COW: Speed up writes

Process a whole sector's worth of COW bits by reading a sector, setting
the bits after skipping any already set bits, then writing it out again.
Make sure we only flush once before writing metadata, and only if we
need to write metadata.

Signed-off-by: Charlie Shepherd <charlie@ctshepherd.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
1 file changed
tree: bdb0f5783e821edb482247c161692ba9528aa060
  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. libcacard/
  14. linux-headers/
  15. linux-user/
  16. net/
  17. pc-bios/
  18. po/
  19. qapi/
  20. qga/
  21. qobject/
  22. qom/
  23. roms/
  24. scripts/
  25. slirp/
  26. stubs/
  27. sysconfigs/
  28. target-alpha/
  29. target-arm/
  30. target-cris/
  31. target-i386/
  32. target-lm32/
  33. target-m68k/
  34. target-microblaze/
  35. target-mips/
  36. target-moxie/
  37. target-openrisc/
  38. target-ppc/
  39. target-s390x/
  40. target-sh4/
  41. target-sparc/
  42. target-unicore32/
  43. target-xtensa/
  44. tcg/
  45. tests/
  46. trace/
  47. ui/
  48. util/
  49. .exrc
  50. .gitignore
  51. .gitmodules
  52. .mailmap
  53. .travis.yml
  54. aio-posix.c
  55. aio-win32.c
  56. arch_init.c
  57. async.c
  58. balloon.c
  59. block-migration.c
  60. block.c
  61. blockdev-nbd.c
  62. blockdev.c
  63. blockjob.c
  64. bt-host.c
  65. bt-vhci.c
  66. Changelog
  67. CODING_STYLE
  68. configure
  69. COPYING
  70. COPYING.LIB
  71. coroutine-gthread.c
  72. coroutine-sigaltstack.c
  73. coroutine-ucontext.c
  74. coroutine-win32.c
  75. cpu-exec.c
  76. cpus.c
  77. cputlb.c
  78. device-hotplug.c
  79. device_tree.c
  80. disas.c
  81. dma-helpers.c
  82. dump.c
  83. exec.c
  84. gdbstub.c
  85. HACKING
  86. hmp-commands.hx
  87. hmp.c
  88. hmp.h
  89. iohandler.c
  90. ioport.c
  91. kvm-all.c
  92. kvm-stub.c
  93. LICENSE
  94. main-loop.c
  95. MAINTAINERS
  96. Makefile
  97. Makefile.objs
  98. Makefile.target
  99. memory.c
  100. memory_mapping.c
  101. migration-exec.c
  102. migration-fd.c
  103. migration-rdma.c
  104. migration-tcp.c
  105. migration-unix.c
  106. migration.c
  107. monitor.c
  108. nbd.c
  109. os-posix.c
  110. os-win32.c
  111. page_cache.c
  112. qapi-schema.json
  113. qdev-monitor.c
  114. qdict-test-data.txt
  115. qemu-bridge-helper.c
  116. qemu-char.c
  117. qemu-coroutine-io.c
  118. qemu-coroutine-lock.c
  119. qemu-coroutine-sleep.c
  120. qemu-coroutine.c
  121. qemu-doc.texi
  122. qemu-img-cmds.hx
  123. qemu-img.c
  124. qemu-img.texi
  125. qemu-io-cmds.c
  126. qemu-io.c
  127. qemu-log.c
  128. qemu-nbd.c
  129. qemu-nbd.texi
  130. qemu-options-wrapper.h
  131. qemu-options.h
  132. qemu-options.hx
  133. qemu-seccomp.c
  134. qemu-tech.texi
  135. qemu-timer.c
  136. qemu.nsi
  137. qemu.sasl
  138. qmp-commands.hx
  139. qmp.c
  140. qtest.c
  141. readline.c
  142. README
  143. rules.mak
  144. savevm.c
  145. spice-qemu-char.c
  146. tcg-runtime.c
  147. tci.c
  148. thread-pool.c
  149. thunk.c
  150. tpm.c
  151. trace-events
  152. translate-all.c
  153. translate-all.h
  154. user-exec.c
  155. VERSION
  156. version.rc
  157. vl.c
  158. xbzrle.c
  159. xen-all.c
  160. xen-mapcache.c
  161. xen-stub.c