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qemu / qemu / f29fbf7c6b1c9a84f6931c1c222716fbe073e6e4
commitf29fbf7c6b1c9a84f6931c1c222716fbe073e6e4[log] [tgz]
authorKevin Wolf <kwolf@redhat.com>Mon Apr 15 16:25:01 2019 +0200
committerKevin Wolf <kwolf@redhat.com>Tue Apr 30 15:29:00 2019 +0200
tree10fec182079ffb17a7acdcdaf91a9c5d2b8ba01f
parentde38b5005e946aa3714963ea4c501e279e7d3666 [diff]
qcow2: Avoid COW during metadata preallocation

Limiting the allocation to INT_MAX bytes isn't particularly clever
because it means that the final cluster will be a partial cluster which
will be completed through a COW operation. This results in unnecessary
data read and write requests which lead to an unwanted non-sparse
filesystem block for metadata preallocation.

Align the maximum allocation size down to the cluster size to avoid this
situation.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
1 file changed
tree: 10fec182079ffb17a7acdcdaf91a9c5d2b8ba01f
  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. slirp/
  37. stubs/
  38. target/
  39. tcg/
  40. tests/
  41. trace/
  42. ui/
  43. util/
  44. capstone
  45. dtc
  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