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From 45958d24d6c9bcdc333844f69f47cacec29cfa0e Mon Sep 17 00:00:00 2001
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From: Max Reitz <mreitz@redhat.com>
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Date: Mon, 4 Nov 2013 22:32:26 +0100
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Subject: [PATCH 33/87] qcow2: Switch L1 table in a single sequence
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RH-Author: Max Reitz <mreitz@redhat.com>
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Message-id: <1383604354-12743-36-git-send-email-mreitz@redhat.com>
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Patchwork-id: 55335
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O-Subject: [RHEL-7.0 qemu-kvm PATCH 35/43] qcow2: Switch L1 table in a single sequence
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Bugzilla: 1004347
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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BZ: 1004347
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Switching the L1 table in memory should be an atomic operation, as far
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as possible. Calling qcow2_free_clusters on the old L1 table on disk is
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not a good idea when the old L1 table is no longer valid and the address
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to the new one hasn't yet been written into the corresponding
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BDRVQcowState field. To be more specific, this can lead to segfaults due
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to qcow2_check_metadata_overlap trying to access the L1 table during the
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free operation.
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit fda74f826baec78d685e5a87fd8a95bfb7bb2243)
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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---
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block/qcow2-cluster.c | 7 +++++--
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1 file changed, 5 insertions(+), 2 deletions(-)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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block/qcow2-cluster.c | 7 +++++--
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1 files changed, 5 insertions(+), 2 deletions(-)
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diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
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index 2d5aa92..c05f182 100644
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--- a/block/qcow2-cluster.c
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+++ b/block/qcow2-cluster.c
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@@ -35,6 +35,7 @@ int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
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BDRVQcowState *s = bs->opaque;
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int new_l1_size2, ret, i;
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uint64_t *new_l1_table;
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+ int64_t old_l1_table_offset, old_l1_size;
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int64_t new_l1_table_offset, new_l1_size;
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uint8_t data[12];
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@@ -106,11 +107,13 @@ int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
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goto fail;
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}
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g_free(s->l1_table);
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- qcow2_free_clusters(bs, s->l1_table_offset, s->l1_size * sizeof(uint64_t),
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- QCOW2_DISCARD_OTHER);
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+ old_l1_table_offset = s->l1_table_offset;
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s->l1_table_offset = new_l1_table_offset;
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s->l1_table = new_l1_table;
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+ old_l1_size = s->l1_size;
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s->l1_size = new_l1_size;
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+ qcow2_free_clusters(bs, old_l1_table_offset, old_l1_size * sizeof(uint64_t),
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+ QCOW2_DISCARD_OTHER);
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return 0;
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fail:
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g_free(new_l1_table);
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--
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1.7.1
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