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raw: Probe required direct I/O alignment

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Add a bs->request_alignment field that contains the required
offset/length alignment for I/O requests and fill it in the raw block
drivers. Use ioctls if possible, else see what alignment it takes for
O_DIRECT to succeed.

While at it, also expose the memory alignment requirements, which may be
(and in practice are) different from the disk alignment requirements.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Paolo Bonzini 2011-11-29 12:42:20 +01:00 • committed by Kevin Wolf
parent 1b7fd72955
commit c25f53b06e
4 changed files with 132 additions and 17 deletions
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102
block/raw-posix.c
View file

@ -127,6 +127,8 @@ typedef struct BDRVRawState {
int fd;
int type;
int open_flags;
size_t buf_align;
#if defined(__linux__)
/* linux floppy specific */
int64_t fd_open_time;
@ -213,6 +215,76 @@ static int raw_normalize_devicepath(const char **filename)
}
#endif
static void raw_probe_alignment(BlockDriverState *bs)
{
BDRVRawState *s = bs->opaque;
char *buf;
unsigned int sector_size;
/* For /dev/sg devices the alignment is not really used.
With buffered I/O, we don't have any restrictions. */
if (bs->sg || !(s->open_flags & O_DIRECT)) {
bs->request_alignment = 1;
s->buf_align = 1;
return;
}
/* Try a few ioctls to get the right size */
bs->request_alignment = 0;
s->buf_align = 0;
#ifdef BLKSSZGET
if (ioctl(s->fd, BLKSSZGET, &sector_size) >= 0) {
bs->request_alignment = sector_size;
}
#endif
#ifdef DKIOCGETBLOCKSIZE
if (ioctl(s->fd, DKIOCGETBLOCKSIZE, &sector_size) >= 0) {
bs->request_alignment = sector_size;
}
#endif
#ifdef DIOCGSECTORSIZE
if (ioctl(s->fd, DIOCGSECTORSIZE, &sector_size) >= 0) {
bs->request_alignment = sector_size;
}
#endif
#ifdef CONFIG_XFS
if (s->is_xfs) {
struct dioattr da;
if (xfsctl(NULL, s->fd, XFS_IOC_DIOINFO, &da) >= 0) {
bs->request_alignment = da.d_miniosz;
/* The kernel returns wrong information for d_mem */
/* s->buf_align = da.d_mem; */
}
}
#endif
/* If we could not get the sizes so far, we can only guess them */
if (!s->buf_align) {
size_t align;
buf = qemu_memalign(MAX_BLOCKSIZE, 2 * MAX_BLOCKSIZE);
for (align = 512; align <= MAX_BLOCKSIZE; align <<= 1) {
if (pread(s->fd, buf + align, MAX_BLOCKSIZE, 0) >= 0) {
s->buf_align = align;
break;
}
}
qemu_vfree(buf);
}
if (!bs->request_alignment) {
size_t align;
buf = qemu_memalign(s->buf_align, MAX_BLOCKSIZE);
for (align = 512; align <= MAX_BLOCKSIZE; align <<= 1) {
if (pread(s->fd, buf, align, 0) >= 0) {
bs->request_alignment = align;
break;
}
}
qemu_vfree(buf);
}
}
static void raw_parse_flags(int bdrv_flags, int *open_flags)
{
assert(open_flags != NULL);
@ -463,7 +535,6 @@ static int raw_reopen_prepare(BDRVReopenState *state,
return ret;
}
static void raw_reopen_commit(BDRVReopenState *state)
{
BDRVRawReopenState *raw_s = state->opaque;
@ -499,23 +570,15 @@ static void raw_reopen_abort(BDRVReopenState *state)
state->opaque = NULL;
}
static int raw_refresh_limits(BlockDriverState *bs)
{
BDRVRawState *s = bs->opaque;
/* XXX: use host sector size if necessary with:
#ifdef DIOCGSECTORSIZE
{
unsigned int sectorsize = 512;
if (!ioctl(fd, DIOCGSECTORSIZE, &sectorsize) &&
sectorsize > bufsize)
bufsize = sectorsize;
}
#endif
#ifdef CONFIG_COCOA
uint32_t blockSize = 512;
if ( !ioctl( fd, DKIOCGETBLOCKSIZE, &blockSize ) && blockSize > bufsize) {
bufsize = blockSize;
}
#endif
*/
raw_probe_alignment(bs);
bs->bl.opt_mem_alignment = s->buf_align;
return 0;
}
static ssize_t handle_aiocb_ioctl(RawPosixAIOData *aiocb)
{
@ -1363,6 +1426,7 @@ static BlockDriver bdrv_file = {
.bdrv_aio_writev = raw_aio_writev,
.bdrv_aio_flush = raw_aio_flush,
.bdrv_aio_discard = raw_aio_discard,
.bdrv_refresh_limits = raw_refresh_limits,
.bdrv_truncate = raw_truncate,
.bdrv_getlength = raw_getlength,
@ -1740,6 +1804,7 @@ static BlockDriver bdrv_host_device = {
.bdrv_aio_writev = raw_aio_writev,
.bdrv_aio_flush = raw_aio_flush,
.bdrv_aio_discard = hdev_aio_discard,
.bdrv_refresh_limits = raw_refresh_limits,
.bdrv_truncate = raw_truncate,
.bdrv_getlength = raw_getlength,
@ -1871,6 +1936,7 @@ static BlockDriver bdrv_host_floppy = {
.bdrv_aio_readv = raw_aio_readv,
.bdrv_aio_writev = raw_aio_writev,
.bdrv_aio_flush = raw_aio_flush,
.bdrv_refresh_limits = raw_refresh_limits,
.bdrv_truncate = raw_truncate,
.bdrv_getlength = raw_getlength,
@ -1981,6 +2047,7 @@ static BlockDriver bdrv_host_cdrom = {
.bdrv_aio_readv = raw_aio_readv,
.bdrv_aio_writev = raw_aio_writev,
.bdrv_aio_flush = raw_aio_flush,
.bdrv_refresh_limits = raw_refresh_limits,
.bdrv_truncate = raw_truncate,
.bdrv_getlength = raw_getlength,
@ -2110,6 +2177,7 @@ static BlockDriver bdrv_host_cdrom = {
.bdrv_aio_readv = raw_aio_readv,
.bdrv_aio_writev = raw_aio_writev,
.bdrv_aio_flush = raw_aio_flush,
.bdrv_refresh_limits = raw_refresh_limits,
.bdrv_truncate = raw_truncate,
.bdrv_getlength = raw_getlength,