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Re: [Qemu-devel] [PATCH 05/10] block/json: Add bdrv_co_get_block_status(
From: |
Benoît Canet |
Subject: |
Re: [Qemu-devel] [PATCH 05/10] block/json: Add bdrv_co_get_block_status() |
Date: |
Wed, 5 Mar 2014 21:41:22 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
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 <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.
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
> >>
> >>
>
- Re: [Qemu-devel] [PATCH 02/10] block/json: Add JSON protocol driver, (continued)
[Qemu-devel] [PATCH 04/10] block/json: Add functions for writing zeroes etc., Max Reitz, 2014/03/03
[Qemu-devel] [PATCH 05/10] block/json: Add bdrv_co_get_block_status(), Max Reitz, 2014/03/03
[Qemu-devel] [PATCH 07/10] block/json: Add bdrv_get_specific_info(), Max Reitz, 2014/03/03
[Qemu-devel] [PATCH 09/10] block/qapi: Ignore filters on top for format name, Max Reitz, 2014/03/03
[Qemu-devel] [PATCH 10/10] iotests: Add test for the JSON protocol, Max Reitz, 2014/03/03