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qemu / qemu / c8bb23cbdbe32f5c326365e0a82e1b0e68cdcd8a
commitc8bb23cbdbe32f5c326365e0a82e1b0e68cdcd8a[log] [tgz]
authorAnton Nefedov <anton.nefedov@virtuozzo.com>Thu May 16 17:27:49 2019 +0300
committerMax Reitz <mreitz@redhat.com>Tue May 28 20:30:55 2019 +0200
tree7169d73a97be9364e328610798c54f8af16b6fa4
parent330c72957196e0ae382abcaa97ebf4eb9bc8574f [diff]
qcow2: skip writing zero buffers to empty COW areas

If COW areas of the newly allocated clusters are zeroes on the backing
image, efficient bdrv_write_zeroes(flags=BDRV_REQ_NO_FALLBACK) can be
used on the whole cluster instead of writing explicit zero buffers later
in perform_cow().

iotest 060:
write to the discarded cluster does not trigger COW anymore.
Use a backing image instead.

Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
Message-id: 20190516142749.81019-2-anton.nefedov@virtuozzo.com
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
7 files changed
tree: 7169d73a97be9364e328610798c54f8af16b6fa4
  1. accel/
  2. audio/
  3. authz/
  4. backends/
  5. block/
  6. bsd-user/
  7. chardev/
  8. contrib/
  9. crypto/
  10. default-configs/
  11. disas/
  12. docs/
  13. fpu/
  14. fsdev/
  15. gdb-xml/
  16. hw/
  17. include/
  18. io/
  19. libdecnumber/
  20. linux-headers/
  21. linux-user/
  22. migration/
  23. nbd/
  24. net/
  25. pc-bios/
  26. po/
  27. python/
  28. qapi/
  29. qga/
  30. qobject/
  31. qom/
  32. replay/
  33. roms/
  34. scripts/
  35. scsi/
  36. stubs/
  37. target/
  38. tcg/
  39. tests/
  40. trace/
  41. ui/
  42. util/
  43. capstone
  44. dtc
  45. slirp
  46. .cirrus.yml
  47. .dir-locals.el
  48. .editorconfig
  49. .exrc
  50. .gdbinit
  51. .gitignore
  52. .gitlab-ci.yml
  53. .gitmodules
  54. .gitpublish
  55. .mailmap
  56. .shippable.yml
  57. .travis.yml
  58. arch_init.c
  59. balloon.c
  60. block.c
  61. blockdev-nbd.c
  62. blockdev.c
  63. blockjob.c
  64. bootdevice.c
  65. bt-host.c
  66. bt-vhci.c
  67. Changelog
  68. CODING_STYLE
  69. configure
  70. COPYING
  71. COPYING.LIB
  72. cpus-common.c
  73. cpus.c
  74. device-hotplug.c
  75. device_tree.c
  76. disas.c
  77. dma-helpers.c
  78. dump.c
  79. exec.c
  80. gdbstub.c
  81. gitdm.config
  82. HACKING
  83. hmp-commands-info.hx
  84. hmp-commands.hx
  85. hmp.c
  86. hmp.h
  87. ioport.c
  88. iothread.c
  89. job-qmp.c
  90. job.c
  91. Kconfig.host
  92. LICENSE
  93. MAINTAINERS
  94. Makefile
  95. Makefile.objs
  96. Makefile.target
  97. memory.c
  98. memory_ldst.inc.c
  99. memory_mapping.c
  100. module-common.c
  101. monitor.c
  102. numa.c
  103. os-posix.c
  104. os-win32.c
  105. qdev-monitor.c
  106. qemu-bridge-helper.c
  107. qemu-deprecated.texi
  108. qemu-doc.texi
  109. qemu-edid.c
  110. qemu-ga.texi
  111. qemu-img-cmds.hx
  112. qemu-img.c
  113. qemu-img.texi
  114. qemu-io-cmds.c
  115. qemu-io.c
  116. qemu-keymap.c
  117. qemu-nbd.c
  118. qemu-nbd.texi
  119. qemu-option-trace.texi
  120. qemu-options-wrapper.h
  121. qemu-options.h
  122. qemu-options.hx
  123. qemu-seccomp.c
  124. qemu-tech.texi
  125. qemu.nsi
  126. qemu.sasl
  127. qmp.c
  128. qtest.c
  129. README
  130. replication.c
  131. replication.h
  132. rules.mak
  133. thunk.c
  134. tpm.c
  135. trace-events
  136. VERSION
  137. version.rc
  138. vl.c
  139. win_dump.c
  140. win_dump.h