The Wednesday 05 Mar 2014 à 21:10:03 (+0100), Max Reitz wrote : > On 05.03.2014 17:11, Benoît Canet wrote: > >The Monday 03 Mar 2014 à 16:28:48 (+0100), Max Reitz wrote : > >>Implement this function in the same way as raw_bsd does: Acknowledge > >>that this is a passthrough driver (always return BDRV_BLOCK_OFFSET_VALID > >>and BDRV_BLOCK_DATA and derive the offset directly from the sector > >>index) and add BDRV_BLOCK_RAW to the returned value. > >> > >>Signed-off-by: Max Reitz <mre...@redhat.com> > >>--- > >> block/json.c | 9 +++++++++ > >> 1 file changed, 9 insertions(+) > >> > >>diff --git a/block/json.c b/block/json.c > >>index a2f4691..7392802 100644 > >>--- a/block/json.c > >>+++ b/block/json.c > >>@@ -113,6 +113,14 @@ static coroutine_fn int > >>json_co_write_zeroes(BlockDriverState *bs, > >> return bdrv_co_write_zeroes(bs, sector_num, nb_sectors, flags); > >> } > >>+static coroutine_fn int64_t json_co_get_block_status(BlockDriverState *bs, > >>+ int64_t sector_num, > >>+ int nb_sectors, int > >>*pnum) > >>+{ > >>+ return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_DATA | > >>+ (sector_num << BDRV_SECTOR_BITS); > >>+} > >I don't understand what is the selling point of this method instead of > >calling > >bdrv_co_get_block_status on bs->file. > >Some information risk to be lost and it does look like magic. > > This is the same what "raw" does. It just is more meaningful: This > way, this function does not pretend to provide the blocks itself but > instead tells the truth; that is, the blocks are provided by an > underlying BDS (bs->file). > > I wasn't really sure what to do myself. Generally, this driver is > actually meant to pretend that it provides the blocks itself. On the > other hand, I tried to imitate the behavior or "raw", since this is > something I can hope to be approximately correct. Also, as I've said > before, the value returned here is in fact at least technically > correct.
The raw_bsd driver have an additional *pnum = nb_sectors; at the begining of the function. Did you left it on purpose ? Best regards Benoît > > > Max > > >Best regards > > > >Benoît > > > >>+ > >> static void json_invalidate_cache(BlockDriverState *bs) > >> { > >> return bdrv_invalidate_cache(bs->file); > >>@@ -159,6 +167,7 @@ static BlockDriver bdrv_json = { > >> .bdrv_aio_discard = json_aio_discard, > >> .bdrv_co_write_zeroes = json_co_write_zeroes, > >>+ .bdrv_co_get_block_status = json_co_get_block_status, > >> .bdrv_invalidate_cache = json_invalidate_cache, > >>-- > >>1.9.0 > >> > >> >