block: use fdatasync instead of fsync if possible

If we are flushing the caches for our image files we only care about the
data (including the metadata required for accessing it) but not things
like timestamp updates.  So try to use fdatasync instead of fsync to
implement the flush operations.

Unfortunately many operating systems still do not support fdatasync,
so we add a qemu_fdatasync wrapper that uses fdatasync if available
as per the _POSIX_SYNCHRONIZED_IO feature macro or fsync otherwise.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
4 files changed
tree: 522dacdca726cc3b8bc321e70791d03a3b543e72
  1. audio/
  2. block/
  3. bsd-user/
  4. darwin-user/
  5. fpu/
  6. gdb-xml/
  7. hw/
  8. linux-user/
  9. pc-bios/
  10. roms/
  11. slirp/
  12. target-alpha/
  13. target-arm/
  14. target-cris/
  15. target-i386/
  16. target-m68k/
  17. target-microblaze/
  18. target-mips/
  19. target-ppc/
  20. target-sh4/
  21. target-sparc/
  22. tcg/
  23. tests/
  24. .gitignore
  25. .gitmodules
  26. a.out.h
  27. acl.c
  28. acl.h
  29. aes.c
  30. aes.h
  31. aio.c
  32. alpha-dis.c
  33. alpha.ld
  34. arm-dis.c
  35. arm-semi.c
  36. arm.ld
  37. balloon.h
  38. block.c
  39. block.h
  40. block_int.h
  41. bswap.h
  42. bt-host.c
  43. bt-host.h
  44. bt-vhci.c
  45. buffered_file.c
  46. buffered_file.h
  47. cache-utils.c
  48. cache-utils.h
  49. Changelog
  50. check-qdict.c
  51. check-qint.c
  52. check-qstring.c
  53. cmd.c
  54. cmd.h
  55. cocoa.m
  56. CODING_STYLE
  57. configure
  58. console.c
  59. console.h
  60. COPYING
  61. COPYING.LIB
  62. cpu-all.h
  63. cpu-common.h
  64. cpu-defs.h
  65. cpu-exec.c
  66. create_config
  67. cris-dis.c
  68. curses.c
  69. curses_keys.h
  70. cutils.c
  71. d3des.c
  72. d3des.h
  73. def-helper.h
  74. device_tree.c
  75. device_tree.h
  76. dis-asm.h
  77. disas.c
  78. disas.h
  79. dma-helpers.c
  80. dma.h
  81. dyngen-exec.h
  82. elf.h
  83. elf_ops.h
  84. envlist.c
  85. envlist.h
  86. exec-all.h
  87. exec.c
  88. feature_to_c.sh
  89. gdbstub.c
  90. gdbstub.h
  91. gen-icount.h
  92. host-utils.c
  93. host-utils.h
  94. hostregs_helper.h
  95. hpet.h
  96. hppa-dis.c
  97. hppa.ld
  98. hxtool
  99. i386-dis.c
  100. i386.ld
  101. ia64.ld
  102. ioport-user.c
  103. ioport.c
  104. ioport.h
  105. keymaps.c
  106. keymaps.h
  107. kvm-all.c
  108. kvm.h
  109. libfdt_env.h
  110. LICENSE
  111. linux-aio.c
  112. loader.c
  113. m68k-dis.c
  114. m68k-semi.c
  115. m68k.ld
  116. MAINTAINERS
  117. Makefile
  118. Makefile.hw
  119. Makefile.target
  120. microblaze-dis.c
  121. migration-exec.c
  122. migration-fd.c
  123. migration-tcp.c
  124. migration-unix.c
  125. migration.c
  126. migration.h
  127. mips-dis.c
  128. mips.ld
  129. module.c
  130. module.h
  131. monitor.c
  132. monitor.h
  133. nbd.c
  134. nbd.h
  135. net-checksum.c
  136. net.c
  137. net.h
  138. osdep.c
  139. osdep.h
  140. path.c
  141. pci-ids.txt
  142. posix-aio-compat.c
  143. ppc-dis.c
  144. ppc.ld
  145. ppc64.ld
  146. qdict-test-data.txt
  147. qdict.c
  148. qdict.h
  149. qemu-aio.h
  150. qemu-binfmt-conf.sh
  151. qemu-char.c
  152. qemu-char.h
  153. qemu-common.h
  154. qemu-config.c
  155. qemu-config.h
  156. qemu-doc.texi
  157. qemu-img-cmds.hx
  158. qemu-img.c
  159. qemu-img.texi
  160. qemu-io.c
  161. qemu-lock.h
  162. qemu-log.h
  163. qemu-malloc.c
  164. qemu-monitor.hx
  165. qemu-nbd.c
  166. qemu-nbd.texi
  167. qemu-option.c
  168. qemu-option.h
  169. qemu-options.hx
  170. qemu-sockets.c
  171. qemu-tech.texi
  172. qemu-thread.c
  173. qemu-thread.h
  174. qemu-timer.h
  175. qemu-tool.c
  176. qemu.sasl
  177. qemu_socket.h
  178. qint.c
  179. qint.h
  180. qobject.h
  181. qstring.c
  182. qstring.h
  183. readline.c
  184. readline.h
  185. README
  186. rules.mak
  187. s390-dis.c
  188. s390.ld
  189. savevm.c
  190. sdl.c
  191. sdl_keysym.h
  192. sdl_zoom.c
  193. sdl_zoom.h
  194. sdl_zoom_template.h
  195. sh4-dis.c
  196. softmmu-semi.h
  197. softmmu_defs.h
  198. softmmu_exec.h
  199. softmmu_header.h
  200. softmmu_template.h
  201. sparc-dis.c
  202. sparc.ld
  203. sparc64.ld
  204. sys-queue.h
  205. sysemu.h
  206. tap-win32.c
  207. targphys.h
  208. texi2pod.pl
  209. thunk.c
  210. thunk.h
  211. TODO
  212. translate-all.c
  213. uboot_image.h
  214. usb-bsd.c
  215. usb-linux.c
  216. usb-stub.c
  217. VERSION
  218. vgafont.h
  219. vl.c
  220. vnc-auth-sasl.c
  221. vnc-auth-sasl.h
  222. vnc-auth-vencrypt.c
  223. vnc-auth-vencrypt.h
  224. vnc-tls.c
  225. vnc-tls.h
  226. vnc.c
  227. vnc.h
  228. vnc_keysym.h
  229. vnchextile.h
  230. x86_64.ld
  231. x_keymap.c
  232. x_keymap.h