Commit fb0d8654 authored by Eric Blake's avatar Eric Blake Committed by Fam Zheng
Browse files

block: Add BDRV_BLOCK_EOF to bdrv_get_block_status() 



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: default avatarEric Blake <eblake@redhat.com>
Message-Id: <20170505021500.19315-2-eblake@redhat.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarFam Zheng <famz@redhat.com>
parent 36f87b45

block/io.c

+11 −4
Original line number Diff line number Diff line
@@ -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;

}

include/block/block.h

+2 −0
Original line number Diff line number Diff line
@@ -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;