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Expand cache= option and use write-through caching by default

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This patch changes the cache= option to accept none, writeback, or writethough
to control the host page cache behavior.  By default, writethrough caching is
now used which internally is implemented by using O_DSYNC to open the disk
images.  When using -snapshot, writeback is used by default since data integrity
it not at all an issue.

cache=none has the same behavior as cache=off previously.  The later syntax is
still supported by now deprecated.  I also cleaned up the O_DIRECT
implementation to avoid many of the #ifdefs.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5485 c046a42c-6fe2-441c-8c8c-71466251a162
This commit is contained in:
aliguori 2008-10-14 14:42:54 +00:00
parent eeb438c1b8
commit 9f7965c7e9
7 changed files with 59 additions and 38 deletions
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5
block.h
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@ -47,7 +47,10 @@ typedef struct QEMUSnapshotInfo {
use a disk image format on top of
it (default for
bdrv_file_open()) */
#define BDRV_O_DIRECT 0x0020
#define BDRV_O_NOCACHE 0x0020 /* do not use the host page cache */
#define BDRV_O_CACHE_WB 0x0040 /* use write-back caching */
#define BDRV_O_CACHE_MASK (BDRV_O_NOCACHE | BDRV_O_CACHE_WB)
void bdrv_info(void);
void bdrv_info_stats(void);