sheepdog: fix loadvm operation

Currently the 'loadvm' opertaion works as following:
1. switch to the snapshot
2. mark current working VDI as a snapshot
3. rely on sd_create_branch to create a new working VDI based on the snapshot

This works not the same as other format as QCOW2. For e.g,

qemu > savevm # get a live snapshot snap1
qemu > savevm # snap2
qemu > loadvm 1 # This will steally create snap3 of the working VDI

Which will result in following snapshot chain:

base <-- snap1 <-- snap2 <-- snap3
          ^
          |
      working VDI

snap3 was unnecessarily created and might be annoying users.

This patch discard the unnecessary 'snap3' creation. and implement
rollback(loadvm) operation to the specified snapshot by
1. switch to the snapshot
2. delete working VDI
3. rely on sd_create_branch to create a new working VDI based on the snapshot

The snapshot chain for above example will be:

base <-- snap1 <-- snap2
          ^
          |
      working VDI

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: Liu Yuan <tailai.ly@taobao.com>
Reviewed-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
1 file changed
tree: 0750e8e83959971d3657a84aed2d9e4d4e2fd588
  1. audio/
  2. backends/
  3. block/
  4. bsd-user/
  5. default-configs/
  6. disas/
  7. docs/
  8. fpu/
  9. fsdev/
  10. gdb-xml/
  11. hw/
  12. include/
  13. ldscripts/
  14. libcacard/
  15. linux-headers/
  16. linux-user/
  17. net/
  18. pc-bios/
  19. po/
  20. qapi/
  21. qga/
  22. QMP/
  23. qobject/
  24. qom/
  25. roms/
  26. scripts/
  27. slirp/
  28. stubs/
  29. sysconfigs/
  30. target-alpha/
  31. target-arm/
  32. target-cris/
  33. target-i386/
  34. target-lm32/
  35. target-m68k/
  36. target-microblaze/
  37. target-mips/
  38. target-moxie/
  39. target-openrisc/
  40. target-ppc/
  41. target-s390x/
  42. target-sh4/
  43. target-sparc/
  44. target-unicore32/
  45. target-xtensa/
  46. tcg/
  47. tests/
  48. trace/
  49. ui/
  50. util/
  51. .exrc
  52. .gitignore
  53. .gitmodules
  54. .mailmap
  55. aio-posix.c
  56. aio-win32.c
  57. arch_init.c
  58. async.c
  59. balloon.c
  60. block-migration.c
  61. block.c
  62. blockdev-nbd.c
  63. blockdev.c
  64. blockjob.c
  65. bt-host.c
  66. bt-vhci.c
  67. Changelog
  68. cmd.c
  69. cmd.h
  70. CODING_STYLE
  71. configure
  72. COPYING
  73. COPYING.LIB
  74. coroutine-gthread.c
  75. coroutine-sigaltstack.c
  76. coroutine-ucontext.c
  77. coroutine-win32.c
  78. cpu-exec.c
  79. cpus.c
  80. cputlb.c
  81. device-hotplug.c
  82. device_tree.c
  83. disas.c
  84. dma-helpers.c
  85. dump-stub.c
  86. dump.c
  87. exec.c
  88. gdbstub.c
  89. HACKING
  90. hmp-commands.hx
  91. hmp.c
  92. hmp.h
  93. iohandler.c
  94. ioport.c
  95. kvm-all.c
  96. kvm-stub.c
  97. LICENSE
  98. main-loop.c
  99. MAINTAINERS
  100. Makefile
  101. Makefile.objs
  102. Makefile.target
  103. memory.c
  104. memory_mapping-stub.c
  105. memory_mapping.c
  106. migration-exec.c
  107. migration-fd.c
  108. migration-tcp.c
  109. migration-unix.c
  110. migration.c
  111. monitor.c
  112. nbd.c
  113. os-posix.c
  114. os-win32.c
  115. page_cache.c
  116. qapi-schema-test.json
  117. qapi-schema.json
  118. qdev-monitor.c
  119. qdict-test-data.txt
  120. qemu-bridge-helper.c
  121. qemu-char.c
  122. qemu-coroutine-io.c
  123. qemu-coroutine-lock.c
  124. qemu-coroutine-sleep.c
  125. qemu-coroutine.c
  126. qemu-doc.texi
  127. qemu-img-cmds.hx
  128. qemu-img.c
  129. qemu-img.texi
  130. qemu-io.c
  131. qemu-log.c
  132. qemu-nbd.c
  133. qemu-nbd.texi
  134. qemu-options-wrapper.h
  135. qemu-options.h
  136. qemu-options.hx
  137. qemu-seccomp.c
  138. qemu-tech.texi
  139. qemu-timer.c
  140. qemu.sasl
  141. qmp-commands.hx
  142. qmp.c
  143. qtest.c
  144. readline.c
  145. README
  146. rules.mak
  147. savevm.c
  148. spice-qemu-char.c
  149. tcg-runtime.c
  150. tci.c
  151. thread-pool.c
  152. thunk.c
  153. tpm.c
  154. trace-events
  155. translate-all.c
  156. translate-all.h
  157. user-exec.c
  158. VERSION
  159. version.rc
  160. vl.c
  161. xbzrle.c
  162. xen-all.c
  163. xen-mapcache.c
  164. xen-stub.c