From: Eric Blake <ebl...@redhat.com>
Just as the block layer already sets BDRV_BLOCK_ALLOCATED as a
shortcut for subsequent operations, there are also some optimizations
that are made easier if we can quickly tell that *pnum will advance
us to the end of a file, via a new BDRV_BLOCK_EOF which gets set
by the block layer.
This just plumbs up the new bit; subsequent patches will make use
of it.
Signed-off-by: Eric Blake <ebl...@redhat.com>
Message-Id: <20170505021500.19315-2-ebl...@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
Signed-off-by: Fam Zheng <f...@redhat.com>
---
block/io.c | 15 +++++++++++----
include/block/block.h | 2 ++
2 files changed, 13 insertions(+), 4 deletions(-)
diff --git a/block/io.c b/block/io.c
index 9bba730..7e6abef 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1711,15 +1711,16 @@ typedef struct BdrvCoGetBlockStatusData {
* Drivers not implementing the functionality are assumed to not support
* backing files, hence all their sectors are reported as allocated.
*
- * If 'sector_num' is beyond the end of the disk image the return value is 0
- * and 'pnum' is set to 0.
+ * If 'sector_num' is beyond the end of the disk image the return value is
+ * BDRV_BLOCK_EOF and 'pnum' is set to 0.
*
* 'pnum' is set to the number of sectors (including and immediately following
* the specified sector) that are known to be in the same
* allocated/unallocated state.
*
* 'nb_sectors' is the max value 'pnum' should be set to. If nb_sectors goes
- * beyond the end of the disk image it will be clamped.
+ * beyond the end of the disk image it will be clamped; if 'pnum' is set to
+ * the end of the image, then the returned value will include BDRV_BLOCK_EOF.
*
* If returned value is positive and BDRV_BLOCK_OFFSET_VALID bit is set, 'file'
* points to the BDS which the sector range is allocated in.
@@ -1740,7 +1741,7 @@ static int64_t coroutine_fn
bdrv_co_get_block_status(BlockDriverState *bs,
if (sector_num >= total_sectors) {
*pnum = 0;
- return 0;
+ return BDRV_BLOCK_EOF;
}
n = total_sectors - sector_num;
@@ -1751,6 +1752,9 @@ static int64_t coroutine_fn
bdrv_co_get_block_status(BlockDriverState *bs,
if (!bs->drv->bdrv_co_get_block_status) {
*pnum = nb_sectors;
ret = BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED;
+ if (sector_num + nb_sectors == total_sectors) {
+ ret |= BDRV_BLOCK_EOF;
+ }
if (bs->drv->protocol_name) {
ret |= BDRV_BLOCK_OFFSET_VALID | (sector_num * BDRV_SECTOR_SIZE);
}
@@ -1814,6 +1818,9 @@ static int64_t coroutine_fn
bdrv_co_get_block_status(BlockDriverState *bs,
out:
bdrv_dec_in_flight(bs);
+ if (ret >= 0 && sector_num + *pnum == total_sectors) {
+ ret |= BDRV_BLOCK_EOF;
+ }
return ret;
}
diff --git a/include/block/block.h b/include/block/block.h
index 85e4be7..4c149ad 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -129,6 +129,7 @@ typedef struct HDGeometry {
* BDRV_BLOCK_OFFSET_VALID: an associated offset exists for accessing raw data
* BDRV_BLOCK_ALLOCATED: the content of the block is determined by this
* layer (short for DATA || ZERO), set by block layer
+ * BDRV_BLOCK_EOF: the returned pnum covers through end of file for this layer
*
* Internal flag:
* BDRV_BLOCK_RAW: used internally to indicate that the request was
@@ -157,6 +158,7 @@ typedef struct HDGeometry {
#define BDRV_BLOCK_OFFSET_VALID 0x04
#define BDRV_BLOCK_RAW 0x08
#define BDRV_BLOCK_ALLOCATED 0x10
+#define BDRV_BLOCK_EOF 0x20
#define BDRV_BLOCK_OFFSET_MASK BDRV_SECTOR_MASK
typedef QSIMPLEQ_HEAD(BlockReopenQueue, BlockReopenQueueEntry)
BlockReopenQueue;
--
2.9.4
