Re: [PATCH v2 3/4] qcow2: add zoned emulation capability

[Stefan Hajnoczi]

On Mon, Aug 14, 2023 at 04:58:01PM +0800, Sam Li wrote:
> By adding zone operations and zoned metadata, the zoned emulation
> capability enables full emulation support of zoned device using
> a qcow2 file. The zoned device metadata includes zone type,
> zoned device state and write pointer of each zone, which is stored
> to an array of unsigned integers.
> 
> Each zone of a zoned device makes state transitions following
> the zone state machine. The zone state machine mainly describes
> five states, IMPLICIT OPEN, EXPLICIT OPEN, FULL, EMPTY and CLOSED.
> READ ONLY and OFFLINE states will generally be affected by device
> internal events. The operations on zones cause corresponding state
> changing.
> 
> Zoned devices have a limit on zone resources, which puts constraints on
> write operations into zones.
> 
> Signed-off-by: Sam Li <faithilikerun@gmail.com>
> ---
>  block/qcow2.c          | 676 ++++++++++++++++++++++++++++++++++++++++-
>  block/qcow2.h          |   2 +
>  docs/interop/qcow2.txt |   2 +
>  3 files changed, 678 insertions(+), 2 deletions(-)
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index c1077c4a4a..5ccf79cbe7 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -194,6 +194,164 @@ qcow2_extract_crypto_opts(QemuOpts *opts, const char 
> *fmt, Error **errp)
>      return cryptoopts_qdict;
>  }
>  
> +#define QCOW2_ZT_IS_CONV(wp)    (wp & 1ULL << 59)
> +
> +static inline int qcow2_get_wp(uint64_t wp)
> +{
> +    /* clear state and type information */
> +    return ((wp << 5) >> 5);
> +}
> +
> +static inline int qcow2_get_zs(uint64_t wp)
> +{
> +    return (wp >> 60);
> +}
> +
> +static inline void qcow2_set_wp(uint64_t *wp, BlockZoneState zs)
> +{
> +    uint64_t addr = qcow2_get_wp(*wp);
> +    addr |= ((uint64_t)zs << 60);
> +    *wp = addr;
> +}

Although the function is called qcow2_set_wp() it seems to actually be
qcow2_set_zs() since it only changes the zone state, not the write
pointer. Want to rename it?

> +
> +/*
> + * File wp tracking: reset zone, finish zone and append zone can
> + * change the value of write pointer. All zone operations will change
> + * the state of that/those zone.
> + * */
> +static inline void qcow2_wp_tracking_helper(int index, uint64_t wp) {
> +    /* format: operations, the wp. */
> +    printf("wps[%d]: 0x%x\n", index, qcow2_get_wp(wp)>>BDRV_SECTOR_BITS);
> +}

This looks like debugging code that shouldn't go into qemu.git. Please
use tracing (docs/devel/tracing.rst) to capture internal information in
production code.

I will review more of this patch series another time because I need to
get going.

Stefan

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