block: add cache=directsync parameter to -drive

This patch adds -drive cache=directsync for O_DIRECT | O_SYNC host file
I/O with no disk write cache presented to the guest.

This mode is useful when guests may not be sending flushes when
appropriate and therefore leave data at risk in case of power failure.
When cache=directsync is used, write operations are only completed to
the guest when data is safely on disk.

This new mode is like cache=writethrough but it bypasses the host page
cache.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
4 files changed
tree: 944fe6b4fb403578fdb43073ce622ef0a34befc6
  1. audio/
  2. block/
  3. bsd-user/
  4. darwin-user/
  5. default-configs/
  6. docs/
  7. fpu/
  8. fsdev/
  9. gdb-xml/
  10. hw/
  11. libcacard/
  12. linux-headers/
  13. linux-user/
  14. net/
  15. pc-bios/
  16. qapi/
  17. qga/
  18. QMP/
  19. roms/
  20. scripts/
  21. slirp/
  22. sysconfigs/
  23. target-alpha/
  24. target-arm/
  25. target-cris/
  26. target-i386/
  27. target-lm32/
  28. target-m68k/
  29. target-microblaze/
  30. target-mips/
  31. target-ppc/
  32. target-s390x/
  33. target-sh4/
  34. target-sparc/
  35. target-unicore32/
  36. tcg/
  37. tests/
  38. ui/
  39. .gitignore
  40. .gitmodules
  41. a.out.h
  42. acl.c
  43. acl.h
  44. aes.c
  45. aes.h
  46. aio.c
  47. alpha-dis.c
  48. alpha.ld
  49. arch_init.c
  50. arch_init.h
  51. arm-dis.c
  52. arm-semi.c
  53. arm.ld
  54. async.c
  55. balloon.c
  56. balloon.h
  57. bitmap.c
  58. bitmap.h
  59. bitops.c
  60. bitops.h
  61. block-migration.c
  62. block-migration.h
  63. block.c
  64. block.h
  65. block_int.h
  66. blockdev.c
  67. blockdev.h
  68. bswap.h
  69. bt-host.c
  70. bt-host.h
  71. bt-vhci.c
  72. buffered_file.c
  73. buffered_file.h
  74. cache-utils.c
  75. cache-utils.h
  76. Changelog
  77. check-qdict.c
  78. check-qfloat.c
  79. check-qint.c
  80. check-qjson.c
  81. check-qlist.c
  82. check-qstring.c
  83. cmd.c
  84. cmd.h
  85. CODING_STYLE
  86. compatfd.c
  87. compatfd.h
  88. compiler.h
  89. config.h
  90. configure
  91. console.c
  92. console.h
  93. COPYING
  94. COPYING.LIB
  95. coroutine-gthread.c
  96. coroutine-ucontext.c
  97. coroutine-win32.c
  98. cpu-all.h
  99. cpu-common.h
  100. cpu-defs.h
  101. cpu-exec.c
  102. cpus.c
  103. cpus.h
  104. cris-dis.c
  105. cursor.c
  106. cursor_hidden.xpm
  107. cursor_left_ptr.xpm
  108. cutils.c
  109. def-helper.h
  110. device_tree.c
  111. device_tree.h
  112. dis-asm.h
  113. disas.c
  114. disas.h
  115. dma-helpers.c
  116. dma.h
  117. dyngen-exec.h
  118. elf.h
  119. envlist.c
  120. envlist.h
  121. error.c
  122. error.h
  123. error_int.h
  124. exec-all.h
  125. exec-memory.h
  126. exec.c
  127. gdbstub.c
  128. gdbstub.h
  129. gen-icount.h
  130. HACKING
  131. hmp-commands.hx
  132. host-utils.c
  133. host-utils.h
  134. hpet.h
  135. hppa-dis.c
  136. hppa.ld
  137. i386-dis.c
  138. i386.ld
  139. ia64-dis.c
  140. ia64.ld
  141. input.c
  142. iohandler.c
  143. ioport-user.c
  144. ioport.c
  145. ioport.h
  146. iorange.h
  147. iov.c
  148. iov.h
  149. json-lexer.c
  150. json-lexer.h
  151. json-parser.c
  152. json-parser.h
  153. json-streamer.c
  154. json-streamer.h
  155. kvm-all.c
  156. kvm-stub.c
  157. kvm.h
  158. libfdt_env.h
  159. LICENSE
  160. linux-aio.c
  161. m68k-dis.c
  162. m68k-semi.c
  163. m68k.ld
  164. MAINTAINERS
  165. Makefile
  166. Makefile.dis
  167. Makefile.hw
  168. Makefile.objs
  169. Makefile.target
  170. Makefile.user
  171. memory.c
  172. memory.h
  173. microblaze-dis.c
  174. migration-exec.c
  175. migration-fd.c
  176. migration-tcp.c
  177. migration-unix.c
  178. migration.c
  179. migration.h
  180. mips-dis.c
  181. mips.ld
  182. module.c
  183. module.h
  184. monitor.c
  185. monitor.h
  186. nbd.c
  187. nbd.h
  188. net.c
  189. net.h
  190. notify.c
  191. notify.h
  192. os-posix.c
  193. os-win32.c
  194. osdep.c
  195. osdep.h
  196. oslib-posix.c
  197. oslib-win32.c
  198. path.c
  199. pci-ids.txt
  200. pflib.c
  201. pflib.h
  202. poison.h
  203. posix-aio-compat.c
  204. ppc-dis.c
  205. ppc.ld
  206. ppc64.ld
  207. qapi-schema-guest.json
  208. qapi-schema-test.json
  209. qbool.c
  210. qbool.h
  211. qdict-test-data.txt
  212. qdict.c
  213. qdict.h
  214. qemu-aio.h
  215. qemu-barrier.h
  216. qemu-char.c
  217. qemu-char.h
  218. qemu-common.h
  219. qemu-config.c
  220. qemu-config.h
  221. qemu-coroutine-int.h
  222. qemu-coroutine-lock.c
  223. qemu-coroutine.c
  224. qemu-coroutine.h
  225. qemu-doc.texi
  226. qemu-error.c
  227. qemu-error.h
  228. qemu-ga.c
  229. qemu-img-cmds.hx
  230. qemu-img.c
  231. qemu-img.texi
  232. qemu-io.c
  233. qemu-lock.h
  234. qemu-log.h
  235. qemu-nbd.c
  236. qemu-nbd.texi
  237. qemu-objects.h
  238. qemu-option.c
  239. qemu-option.h
  240. qemu-options.h
  241. qemu-options.hx
  242. qemu-os-posix.h
  243. qemu-os-win32.h
  244. qemu-progress.c
  245. qemu-queue.h
  246. qemu-sockets.c
  247. qemu-tech.texi
  248. qemu-thread-posix.c
  249. qemu-thread-posix.h
  250. qemu-thread-win32.c
  251. qemu-thread-win32.h
  252. qemu-thread.h
  253. qemu-timer-common.c
  254. qemu-timer.c
  255. qemu-timer.h
  256. qemu-tool.c
  257. qemu-x509.h
  258. qemu.sasl
  259. qemu_socket.h
  260. qerror.c
  261. qerror.h
  262. qfloat.c
  263. qfloat.h
  264. qint.c
  265. qint.h
  266. qjson.c
  267. qjson.h
  268. qlist.c
  269. qlist.h
  270. qmp-commands.hx
  271. qobject.h
  272. qstring.c
  273. qstring.h
  274. range.h
  275. readline.c
  276. readline.h
  277. README
  278. rules.mak
  279. rwhandler.c
  280. rwhandler.h
  281. s390-dis.c
  282. s390.ld
  283. savevm.c
  284. sh4-dis.c
  285. simpletrace.c
  286. simpletrace.h
  287. softmmu-semi.h
  288. softmmu_defs.h
  289. softmmu_exec.h
  290. softmmu_header.h
  291. softmmu_template.h
  292. sparc-dis.c
  293. sparc.ld
  294. sparc64.ld
  295. spice-qemu-char.c
  296. sysemu.h
  297. targphys.h
  298. tcg-runtime.c
  299. test-coroutine.c
  300. test-qmp-commands.c
  301. test-visitor.c
  302. thunk.c
  303. thunk.h
  304. TODO
  305. trace-events
  306. translate-all.c
  307. uboot_image.h
  308. usb-bsd.c
  309. usb-linux.c
  310. usb-redir.c
  311. usb-stub.c
  312. user-exec.c
  313. VERSION
  314. version.rc
  315. vgafont.h
  316. vl.c
  317. x86_64.ld
  318. xen-all.c
  319. xen-mapcache.c
  320. xen-mapcache.h
  321. xen-stub.c