /dev/sdXX
qemu-io> write -P 0xcc 0 2M
qemu-io> write -z 0 1M
qemu-io> read -P 0x00 0 512
qemu-io> read -v 0 512
00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
...
And similarly with discard instead of "write -z".
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/block/raw-aio.h b/block/raw-aio.h
index c61f159..7ad0a8a 100644
--- a/block/raw-aio.h
+++ b/block/raw-aio.h
@@ -21,9 +21,10 @@
#define QEMU_AIO_IOCTL 0x0004
#define QEMU_AIO_FLUSH 0x0008
#define QEMU_AIO_DISCARD 0x0010
+#define QEMU_AIO_WRITE_ZEROES 0x0020
#define QEMU_AIO_TYPE_MASK \
(QEMU_AIO_READ|QEMU_AIO_WRITE|QEMU_AIO_IOCTL|QEMU_AIO_FLUSH| \
- QEMU_AIO_DISCARD)
+ QEMU_AIO_DISCARD|QEMU_AIO_WRITE_ZEROES)
/* AIO flags */
#define QEMU_AIO_MISALIGNED 0x1000
diff --git a/block/raw-posix.c b/block/raw-posix.c
index b3feed6..10c6b34 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -142,6 +142,7 @@
bool is_xfs:1;
#endif
bool has_discard:1;
+ bool has_write_zeroes:1;
bool discard_zeroes:1;
} BDRVRawState;
@@ -326,6 +327,7 @@
#endif
s->has_discard = true;
+ s->has_write_zeroes = true;
if (fstat(s->fd, &st) < 0) {
error_setg_errno(errp, errno, "Could not stat file");
@@ -344,9 +346,11 @@
#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.
+ * Same for BLKZEROOUT.
*/
if (!(bs->open_flags & BDRV_O_NOCACHE)) {
s->discard_zeroes = false;
+ s->has_write_zeroes = false;
}
#endif
}
@@ -702,6 +706,23 @@
}
#ifdef CONFIG_XFS
+static int xfs_write_zeroes(BDRVRawState *s, int64_t offset, uint64_t bytes)
+{
+ struct xfs_flock64 fl;
+
+ memset(&fl, 0, sizeof(fl));
+ fl.l_whence = SEEK_SET;
+ fl.l_start = offset;
+ fl.l_len = bytes;
+
+ if (xfsctl(NULL, s->fd, XFS_IOC_ZERO_RANGE, &fl) < 0) {
+ DEBUG_BLOCK_PRINT("cannot write zero range (%s)\n", strerror(errno));
+ return -errno;
+ }
+
+ return 0;
+}
+
static int xfs_discard(BDRVRawState *s, int64_t offset, uint64_t bytes)
{
struct xfs_flock64 fl;
@@ -720,6 +741,42 @@
}
#endif
+static ssize_t handle_aiocb_write_zeroes(RawPosixAIOData *aiocb)
+{
+ int ret = -EOPNOTSUPP;
+ BDRVRawState *s = aiocb->bs->opaque;
+
+ if (s->has_write_zeroes == 0) {
+ return -ENOTSUP;
+ }
+
+ if (aiocb->aio_type & QEMU_AIO_BLKDEV) {
+#ifdef BLKZEROOUT
+ do {
+ uint64_t range[2] = { aiocb->aio_offset, aiocb->aio_nbytes };
+ if (ioctl(aiocb->aio_fildes, BLKZEROOUT, range) == 0) {
+ return 0;
+ }
+ } while (errno == EINTR);
+
+ ret = -errno;
+#endif
+ } else {
+#ifdef CONFIG_XFS
+ if (s->is_xfs) {
+ return xfs_write_zeroes(s, aiocb->aio_offset, aiocb->aio_nbytes);
+ }
+#endif
+ }
+
+ if (ret == -ENODEV || ret == -ENOSYS || ret == -EOPNOTSUPP ||
+ ret == -ENOTTY) {
+ s->has_write_zeroes = false;
+ ret = -ENOTSUP;
+ }
+ return ret;
+}
+
static ssize_t handle_aiocb_discard(RawPosixAIOData *aiocb)
{
int ret = -EOPNOTSUPP;
@@ -804,6 +861,9 @@
case QEMU_AIO_DISCARD:
ret = handle_aiocb_discard(aiocb);
break;
+ case QEMU_AIO_WRITE_ZEROES:
+ ret = handle_aiocb_write_zeroes(aiocb);
+ break;
default:
fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
ret = -EINVAL;
@@ -1256,13 +1316,13 @@
BDRVRawState *s = bs->opaque;
if (!(flags & BDRV_REQ_MAY_UNMAP)) {
- return -ENOTSUP;
+ return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
+ QEMU_AIO_WRITE_ZEROES);
+ } else if (s->discard_zeroes) {
+ return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
+ QEMU_AIO_DISCARD);
}
- if (!s->discard_zeroes) {
- return -ENOTSUP;
- }
- return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
- QEMU_AIO_DISCARD);
+ return -ENOTSUP;
}
static int raw_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
@@ -1613,13 +1673,13 @@
return rc;
}
if (!(flags & BDRV_REQ_MAY_UNMAP)) {
- return -ENOTSUP;
+ return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
+ QEMU_AIO_WRITE_ZEROES|QEMU_AIO_BLKDEV);
+ } else if (s->discard_zeroes) {
+ return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
+ QEMU_AIO_DISCARD|QEMU_AIO_BLKDEV);
}
- if (!s->discard_zeroes) {
- return -ENOTSUP;
- }
- return paio_submit_co(bs, s->fd, sector_num, NULL, nb_sectors,
- QEMU_AIO_DISCARD|QEMU_AIO_BLKDEV);
+ return -ENOTSUP;
}
static int hdev_create(const char *filename, QEMUOptionParameter *options,
