Define the return value of get_block_status. Bits 0, 1, 2 and 8-62
are valid; bit 63 (the sign bit) is reserved for errors. Bits 3-7
are left for future extensions.
The return code is compatible with the old is_allocated API: returning
just 0 or 1 (aka BDRV_BLOCK_DATA) will not cause any behavioral change
in clients of is_allocated. We will return more precise information
in the next patches.
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
block.c | 7 +++++--
include/block/block.h | 23 +++++++++++++++++++++++
2 files changed, 28 insertions(+), 2 deletions(-)
diff --git a/block.c b/block.c
index aa1a5f7..8931cac 100644
--- a/block.c
+++ b/block.c
@@ -2976,7 +2976,7 @@ static int64_t coroutine_fn
bdrv_co_get_block_status(BlockDriverState *bs,
if (!bs->drv->bdrv_co_get_block_status) {
*pnum = nb_sectors;
- return 1;
+ return BDRV_BLOCK_DATA;
}
return bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors, pnum);
@@ -3026,7 +3026,10 @@ int64_t bdrv_get_block_status(BlockDriverState *bs,
int64_t sector_num,
int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, int *pnum)
{
- return bdrv_get_block_status(bs, sector_num, nb_sectors, pnum);
+ int64_t ret = bdrv_get_block_status(bs, sector_num, nb_sectors, pnum);
+ return
+ (ret & BDRV_BLOCK_DATA) ||
+ ((ret & BDRV_BLOCK_ZERO) && !bdrv_has_zero_init(bs));
}
/*
diff --git a/include/block/block.h b/include/block/block.h
index 2b50b51..9e44bdd 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -81,6 +81,29 @@ typedef struct BlockDevOps {
#define BDRV_SECTOR_SIZE (1ULL << BDRV_SECTOR_BITS)
#define BDRV_SECTOR_MASK ~(BDRV_SECTOR_SIZE - 1)
+/* BDRV_BLOCK_DATA: data is read from bs->file or another file
+ * BDRV_BLOCK_ZERO: sectors read as zero
+ * BDRV_BLOCK_OFFSET_VALID: contents of sector available in bs->file at offset
+ *
+ * DATA == 0 && ZERO == 0 means that data is read from backing_hd if present.
+ *
+ * DATA ZERO OFFSET_VALID
+ * t t t sectors read as zero, bs->file is zero at offset
+ * t f t sectors read as valid from bs->file at offset
+ * f t t sectors preallocated, read as zero, bs->file not
+ * necessarily zero at offset
+ * f f t sectors preallocated but read from backing_hd,
+ * bs->file contains garbage at offset
+ * t t f sectors preallocated, read as zero, unknown offset
+ * t f f sectors read from unknown file or offset
+ * f t f not allocated or unknown offset, read as zero
+ * f f f not allocated or unknown offset, read from backing_hd
+ */
+#define BDRV_BLOCK_DATA 1
+#define BDRV_BLOCK_ZERO 2
+#define BDRV_BLOCK_OFFSET_VALID 4
+#define BDRV_BLOCK_OFFSET_MASK BDRV_SECTOR_MASK
+
typedef enum {
BDRV_ACTION_REPORT, BDRV_ACTION_IGNORE, BDRV_ACTION_STOP
} BlockErrorAction;
--
1.8.2.1
