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From: | Max Reitz |
Subject: | Re: [Qemu-devel] [PATCH 05/10] block/json: Add bdrv_co_get_block_status() |
Date: | Wed, 05 Mar 2014 21:10:03 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 |
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 <address@hidden> --- 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.
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
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