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[Qemu-devel] [PATCH 09/14] qemu-img rebase: Fix for undersized backing f
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH 09/14] qemu-img rebase: Fix for undersized backing files |
Date: |
Thu, 15 Dec 2011 15:09:24 +0100 |
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 <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
---
qemu-img.c | 42 +++++++++++++++++++++++++++++++++---------
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 */
--
1.7.6.4
- [Qemu-devel] [PULL 00/14] Block patches, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 01/14] block: bdrv_aio_* do not return NULL, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 02/14] block: simplify failure handling for bdrv_aio_multiwrite, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 06/14] block: avoid useless checks on acb->bh, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 03/14] block: qemu_aio_get does not return NULL, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 07/14] block/qcow2.c: call qcow2_free_snapshots in the function of qcow2_close, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 04/14] dma: the passed io_func does not return NULL, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 08/14] rbd: always set out parameter in qemu_rbd_snap_list, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 05/14] block: dma_bdrv_* does not return NULL, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 11/14] qcow2: Allow >4 GB VM state, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 09/14] qemu-img rebase: Fix for undersized backing files,
Kevin Wolf <=
- [Qemu-devel] [PATCH 13/14] block/cow: Return real error code, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 14/14] qiov: prevent double free or use-after-free, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 10/14] Documentation: Add qemu-img -t parameter in man page, Kevin Wolf, 2011/12/15
- [Qemu-devel] [PATCH 12/14] coroutine: switch per-thread free pool to a global pool, Kevin Wolf, 2011/12/15
- Re: [Qemu-devel] [PULL 00/14] Block patches, Anthony Liguori, 2011/12/19