sheepdog: support 'qemu-img snapshot -a'
Just call sd_create_branch() in the snapshot_goto to rollback the image is good enough. With this patch, 'loadvm' process for sheepdog is modified: Suppose we have a snapshot chain A --> B --> C, we do 'loadvm A' so as to get a new chain, A --> B | V C1 in the old code: 1 reload inode of A (in snapshot_goto) 2 read vmstate via A's vdi_id (loadvm_state) 3 delete C and create C1, reload inode of C1 (sd_create_branch on write) with this patch applied: 1 reload inode of A, delete C and create C1 (in snapshot_goto) 2 read vmstate via C1's parent, that is A's vdi_id (loadvm_state) This will fix the possible bug that QEMU exit between 2 and 3 in the old code Cc: qemu-devel@nongnu.org Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp> Cc: Kevin Wolf <kwolf@redhat.com> Cc: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: NLiu Yuan <namei.unix@gmail.com> Signed-off-by: NKevin Wolf <kwolf@redhat.com>
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