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Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API |
Date: |
Wed, 18 Jul 2012 11:03:23 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 |
Il 18/07/2012 10:51, Wenchao Xia ha scritto:
> Hi, following is API draft, prototypes were taken from qemu/block.h,
> and the API prefix is changed frpm bdrv to qbdrvs, to declare related
> object is BlockDriverState, not BlockDriver. One issue here is it may
> require include block_int.h, which is not LGPL2 licensed yet.
block_int.h is BSD-licensed. It's compatible.
> API format is kept mostly the same with qemu generic block layer, to
> make it easier for implement, and easier to make qemu migrate on it if
> possible.
I'll note that img_create, and almost all retrieval functions cannot be
implemented on top of NBD.
> /* structure init and uninit */
> BlockDriverState *qbdrvs_new(const char *device_name);
device_name is not needed in the library.
> void qbdrvs_delete(BlockDriverState *bs);
Being able to reuse the same BDS with close/open is one of the worst
parts of the QEMU block layer. It is only needed to implement eject in
QEMU. Let's get things right, and only have open/close:
int qbdrvs_open(BlockDriverState **bs, const char *filename, int flags,
const char *format_name);
void qbdrvs_close(BlockDriverState *bs);
>
>
> /* file open and close */
> int qbdrvs_open(BlockDriverState *bs, const char *filename, int flags,
> BlockDriver *drv);
You didn't have an API to find the BlockDriver *. Let's just pass a
format name, or NULL for probing (see above). This is consistent with
qbdrvs_img_create.
> void qbdrvs_close(BlockDriverState *bs);
> int qbdrvs_img_create(const char *filename, const char *fmt,
> const char *base_filename, const char *base_fmt,
> char *options, uint64_t img_size, int flags);
>
>
> /* sync access */
> int qbdrvs_read(BlockDriverState *bs, int64_t sector_num,
> uint8_t *buf, int nb_sectors);
> int qbdrvs_write(BlockDriverState *bs, int64_t sector_num,
> const uint8_t *buf, int nb_sectors);
I would like to have also a scatter gather API (qbdrvs_readv and
qbdrvs_writev) taking a "struct iovec *iov, int niov" instead of
"uint8_t *buf, int nb_sectors".
flush is missing.
>
> /* info retrieve */
> //sector, size and geometry info
> int qbdrvs_get_info(BlockDriverState *bs, BlockDriverInfo *bdi);
One problem here is that BlockDriverInfo may grow in the future. This
is a problem for the ABI of the library. I don't have any particular
ideas here, except adding a separate API to the library for each member
of BlockDriverInfo.
> int64_t qbdrvs_getlength(BlockDriverState *bs);
qbdrvs_get_length.
> int64_t qbdrvs_get_allocated_file_size(BlockDriverState *bs);
> void qbdrvs_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr);
Not needed, it's the same as bdrv_getlength.
> //image type
> const char *qbdrvs_get_format_name(BlockDriverState *bs);
> //backing file info
> void qbdrvs_get_backing_filename(BlockDriverState *bs,
> char *filename, int filename_size);
> void qbdrvs_get_full_backing_filename(BlockDriverState *bs,
> char *dest, size_t sz);
>
>
> /* advanced image content access */
> int qbdrvs_is_allocated(BlockDriverState *bs, int64_t sector_num, int
> nb_sectors,
> int *pnum);
> int qbdrvs_discard(BlockDriverState *bs, int64_t sector_num, int
> nb_sectors);
> int qbdrvs_has_zero_init(BlockDriverState *bs);
Paolo
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, (continued)
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Paolo Bonzini, 2012/07/13
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Paolo Bonzini, 2012/07/13
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Michael Tokarev, 2012/07/13
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Blue Swirl, 2012/07/13
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Stefan Weil, 2012/07/13
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Lluís Vilanova, 2012/07/13
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Stefan Hajnoczi, 2012/07/16
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Wenchao Xia, 2012/07/16
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Paolo Bonzini, 2012/07/16
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Wenchao Xia, 2012/07/18
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API,
Paolo Bonzini <=
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Kevin Wolf, 2012/07/18
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Stefan Hajnoczi, 2012/07/18
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Paolo Bonzini, 2012/07/18
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Stefan Hajnoczi, 2012/07/18
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Andreas Färber, 2012/07/18
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Kevin Wolf, 2012/07/18
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Daniel P. Berrange, 2012/07/18
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Paolo Bonzini, 2012/07/18
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Daniel P. Berrange, 2012/07/18
- Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API, Kevin Wolf, 2012/07/18