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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>
This commit is contained in:
Paolo Bonzini 2013-11-22 13:39:57 +01:00 committed by Stefan Hajnoczi
parent d0b4503ed2
commit 97a2ae3453
2 changed files with 74 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
block/raw-aio.h
View File

@ -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

84
block/raw-posix.c
View File

@ -142,6 +142,7 @@ typedef struct BDRVRawState {
bool is_xfs:1;
#endif
bool has_discard:1;
bool has_write_zeroes:1;
bool discard_zeroes:1;
} BDRVRawState;
@ -326,6 +327,7 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
#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 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
#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 @@ static ssize_t handle_aiocb_rw(RawPosixAIOData *aiocb)
}
#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 @@ static int xfs_discard(BDRVRawState *s, int64_t offset, uint64_t bytes)
}
#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 @@ static int aio_worker(void *arg)
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 @@ static int coroutine_fn raw_co_write_zeroes(
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 @@ static coroutine_fn int hdev_co_write_zeroes(BlockDriverState *bs,
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,