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authorKevin Wolf <kwolf@redhat.com>2011-12-07 12:42:10 +0100
committerKevin Wolf <kwolf@redhat.com>2011-12-15 12:40:08 +0100
commit87a1b3e381c282b143023c411df284175f0b656b (patch)
tree6d745436e5ddb479ac315ccceac8803c4a7e35f9 /qemu-img.c
parentb9c532903fa528891c0eceb34ea40a0c47bfb5db (diff)
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qemu-img rebase: Fix for undersized backing files
Backing files may be smaller than the corresponding COW file. When reading directly from the backing file, qemu-img rebase must consider this and assume zero sectors after the end of backing files. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Diffstat (limited to 'qemu-img.c')
-rw-r--r--qemu-img.c42
1 files changed, 33 insertions, 9 deletions
diff --git a/qemu-img.c b/qemu-img.c
index 8bdae66..01cc0d3 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1420,6 +1420,8 @@ static int img_rebase(int argc, char **argv)
*/
if (!unsafe) {
uint64_t num_sectors;
+ uint64_t old_backing_num_sectors;
+ uint64_t new_backing_num_sectors;
uint64_t sector;
int n;
uint8_t * buf_old;
@@ -1430,6 +1432,8 @@ static int img_rebase(int argc, char **argv)
buf_new = qemu_blockalign(bs, IO_BUF_SIZE);
bdrv_get_geometry(bs, &num_sectors);
+ bdrv_get_geometry(bs_old_backing, &old_backing_num_sectors);
+ bdrv_get_geometry(bs_new_backing, &new_backing_num_sectors);
local_progress = (float)100 /
(num_sectors / MIN(num_sectors, IO_BUF_SIZE / 512));
@@ -1448,16 +1452,36 @@ static int img_rebase(int argc, char **argv)
continue;
}
- /* Read old and new backing file */
- ret = bdrv_read(bs_old_backing, sector, buf_old, n);
- if (ret < 0) {
- error_report("error while reading from old backing file");
- goto out;
+ /*
+ * Read old and new backing file and take into consideration that
+ * backing files may be smaller than the COW image.
+ */
+ if (sector >= old_backing_num_sectors) {
+ memset(buf_old, 0, n * BDRV_SECTOR_SIZE);
+ } else {
+ if (sector + n > old_backing_num_sectors) {
+ n = old_backing_num_sectors - sector;
+ }
+
+ ret = bdrv_read(bs_old_backing, sector, buf_old, n);
+ if (ret < 0) {
+ error_report("error while reading from old backing file");
+ goto out;
+ }
}
- ret = bdrv_read(bs_new_backing, sector, buf_new, n);
- if (ret < 0) {
- error_report("error while reading from new backing file");
- goto out;
+
+ if (sector >= new_backing_num_sectors) {
+ memset(buf_new, 0, n * BDRV_SECTOR_SIZE);
+ } else {
+ if (sector + n > new_backing_num_sectors) {
+ n = new_backing_num_sectors - sector;
+ }
+
+ ret = bdrv_read(bs_new_backing, sector, buf_new, n);
+ if (ret < 0) {
+ error_report("error while reading from new backing file");
+ goto out;
+ }
}
/* If they differ, we need to write to the COW file */