aboutsummaryrefslogtreecommitdiff
path: root/block.c
diff options
context:
space:
mode:
authorStefan Hajnoczi <stefanha@linux.vnet.ibm.com>2011-11-28 16:08:47 +0000
committerKevin Wolf <kwolf@redhat.com>2011-12-05 14:51:38 +0100
commit53fec9d3fd3d3a4ded4b92dfa843436bf71380f1 (patch)
tree7d819dc00ebd08495bcc3b6649e4bbd7d1536a39 /block.c
parentdbffbdcfff69431b622866ac5ea78df74fdc02d4 (diff)
block: add interface to toggle copy-on-read
The bdrv_enable_copy_on_read()/bdrv_disable_copy_on_read() functions can be used to programmatically enable or disable copy-on-read for a block device. Later patches add the actual copy-on-read logic. Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/block.c b/block.c
index 16436670dc..9b3cb75646 100644
--- a/block.c
+++ b/block.c
@@ -538,6 +538,22 @@ int bdrv_parse_cache_flags(const char *mode, int *flags)
return 0;
}
+/**
+ * The copy-on-read flag is actually a reference count so multiple users may
+ * use the feature without worrying about clobbering its previous state.
+ * Copy-on-read stays enabled until all users have called to disable it.
+ */
+void bdrv_enable_copy_on_read(BlockDriverState *bs)
+{
+ bs->copy_on_read++;
+}
+
+void bdrv_disable_copy_on_read(BlockDriverState *bs)
+{
+ assert(bs->copy_on_read > 0);
+ bs->copy_on_read--;
+}
+
/*
* Common part for opening disk images and files
*/
@@ -559,6 +575,11 @@ static int bdrv_open_common(BlockDriverState *bs, const char *filename,
bs->growable = 0;
bs->buffer_alignment = 512;
+ assert(bs->copy_on_read == 0); /* bdrv_new() and bdrv_close() make it so */
+ if ((flags & BDRV_O_RDWR) && (flags & BDRV_O_COPY_ON_READ)) {
+ bdrv_enable_copy_on_read(bs);
+ }
+
pstrcpy(bs->filename, sizeof(bs->filename), filename);
bs->backing_file[0] = '\0';
@@ -801,6 +822,7 @@ void bdrv_close(BlockDriverState *bs)
#endif
bs->opaque = NULL;
bs->drv = NULL;
+ bs->copy_on_read = 0;
if (bs->file != NULL) {
bdrv_close(bs->file);