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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
parentdbffbdcfff69431b622866ac5ea78df74fdc02d4 (diff)
downloadqemu-arm-53fec9d3fd3d3a4ded4b92dfa843436bf71380f1.tar.gz
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>
-rw-r--r--block.c22
-rw-r--r--block.h4
-rw-r--r--block_int.h2
3 files changed, 28 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);
diff --git a/block.h b/block.h
index 8482dbce75..5f8a98a746 100644
--- a/block.h
+++ b/block.h
@@ -70,6 +70,7 @@ typedef struct BlockDevOps {
#define BDRV_O_NATIVE_AIO 0x0080 /* use native AIO instead of the thread pool */
#define BDRV_O_NO_BACKING 0x0100 /* don't open the backing file */
#define BDRV_O_NO_FLUSH 0x0200 /* disable flushing on this disk */
+#define BDRV_O_COPY_ON_READ 0x0400 /* copy read backing sectors into image */
#define BDRV_O_CACHE_MASK (BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH)
@@ -312,6 +313,9 @@ void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector,
int nr_sectors);
int64_t bdrv_get_dirty_count(BlockDriverState *bs);
+void bdrv_enable_copy_on_read(BlockDriverState *bs);
+void bdrv_disable_copy_on_read(BlockDriverState *bs);
+
void bdrv_set_in_use(BlockDriverState *bs, int in_use);
int bdrv_in_use(BlockDriverState *bs);
diff --git a/block_int.h b/block_int.h
index ea818e4e71..311bd2a6fa 100644
--- a/block_int.h
+++ b/block_int.h
@@ -198,6 +198,8 @@ struct BlockDriverState {
int encrypted; /* if true, the media is encrypted */
int valid_key; /* if true, a valid encryption key has been set */
int sg; /* if true, the device is a /dev/sg* */
+ int copy_on_read; /* if true, copy read backing sectors into image
+ note this is a reference count */
BlockDriver *drv; /* NULL means no media */
void *opaque;