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block: clarify the meaning of BDRV_O_NOCACHE

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Change BDRV_O_NOCACHE to only imply bypassing the host OS file cache,
but no writeback semantics.  All existing callers are changed to also
specify BDRV_O_CACHE_WB to give them writeback semantics.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Christoph Hellwig 2011-05-17 18:04:06 +02:00 committed by Kevin Wolf
parent 69c38b8fce
commit a659979328
7 changed files with 13 additions and 19 deletions
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8
block.c
View File

@ -439,13 +439,7 @@ static int bdrv_open_common(BlockDriverState *bs, const char *filename,
bs->drv = drv;
bs->opaque = qemu_mallocz(drv->instance_size);
/*
* Yes, BDRV_O_NOCACHE aka O_DIRECT means we have to present a
* write cache to the guest. We do need the fdatasync to flush
* out transactions for block allocations, and we maybe have a
* volatile write cache in our backing device to deal with.
*/
if (flags & (BDRV_O_CACHE_WB|BDRV_O_NOCACHE))
if (flags & BDRV_O_CACHE_WB)
bs->enable_write_cache = 1;
/*

2
block/qcow2.c
View File

@ -229,7 +229,7 @@ static int qcow2_open(BlockDriverState *bs, int flags)
}
/* alloc L2 table/refcount block cache */
writethrough = ((flags & BDRV_O_CACHE_MASK) == 0);
writethrough = ((flags & BDRV_O_CACHE_WB) == 0);
s->l2_table_cache = qcow2_cache_create(bs, L2_CACHE_SIZE, writethrough);
s->refcount_block_cache = qcow2_cache_create(bs, REFCOUNT_CACHE_SIZE,
writethrough);

2
block/raw-posix.c
View File

@ -154,7 +154,7 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
* and O_DIRECT for no caching. */
if ((bdrv_flags & BDRV_O_NOCACHE))
s->open_flags |= O_DIRECT;
else if (!(bdrv_flags & BDRV_O_CACHE_WB))
if (!(bdrv_flags & BDRV_O_CACHE_WB))
s->open_flags |= O_DSYNC;
s->fd = -1;

12
block/raw-win32.c
View File

@ -88,9 +88,9 @@ static int raw_open(BlockDriverState *bs, const char *filename, int flags)
}
overlapped = FILE_ATTRIBUTE_NORMAL;
if ((flags & BDRV_O_NOCACHE))
overlapped |= FILE_FLAG_NO_BUFFERING | FILE_FLAG_WRITE_THROUGH;
else if (!(flags & BDRV_O_CACHE_WB))
if (flags & BDRV_O_NOCACHE)
overlapped |= FILE_FLAG_NO_BUFFERING;
if (!(flags & BDRV_O_CACHE_WB))
overlapped |= FILE_FLAG_WRITE_THROUGH;
s->hfile = CreateFile(filename, access_flags,
FILE_SHARE_READ, NULL,
@ -349,9 +349,9 @@ static int hdev_open(BlockDriverState *bs, const char *filename, int flags)
create_flags = OPEN_EXISTING;
overlapped = FILE_ATTRIBUTE_NORMAL;
if ((flags & BDRV_O_NOCACHE))
overlapped |= FILE_FLAG_NO_BUFFERING | FILE_FLAG_WRITE_THROUGH;
else if (!(flags & BDRV_O_CACHE_WB))
if (flags & BDRV_O_NOCACHE)
overlapped |= FILE_FLAG_NO_BUFFERING;
if (!(flags & BDRV_O_CACHE_WB))
overlapped |= FILE_FLAG_WRITE_THROUGH;
s->hfile = CreateFile(filename, access_flags,
FILE_SHARE_READ, NULL,

2
blockdev.c
View File

@ -326,7 +326,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
if ((buf = qemu_opt_get(opts, "cache")) != NULL) {
if (!strcmp(buf, "off") || !strcmp(buf, "none")) {
bdrv_flags |= BDRV_O_NOCACHE;
bdrv_flags |= BDRV_O_NOCACHE | BDRV_O_CACHE_WB;
} else if (!strcmp(buf, "writeback")) {
bdrv_flags |= BDRV_O_CACHE_WB;
} else if (!strcmp(buf, "unsafe")) {

4
qemu-io.c
View File

@ -1655,7 +1655,7 @@ open_f(int argc, char **argv)
flags |= BDRV_O_SNAPSHOT;
break;
case 'n':
flags |= BDRV_O_NOCACHE;
flags |= BDRV_O_NOCACHE | BDRV_O_CACHE_WB;
break;
case 'r':
readonly = 1;
@ -1751,7 +1751,7 @@ int main(int argc, char **argv)
flags |= BDRV_O_SNAPSHOT;
break;
case 'n':
flags |= BDRV_O_NOCACHE;
flags |= BDRV_O_NOCACHE | BDRV_O_CACHE_WB;
break;
case 'c':
add_user_command(optarg);

2
qemu-nbd.c
View File

@ -238,7 +238,7 @@ int main(int argc, char **argv)
flags |= BDRV_O_SNAPSHOT;
break;
case 'n':
flags |= BDRV_O_NOCACHE;
flags |= BDRV_O_NOCACHE | BDRV_O_CACHE_WB;
break;
case 'b':
bindto = optarg;