Commit 5500316d authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Kevin Wolf

block: implement is_allocated for raw

Either FIEMAP, or SEEK_DATA+SEEK_HOLE can be used to implement the
is_allocated callback for raw files.  On Linux ext4, btrfs and XFS
all support it.
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 87267753
......@@ -52,6 +52,10 @@
#include <sys/param.h>
#include <linux/cdrom.h>
#include <linux/fd.h>
#include <linux/fs.h>
#endif
#ifdef CONFIG_FIEMAP
#include <linux/fiemap.h>
#endif
#if defined (__FreeBSD__) || defined(__FreeBSD_kernel__)
#include <sys/disk.h>
......@@ -583,6 +587,99 @@ static int raw_create(const char *filename, QEMUOptionParameter *options)
return result;
}
/*
* Returns true iff the specified sector is present in the disk image. Drivers
* not implementing the functionality are assumed to not support backing files,
* hence all their sectors are reported as allocated.
*
* If 'sector_num' is beyond the end of the disk image the return value is 0
* and 'pnum' is set to 0.
*
* 'pnum' is set to the number of sectors (including and immediately following
* the specified sector) that are known to be in the same
* allocated/unallocated state.
*
* 'nb_sectors' is the max value 'pnum' should be set to. If nb_sectors goes
* beyond the end of the disk image it will be clamped.
*/
static int coroutine_fn raw_co_is_allocated(BlockDriverState *bs,
int64_t sector_num,
int nb_sectors, int *pnum)
{
BDRVRawState *s = bs->opaque;
off_t start, data, hole;
int ret;
ret = fd_open(bs);
if (ret < 0) {
return ret;
}
start = sector_num * BDRV_SECTOR_SIZE;
#ifdef CONFIG_FIEMAP
struct {
struct fiemap fm;
struct fiemap_extent fe;
} f;
f.fm.fm_start = start;
f.fm.fm_length = (int64_t)nb_sectors * BDRV_SECTOR_SIZE;
f.fm.fm_flags = 0;
f.fm.fm_extent_count = 1;
f.fm.fm_reserved = 0;
if (ioctl(s->fd, FS_IOC_FIEMAP, &f) == -1) {
/* Assume everything is allocated. */
*pnum = nb_sectors;
return 1;
}
if (f.fm.fm_mapped_extents == 0) {
/* No extents found, data is beyond f.fm.fm_start + f.fm.fm_length.
* f.fm.fm_start + f.fm.fm_length must be clamped to the file size!
*/
off_t length = lseek(s->fd, 0, SEEK_END);
hole = f.fm.fm_start;
data = MIN(f.fm.fm_start + f.fm.fm_length, length);
} else {
data = f.fe.fe_logical;
hole = f.fe.fe_logical + f.fe.fe_length;
}
#elif defined SEEK_HOLE && defined SEEK_DATA
hole = lseek(s->fd, start, SEEK_HOLE);
if (hole == -1) {
/* -ENXIO indicates that sector_num was past the end of the file.
* There is a virtual hole there. */
assert(errno != -ENXIO);
/* Most likely EINVAL. Assume everything is allocated. */
*pnum = nb_sectors;
return 1;
}
if (hole > start) {
data = start;
} else {
/* On a hole. We need another syscall to find its end. */
data = lseek(s->fd, start, SEEK_DATA);
if (data == -1) {
data = lseek(s->fd, 0, SEEK_END);
}
}
#else
*pnum = nb_sectors;
return 1;
#endif
if (data <= start) {
/* On a data extent, compute sectors to the end of the extent. */
*pnum = MIN(nb_sectors, (hole - start) / BDRV_SECTOR_SIZE);
return 1;
} else {
/* On a hole, compute sectors to the beginning of the next extent. */
*pnum = MIN(nb_sectors, (data - start) / BDRV_SECTOR_SIZE);
return 0;
}
}
#ifdef CONFIG_XFS
static int xfs_discard(BDRVRawState *s, int64_t sector_num, int nb_sectors)
{
......@@ -634,6 +731,7 @@ static BlockDriver bdrv_file = {
.bdrv_close = raw_close,
.bdrv_create = raw_create,
.bdrv_co_discard = raw_co_discard,
.bdrv_co_is_allocated = raw_co_is_allocated,
.bdrv_aio_readv = raw_aio_readv,
.bdrv_aio_writev = raw_aio_writev,
......
......@@ -25,6 +25,13 @@ static void raw_close(BlockDriverState *bs)
{
}
static int coroutine_fn raw_co_is_allocated(BlockDriverState *bs,
int64_t sector_num,
int nb_sectors, int *pnum)
{
return bdrv_co_is_allocated(bs->file, sector_num, nb_sectors, pnum);
}
static int64_t raw_getlength(BlockDriverState *bs)
{
return bdrv_getlength(bs->file);
......@@ -108,6 +115,7 @@ static BlockDriver bdrv_raw = {
.bdrv_co_readv = raw_co_readv,
.bdrv_co_writev = raw_co_writev,
.bdrv_co_is_allocated = raw_co_is_allocated,
.bdrv_co_discard = raw_co_discard,
.bdrv_probe = raw_probe,
......
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