On 28.10.2015 14:43, Alberto Garcia wrote: > 'block-commit' needs write access to two different nodes of the chain: > > - 'base', because that's where the data is written to. > - the overlay of 'top', because it needs to update the backing file > string to point to 'base' after the operation. > > Both images have to be opened in read-write mode, and commit_start() > takes care of reopening them if necessary. > > With the current implementation, however, when overlay_bs is reopened > in read-write mode it has the side effect of making 'base' read-only > again, eventually making 'block-commit' fail. > > This needs to be fixed in bdrv_reopen(), but until we get to that it > can be worked around simply by swapping the order of base and > overlay_bs in the reopen queue. > > In order to reproduce this bug, overlay_bs needs to be initially in > read-only mode. That is: the 'top' parameter of 'block-commit' cannot > be the active layer nor its immediate backing chain. > > Signed-off-by: Alberto Garcia <[email protected]> > --- > block/commit.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-)
Reviewed-by: Max Reitz <[email protected]>
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