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authoraliguori <aliguori@c046a42c-6fe2-441c-8c8c-71466251a162>2008-10-14 14:42:54 +0000
committeraliguori <aliguori@c046a42c-6fe2-441c-8c8c-71466251a162>2008-10-14 14:42:54 +0000
commit9f7965c7e965c8b80da27048017a360b3c57c4af (patch)
tree9a7b218b7a7b590fe926f1c282dfa0916f19092c /block-raw-posix.c
parenteeb438c1b84468e8faa7e69bec86b78b45f2347f (diff)
Expand cache= option and use write-through caching by default
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
Diffstat (limited to 'block-raw-posix.c')
-rw-r--r--block-raw-posix.c41
1 files changed, 17 insertions, 24 deletions
diff --git a/block-raw-posix.c b/block-raw-posix.c
index 83a358cd4d..4c04dbf8da 100644
--- a/block-raw-posix.c
+++ b/block-raw-posix.c
@@ -73,6 +73,11 @@
#define DEBUG_BLOCK_PRINT(formatCstr, args...)
#endif
+/* Approximate O_DIRECT with O_DSYNC if O_DIRECT isn't available */
+#ifndef O_DIRECT
+#define O_DIRECT O_DSYNC
+#endif
+
#define FTYPE_FILE 0
#define FTYPE_CD 1
#define FTYPE_FD 2
@@ -101,9 +106,7 @@ typedef struct BDRVRawState {
int fd_got_error;
int fd_media_changed;
#endif
-#if defined(O_DIRECT)
uint8_t* aligned_buf;
-#endif
} BDRVRawState;
static int posix_aio_init(void);
@@ -129,10 +132,13 @@ static int raw_open(BlockDriverState *bs, const char *filename, int flags)
}
if (flags & BDRV_O_CREAT)
open_flags |= O_CREAT | O_TRUNC;
-#ifdef O_DIRECT
- if (flags & BDRV_O_DIRECT)
+
+ /* Use O_DSYNC for write-through caching, no flags for write-back caching,
+ * and O_DIRECT for no caching. */
+ if ((flags & BDRV_O_NOCACHE))
open_flags |= O_DIRECT;
-#endif
+ else if (!(flags & BDRV_O_CACHE_WB))
+ open_flags |= O_DSYNC;
s->type = FTYPE_FILE;
@@ -146,9 +152,8 @@ static int raw_open(BlockDriverState *bs, const char *filename, int flags)
s->fd = fd;
for (i = 0; i < RAW_FD_POOL_SIZE; i++)
s->fd_pool[i] = -1;
-#if defined(O_DIRECT)
s->aligned_buf = NULL;
- if (flags & BDRV_O_DIRECT) {
+ if ((flags & BDRV_O_NOCACHE)) {
s->aligned_buf = qemu_memalign(512, ALIGNED_BUFFER_SIZE);
if (s->aligned_buf == NULL) {
ret = -errno;
@@ -156,7 +161,6 @@ static int raw_open(BlockDriverState *bs, const char *filename, int flags)
return ret;
}
}
-#endif
return 0;
}
@@ -281,7 +285,6 @@ label__raw_write__success:
}
-#if defined(O_DIRECT)
/*
* offset and count are in bytes and possibly not aligned. For files opened
* with O_DIRECT, necessary alignments are ensured before calling
@@ -432,12 +435,6 @@ static int raw_pwrite(BlockDriverState *bs, int64_t offset,
return raw_pwrite_aligned(bs, offset, buf, count) + sum;
}
-#else
-#define raw_pread raw_pread_aligned
-#define raw_pwrite raw_pwrite_aligned
-#endif
-
-
#ifdef CONFIG_AIO
/***********************************************************/
/* Unix AIO using POSIX AIO */
@@ -661,7 +658,6 @@ static BlockDriverAIOCB *raw_aio_read(BlockDriverState *bs,
* If O_DIRECT is used and the buffer is not aligned fall back
* to synchronous IO.
*/
-#if defined(O_DIRECT)
BDRVRawState *s = bs->opaque;
if (unlikely(s->aligned_buf != NULL && ((uintptr_t) buf % 512))) {
@@ -672,7 +668,6 @@ static BlockDriverAIOCB *raw_aio_read(BlockDriverState *bs,
qemu_bh_schedule(bh);
return &acb->common;
}
-#endif
acb = raw_aio_setup(bs, sector_num, buf, nb_sectors, cb, opaque);
if (!acb)
@@ -694,7 +689,6 @@ static BlockDriverAIOCB *raw_aio_write(BlockDriverState *bs,
* If O_DIRECT is used and the buffer is not aligned fall back
* to synchronous IO.
*/
-#if defined(O_DIRECT)
BDRVRawState *s = bs->opaque;
if (unlikely(s->aligned_buf != NULL && ((uintptr_t) buf % 512))) {
@@ -705,7 +699,6 @@ static BlockDriverAIOCB *raw_aio_write(BlockDriverState *bs,
qemu_bh_schedule(bh);
return &acb->common;
}
-#endif
acb = raw_aio_setup(bs, sector_num, (uint8_t*)buf, nb_sectors, cb, opaque);
if (!acb)
@@ -770,10 +763,8 @@ static void raw_close(BlockDriverState *bs)
if (s->fd >= 0) {
close(s->fd);
s->fd = -1;
-#if defined(O_DIRECT)
if (s->aligned_buf != NULL)
qemu_free(s->aligned_buf);
-#endif
}
raw_close_fd_pool(s);
}
@@ -1003,10 +994,12 @@ static int hdev_open(BlockDriverState *bs, const char *filename, int flags)
open_flags |= O_RDONLY;
bs->read_only = 1;
}
-#ifdef O_DIRECT
- if (flags & BDRV_O_DIRECT)
+ /* Use O_DSYNC for write-through caching, no flags for write-back caching,
+ * and O_DIRECT for no caching. */
+ if ((flags & BDRV_O_NOCACHE))
open_flags |= O_DIRECT;
-#endif
+ else if (!(flags & BDRV_O_CACHE_WB))
+ open_flags |= O_DSYNC;
s->type = FTYPE_FILE;
#if defined(__linux__)