87 lines
3.2 KiB
Diff
87 lines
3.2 KiB
Diff
From 5bb37d151b026759ee35f04212b11b4d625c7431 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Wed, 7 Dec 2011 12:42:10 +0100
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Subject: [PATCH 23/25] qemu-img rebase: Fix for undersized backing files
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Backing files may be smaller than the corresponding COW file. When
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reading directly from the backing file, qemu-img rebase must consider
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this and assume zero sectors after the end of backing files.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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---
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qemu-img.c | 42 +++++++++++++++++++++++++++++++++---------
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1 files changed, 33 insertions(+), 9 deletions(-)
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diff --git a/qemu-img.c b/qemu-img.c
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index 8bdae66..01cc0d3 100644
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--- a/qemu-img.c
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+++ b/qemu-img.c
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@@ -1420,6 +1420,8 @@ static int img_rebase(int argc, char **argv)
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*/
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if (!unsafe) {
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uint64_t num_sectors;
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+ uint64_t old_backing_num_sectors;
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+ uint64_t new_backing_num_sectors;
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uint64_t sector;
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int n;
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uint8_t * buf_old;
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@@ -1430,6 +1432,8 @@ static int img_rebase(int argc, char **argv)
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buf_new = qemu_blockalign(bs, IO_BUF_SIZE);
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bdrv_get_geometry(bs, &num_sectors);
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+ bdrv_get_geometry(bs_old_backing, &old_backing_num_sectors);
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+ bdrv_get_geometry(bs_new_backing, &new_backing_num_sectors);
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local_progress = (float)100 /
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(num_sectors / MIN(num_sectors, IO_BUF_SIZE / 512));
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@@ -1448,16 +1452,36 @@ static int img_rebase(int argc, char **argv)
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continue;
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}
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- /* Read old and new backing file */
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- ret = bdrv_read(bs_old_backing, sector, buf_old, n);
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- if (ret < 0) {
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- error_report("error while reading from old backing file");
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- goto out;
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+ /*
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+ * Read old and new backing file and take into consideration that
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+ * backing files may be smaller than the COW image.
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+ */
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+ if (sector >= old_backing_num_sectors) {
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+ memset(buf_old, 0, n * BDRV_SECTOR_SIZE);
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+ } else {
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+ if (sector + n > old_backing_num_sectors) {
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+ n = old_backing_num_sectors - sector;
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+ }
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+
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+ ret = bdrv_read(bs_old_backing, sector, buf_old, n);
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+ if (ret < 0) {
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+ error_report("error while reading from old backing file");
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+ goto out;
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+ }
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}
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- ret = bdrv_read(bs_new_backing, sector, buf_new, n);
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- if (ret < 0) {
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- error_report("error while reading from new backing file");
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- goto out;
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+
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+ if (sector >= new_backing_num_sectors) {
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+ memset(buf_new, 0, n * BDRV_SECTOR_SIZE);
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+ } else {
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+ if (sector + n > new_backing_num_sectors) {
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+ n = new_backing_num_sectors - sector;
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+ }
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+
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+ ret = bdrv_read(bs_new_backing, sector, buf_new, n);
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+ if (ret < 0) {
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+ error_report("error while reading from new backing file");
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+ goto out;
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+ }
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}
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/* If they differ, we need to write to the COW file */
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--
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1.7.7.5
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