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The current implementation of alloc_refcount_block and grow_refcount_table has fundamental problems regarding error handling. There are some places where an I/O error means that the image is going to be corrupted. I have found that the only way to fix this is to completely rewrite the thing. In detail, the problem is that the refcount blocks itself are allocated using alloc_refcount_noref (to avoid endless recursion when updating the refcount of the new refcount block, which migh access just the same refcount block but its allocation is not yet completed...). Only at the end of the refcount allocation the refcount of the refcount block is increased. If an error happens in between, the refcount block is in use, but has a refcount of zero and will likely be overwritten later. The new approach is explained in comments in the code. The trick is basically to let new refcount blocks describe their own refcount, so their refcount will be automatically changed when they are hooked up in the refcount table. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> |
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| bochs.c | ||
| cloop.c | ||
| cow.c | ||
| curl.c | ||
| dmg.c | ||
| nbd.c | ||
| parallels.c | ||
| qcow2-cluster.c | ||
| qcow2-refcount.c | ||
| qcow2-snapshot.c | ||
| qcow2.c | ||
| qcow2.h | ||
| qcow.c | ||
| raw-posix-aio.h | ||
| raw-posix.c | ||
| raw-win32.c | ||
| vdi.c | ||
| vmdk.c | ||
| vpc.c | ||
| vvfat.c | ||