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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>
This commit is contained in:
Stefan Hajnoczi 2011-11-28 16:08:47 +00:00 committed by Kevin Wolf
parent dbffbdcfff
commit 53fec9d3fd
3 changed files with 28 additions and 0 deletions
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22
block.c
View File

@ -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);

4
block.h
View File

@ -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);

2
block_int.h
View File

@ -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;