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qemu-img: rebase: stop when reaching EOF of old backing file 

In case when we're rebasing within one backing chain, and when target image
is larger than old backing file, bdrv_is_allocated_above() ends up setting
*pnum = 0.  As a result, target offset isn't getting incremented, and we
get stuck in an infinite for loop.  Let's detect this case and proceed
further down the loop body, as the offsets beyond the old backing size need
to be explicitly zeroed.

Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Message-ID: <20230919165804.439110-2-andrey.drobyshev@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 8b097fd6b0)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Andrey Drobyshev 2023-09-19 19:57:57 +03:00 committed by Michael Tokarev
parent de18cbdaf2
commit bd8d9c618a
1 changed files with 12 additions and 1 deletions
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13
qemu-img.c
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@ -3801,6 +3801,8 @@ static int img_rebase(int argc, char **argv)
}
if (prefix_chain_bs) {
uint64_t bytes = n;
/*
* If cluster wasn't changed since prefix_chain, we don't need
* to take action
@ -3813,9 +3815,18 @@ static int img_rebase(int argc, char **argv)
strerror(-ret));
goto out;
}
if (!ret) {
if (!ret && n) {
continue;
}
if (!n) {
/*
* If we've reached EOF of the old backing, it means that
* offsets beyond the old backing size were read as zeroes.
* Now we will need to explicitly zero the cluster in
* order to preserve that state after the rebase.
*/
n = bytes;
}
}
/*