Re: [Qemu-devel] [PATCH v2 06/16] Fold postcopy_ram_discard_range into ram_discard_range

[Laurent Vivier]

On 06/02/2017 18:32, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
> 
> Using the previously created ram_block_discard_range,
> kill off postcopy_ram_discard_range.
> ram_discard_range is just a wrapper that does the name lookup.
> 
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
>  include/migration/postcopy-ram.h |  7 -------
>  migration/postcopy-ram.c         | 30 +-----------------------------
>  migration/ram.c                  | 24 +++---------------------
>  migration/trace-events           |  2 +-
>  4 files changed, 5 insertions(+), 58 deletions(-)
> 
> diff --git a/include/migration/postcopy-ram.h 
> b/include/migration/postcopy-ram.h
> index b6a7491f..43bbbca 100644
> --- a/include/migration/postcopy-ram.h
> +++ b/include/migration/postcopy-ram.h
> @@ -35,13 +35,6 @@ int postcopy_ram_incoming_init(MigrationIncomingState 
> *mis, size_t ram_pages);
>  int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis);
>  
>  /*
> - * Discard the contents of 'length' bytes from 'start'
> - * We can assume that if we've been called postcopy_ram_hosttest returned 
> true
> - */
> -int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
> -                               size_t length);
> -
> -/*
>   * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
>   * however leaving it until after precopy means that most of the precopy
>   * data is still THPd
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index a40dddb..1e3d22f 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -200,27 +200,6 @@ out:
>      return ret;
>  }
>  
> -/**
> - * postcopy_ram_discard_range: Discard a range of memory.
> - * We can assume that if we've been called postcopy_ram_hosttest returned 
> true.
> - *
> - * @mis: Current incoming migration state.
> - * @start, @length: range of memory to discard.
> - *
> - * returns: 0 on success.
> - */
> -int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
> -                               size_t length)
> -{
> -    trace_postcopy_ram_discard_range(start, length);
> -    if (madvise(start, length, MADV_DONTNEED)) {
> -        error_report("%s MADV_DONTNEED: %s", __func__, strerror(errno));
> -        return -1;
> -    }
> -
> -    return 0;
> -}
> -
>  /*
>   * Setup an area of RAM so that it *can* be used for postcopy later; this
>   * must be done right at the start prior to pre-copy.
> @@ -239,7 +218,7 @@ static int init_range(const char *block_name, void 
> *host_addr,
>       * - we're going to get the copy from the source anyway.
>       * (Precopy will just overwrite this data, so doesn't need the discard)
>       */
> -    if (postcopy_ram_discard_range(mis, host_addr, length)) {
> +    if (ram_discard_range(mis, block_name, 0, length)) {
>          return -1;
>      }
>  
> @@ -658,13 +637,6 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState 
> *mis)
>      return -1;
>  }
>  
> -int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
> -                               size_t length)
> -{
> -    assert(0);
> -    return -1;
> -}
> -
>  int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
>  {
>      assert(0);
> diff --git a/migration/ram.c b/migration/ram.c
> index d33bd21..136996a 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1845,6 +1845,8 @@ int ram_discard_range(MigrationIncomingState *mis,
>  {
>      int ret = -1;
>  
> +    trace_ram_discard_range(block_name, start, length);
> +
>      rcu_read_lock();

I think you take the rcu_read_lock() twice: here and in
ram_block_discard_range().

I think you should merge this patch with PATCH 04/16, as it's just code
copy.

Laurent