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block/vpc: Fix conversion from size to disk geometry

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The VHD algorithm calculates a disk geometry
which is usually smaller than the requested size.

QEMU tried to round up but failed for certain sizes:

qemu-img create -f vpc disk.vpc 9437184
would create an image with 9435136 bytes
(which is too small for qemu-img convert).

Instead of hacking the geometry algorithm, the patch
increases the number of sectors until we get enough
sectors.

Cc: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Weil 2010-05-10 21:46:26 +02:00 committed by Kevin Wolf
parent 1dec5a7097
commit dede4188cc
1 changed files with 12 additions and 9 deletions
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21
block/vpc.c
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@ -463,9 +463,7 @@ static int calculate_geometry(int64_t total_sectors, uint16_t* cyls,
}
}
// Note: Rounding up deviates from the Virtual PC behaviour
// However, we need this to avoid truncating images in qemu-img convert
*cyls = (cyls_times_heads + *heads - 1) / *heads;
*cyls = cyls_times_heads / *heads;
return 0;
}
@ -477,9 +475,9 @@ static int vpc_create(const char *filename, QEMUOptionParameter *options)
struct vhd_dyndisk_header* dyndisk_header =
(struct vhd_dyndisk_header*) buf;
int fd, i;
uint16_t cyls;
uint8_t heads;
uint8_t secs_per_cyl;
uint16_t cyls = 0;
uint8_t heads = 0;
uint8_t secs_per_cyl = 0;
size_t block_size, num_bat_entries;
int64_t total_sectors = 0;
@ -496,9 +494,14 @@ static int vpc_create(const char *filename, QEMUOptionParameter *options)
if (fd < 0)
return -EIO;
// Calculate matching total_size and geometry
if (calculate_geometry(total_sectors, &cyls, &heads, &secs_per_cyl))
return -EFBIG;
/* Calculate matching total_size and geometry. Increase the number of
sectors requested until we get enough (or fail). */
for (i = 0; total_sectors > (int64_t)cyls * heads * secs_per_cyl; i++) {
if (calculate_geometry(total_sectors + i,
&cyls, &heads, &secs_per_cyl)) {
return -EFBIG;
}
}
total_sectors = (int64_t) cyls * heads * secs_per_cyl;
// Prepare the Hard Disk Footer